/*
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 * Copyright 1991- The GROMACS Authors
 * and the project initiators Erik Lindahl, Berk Hess and David van der Spoel.
 * Consult the AUTHORS/COPYING files and https://www.gromacs.org for details.
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 */
/*! \internal \file
 *
 * \brief This file defines low-level functions necessary for
 * computing energies and forces for listed interactions.
 *
 * \author Mark Abraham <mark.j.abraham@gmail.com>
 *
 * \ingroup module_listed_forces
 */
#include "gmxpre.h"

#include "bonded.h"

#include "config.h"

#include <cassert>
#include <cmath>

#include <algorithm>

#include "gromacs/gmxlib/nrnb.h"
#include "gromacs/listed_forces/disre.h"
#include "gromacs/listed_forces/orires.h"
#include "gromacs/math/functions.h"
#include "gromacs/math/units.h"
#include "gromacs/math/utilities.h"
#include "gromacs/math/vec.h"
#include "gromacs/mdtypes/fcdata.h"
#include "gromacs/mdtypes/mdatom.h"
#include "gromacs/pbcutil/ishift.h"
#include "gromacs/pbcutil/pbc.h"
#include "gromacs/pbcutil/pbc_simd.h"
#include "gromacs/simd/simd.h"
#include "gromacs/simd/simd_math.h"
#include "gromacs/simd/vector_operations.h"
#include "gromacs/utility/arrayref.h"
#include "gromacs/utility/basedefinitions.h"
#include "gromacs/utility/enumerationhelpers.h"
#include "gromacs/utility/fatalerror.h"
#include "gromacs/utility/real.h"
#include "gromacs/utility/smalloc.h"

#include "listed_internal.h"
#include "restcbt.h"

using namespace gmx; // TODO: Remove when this file is moved into gmx namespace

const EnumerationArray<BondedKernelFlavor, std::string> c_bondedKernelFlavorStrings = {
    "forces, using SIMD when available",
    "forces, not using SIMD",
    "forces, virial, and energy (ie. not using SIMD)",
    "forces and energy (ie. not using SIMD)"
};
namespace
{

//! Type of CPU function to compute a bonded interaction.
using BondedFunction = real (*)(int                       nbonds,
                                const t_iatom             iatoms[],
                                const t_iparams           iparams[],
                                const rvec                x[],
                                rvec4                     f[],
                                rvec                      fshift[],
                                const t_pbc*              pbc,
                                real                      lambda,
                                real*                     dvdlambda,
                                gmx::ArrayRef<const real> charge,
                                t_fcdata*                 fcd,
                                t_disresdata*             disresdata,
                                t_oriresdata*             oriresdata,
                                int*                      ddgatindex);

/*! \brief Mysterious CMAP coefficient matrix */
const int cmap_coeff_matrix[] = {
    1,  0,  -3, 2,  0,  0, 0,  0,  -3, 0,  9,  -6, 2, 0,  -6, 4,  0,  0,  0, 0,  0, 0, 0,  0,
    3,  0,  -9, 6,  -2, 0, 6,  -4, 0,  0,  0,  0,  0, 0,  0,  0,  0,  0,  9, -6, 0, 0, -6, 4,
    0,  0,  3,  -2, 0,  0, 0,  0,  0,  0,  -9, 6,  0, 0,  6,  -4, 0,  0,  0, 0,  1, 0, -3, 2,
    -2, 0,  6,  -4, 1,  0, -3, 2,  0,  0,  0,  0,  0, 0,  0,  0,  -1, 0,  3, -2, 1, 0, -3, 2,
    0,  0,  0,  0,  0,  0, 0,  0,  0,  0,  -3, 2,  0, 0,  3,  -2, 0,  0,  0, 0,  0, 0, 3,  -2,
    0,  0,  -6, 4,  0,  0, 3,  -2, 0,  1,  -2, 1,  0, 0,  0,  0,  0,  -3, 6, -3, 0, 2, -4, 2,
    0,  0,  0,  0,  0,  0, 0,  0,  0,  3,  -6, 3,  0, -2, 4,  -2, 0,  0,  0, 0,  0, 0, 0,  0,
    0,  0,  -3, 3,  0,  0, 2,  -2, 0,  0,  -1, 1,  0, 0,  0,  0,  0,  0,  3, -3, 0, 0, -2, 2,
    0,  0,  0,  0,  0,  1, -2, 1,  0,  -2, 4,  -2, 0, 1,  -2, 1,  0,  0,  0, 0,  0, 0, 0,  0,
    0,  -1, 2,  -1, 0,  1, -2, 1,  0,  0,  0,  0,  0, 0,  0,  0,  0,  0,  1, -1, 0, 0, -1, 1,
    0,  0,  0,  0,  0,  0, -1, 1,  0,  0,  2,  -2, 0, 0,  -1, 1
};


/*! \brief Compute dx = xi - xj, modulo PBC if non-NULL
 *
 * \todo This kind of code appears in many places. Consolidate it */
int pbc_rvec_sub(const t_pbc* pbc, const rvec xi, const rvec xj, rvec dx)
{
    if (pbc)
    {
        return pbc_dx_aiuc(pbc, xi, xj, dx);
    }
    else
    {
        rvec_sub(xi, xj, dx);
        return c_centralShiftIndex;
    }
}

} // namespace

//! \cond
real bond_angle(const rvec   xi,
                const rvec   xj,
                const rvec   xk,
                const t_pbc* pbc,
                rvec         r_ij,
                rvec         r_kj,
                real*        costh,
                int*         t1,
                int*         t2)
/* Return value is the angle between the bonds i-j and j-k */
{
    /* 41 FLOPS */
    real th;

    *t1 = pbc_rvec_sub(pbc, xi, xj, r_ij); /*  3		*/
    *t2 = pbc_rvec_sub(pbc, xk, xj, r_kj); /*  3		*/

    *costh = cos_angle(r_ij, r_kj); /* 25		*/
    th     = std::acos(*costh);     /* 10		*/
    /* 41 TOTAL	*/
    return th;
}

real dih_angle(const rvec   xi,
               const rvec   xj,
               const rvec   xk,
               const rvec   xl,
               const t_pbc* pbc,
               rvec         r_ij,
               rvec         r_kj,
               rvec         r_kl,
               rvec         m,
               rvec         n,
               int*         t1,
               int*         t2,
               int*         t3)
{
    *t1 = pbc_rvec_sub(pbc, xi, xj, r_ij); /*  3        */
    *t2 = pbc_rvec_sub(pbc, xk, xj, r_kj); /*  3		*/
    *t3 = pbc_rvec_sub(pbc, xk, xl, r_kl); /*  3		*/

    cprod(r_ij, r_kj, m);        /*  9        */
    cprod(r_kj, r_kl, n);        /*  9		*/
    real phi  = gmx_angle(m, n); /* 49 (assuming 25 for atan2) */
    real ipr  = iprod(r_ij, n);  /*  5        */
    real sign = (ipr < 0.0) ? -1.0 : 1.0;
    phi       = sign * phi; /*  1		*/
    /* 82 TOTAL	*/
    return phi;
}
//! \endcond

void make_dp_periodic(real* dp) /* 1 flop? */
{
    /* dp cannot be outside (-pi,pi) */
    if (*dp >= M_PI)
    {
        *dp -= 2 * M_PI;
    }
    else if (*dp < -M_PI)
    {
        *dp += 2 * M_PI;
    }
}

namespace
{

/*! \brief Spreads and accumulates the bonded forces to the two atoms and adds the virial contribution when needed
 *
 * \p shiftIndex is used as the periodic shift.
 */
template<BondedKernelFlavor flavor>
inline void spreadBondForces(const real bondForce,
                             const rvec dx,
                             const int  ai,
                             const int  aj,
                             rvec4*     f,
                             int        shiftIndex,
                             rvec*      fshift)
{
    for (int m = 0; m < DIM; m++) /*  15          */
    {
        const real fij = bondForce * dx[m];
        f[ai][m] += fij;
        f[aj][m] -= fij;
        if (computeVirial(flavor))
        {
            fshift[shiftIndex][m] += fij;
            fshift[c_centralShiftIndex][m] -= fij;
        }
    }
}

/*! \brief Morse potential bond
 *
 * By Frank Everdij. Three parameters needed:
 *
 * b0 = equilibrium distance in nm
 * be = beta in nm^-1 (actually, it's nu_e*Sqrt(2*pi*pi*mu/D_e))
 * cb = well depth in kJ/mol
 *
 * Note: the potential is referenced to be +cb at infinite separation
 *       and zero at the equilibrium distance!
 */
template<BondedKernelFlavor flavor>
real morse_bonds(int             nbonds,
                 const t_iatom   forceatoms[],
                 const t_iparams forceparams[],
                 const rvec      x[],
                 rvec4           f[],
                 rvec            fshift[],
                 const t_pbc*    pbc,
                 real            lambda,
                 real*           dvdlambda,
                 gmx::ArrayRef<const real> /*charge*/,
                 t_fcdata gmx_unused* fcd,
                 t_disresdata gmx_unused* disresdata,
                 t_oriresdata gmx_unused* oriresdata,
                 int gmx_unused* global_atom_index)
{
    const real one = 1.0;
    const real two = 2.0;
    real       dr, dr2, temp, omtemp, cbomtemp, fbond, vbond, vtot;
    real       b0, be, cb, b0A, beA, cbA, b0B, beB, cbB, L1;
    rvec       dx;
    int        i, ki, type, ai, aj;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];

        b0A = forceparams[type].morse.b0A;
        beA = forceparams[type].morse.betaA;
        cbA = forceparams[type].morse.cbA;

        b0B = forceparams[type].morse.b0B;
        beB = forceparams[type].morse.betaB;
        cbB = forceparams[type].morse.cbB;

        L1 = one - lambda;            /* 1 */
        b0 = L1 * b0A + lambda * b0B; /* 3 */
        be = L1 * beA + lambda * beB; /* 3 */
        cb = L1 * cbA + lambda * cbB; /* 3 */

        ki   = pbc_rvec_sub(pbc, x[ai], x[aj], dx); /*   3          */
        dr2  = iprod(dx, dx);                       /*   5          */
        dr   = dr2 * gmx::invsqrt(dr2);             /*  10          */
        temp = std::exp(-be * (dr - b0));           /*  12          */

        if (temp == one)
        {
            /* bonds are constrainted. This may _not_ include bond constraints if they are lambda dependent */
            *dvdlambda += cbB - cbA;
            continue;
        }

        omtemp   = one - temp;                                      /*   1          */
        cbomtemp = cb * omtemp;                                     /*   1          */
        vbond    = cbomtemp * omtemp;                               /*   1          */
        fbond    = -two * be * temp * cbomtemp * gmx::invsqrt(dr2); /*   9          */
        vtot += vbond;                                              /*   1          */

        *dvdlambda += (cbB - cbA) * omtemp * omtemp
                      - (2 - 2 * omtemp) * omtemp * cb * ((b0B - b0A) * be - (beB - beA) * (dr - b0)); /* 15 */

        spreadBondForces<flavor>(fbond, dx, ai, aj, f, ki, fshift); /* 15 */
    }                                                               /*  83 TOTAL    */
    return vtot;
}

//! \cond
template<BondedKernelFlavor flavor>
real cubic_bonds(int             nbonds,
                 const t_iatom   forceatoms[],
                 const t_iparams forceparams[],
                 const rvec      x[],
                 rvec4           f[],
                 rvec            fshift[],
                 const t_pbc*    pbc,
                 real gmx_unused lambda,
                 real gmx_unused* dvdlambda,
                 gmx::ArrayRef<const real> /*charge*/,
                 t_fcdata gmx_unused* fcd,
                 t_disresdata gmx_unused* disresdata,
                 t_oriresdata gmx_unused* oriresdata,
                 int gmx_unused* global_atom_index)
{
    const real three = 3.0;
    const real two   = 2.0;
    real       kb, b0, kcub;
    real       dr, dr2, dist, kdist, kdist2, fbond, vbond, vtot;
    rvec       dx;
    int        i, ki, type, ai, aj;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];

        b0   = forceparams[type].cubic.b0;
        kb   = forceparams[type].cubic.kb;
        kcub = forceparams[type].cubic.kcub;

        ki  = pbc_rvec_sub(pbc, x[ai], x[aj], dx); /*   3          */
        dr2 = iprod(dx, dx);                       /*   5          */

        if (dr2 == 0.0)
        {
            continue;
        }

        dr     = dr2 * gmx::invsqrt(dr2); /*  10          */
        dist   = dr - b0;
        kdist  = kb * dist;
        kdist2 = kdist * dist;

        vbond = kdist2 + kcub * kdist2 * dist;
        fbond = -(two * kdist + three * kdist2 * kcub) / dr;

        vtot += vbond; /* 21 */

        spreadBondForces<flavor>(fbond, dx, ai, aj, f, ki, fshift); /* 15 */
    }                                                               /*  54 TOTAL    */
    return vtot;
}

template<BondedKernelFlavor flavor>
real FENE_bonds(int             nbonds,
                const t_iatom   forceatoms[],
                const t_iparams forceparams[],
                const rvec      x[],
                rvec4           f[],
                rvec            fshift[],
                const t_pbc*    pbc,
                real gmx_unused lambda,
                real gmx_unused* dvdlambda,
                gmx::ArrayRef<const real> /*charge*/,
                t_fcdata gmx_unused* fcd,
                t_disresdata gmx_unused* disresdata,
                t_oriresdata gmx_unused* oriresdata,
                int*                     global_atom_index)
{
    const real half = 0.5;
    const real one  = 1.0;
    real       bm, kb;
    real       dr2, bm2, omdr2obm2, fbond, vbond, vtot;
    rvec       dx;
    int        i, ki, type, ai, aj;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];

        bm = forceparams[type].fene.bm;
        kb = forceparams[type].fene.kb;

        ki  = pbc_rvec_sub(pbc, x[ai], x[aj], dx); /*   3          */
        dr2 = iprod(dx, dx);                       /*   5          */

        if (dr2 == 0.0)
        {
            continue;
        }

        bm2 = bm * bm;

        if (dr2 >= bm2)
        {
            gmx_fatal(FARGS,
                      "r^2 (%f) >= bm^2 (%f) in FENE bond between atoms %d and %d",
                      dr2,
                      bm2,
                      glatnr(global_atom_index, ai),
                      glatnr(global_atom_index, aj));
        }

        omdr2obm2 = one - dr2 / bm2;

        vbond = -half * kb * bm2 * std::log(omdr2obm2);
        fbond = -kb / omdr2obm2;

        vtot += vbond; /* 35 */

        spreadBondForces<flavor>(fbond, dx, ai, aj, f, ki, fshift); /* 15 */
    }                                                               /*  58 TOTAL    */
    return vtot;
}

real harmonic(real kA, real kB, real xA, real xB, real x, real lambda, real* V, real* F)
{
    const real half = 0.5;
    real       L1, kk, x0, dx, dx2;
    real       v, f, dvdlambda;

    L1 = 1.0 - lambda;
    kk = L1 * kA + lambda * kB;
    x0 = L1 * xA + lambda * xB;

    dx  = x - x0;
    dx2 = dx * dx;

    f         = -kk * dx;
    v         = half * kk * dx2;
    dvdlambda = half * (kB - kA) * dx2 + (xA - xB) * kk * dx;

    *F = f;
    *V = v;

    return dvdlambda;

    /* That was 19 flops */
}

template<BondedKernelFlavor flavor>
std::enable_if_t<flavor != BondedKernelFlavor::ForcesSimdWhenAvailable || !GMX_SIMD_HAVE_REAL, real>
bonds(int             nbonds,
      const t_iatom   forceatoms[],
      const t_iparams forceparams[],
      const rvec      x[],
      rvec4           f[],
      rvec            fshift[],
      const t_pbc*    pbc,
      real            lambda,
      real*           dvdlambda,
      gmx::ArrayRef<const real> /*charge*/,
      t_fcdata gmx_unused* fcd,
      t_disresdata gmx_unused* disresdata,
      t_oriresdata gmx_unused* oriresdata,
      int gmx_unused* global_atom_index)
{
    int  i, ki, ai, aj, type;
    real dr, dr2, fbond, vbond, vtot;
    rvec dx;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];

        ki  = pbc_rvec_sub(pbc, x[ai], x[aj], dx); /*   3      */
        dr2 = iprod(dx, dx);                       /*   5		*/
        dr  = std::sqrt(dr2);                      /*  10		*/

        *dvdlambda += harmonic(forceparams[type].harmonic.krA,
                               forceparams[type].harmonic.krB,
                               forceparams[type].harmonic.rA,
                               forceparams[type].harmonic.rB,
                               dr,
                               lambda,
                               &vbond,
                               &fbond); /*  19  */

        if (dr2 == 0.0)
        {
            continue;
        }


        vtot += vbond;              /* 1*/
        fbond *= gmx::invsqrt(dr2); /*   6		*/

        spreadBondForces<flavor>(fbond, dx, ai, aj, f, ki, fshift); /* 15 */
    }                                                               /* 59 TOTAL	*/
    return vtot;
}

#if GMX_SIMD_HAVE_REAL

/*! \brief Computes forces (only) for harmonic bonds using SIMD intrinsics
 *
 * As plain-C bonds(), but using SIMD to calculate many bonds at once.
 * This routines does not calculate energies and shift forces.
 */
template<BondedKernelFlavor flavor>
std::enable_if_t<flavor == BondedKernelFlavor::ForcesSimdWhenAvailable, real>
bonds(int             nbonds,
      const t_iatom   forceatoms[],
      const t_iparams forceparams[],
      const rvec      x[],
      rvec4           f[],
      rvec gmx_unused fshift[],
      const t_pbc*    pbc,
      real gmx_unused lambda,
      real gmx_unused* dvdlambda,
      gmx::ArrayRef<const real> /*charge*/,
      t_fcdata gmx_unused* fcd,
      t_disresdata gmx_unused* disresdata,
      t_oriresdata gmx_unused* oriresdata,
      int gmx_unused* global_atom_index)
{
    constexpr int                            nfa1 = 3;
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t ai[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t aj[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) real         coeff[2 * GMX_SIMD_REAL_WIDTH];

    alignas(GMX_SIMD_ALIGNMENT) real pbc_simd[9 * GMX_SIMD_REAL_WIDTH];

    set_pbc_simd(pbc, pbc_simd);

    const SimdReal real_eps = SimdReal(GMX_REAL_EPS);

    /* nbonds is the number of bonds times nfa1, here we step GMX_SIMD_REAL_WIDTH angles */
    for (int i = 0; i < nbonds; i += GMX_SIMD_REAL_WIDTH * nfa1)
    {
        /* Collect atoms for GMX_SIMD_REAL_WIDTH angles.
         * iu indexes into forceatoms, we should not let iu go beyond nbonds.
         */
        int iu = i;
        for (int s = 0; s < GMX_SIMD_REAL_WIDTH; s++)
        {
            const int type = forceatoms[iu];
            ai[s]          = forceatoms[iu + 1];
            aj[s]          = forceatoms[iu + 2];

            /* At the end fill the arrays with the last atoms and 0 params */
            if (i + s * nfa1 < nbonds)
            {
                coeff[s]                       = forceparams[type].harmonic.krA;
                coeff[GMX_SIMD_REAL_WIDTH + s] = forceparams[type].harmonic.rA;

                if (iu + nfa1 < nbonds)
                {
                    iu += nfa1;
                }
            }
            else
            {
                coeff[s]                       = 0;
                coeff[GMX_SIMD_REAL_WIDTH + s] = 0;
            }
        }

        /* Store the non PBC corrected distances packed and aligned */
        SimdReal xi, yi, zi;
        SimdReal xj, yj, zj;
        gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), ai, &xi, &yi, &zi);
        gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), aj, &xj, &yj, &zj);
        SimdReal rij_x = xi - xj;
        SimdReal rij_y = yi - yj;
        SimdReal rij_z = zi - zj;

        pbc_correct_dx_simd(&rij_x, &rij_y, &rij_z, pbc_simd);

        const SimdReal dist2 = rij_x * rij_x + rij_y * rij_y + rij_z * rij_z;
        // Here we avoid sqrt(0), the force will be zero because rij=0
        const SimdReal invDist = invsqrt(max(dist2, real_eps));

        const SimdReal k  = load<SimdReal>(coeff);
        const SimdReal r0 = load<SimdReal>(coeff + GMX_SIMD_REAL_WIDTH);

        // Compute the force divided by the distance
        const SimdReal forceOverR = -k * (dist2 * invDist - r0) * invDist;

        const SimdReal f_x = forceOverR * rij_x;
        const SimdReal f_y = forceOverR * rij_y;
        const SimdReal f_z = forceOverR * rij_z;

        transposeScatterIncrU<4>(reinterpret_cast<real*>(f), ai, f_x, f_y, f_z);
        transposeScatterDecrU<4>(reinterpret_cast<real*>(f), aj, f_x, f_y, f_z);
    }

    return 0;
}

#endif // GMX_SIMD_HAVE_REAL

template<BondedKernelFlavor flavor>
real restraint_bonds(int             nbonds,
                     const t_iatom   forceatoms[],
                     const t_iparams forceparams[],
                     const rvec      x[],
                     rvec4           f[],
                     rvec            fshift[],
                     const t_pbc*    pbc,
                     real            lambda,
                     real*           dvdlambda,
                     gmx::ArrayRef<const real> /*charge*/,
                     t_fcdata gmx_unused* fcd,
                     t_disresdata gmx_unused* disresdata,
                     t_oriresdata gmx_unused* oriresdata,
                     int gmx_unused* global_atom_index)
{
    int  i, ki, ai, aj, type;
    real dr, dr2, fbond, vbond, vtot;
    real L1;
    real low, dlow, up1, dup1, up2, dup2, k, dk;
    real drh, drh2;
    rvec dx;

    L1 = 1.0 - lambda;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];

        ki  = pbc_rvec_sub(pbc, x[ai], x[aj], dx); /*   3      */
        dr2 = iprod(dx, dx);                       /*   5		*/
        dr  = dr2 * gmx::invsqrt(dr2);             /*  10		*/

        low  = L1 * forceparams[type].restraint.lowA + lambda * forceparams[type].restraint.lowB;
        dlow = -forceparams[type].restraint.lowA + forceparams[type].restraint.lowB;
        up1  = L1 * forceparams[type].restraint.up1A + lambda * forceparams[type].restraint.up1B;
        dup1 = -forceparams[type].restraint.up1A + forceparams[type].restraint.up1B;
        up2  = L1 * forceparams[type].restraint.up2A + lambda * forceparams[type].restraint.up2B;
        dup2 = -forceparams[type].restraint.up2A + forceparams[type].restraint.up2B;
        k    = L1 * forceparams[type].restraint.kA + lambda * forceparams[type].restraint.kB;
        dk   = -forceparams[type].restraint.kA + forceparams[type].restraint.kB;
        /* 24 */

        if (dr < low)
        {
            drh   = dr - low;
            drh2  = drh * drh;
            vbond = 0.5 * k * drh2;
            fbond = -k * drh;
            *dvdlambda += 0.5 * dk * drh2 - k * dlow * drh;
        } /* 11 */
        else if (dr <= up1)
        {
            vbond = 0;
            fbond = 0;
        }
        else if (dr <= up2)
        {
            drh   = dr - up1;
            drh2  = drh * drh;
            vbond = 0.5 * k * drh2;
            fbond = -k * drh;
            *dvdlambda += 0.5 * dk * drh2 - k * dup1 * drh;
        } /* 11	*/
        else
        {
            drh   = dr - up2;
            vbond = k * (up2 - up1) * (0.5 * (up2 - up1) + drh);
            fbond = -k * (up2 - up1);
            *dvdlambda += dk * (up2 - up1) * (0.5 * (up2 - up1) + drh)
                          + k * (dup2 - dup1) * (up2 - up1 + drh) - k * (up2 - up1) * dup2;
        }

        if (dr2 == 0.0)
        {
            continue;
        }

        vtot += vbond;              /* 1*/
        fbond *= gmx::invsqrt(dr2); /*   6		*/

        spreadBondForces<flavor>(fbond, dx, ai, aj, f, ki, fshift); /* 15 */
    }                                                               /* 59 TOTAL	*/

    return vtot;
}

template<BondedKernelFlavor flavor>
real polarize(int                       nbonds,
              const t_iatom             forceatoms[],
              const t_iparams           forceparams[],
              const rvec                x[],
              rvec4                     f[],
              rvec                      fshift[],
              const t_pbc*              pbc,
              real                      lambda,
              real*                     dvdlambda,
              gmx::ArrayRef<const real> charge,
              t_fcdata gmx_unused* fcd,
              t_disresdata gmx_unused* disresdata,
              t_oriresdata gmx_unused* oriresdata,
              int gmx_unused* global_atom_index)
{
    int  i, ki, ai, aj, type;
    real dr, dr2, fbond, vbond, vtot, ksh;
    rvec dx;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ksh  = gmx::square(charge[aj]) * gmx::c_one4PiEps0 / forceparams[type].polarize.alpha;

        ki  = pbc_rvec_sub(pbc, x[ai], x[aj], dx); /*   3      */
        dr2 = iprod(dx, dx);                       /*   5		*/
        dr  = std::sqrt(dr2);                      /*  10		*/

        *dvdlambda += harmonic(ksh, ksh, 0, 0, dr, lambda, &vbond, &fbond); /*  19  */

        if (dr2 == 0.0)
        {
            continue;
        }

        vtot += vbond;              /* 1*/
        fbond *= gmx::invsqrt(dr2); /*   6		*/

        spreadBondForces<flavor>(fbond, dx, ai, aj, f, ki, fshift); /* 15 */
    }                                                               /* 59 TOTAL	*/
    return vtot;
}

template<BondedKernelFlavor flavor>
real anharm_polarize(int                       nbonds,
                     const t_iatom             forceatoms[],
                     const t_iparams           forceparams[],
                     const rvec                x[],
                     rvec4                     f[],
                     rvec                      fshift[],
                     const t_pbc*              pbc,
                     real                      lambda,
                     real*                     dvdlambda,
                     gmx::ArrayRef<const real> charge,
                     t_fcdata gmx_unused* fcd,
                     t_disresdata gmx_unused* disresdata,
                     t_oriresdata gmx_unused* oriresdata,
                     int gmx_unused* global_atom_index)
{
    int  i, ki, ai, aj, type;
    real dr, dr2, fbond, vbond, vtot, ksh, khyp, drcut, ddr, ddr3;
    rvec dx;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ksh = gmx::square(charge[aj]) * gmx::c_one4PiEps0 / forceparams[type].anharm_polarize.alpha; /* 7*/
        khyp  = forceparams[type].anharm_polarize.khyp;
        drcut = forceparams[type].anharm_polarize.drcut;

        ki  = pbc_rvec_sub(pbc, x[ai], x[aj], dx); /*   3      */
        dr2 = iprod(dx, dx);                       /*   5		*/
        dr  = dr2 * gmx::invsqrt(dr2);             /*  10		*/

        *dvdlambda += harmonic(ksh, ksh, 0, 0, dr, lambda, &vbond, &fbond); /*  19  */

        if (dr2 == 0.0)
        {
            continue;
        }

        if (dr > drcut)
        {
            ddr  = dr - drcut;
            ddr3 = ddr * ddr * ddr;
            vbond += khyp * ddr * ddr3;
            fbond -= 4 * khyp * ddr3;
        }
        fbond *= gmx::invsqrt(dr2); /*   6		*/
        vtot += vbond;              /* 1*/

        spreadBondForces<flavor>(fbond, dx, ai, aj, f, ki, fshift); /* 15 */
    }                                                               /* 72 TOTAL	*/
    return vtot;
}

template<BondedKernelFlavor flavor>
real water_pol(int             nbonds,
               const t_iatom   forceatoms[],
               const t_iparams forceparams[],
               const rvec      x[],
               rvec4           f[],
               rvec gmx_unused fshift[],
               const t_pbc gmx_unused* pbc,
               real gmx_unused         lambda,
               real gmx_unused*          dvdlambda,
               gmx::ArrayRef<const real> charge,
               t_fcdata gmx_unused* fcd,
               t_disresdata gmx_unused* disresdata,
               t_oriresdata gmx_unused* oriresdata,
               int gmx_unused* global_atom_index)
{
    /* This routine implements anisotropic polarizibility for water, through
     * a shell connected to a dummy with spring constant that differ in the
     * three spatial dimensions in the molecular frame.
     */
    int  i, m, aO, aH1, aH2, aD, aS, type, type0, ki;
    rvec dOH1, dOH2, dHH, dOD, dDS, nW, kk, dx, kdx, proj;
    real vtot, fij, r_HH, r_OD, r_nW, tx, ty, tz, qS;

    vtot = 0.0;
    if (nbonds > 0)
    {
        type0  = forceatoms[0];
        aS     = forceatoms[5];
        qS     = charge[aS];
        kk[XX] = gmx::square(qS) * gmx::c_one4PiEps0 / forceparams[type0].wpol.al_x;
        kk[YY] = gmx::square(qS) * gmx::c_one4PiEps0 / forceparams[type0].wpol.al_y;
        kk[ZZ] = gmx::square(qS) * gmx::c_one4PiEps0 / forceparams[type0].wpol.al_z;
        r_HH   = 1.0 / forceparams[type0].wpol.rHH;
        for (i = 0; (i < nbonds); i += 6)
        {
            type = forceatoms[i];
            if (type != type0)
            {
                gmx_fatal(FARGS, "Sorry, type = %d, type0 = %d, file = %s, line = %d", type, type0, __FILE__, __LINE__);
            }
            aO  = forceatoms[i + 1];
            aH1 = forceatoms[i + 2];
            aH2 = forceatoms[i + 3];
            aD  = forceatoms[i + 4];
            aS  = forceatoms[i + 5];

            /* Compute vectors describing the water frame */
            pbc_rvec_sub(pbc, x[aH1], x[aO], dOH1);
            pbc_rvec_sub(pbc, x[aH2], x[aO], dOH2);
            pbc_rvec_sub(pbc, x[aH2], x[aH1], dHH);
            pbc_rvec_sub(pbc, x[aD], x[aO], dOD);
            ki = pbc_rvec_sub(pbc, x[aS], x[aD], dDS);
            cprod(dOH1, dOH2, nW);

            /* Compute inverse length of normal vector
             * (this one could be precomputed, but I'm too lazy now)
             */
            r_nW = gmx::invsqrt(iprod(nW, nW));
            /* This is for precision, but does not make a big difference,
             * it can go later.
             */
            r_OD = gmx::invsqrt(iprod(dOD, dOD));

            /* Normalize the vectors in the water frame */
            svmul(r_nW, nW, nW);
            svmul(r_HH, dHH, dHH);
            svmul(r_OD, dOD, dOD);

            /* Compute displacement of shell along components of the vector */
            dx[ZZ] = iprod(dDS, dOD);
            /* Compute projection on the XY plane: dDS - dx[ZZ]*dOD */
            for (m = 0; (m < DIM); m++)
            {
                proj[m] = dDS[m] - dx[ZZ] * dOD[m];
            }

            /*dx[XX] = iprod(dDS,nW);
               dx[YY] = iprod(dDS,dHH);*/
            dx[XX] = iprod(proj, nW);
            for (m = 0; (m < DIM); m++)
            {
                proj[m] -= dx[XX] * nW[m];
            }
            dx[YY] = iprod(proj, dHH);
            /* Now compute the forces and energy */
            kdx[XX] = kk[XX] * dx[XX];
            kdx[YY] = kk[YY] * dx[YY];
            kdx[ZZ] = kk[ZZ] * dx[ZZ];
            vtot += iprod(dx, kdx);

            for (m = 0; (m < DIM); m++)
            {
                /* This is a tensor operation but written out for speed */
                tx  = nW[m] * kdx[XX];
                ty  = dHH[m] * kdx[YY];
                tz  = dOD[m] * kdx[ZZ];
                fij = -tx - ty - tz;
                f[aS][m] += fij;
                f[aD][m] -= fij;
                if (computeVirial(flavor))
                {
                    fshift[ki][m] += fij;
                    fshift[c_centralShiftIndex][m] -= fij;
                }
            }
        }
    }
    return 0.5 * vtot;
}

template<BondedKernelFlavor flavor>
static real
do_1_thole(const rvec xi, const rvec xj, rvec fi, rvec fj, const t_pbc* pbc, real qq, rvec fshift[], real afac)
{
    rvec r12;
    real r12sq, r12_1, r12bar, v0, v1, fscal, ebar, fff;
    int  m, t;

    t = pbc_rvec_sub(pbc, xi, xj, r12); /*  3 */

    r12sq  = iprod(r12, r12);                                                     /*  5 */
    r12_1  = gmx::invsqrt(r12sq);                                                 /*  5 */
    r12bar = afac / r12_1;                                                        /*  5 */
    v0     = qq * gmx::c_one4PiEps0 * r12_1;                                      /*  2 */
    ebar   = std::exp(-r12bar);                                                   /*  5 */
    v1     = (1 - (1 + 0.5 * r12bar) * ebar);                                     /*  4 */
    fscal  = ((v0 * r12_1) * v1 - v0 * 0.5 * afac * ebar * (r12bar + 1)) * r12_1; /* 9 */

    for (m = 0; (m < DIM); m++)
    {
        fff = fscal * r12[m];
        fi[m] += fff;
        fj[m] -= fff;
        if (computeVirial(flavor))
        {
            fshift[t][m] += fff;
            fshift[c_centralShiftIndex][m] -= fff;
        }
    } /* 15 */

    return v0 * v1; /* 1 */
    /* 54 */
}

template<BondedKernelFlavor flavor>
real thole_pol(int             nbonds,
               const t_iatom   forceatoms[],
               const t_iparams forceparams[],
               const rvec      x[],
               rvec4           f[],
               rvec            fshift[],
               const t_pbc*    pbc,
               real gmx_unused lambda,
               real gmx_unused*          dvdlambda,
               gmx::ArrayRef<const real> charge,
               t_fcdata gmx_unused* fcd,
               t_disresdata gmx_unused* disresdata,
               t_oriresdata gmx_unused* oriresdata,
               int gmx_unused* global_atom_index)
{
    /* Interaction between two pairs of particles with opposite charge */
    int  i, type, a1, da1, a2, da2;
    real q1, q2, qq, a, al1, al2, afac;
    real V = 0;

    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        a1   = forceatoms[i++];
        da1  = forceatoms[i++];
        a2   = forceatoms[i++];
        da2  = forceatoms[i++];
        q1   = charge[da1];
        q2   = charge[da2];
        a    = forceparams[type].thole.a;
        al1  = forceparams[type].thole.alpha1;
        al2  = forceparams[type].thole.alpha2;
        qq   = q1 * q2;
        afac = a * gmx::invsixthroot(al1 * al2);
        V += do_1_thole<flavor>(x[a1], x[a2], f[a1], f[a2], pbc, qq, fshift, afac);
        V += do_1_thole<flavor>(x[da1], x[a2], f[da1], f[a2], pbc, -qq, fshift, afac);
        V += do_1_thole<flavor>(x[a1], x[da2], f[a1], f[da2], pbc, -qq, fshift, afac);
        V += do_1_thole<flavor>(x[da1], x[da2], f[da1], f[da2], pbc, qq, fshift, afac);
    }
    /* 290 flops */
    return V;
}

// Avoid gcc 386 -O3 code generation bug in this function (see Issue
// #3205 for more information)
#if defined(__GNUC__) && defined(__i386__) && defined(__OPTIMIZE__)
#    pragma GCC push_options
#    pragma GCC optimize("O1")
#    define avoid_gcc_i386_o3_code_generation_bug
#endif

template<BondedKernelFlavor flavor>
std::enable_if_t<flavor != BondedKernelFlavor::ForcesSimdWhenAvailable || !GMX_SIMD_HAVE_REAL, real>
angles(int             nbonds,
       const t_iatom   forceatoms[],
       const t_iparams forceparams[],
       const rvec      x[],
       rvec4           f[],
       rvec            fshift[],
       const t_pbc*    pbc,
       real            lambda,
       real*           dvdlambda,
       gmx::ArrayRef<const real> /*charge*/,
       t_fcdata gmx_unused* fcd,
       t_disresdata gmx_unused* disresdata,
       t_oriresdata gmx_unused* oriresdata,
       int gmx_unused* global_atom_index)
{
    int  i, ai, aj, ak, t1, t2, type;
    rvec r_ij, r_kj;
    real cos_theta, cos_theta2, theta, dVdt, va, vtot;

    vtot = 0.0;
    for (i = 0; i < nbonds;)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];

        theta = bond_angle(x[ai], x[aj], x[ak], pbc, r_ij, r_kj, &cos_theta, &t1, &t2); /*  41 */

        *dvdlambda += harmonic(forceparams[type].harmonic.krA,
                               forceparams[type].harmonic.krB,
                               forceparams[type].harmonic.rA * gmx::c_deg2Rad,
                               forceparams[type].harmonic.rB * gmx::c_deg2Rad,
                               theta,
                               lambda,
                               &va,
                               &dVdt); /*  21  */
        vtot += va;

        cos_theta2 = gmx::square(cos_theta);
        if (cos_theta2 < 1)
        {
            int  m;
            real st, sth;
            real cik, cii, ckk;
            real nrkj2, nrij2;
            real nrkj_1, nrij_1;
            rvec f_i, f_j, f_k;

            st    = dVdt * gmx::invsqrt(1 - cos_theta2); /*  12		*/
            sth   = st * cos_theta;                      /*   1		*/
            nrij2 = iprod(r_ij, r_ij);                   /*   5		*/
            nrkj2 = iprod(r_kj, r_kj);                   /*   5		*/

            nrij_1 = gmx::invsqrt(nrij2); /*  10		*/
            nrkj_1 = gmx::invsqrt(nrkj2); /*  10		*/

            cik = st * nrij_1 * nrkj_1;  /*   2		*/
            cii = sth * nrij_1 * nrij_1; /*   2		*/
            ckk = sth * nrkj_1 * nrkj_1; /*   2		*/

            for (m = 0; m < DIM; m++)
            { /*  39		*/
                f_i[m] = -(cik * r_kj[m] - cii * r_ij[m]);
                f_k[m] = -(cik * r_ij[m] - ckk * r_kj[m]);
                f_j[m] = -f_i[m] - f_k[m];
                f[ai][m] += f_i[m];
                f[aj][m] += f_j[m];
                f[ak][m] += f_k[m];
            }
            if (computeVirial(flavor))
            {
                rvec_inc(fshift[t1], f_i);
                rvec_inc(fshift[c_centralShiftIndex], f_j);
                rvec_inc(fshift[t2], f_k);
            }
        } /* 161 TOTAL	*/
    }

    return vtot;
}

#ifdef avoid_gcc_i386_o3_code_generation_bug
#    pragma GCC pop_options
#    undef avoid_gcc_i386_o3_code_generation_bug
#endif

#if GMX_SIMD_HAVE_REAL

/* As angles, but using SIMD to calculate many angles at once.
 * This routines does not calculate energies and shift forces.
 */
template<BondedKernelFlavor flavor>
std::enable_if_t<flavor == BondedKernelFlavor::ForcesSimdWhenAvailable, real>
angles(int             nbonds,
       const t_iatom   forceatoms[],
       const t_iparams forceparams[],
       const rvec      x[],
       rvec4           f[],
       rvec gmx_unused fshift[],
       const t_pbc*    pbc,
       real gmx_unused lambda,
       real gmx_unused* dvdlambda,
       gmx::ArrayRef<const real> /*charge*/,
       t_fcdata gmx_unused* fcd,
       t_disresdata gmx_unused* disresdata,
       t_oriresdata gmx_unused* oriresdata,
       int gmx_unused* global_atom_index)
{
    const int                                nfa1 = 4;
    int                                      i, iu, s;
    int                                      type;
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t ai[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t aj[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t ak[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) real         coeff[2 * GMX_SIMD_REAL_WIDTH];
    SimdReal                                 deg2rad_S(gmx::c_deg2Rad);
    SimdReal                                 xi_S, yi_S, zi_S;
    SimdReal                                 xj_S, yj_S, zj_S;
    SimdReal                                 xk_S, yk_S, zk_S;
    SimdReal                                 k_S, theta0_S;
    SimdReal                                 rijx_S, rijy_S, rijz_S;
    SimdReal                                 rkjx_S, rkjy_S, rkjz_S;
    SimdReal                                 one_S(1.0);
    SimdReal one_min_eps_S(1.0_real - GMX_REAL_EPS); // Largest number < 1

    SimdReal                         rij_rkj_S;
    SimdReal                         nrij2_S, nrij_1_S;
    SimdReal                         nrkj2_S, nrkj_1_S;
    SimdReal                         cos_S, invsin_S;
    SimdReal                         cos2_S;
    SimdReal                         theta_S;
    SimdReal                         st_S, sth_S;
    SimdReal                         cik_S, cii_S, ckk_S;
    SimdReal                         f_ix_S, f_iy_S, f_iz_S;
    SimdReal                         f_kx_S, f_ky_S, f_kz_S;
    alignas(GMX_SIMD_ALIGNMENT) real pbc_simd[9 * GMX_SIMD_REAL_WIDTH];

    set_pbc_simd(pbc, pbc_simd);

    /* nbonds is the number of angles times nfa1, here we step GMX_SIMD_REAL_WIDTH angles */
    for (i = 0; (i < nbonds); i += GMX_SIMD_REAL_WIDTH * nfa1)
    {
        /* Collect atoms for GMX_SIMD_REAL_WIDTH angles.
         * iu indexes into forceatoms, we should not let iu go beyond nbonds.
         */
        iu = i;
        for (s = 0; s < GMX_SIMD_REAL_WIDTH; s++)
        {
            type  = forceatoms[iu];
            ai[s] = forceatoms[iu + 1];
            aj[s] = forceatoms[iu + 2];
            ak[s] = forceatoms[iu + 3];

            /* At the end fill the arrays with the last atoms and 0 params */
            if (i + s * nfa1 < nbonds)
            {
                coeff[s]                       = forceparams[type].harmonic.krA;
                coeff[GMX_SIMD_REAL_WIDTH + s] = forceparams[type].harmonic.rA;

                if (iu + nfa1 < nbonds)
                {
                    iu += nfa1;
                }
            }
            else
            {
                coeff[s]                       = 0;
                coeff[GMX_SIMD_REAL_WIDTH + s] = 0;
            }
        }

        /* Store the non PBC corrected distances packed and aligned */
        gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), ai, &xi_S, &yi_S, &zi_S);
        gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), aj, &xj_S, &yj_S, &zj_S);
        gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), ak, &xk_S, &yk_S, &zk_S);
        rijx_S = xi_S - xj_S;
        rijy_S = yi_S - yj_S;
        rijz_S = zi_S - zj_S;
        rkjx_S = xk_S - xj_S;
        rkjy_S = yk_S - yj_S;
        rkjz_S = zk_S - zj_S;

        k_S      = load<SimdReal>(coeff);
        theta0_S = load<SimdReal>(coeff + GMX_SIMD_REAL_WIDTH) * deg2rad_S;

        pbc_correct_dx_simd(&rijx_S, &rijy_S, &rijz_S, pbc_simd);
        pbc_correct_dx_simd(&rkjx_S, &rkjy_S, &rkjz_S, pbc_simd);

        rij_rkj_S = iprod(rijx_S, rijy_S, rijz_S, rkjx_S, rkjy_S, rkjz_S);

        nrij2_S = norm2(rijx_S, rijy_S, rijz_S);
        nrkj2_S = norm2(rkjx_S, rkjy_S, rkjz_S);

        nrij_1_S = invsqrt(nrij2_S);
        nrkj_1_S = invsqrt(nrkj2_S);

        cos_S = rij_rkj_S * nrij_1_S * nrkj_1_S;

        /* We compute cos^2 using a division instead of squaring cos_S,
         * as we would then get additional error contributions from
         * the two invsqrt operations, which get amplified by
         * the 1/sqrt(1-cos^2) for cos values close to 1.
         *
         * Note that the non-SIMD version of angles() avoids this issue
         * by computing the cosine using double precision.
         */
        cos2_S = rij_rkj_S * rij_rkj_S / (nrij2_S * nrkj2_S);

        /* To allow for 0 and 180 degrees, we need to avoid issues when
         * the cosine is close to -1 and 1. For acos() the argument needs
         * to be in that range. For cos^2 we take the min of cos^2 and 1 - 1bit,
         * so we can safely compute 1/sin as 1/sqrt(1 - cos^2).
         */
        cos_S  = max(cos_S, -one_S);
        cos_S  = min(cos_S, one_S);
        cos2_S = min(cos2_S, one_min_eps_S);

        theta_S = acos(cos_S);

        invsin_S = invsqrt(one_S - cos2_S);

        st_S  = k_S * (theta0_S - theta_S) * invsin_S;
        sth_S = st_S * cos_S;

        cik_S = st_S * nrij_1_S * nrkj_1_S;
        cii_S = sth_S * nrij_1_S * nrij_1_S;
        ckk_S = sth_S * nrkj_1_S * nrkj_1_S;

        f_ix_S = cii_S * rijx_S;
        f_ix_S = fnma(cik_S, rkjx_S, f_ix_S);
        f_iy_S = cii_S * rijy_S;
        f_iy_S = fnma(cik_S, rkjy_S, f_iy_S);
        f_iz_S = cii_S * rijz_S;
        f_iz_S = fnma(cik_S, rkjz_S, f_iz_S);
        f_kx_S = ckk_S * rkjx_S;
        f_kx_S = fnma(cik_S, rijx_S, f_kx_S);
        f_ky_S = ckk_S * rkjy_S;
        f_ky_S = fnma(cik_S, rijy_S, f_ky_S);
        f_kz_S = ckk_S * rkjz_S;
        f_kz_S = fnma(cik_S, rijz_S, f_kz_S);

        transposeScatterIncrU<4>(reinterpret_cast<real*>(f), ai, f_ix_S, f_iy_S, f_iz_S);
        transposeScatterDecrU<4>(
                reinterpret_cast<real*>(f), aj, f_ix_S + f_kx_S, f_iy_S + f_ky_S, f_iz_S + f_kz_S);
        transposeScatterIncrU<4>(reinterpret_cast<real*>(f), ak, f_kx_S, f_ky_S, f_kz_S);
    }

    return 0;
}

#endif // GMX_SIMD_HAVE_REAL

template<BondedKernelFlavor flavor>
real linear_angles(int             nbonds,
                   const t_iatom   forceatoms[],
                   const t_iparams forceparams[],
                   const rvec      x[],
                   rvec4           f[],
                   rvec            fshift[],
                   const t_pbc*    pbc,
                   real            lambda,
                   real*           dvdlambda,
                   gmx::ArrayRef<const real> /*charge*/,
                   t_fcdata gmx_unused* fcd,
                   t_disresdata gmx_unused* disresdata,
                   t_oriresdata gmx_unused* oriresdata,
                   int gmx_unused* global_atom_index)
{
    int  i, m, ai, aj, ak, t1, t2, type;
    rvec f_i, f_j, f_k;
    real L1, kA, kB, aA, aB, dr, dr2, va, vtot, a, b, klin;
    rvec r_ij, r_kj, r_ik, dx;

    L1   = 1 - lambda;
    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];

        kA   = forceparams[type].linangle.klinA;
        kB   = forceparams[type].linangle.klinB;
        klin = L1 * kA + lambda * kB;

        aA = forceparams[type].linangle.aA;
        aB = forceparams[type].linangle.aB;
        a  = L1 * aA + lambda * aB;
        b  = 1 - a;

        t1 = pbc_rvec_sub(pbc, x[ai], x[aj], r_ij);
        t2 = pbc_rvec_sub(pbc, x[ak], x[aj], r_kj);
        rvec_sub(r_ij, r_kj, r_ik);

        dr2 = 0;
        for (m = 0; (m < DIM); m++)
        {
            dr = -a * r_ij[m] - b * r_kj[m];
            dr2 += dr * dr;
            dx[m]  = dr;
            f_i[m] = a * klin * dr;
            f_k[m] = b * klin * dr;
            f_j[m] = -(f_i[m] + f_k[m]);
            f[ai][m] += f_i[m];
            f[aj][m] += f_j[m];
            f[ak][m] += f_k[m];
        }
        va = 0.5 * klin * dr2;
        *dvdlambda += 0.5 * (kB - kA) * dr2 + klin * (aB - aA) * iprod(dx, r_ik);

        vtot += va;

        if (computeVirial(flavor))
        {
            rvec_inc(fshift[t1], f_i);
            rvec_inc(fshift[c_centralShiftIndex], f_j);
            rvec_inc(fshift[t2], f_k);
        }
    } /* 57 TOTAL	*/
    return vtot;
}

template<BondedKernelFlavor flavor>
std::enable_if_t<flavor != BondedKernelFlavor::ForcesSimdWhenAvailable || !GMX_SIMD_HAVE_REAL, real>
urey_bradley(int             nbonds,
             const t_iatom   forceatoms[],
             const t_iparams forceparams[],
             const rvec      x[],
             rvec4           f[],
             rvec            fshift[],
             const t_pbc*    pbc,
             real            lambda,
             real*           dvdlambda,
             gmx::ArrayRef<const real> /*charge*/,
             t_fcdata gmx_unused* fcd,
             t_disresdata gmx_unused* disresdata,
             t_oriresdata gmx_unused* oriresdata,
             int gmx_unused* global_atom_index)
{
    int  i, m, ai, aj, ak, t1, t2, type, ki;
    rvec r_ij, r_kj, r_ik;
    real cos_theta, cos_theta2, theta;
    real dVdt, va, vtot, dr, dr2, vbond, fbond, fik;
    real kthA, th0A, kUBA, r13A, kthB, th0B, kUBB, r13B;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];
        th0A = forceparams[type].u_b.thetaA * gmx::c_deg2Rad;
        kthA = forceparams[type].u_b.kthetaA;
        r13A = forceparams[type].u_b.r13A;
        kUBA = forceparams[type].u_b.kUBA;
        th0B = forceparams[type].u_b.thetaB * gmx::c_deg2Rad;
        kthB = forceparams[type].u_b.kthetaB;
        r13B = forceparams[type].u_b.r13B;
        kUBB = forceparams[type].u_b.kUBB;

        theta = bond_angle(x[ai], x[aj], x[ak], pbc, r_ij, r_kj, &cos_theta, &t1, &t2); /*  41 */

        *dvdlambda += harmonic(kthA, kthB, th0A, th0B, theta, lambda, &va, &dVdt); /*  21  */
        vtot += va;

        ki  = pbc_rvec_sub(pbc, x[ai], x[ak], r_ik); /*   3      */
        dr2 = iprod(r_ik, r_ik);                     /*   5		*/
        dr  = dr2 * gmx::invsqrt(dr2);               /*  10		*/

        *dvdlambda += harmonic(kUBA, kUBB, r13A, r13B, dr, lambda, &vbond, &fbond); /*  19  */

        cos_theta2 = gmx::square(cos_theta); /*   1		*/
        if (cos_theta2 < 1)
        {
            real st, sth;
            real cik, cii, ckk;
            real nrkj2, nrij2;
            rvec f_i, f_j, f_k;

            st    = dVdt * gmx::invsqrt(1 - cos_theta2); /*  12		*/
            sth   = st * cos_theta;                      /*   1		*/
            nrkj2 = iprod(r_kj, r_kj);                   /*   5		*/
            nrij2 = iprod(r_ij, r_ij);

            cik = st * gmx::invsqrt(nrkj2 * nrij2); /*  12		*/
            cii = sth / nrij2;                      /*  10		*/
            ckk = sth / nrkj2;                      /*  10		*/

            for (m = 0; (m < DIM); m++) /*  39		*/
            {
                f_i[m] = -(cik * r_kj[m] - cii * r_ij[m]);
                f_k[m] = -(cik * r_ij[m] - ckk * r_kj[m]);
                f_j[m] = -f_i[m] - f_k[m];
                f[ai][m] += f_i[m];
                f[aj][m] += f_j[m];
                f[ak][m] += f_k[m];
            }
            if (computeVirial(flavor))
            {
                rvec_inc(fshift[t1], f_i);
                rvec_inc(fshift[c_centralShiftIndex], f_j);
                rvec_inc(fshift[t2], f_k);
            }
        } /* 161 TOTAL	*/
        /* Time for the bond calculations */
        if (dr2 == 0.0)
        {
            continue;
        }

        vtot += vbond;              /* 1*/
        fbond *= gmx::invsqrt(dr2); /*   6		*/

        for (m = 0; (m < DIM); m++) /*  15		*/
        {
            fik = fbond * r_ik[m];
            f[ai][m] += fik;
            f[ak][m] -= fik;
            if (computeVirial(flavor))
            {
                fshift[ki][m] += fik;
                fshift[c_centralShiftIndex][m] -= fik;
            }
        }
    }
    return vtot;
}

#if GMX_SIMD_HAVE_REAL

/* As urey_bradley, but using SIMD to calculate many potentials at once.
 * This routines does not calculate energies and shift forces.
 */
template<BondedKernelFlavor flavor>
std::enable_if_t<flavor == BondedKernelFlavor::ForcesSimdWhenAvailable, real>
urey_bradley(int             nbonds,
             const t_iatom   forceatoms[],
             const t_iparams forceparams[],
             const rvec      x[],
             rvec4           f[],
             rvec gmx_unused fshift[],
             const t_pbc*    pbc,
             real gmx_unused lambda,
             real gmx_unused* dvdlambda,
             gmx::ArrayRef<const real> /*charge*/,
             t_fcdata gmx_unused* fcd,
             t_disresdata gmx_unused* disresdata,
             t_oriresdata gmx_unused* oriresdata,
             int gmx_unused* global_atom_index)
{
    constexpr int                            nfa1 = 4;
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t ai[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t aj[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t ak[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) real         coeff[4 * GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) real         pbc_simd[9 * GMX_SIMD_REAL_WIDTH];

    set_pbc_simd(pbc, pbc_simd);

    /* nbonds is the number of angles times nfa1, here we step GMX_SIMD_REAL_WIDTH angles */
    for (int i = 0; i < nbonds; i += GMX_SIMD_REAL_WIDTH * nfa1)
    {
        /* Collect atoms for GMX_SIMD_REAL_WIDTH angles.
         * iu indexes into forceatoms, we should not let iu go beyond nbonds.
         */
        int iu = i;
        for (int s = 0; s < GMX_SIMD_REAL_WIDTH; s++)
        {
            const int type = forceatoms[iu];
            ai[s]          = forceatoms[iu + 1];
            aj[s]          = forceatoms[iu + 2];
            ak[s]          = forceatoms[iu + 3];

            /* At the end fill the arrays with the last atoms and 0 params */
            if (i + s * nfa1 < nbonds)
            {
                coeff[s]                           = forceparams[type].u_b.kthetaA;
                coeff[GMX_SIMD_REAL_WIDTH + s]     = forceparams[type].u_b.thetaA;
                coeff[GMX_SIMD_REAL_WIDTH * 2 + s] = forceparams[type].u_b.kUBA;
                coeff[GMX_SIMD_REAL_WIDTH * 3 + s] = forceparams[type].u_b.r13A;

                if (iu + nfa1 < nbonds)
                {
                    iu += nfa1;
                }
            }
            else
            {
                coeff[s]                           = 0;
                coeff[GMX_SIMD_REAL_WIDTH + s]     = 0;
                coeff[GMX_SIMD_REAL_WIDTH * 2 + s] = 0;
                coeff[GMX_SIMD_REAL_WIDTH * 3 + s] = 0;
            }
        }

        SimdReal xi_S, yi_S, zi_S;
        SimdReal xj_S, yj_S, zj_S;
        SimdReal xk_S, yk_S, zk_S;

        /* Store the non PBC corrected distances packed and aligned */
        gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), ai, &xi_S, &yi_S, &zi_S);
        gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), aj, &xj_S, &yj_S, &zj_S);
        gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), ak, &xk_S, &yk_S, &zk_S);
        SimdReal rijx_S = xi_S - xj_S;
        SimdReal rijy_S = yi_S - yj_S;
        SimdReal rijz_S = zi_S - zj_S;
        SimdReal rkjx_S = xk_S - xj_S;
        SimdReal rkjy_S = yk_S - yj_S;
        SimdReal rkjz_S = zk_S - zj_S;
        SimdReal rikx_S = xi_S - xk_S;
        SimdReal riky_S = yi_S - yk_S;
        SimdReal rikz_S = zi_S - zk_S;

        const SimdReal ktheta_S = load<SimdReal>(coeff);
        const SimdReal theta0_S = load<SimdReal>(coeff + GMX_SIMD_REAL_WIDTH) * gmx::c_deg2Rad;
        const SimdReal kUB_S    = load<SimdReal>(coeff + 2 * GMX_SIMD_REAL_WIDTH);
        const SimdReal r13_S    = load<SimdReal>(coeff + 3 * GMX_SIMD_REAL_WIDTH);

        pbc_correct_dx_simd(&rijx_S, &rijy_S, &rijz_S, pbc_simd);
        pbc_correct_dx_simd(&rkjx_S, &rkjy_S, &rkjz_S, pbc_simd);
        pbc_correct_dx_simd(&rikx_S, &riky_S, &rikz_S, pbc_simd);

        const SimdReal rij_rkj_S = iprod(rijx_S, rijy_S, rijz_S, rkjx_S, rkjy_S, rkjz_S);

        const SimdReal dr2_S = iprod(rikx_S, riky_S, rikz_S, rikx_S, riky_S, rikz_S);

        const SimdReal nrij2_S = norm2(rijx_S, rijy_S, rijz_S);
        const SimdReal nrkj2_S = norm2(rkjx_S, rkjy_S, rkjz_S);

        const SimdReal nrij_1_S = invsqrt(nrij2_S);
        const SimdReal nrkj_1_S = invsqrt(nrkj2_S);
        const SimdReal invdr2_S = invsqrt(dr2_S);
        const SimdReal dr_S     = dr2_S * invdr2_S;

        constexpr real min_one_plus_eps = -1.0 + 2.0 * GMX_REAL_EPS; // Smallest number > -1

        /* To allow for 180 degrees, we take the max of cos and -1 + 1bit,
         * so we can safely get the 1/sin from 1/sqrt(1 - cos^2).
         * This also ensures that rounding errors would cause the argument
         * of simdAcos to be < -1.
         * Note that we do not take precautions for cos(0)=1, so the bonds
         * in an angle should not align at an angle of 0 degrees.
         */
        const SimdReal cos_S = max(rij_rkj_S * nrij_1_S * nrkj_1_S, min_one_plus_eps);

        const SimdReal theta_S  = acos(cos_S);
        const SimdReal invsin_S = invsqrt(1.0 - cos_S * cos_S);
        const SimdReal st_S     = ktheta_S * (theta0_S - theta_S) * invsin_S;
        const SimdReal sth_S    = st_S * cos_S;

        const SimdReal cik_S = st_S * nrij_1_S * nrkj_1_S;
        const SimdReal cii_S = sth_S * nrij_1_S * nrij_1_S;
        const SimdReal ckk_S = sth_S * nrkj_1_S * nrkj_1_S;

        const SimdReal sUB_S = kUB_S * (r13_S - dr_S) * invdr2_S;

        const SimdReal f_ikx_S = sUB_S * rikx_S;
        const SimdReal f_iky_S = sUB_S * riky_S;
        const SimdReal f_ikz_S = sUB_S * rikz_S;

        const SimdReal f_ix_S = fnma(cik_S, rkjx_S, cii_S * rijx_S) + f_ikx_S;
        const SimdReal f_iy_S = fnma(cik_S, rkjy_S, cii_S * rijy_S) + f_iky_S;
        const SimdReal f_iz_S = fnma(cik_S, rkjz_S, cii_S * rijz_S) + f_ikz_S;
        const SimdReal f_kx_S = fnma(cik_S, rijx_S, ckk_S * rkjx_S) - f_ikx_S;
        const SimdReal f_ky_S = fnma(cik_S, rijy_S, ckk_S * rkjy_S) - f_iky_S;
        const SimdReal f_kz_S = fnma(cik_S, rijz_S, ckk_S * rkjz_S) - f_ikz_S;

        transposeScatterIncrU<4>(reinterpret_cast<real*>(f), ai, f_ix_S, f_iy_S, f_iz_S);
        transposeScatterDecrU<4>(
                reinterpret_cast<real*>(f), aj, f_ix_S + f_kx_S, f_iy_S + f_ky_S, f_iz_S + f_kz_S);
        transposeScatterIncrU<4>(reinterpret_cast<real*>(f), ak, f_kx_S, f_ky_S, f_kz_S);
    }

    return 0;
}

#endif // GMX_SIMD_HAVE_REAL

template<BondedKernelFlavor flavor>
real quartic_angles(int             nbonds,
                    const t_iatom   forceatoms[],
                    const t_iparams forceparams[],
                    const rvec      x[],
                    rvec4           f[],
                    rvec            fshift[],
                    const t_pbc*    pbc,
                    real gmx_unused lambda,
                    real gmx_unused* dvdlambda,
                    gmx::ArrayRef<const real> /*charge*/,
                    t_fcdata gmx_unused* fcd,
                    t_disresdata gmx_unused* disresdata,
                    t_oriresdata gmx_unused* oriresdata,
                    int gmx_unused* global_atom_index)
{
    int  i, j, ai, aj, ak, t1, t2, type;
    rvec r_ij, r_kj;
    real cos_theta, cos_theta2, theta, dt, dVdt, va, dtp, c, vtot;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];

        theta = bond_angle(x[ai], x[aj], x[ak], pbc, r_ij, r_kj, &cos_theta, &t1, &t2); /*  41 */

        dt = theta - forceparams[type].qangle.theta * gmx::c_deg2Rad; /* 2          */

        dVdt = 0;
        va   = forceparams[type].qangle.c[0];
        dtp  = 1.0;
        for (j = 1; j <= 4; j++)
        {
            c = forceparams[type].qangle.c[j];
            dVdt -= j * c * dtp;
            dtp *= dt;
            va += c * dtp;
        }
        /* 20 */

        vtot += va;

        cos_theta2 = gmx::square(cos_theta); /*   1		*/
        if (cos_theta2 < 1)
        {
            int  m;
            real st, sth;
            real cik, cii, ckk;
            real nrkj2, nrij2;
            rvec f_i, f_j, f_k;

            st    = dVdt * gmx::invsqrt(1 - cos_theta2); /*  12		*/
            sth   = st * cos_theta;                      /*   1		*/
            nrkj2 = iprod(r_kj, r_kj);                   /*   5		*/
            nrij2 = iprod(r_ij, r_ij);

            cik = st * gmx::invsqrt(nrkj2 * nrij2); /*  12		*/
            cii = sth / nrij2;                      /*  10		*/
            ckk = sth / nrkj2;                      /*  10		*/

            for (m = 0; (m < DIM); m++) /*  39		*/
            {
                f_i[m] = -(cik * r_kj[m] - cii * r_ij[m]);
                f_k[m] = -(cik * r_ij[m] - ckk * r_kj[m]);
                f_j[m] = -f_i[m] - f_k[m];
                f[ai][m] += f_i[m];
                f[aj][m] += f_j[m];
                f[ak][m] += f_k[m];
            }

            if (computeVirial(flavor))
            {
                rvec_inc(fshift[t1], f_i);
                rvec_inc(fshift[c_centralShiftIndex], f_j);
                rvec_inc(fshift[t2], f_k);
            }
        } /* 153 TOTAL	*/
    }
    return vtot;
}


#if GMX_SIMD_HAVE_REAL

/* As dih_angle above, but calculates 4 dihedral angles at once using SIMD,
 * also calculates the pre-factor required for the dihedral force update.
 * Note that bv and buf should be register aligned.
 */
inline void dih_angle_simd(const rvec* x,
                           const int*  ai,
                           const int*  aj,
                           const int*  ak,
                           const int*  al,
                           const real* pbc_simd,
                           SimdReal*   phi_S,
                           SimdReal*   mx_S,
                           SimdReal*   my_S,
                           SimdReal*   mz_S,
                           SimdReal*   nx_S,
                           SimdReal*   ny_S,
                           SimdReal*   nz_S,
                           SimdReal*   nrkj_m2_S,
                           SimdReal*   nrkj_n2_S,
                           SimdReal*   p_S,
                           SimdReal*   q_S)
{
    SimdReal xi_S, yi_S, zi_S;
    SimdReal xj_S, yj_S, zj_S;
    SimdReal xk_S, yk_S, zk_S;
    SimdReal xl_S, yl_S, zl_S;
    SimdReal rijx_S, rijy_S, rijz_S;
    SimdReal rkjx_S, rkjy_S, rkjz_S;
    SimdReal rklx_S, rkly_S, rklz_S;
    SimdReal cx_S, cy_S, cz_S;
    SimdReal cn_S;
    SimdReal s_S;
    SimdReal ipr_S;
    SimdReal iprm_S, iprn_S;
    SimdReal nrkj2_S, nrkj_1_S, nrkj_2_S, nrkj_S;
    SimdReal toler_S;
    SimdReal nrkj2_min_S;
    SimdReal real_eps_S;

    /* Used to avoid division by zero.
     * We take into acount that we multiply the result by real_eps_S.
     */
    nrkj2_min_S = SimdReal(GMX_REAL_MIN / (2 * GMX_REAL_EPS));

    /* The value of the last significant bit (GMX_REAL_EPS is half of that) */
    real_eps_S = SimdReal(2 * GMX_REAL_EPS);

    /* Store the non PBC corrected distances packed and aligned */
    gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), ai, &xi_S, &yi_S, &zi_S);
    gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), aj, &xj_S, &yj_S, &zj_S);
    gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), ak, &xk_S, &yk_S, &zk_S);
    gatherLoadUTranspose<3>(reinterpret_cast<const real*>(x), al, &xl_S, &yl_S, &zl_S);
    rijx_S = xi_S - xj_S;
    rijy_S = yi_S - yj_S;
    rijz_S = zi_S - zj_S;
    rkjx_S = xk_S - xj_S;
    rkjy_S = yk_S - yj_S;
    rkjz_S = zk_S - zj_S;
    rklx_S = xk_S - xl_S;
    rkly_S = yk_S - yl_S;
    rklz_S = zk_S - zl_S;

    pbc_correct_dx_simd(&rijx_S, &rijy_S, &rijz_S, pbc_simd);
    pbc_correct_dx_simd(&rkjx_S, &rkjy_S, &rkjz_S, pbc_simd);
    pbc_correct_dx_simd(&rklx_S, &rkly_S, &rklz_S, pbc_simd);

    cprod(rijx_S, rijy_S, rijz_S, rkjx_S, rkjy_S, rkjz_S, mx_S, my_S, mz_S);

    cprod(rkjx_S, rkjy_S, rkjz_S, rklx_S, rkly_S, rklz_S, nx_S, ny_S, nz_S);

    cprod(*mx_S, *my_S, *mz_S, *nx_S, *ny_S, *nz_S, &cx_S, &cy_S, &cz_S);

    cn_S = sqrt(norm2(cx_S, cy_S, cz_S));

    s_S = iprod(*mx_S, *my_S, *mz_S, *nx_S, *ny_S, *nz_S);

    /* Determine the dihedral angle, the sign might need correction */
    *phi_S = atan2(cn_S, s_S);

    ipr_S = iprod(rijx_S, rijy_S, rijz_S, *nx_S, *ny_S, *nz_S);

    iprm_S = norm2(*mx_S, *my_S, *mz_S);
    iprn_S = norm2(*nx_S, *ny_S, *nz_S);

    nrkj2_S = norm2(rkjx_S, rkjy_S, rkjz_S);

    /* Avoid division by zero. When zero, the result is multiplied by 0
     * anyhow, so the 3 max below do not affect the final result.
     */
    nrkj2_S  = max(nrkj2_S, nrkj2_min_S);
    nrkj_1_S = invsqrt(nrkj2_S);
    nrkj_2_S = nrkj_1_S * nrkj_1_S;
    nrkj_S   = nrkj2_S * nrkj_1_S;

    toler_S = nrkj2_S * real_eps_S;

    /* Here the plain-C code uses a conditional, but we can't do that in SIMD.
     * So we take a max with the tolerance instead. Since we multiply with
     * m or n later, the max does not affect the results.
     */
    iprm_S     = max(iprm_S, toler_S);
    iprn_S     = max(iprn_S, toler_S);
    *nrkj_m2_S = nrkj_S * inv(iprm_S);
    *nrkj_n2_S = nrkj_S * inv(iprn_S);

    /* Set sign of phi_S with the sign of ipr_S; phi_S is currently positive */
    *phi_S = copysign(*phi_S, ipr_S);
    *p_S   = iprod(rijx_S, rijy_S, rijz_S, rkjx_S, rkjy_S, rkjz_S);
    *p_S   = *p_S * nrkj_2_S;

    *q_S = iprod(rklx_S, rkly_S, rklz_S, rkjx_S, rkjy_S, rkjz_S);
    *q_S = *q_S * nrkj_2_S;
}

#endif // GMX_SIMD_HAVE_REAL

} // namespace

template<BondedKernelFlavor flavor>
void do_dih_fup(int          i,
                int          j,
                int          k,
                int          l,
                real         ddphi,
                rvec         r_ij,
                rvec         r_kj,
                rvec         r_kl,
                rvec         m,
                rvec         n,
                rvec4        f[],
                rvec         fshift[],
                const t_pbc* pbc,
                const rvec   x[],
                int          t1,
                int          t2,
                int          t3)
{
    /* 143 FLOPS */
    rvec f_i, f_j, f_k, f_l;
    rvec uvec, vvec, svec, dx_jl;
    real iprm, iprn, nrkj, nrkj2, nrkj_1, nrkj_2;
    real a, b, p, q, toler;

    iprm  = iprod(m, m);       /*  5    */
    iprn  = iprod(n, n);       /*  5	*/
    nrkj2 = iprod(r_kj, r_kj); /*  5	*/
    toler = nrkj2 * GMX_REAL_EPS;
    if ((iprm > toler) && (iprn > toler))
    {
        nrkj_1 = gmx::invsqrt(nrkj2);  /* 10	*/
        nrkj_2 = nrkj_1 * nrkj_1;      /*  1	*/
        nrkj   = nrkj2 * nrkj_1;       /*  1	*/
        a      = -ddphi * nrkj / iprm; /* 11	*/
        svmul(a, m, f_i);              /*  3	*/
        b = ddphi * nrkj / iprn;       /* 11	*/
        svmul(b, n, f_l);              /*  3  */
        p = iprod(r_ij, r_kj);         /*  5	*/
        p *= nrkj_2;                   /*  1	*/
        q = iprod(r_kl, r_kj);         /*  5	*/
        q *= nrkj_2;                   /*  1	*/
        svmul(p, f_i, uvec);           /*  3	*/
        svmul(q, f_l, vvec);           /*  3	*/
        rvec_sub(uvec, vvec, svec);    /*  3	*/
        rvec_sub(f_i, svec, f_j);      /*  3	*/
        rvec_add(f_l, svec, f_k);      /*  3	*/
        rvec_inc(f[i], f_i);           /*  3	*/
        rvec_dec(f[j], f_j);           /*  3	*/
        rvec_dec(f[k], f_k);           /*  3	*/
        rvec_inc(f[l], f_l);           /*  3	*/

        if (computeVirial(flavor))
        {
            if (pbc)
            {
                t3 = pbc_rvec_sub(pbc, x[l], x[j], dx_jl);
            }
            else
            {
                t3 = c_centralShiftIndex;
            }

            rvec_inc(fshift[t1], f_i);
            rvec_dec(fshift[c_centralShiftIndex], f_j);
            rvec_dec(fshift[t2], f_k);
            rvec_inc(fshift[t3], f_l);
        }
    }
    /* 112 TOTAL    */
}

namespace
{

#if GMX_SIMD_HAVE_REAL
/* As do_dih_fup_noshiftf above, but with SIMD and pre-calculated pre-factors */
inline void gmx_simdcall do_dih_fup_noshiftf_simd(const int* ai,
                                                  const int* aj,
                                                  const int* ak,
                                                  const int* al,
                                                  SimdReal   p,
                                                  SimdReal   q,
                                                  SimdReal   f_i_x,
                                                  SimdReal   f_i_y,
                                                  SimdReal   f_i_z,
                                                  SimdReal   mf_l_x,
                                                  SimdReal   mf_l_y,
                                                  SimdReal   mf_l_z,
                                                  rvec4      f[])
{
    SimdReal sx    = p * f_i_x + q * mf_l_x;
    SimdReal sy    = p * f_i_y + q * mf_l_y;
    SimdReal sz    = p * f_i_z + q * mf_l_z;
    SimdReal f_j_x = f_i_x - sx;
    SimdReal f_j_y = f_i_y - sy;
    SimdReal f_j_z = f_i_z - sz;
    SimdReal f_k_x = mf_l_x - sx;
    SimdReal f_k_y = mf_l_y - sy;
    SimdReal f_k_z = mf_l_z - sz;
    transposeScatterIncrU<4>(reinterpret_cast<real*>(f), ai, f_i_x, f_i_y, f_i_z);
    transposeScatterDecrU<4>(reinterpret_cast<real*>(f), aj, f_j_x, f_j_y, f_j_z);
    transposeScatterIncrU<4>(reinterpret_cast<real*>(f), ak, f_k_x, f_k_y, f_k_z);
    transposeScatterDecrU<4>(reinterpret_cast<real*>(f), al, mf_l_x, mf_l_y, mf_l_z);
}
#endif // GMX_SIMD_HAVE_REAL

/*! \brief Computes and returns the proper dihedral force
 *
 * With the appropriate kernel flavor, also computes and accumulates
 * the energy and dV/dlambda.
 */
template<BondedKernelFlavor flavor>
real dopdihs(real cpA, real cpB, real phiA, real phiB, int mult, real phi, real lambda, real* V, real* dvdlambda)
{
    const real L1   = 1.0 - lambda;
    const real ph0  = (L1 * phiA + lambda * phiB) * gmx::c_deg2Rad;
    const real dph0 = (phiB - phiA) * gmx::c_deg2Rad;
    const real cp   = L1 * cpA + lambda * cpB;

    const real mdphi = mult * phi - ph0;
    const real sdphi = std::sin(mdphi);
    const real ddphi = -cp * mult * sdphi;
    if (computeEnergy(flavor))
    {
        const real v1 = 1 + std::cos(mdphi);
        *V += cp * v1;

        *dvdlambda += (cpB - cpA) * v1 + cp * dph0 * sdphi;
    }

    return ddphi;
    /* That was 40 flops */
}

/*! \brief Similar to \p dopdihs(), except for a minus sign and a different treatment of mult/phi0 */
real dopdihs_min(real cpA, real cpB, real phiA, real phiB, int mult, real phi, real lambda, real* V, real* F)
{
    real v, dvdlambda, mdphi, v1, sdphi, ddphi;
    real L1   = 1.0 - lambda;
    real ph0  = (L1 * phiA + lambda * phiB) * gmx::c_deg2Rad;
    real dph0 = (phiB - phiA) * gmx::c_deg2Rad;
    real cp   = L1 * cpA + lambda * cpB;

    mdphi = mult * (phi - ph0);
    sdphi = std::sin(mdphi);
    ddphi = cp * mult * sdphi;
    v1    = 1.0 - std::cos(mdphi);
    v     = cp * v1;

    dvdlambda = (cpB - cpA) * v1 + cp * dph0 * sdphi;

    *V = v;
    *F = ddphi;

    return dvdlambda;

    /* That was 40 flops */
}

template<BondedKernelFlavor flavor>
std::enable_if_t<flavor != BondedKernelFlavor::ForcesSimdWhenAvailable || !GMX_SIMD_HAVE_REAL, real>
pdihs(int             nbonds,
      const t_iatom   forceatoms[],
      const t_iparams forceparams[],
      const rvec      x[],
      rvec4           f[],
      rvec            fshift[],
      const t_pbc*    pbc,
      real            lambda,
      real*           dvdlambda,
      gmx::ArrayRef<const real> /*charge*/,
      t_fcdata gmx_unused* fcd,
      t_disresdata gmx_unused* disresdata,
      t_oriresdata gmx_unused* oriresdata,
      int gmx_unused* global_atom_index)
{
    int  t1, t2, t3;
    rvec r_ij, r_kj, r_kl, m, n;

    real vtot = 0.0;

    for (int i = 0; i < nbonds;)
    {
        const int ai = forceatoms[i + 1];
        const int aj = forceatoms[i + 2];
        const int ak = forceatoms[i + 3];
        const int al = forceatoms[i + 4];

        const real phi =
                dih_angle(x[ai], x[aj], x[ak], x[al], pbc, r_ij, r_kj, r_kl, m, n, &t1, &t2, &t3); /*  84 */

        /* Loop over dihedrals working on the same atoms,
         * so we avoid recalculating angles and distributing forces.
         */
        real ddphi_tot = 0;
        do
        {
            const int type = forceatoms[i];
            ddphi_tot += dopdihs<flavor>(forceparams[type].pdihs.cpA,
                                         forceparams[type].pdihs.cpB,
                                         forceparams[type].pdihs.phiA,
                                         forceparams[type].pdihs.phiB,
                                         forceparams[type].pdihs.mult,
                                         phi,
                                         lambda,
                                         &vtot,
                                         dvdlambda);

            i += 5;
        } while (i < nbonds && forceatoms[i + 1] == ai && forceatoms[i + 2] == aj
                 && forceatoms[i + 3] == ak && forceatoms[i + 4] == al);

        do_dih_fup<flavor>(
                ai, aj, ak, al, ddphi_tot, r_ij, r_kj, r_kl, m, n, f, fshift, pbc, x, t1, t2, t3); /* 112		*/
    } /* 223 TOTAL  */

    return vtot;
}

#if GMX_SIMD_HAVE_REAL

/* As pdihs above, but using SIMD to calculate multiple dihedrals at once */
template<BondedKernelFlavor flavor>
std::enable_if_t<flavor == BondedKernelFlavor::ForcesSimdWhenAvailable, real>
pdihs(int             nbonds,
      const t_iatom   forceatoms[],
      const t_iparams forceparams[],
      const rvec      x[],
      rvec4           f[],
      rvec gmx_unused fshift[],
      const t_pbc*    pbc,
      real gmx_unused lambda,
      real gmx_unused* dvdlambda,
      gmx::ArrayRef<const real> /*charge*/,
      t_fcdata gmx_unused* fcd,
      t_disresdata gmx_unused* disresdata,
      t_oriresdata gmx_unused* oriresdata,
      int gmx_unused* global_atom_index)
{
    const int                                nfa1 = 5;
    int                                      i, iu, s;
    int                                      type;
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t ai[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t aj[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t ak[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t al[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) real         buf[3 * GMX_SIMD_REAL_WIDTH];
    real *                                   cp, *phi0, *mult;
    SimdReal                                 deg2rad_S(gmx::c_deg2Rad);
    SimdReal                                 p_S, q_S;
    SimdReal                                 phi0_S, phi_S;
    SimdReal                                 mx_S, my_S, mz_S;
    SimdReal                                 nx_S, ny_S, nz_S;
    SimdReal                                 nrkj_m2_S, nrkj_n2_S;
    SimdReal                                 cp_S, mdphi_S, mult_S;
    SimdReal                                 sin_S, cos_S;
    SimdReal                                 mddphi_S;
    SimdReal                                 sf_i_S, msf_l_S;
    alignas(GMX_SIMD_ALIGNMENT) real         pbc_simd[9 * GMX_SIMD_REAL_WIDTH];

    /* Extract aligned pointer for parameters and variables */
    cp   = buf + 0 * GMX_SIMD_REAL_WIDTH;
    phi0 = buf + 1 * GMX_SIMD_REAL_WIDTH;
    mult = buf + 2 * GMX_SIMD_REAL_WIDTH;

    set_pbc_simd(pbc, pbc_simd);

    /* nbonds is the number of dihedrals times nfa1, here we step GMX_SIMD_REAL_WIDTH dihs */
    for (i = 0; (i < nbonds); i += GMX_SIMD_REAL_WIDTH * nfa1)
    {
        /* Collect atoms quadruplets for GMX_SIMD_REAL_WIDTH dihedrals.
         * iu indexes into forceatoms, we should not let iu go beyond nbonds.
         */
        iu = i;
        for (s = 0; s < GMX_SIMD_REAL_WIDTH; s++)
        {
            type  = forceatoms[iu];
            ai[s] = forceatoms[iu + 1];
            aj[s] = forceatoms[iu + 2];
            ak[s] = forceatoms[iu + 3];
            al[s] = forceatoms[iu + 4];

            /* At the end fill the arrays with the last atoms and 0 params */
            if (i + s * nfa1 < nbonds)
            {
                cp[s]   = forceparams[type].pdihs.cpA;
                phi0[s] = forceparams[type].pdihs.phiA;
                mult[s] = forceparams[type].pdihs.mult;

                if (iu + nfa1 < nbonds)
                {
                    iu += nfa1;
                }
            }
            else
            {
                cp[s]   = 0;
                phi0[s] = 0;
                mult[s] = 0;
            }
        }

        /* Calculate GMX_SIMD_REAL_WIDTH dihedral angles at once */
        dih_angle_simd(
                x, ai, aj, ak, al, pbc_simd, &phi_S, &mx_S, &my_S, &mz_S, &nx_S, &ny_S, &nz_S, &nrkj_m2_S, &nrkj_n2_S, &p_S, &q_S);

        cp_S   = load<SimdReal>(cp);
        phi0_S = load<SimdReal>(phi0) * deg2rad_S;
        mult_S = load<SimdReal>(mult);

        mdphi_S = fms(mult_S, phi_S, phi0_S);

        /* Calculate GMX_SIMD_REAL_WIDTH sines at once */
        sincos(mdphi_S, &sin_S, &cos_S);
        mddphi_S = cp_S * mult_S * sin_S;
        sf_i_S   = mddphi_S * nrkj_m2_S;
        msf_l_S  = mddphi_S * nrkj_n2_S;

        /* After this m?_S will contain f[i] */
        mx_S = sf_i_S * mx_S;
        my_S = sf_i_S * my_S;
        mz_S = sf_i_S * mz_S;

        /* After this m?_S will contain -f[l] */
        nx_S = msf_l_S * nx_S;
        ny_S = msf_l_S * ny_S;
        nz_S = msf_l_S * nz_S;

        do_dih_fup_noshiftf_simd(ai, aj, ak, al, p_S, q_S, mx_S, my_S, mz_S, nx_S, ny_S, nz_S, f);
    }

    return 0;
}

/* This is mostly a copy of the SIMD flavor of pdihs above, but with using
 * the RB potential instead of a harmonic potential.
 * This function can replace rbdihs() when no energy and virial are needed.
 */
template<BondedKernelFlavor flavor>
std::enable_if_t<flavor == BondedKernelFlavor::ForcesSimdWhenAvailable, real>
rbdihs(int             nbonds,
       const t_iatom   forceatoms[],
       const t_iparams forceparams[],
       const rvec      x[],
       rvec4           f[],
       rvec gmx_unused fshift[],
       const t_pbc*    pbc,
       real gmx_unused lambda,
       real gmx_unused* dvdlambda,
       gmx::ArrayRef<const real> /*charge*/,
       t_fcdata gmx_unused* fcd,
       t_disresdata gmx_unused* disresdata,
       t_oriresdata gmx_unused* oriresdata,
       int gmx_unused* global_atom_index)
{
    const int                                nfa1 = 5;
    int                                      i, iu, s, j;
    int                                      type;
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t ai[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t aj[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t ak[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) std::int32_t al[GMX_SIMD_REAL_WIDTH];
    alignas(GMX_SIMD_ALIGNMENT) real         parm[NR_RBDIHS * GMX_SIMD_REAL_WIDTH];

    SimdReal                         p_S, q_S;
    SimdReal                         phi_S;
    SimdReal                         ddphi_S, cosfac_S;
    SimdReal                         mx_S, my_S, mz_S;
    SimdReal                         nx_S, ny_S, nz_S;
    SimdReal                         nrkj_m2_S, nrkj_n2_S;
    SimdReal                         parm_S, c_S;
    SimdReal                         sin_S, cos_S;
    SimdReal                         sf_i_S, msf_l_S;
    alignas(GMX_SIMD_ALIGNMENT) real pbc_simd[9 * GMX_SIMD_REAL_WIDTH];

    SimdReal pi_S(M_PI);
    SimdReal one_S(1.0);

    set_pbc_simd(pbc, pbc_simd);

    /* nbonds is the number of dihedrals times nfa1, here we step GMX_SIMD_REAL_WIDTH dihs */
    for (i = 0; (i < nbonds); i += GMX_SIMD_REAL_WIDTH * nfa1)
    {
        /* Collect atoms quadruplets for GMX_SIMD_REAL_WIDTH dihedrals.
         * iu indexes into forceatoms, we should not let iu go beyond nbonds.
         */
        iu = i;
        for (s = 0; s < GMX_SIMD_REAL_WIDTH; s++)
        {
            type  = forceatoms[iu];
            ai[s] = forceatoms[iu + 1];
            aj[s] = forceatoms[iu + 2];
            ak[s] = forceatoms[iu + 3];
            al[s] = forceatoms[iu + 4];

            /* At the end fill the arrays with the last atoms and 0 params */
            if (i + s * nfa1 < nbonds)
            {
                /* We don't need the first parameter, since that's a constant
                 * which only affects the energies, not the forces.
                 */
                for (j = 1; j < NR_RBDIHS; j++)
                {
                    parm[j * GMX_SIMD_REAL_WIDTH + s] = forceparams[type].rbdihs.rbcA[j];
                }

                if (iu + nfa1 < nbonds)
                {
                    iu += nfa1;
                }
            }
            else
            {
                for (j = 1; j < NR_RBDIHS; j++)
                {
                    parm[j * GMX_SIMD_REAL_WIDTH + s] = 0;
                }
            }
        }

        /* Calculate GMX_SIMD_REAL_WIDTH dihedral angles at once */
        dih_angle_simd(
                x, ai, aj, ak, al, pbc_simd, &phi_S, &mx_S, &my_S, &mz_S, &nx_S, &ny_S, &nz_S, &nrkj_m2_S, &nrkj_n2_S, &p_S, &q_S);

        /* Change to polymer convention */
        phi_S = phi_S - pi_S;

        sincos(phi_S, &sin_S, &cos_S);

        ddphi_S  = setZero();
        c_S      = one_S;
        cosfac_S = one_S;
        for (j = 1; j < NR_RBDIHS; j++)
        {
            parm_S   = load<SimdReal>(parm + j * GMX_SIMD_REAL_WIDTH);
            ddphi_S  = fma(c_S * parm_S, cosfac_S, ddphi_S);
            cosfac_S = cosfac_S * cos_S;
            c_S      = c_S + one_S;
        }

        /* Note that here we do not use the minus sign which is present
         * in the normal RB code. This is corrected for through (m)sf below.
         */
        ddphi_S = ddphi_S * sin_S;

        sf_i_S  = ddphi_S * nrkj_m2_S;
        msf_l_S = ddphi_S * nrkj_n2_S;

        /* After this m?_S will contain f[i] */
        mx_S = sf_i_S * mx_S;
        my_S = sf_i_S * my_S;
        mz_S = sf_i_S * mz_S;

        /* After this m?_S will contain -f[l] */
        nx_S = msf_l_S * nx_S;
        ny_S = msf_l_S * ny_S;
        nz_S = msf_l_S * nz_S;

        do_dih_fup_noshiftf_simd(ai, aj, ak, al, p_S, q_S, mx_S, my_S, mz_S, nx_S, ny_S, nz_S, f);
    }

    return 0;
}

#endif // GMX_SIMD_HAVE_REAL


template<BondedKernelFlavor flavor>
real idihs(int             nbonds,
           const t_iatom   forceatoms[],
           const t_iparams forceparams[],
           const rvec      x[],
           rvec4           f[],
           rvec            fshift[],
           const t_pbc*    pbc,
           real            lambda,
           real*           dvdlambda,
           gmx::ArrayRef<const real> /*charge*/,
           t_fcdata gmx_unused* fcd,
           t_disresdata gmx_unused* disresdata,
           t_oriresdata gmx_unused* oriresdata,
           int gmx_unused* global_atom_index)
{
    int  i, type, ai, aj, ak, al;
    int  t1, t2, t3;
    real phi, phi0, dphi0, ddphi, vtot;
    rvec r_ij, r_kj, r_kl, m, n;
    real L1, kk, dp, dp2, kA, kB, pA, pB, dvdl_term;

    L1        = 1.0 - lambda;
    dvdl_term = 0;
    vtot      = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];
        al   = forceatoms[i++];

        phi = dih_angle(x[ai], x[aj], x[ak], x[al], pbc, r_ij, r_kj, r_kl, m, n, &t1, &t2, &t3); /*  84		*/

        /* phi can jump if phi0 is close to Pi/-Pi, which will cause huge
         * force changes if we just apply a normal harmonic.
         * Instead, we first calculate phi-phi0 and take it modulo (-Pi,Pi).
         * This means we will never have the periodicity problem, unless
         * the dihedral is Pi away from phiO, which is very unlikely due to
         * the potential.
         */
        kA = forceparams[type].harmonic.krA;
        kB = forceparams[type].harmonic.krB;
        pA = forceparams[type].harmonic.rA;
        pB = forceparams[type].harmonic.rB;

        kk    = L1 * kA + lambda * kB;
        phi0  = (L1 * pA + lambda * pB) * gmx::c_deg2Rad;
        dphi0 = (pB - pA) * gmx::c_deg2Rad;

        dp = phi - phi0;

        make_dp_periodic(&dp);

        dp2 = dp * dp;

        vtot += 0.5 * kk * dp2;
        ddphi = -kk * dp;

        dvdl_term += 0.5 * (kB - kA) * dp2 - kk * dphi0 * dp;

        do_dih_fup<flavor>(ai, aj, ak, al, -ddphi, r_ij, r_kj, r_kl, m, n, f, fshift, pbc, x, t1, t2, t3); /* 112		*/
        /* 218 TOTAL	*/
    }

    *dvdlambda += dvdl_term;
    return vtot;
}

/*! \brief Computes angle restraints of two different types */
template<BondedKernelFlavor flavor>
real low_angres(int             nbonds,
                const t_iatom   forceatoms[],
                const t_iparams forceparams[],
                const rvec      x[],
                rvec4           f[],
                rvec            fshift[],
                const t_pbc*    pbc,
                real            lambda,
                real*           dvdlambda,
                gmx_bool        bZAxis)
{
    int  i, m, type, ai, aj, ak, al;
    int  t1, t2;
    real phi, cos_phi, cos_phi2, vid, vtot, dVdphi;
    rvec r_ij, r_kl, f_i, f_k = { 0, 0, 0 };
    real st, sth, nrij2, nrkl2, c, cij, ckl;

    t2 = 0; /* avoid warning with gcc-3.3. It is never used uninitialized */

    vtot = 0.0;
    ak = al = 0; /* to avoid warnings */
    for (i = 0; i < nbonds;)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        t1   = pbc_rvec_sub(pbc, x[aj], x[ai], r_ij); /*  3		*/
        if (!bZAxis)
        {
            ak = forceatoms[i++];
            al = forceatoms[i++];
            t2 = pbc_rvec_sub(pbc, x[al], x[ak], r_kl); /*  3		*/
        }
        else
        {
            r_kl[XX] = 0;
            r_kl[YY] = 0;
            r_kl[ZZ] = 1;
        }

        cos_phi = cos_angle(r_ij, r_kl); /* 25		*/
        phi     = std::acos(cos_phi);    /* 10           */

        *dvdlambda += dopdihs_min(forceparams[type].pdihs.cpA,
                                  forceparams[type].pdihs.cpB,
                                  forceparams[type].pdihs.phiA,
                                  forceparams[type].pdihs.phiB,
                                  forceparams[type].pdihs.mult,
                                  phi,
                                  lambda,
                                  &vid,
                                  &dVdphi); /*  40 */

        vtot += vid;

        cos_phi2 = gmx::square(cos_phi); /*   1		*/
        if (cos_phi2 < 1)
        {
            st    = -dVdphi * gmx::invsqrt(1 - cos_phi2); /*  12		*/
            sth   = st * cos_phi;                         /*   1		*/
            nrij2 = iprod(r_ij, r_ij);                    /*   5		*/
            nrkl2 = iprod(r_kl, r_kl);                    /*   5          */

            c   = st * gmx::invsqrt(nrij2 * nrkl2); /*  11		*/
            cij = sth / nrij2;                      /*  10		*/
            ckl = sth / nrkl2;                      /*  10		*/

            for (m = 0; m < DIM; m++) /*  18+18       */
            {
                f_i[m] = (c * r_kl[m] - cij * r_ij[m]);
                f[ai][m] += f_i[m];
                f[aj][m] -= f_i[m];
                if (!bZAxis)
                {
                    f_k[m] = (c * r_ij[m] - ckl * r_kl[m]);
                    f[ak][m] += f_k[m];
                    f[al][m] -= f_k[m];
                }
            }

            if (computeVirial(flavor))
            {
                rvec_inc(fshift[t1], f_i);
                rvec_dec(fshift[c_centralShiftIndex], f_i);
                if (!bZAxis)
                {
                    rvec_inc(fshift[t2], f_k);
                    rvec_dec(fshift[c_centralShiftIndex], f_k);
                }
            }
        }
    }

    return vtot; /*  184 / 157 (bZAxis)  total  */
}

template<BondedKernelFlavor flavor>
real angres(int             nbonds,
            const t_iatom   forceatoms[],
            const t_iparams forceparams[],
            const rvec      x[],
            rvec4           f[],
            rvec            fshift[],
            const t_pbc*    pbc,
            real            lambda,
            real*           dvdlambda,
            gmx::ArrayRef<const real> /*charge*/,
            t_fcdata gmx_unused* fcd,
            t_disresdata gmx_unused* disresdata,
            t_oriresdata gmx_unused* oriresdata,
            int gmx_unused* global_atom_index)
{
    return low_angres<flavor>(nbonds, forceatoms, forceparams, x, f, fshift, pbc, lambda, dvdlambda, FALSE);
}

template<BondedKernelFlavor flavor>
real angresz(int             nbonds,
             const t_iatom   forceatoms[],
             const t_iparams forceparams[],
             const rvec      x[],
             rvec4           f[],
             rvec            fshift[],
             const t_pbc*    pbc,
             real            lambda,
             real*           dvdlambda,
             gmx::ArrayRef<const real> /*charge*/,
             t_fcdata gmx_unused* fcd,
             t_disresdata gmx_unused* disresdata,
             t_oriresdata gmx_unused* oriresdata,
             int gmx_unused* global_atom_index)
{
    return low_angres<flavor>(nbonds, forceatoms, forceparams, x, f, fshift, pbc, lambda, dvdlambda, TRUE);
}

template<BondedKernelFlavor flavor>
real dihres(int             nbonds,
            const t_iatom   forceatoms[],
            const t_iparams forceparams[],
            const rvec      x[],
            rvec4           f[],
            rvec            fshift[],
            const t_pbc*    pbc,
            real            lambda,
            real*           dvdlambda,
            gmx::ArrayRef<const real> /*charge*/,
            t_fcdata gmx_unused* fcd,
            t_disresdata gmx_unused* disresdata,
            t_oriresdata gmx_unused* oriresdata,
            int gmx_unused* global_atom_index)
{
    real vtot = 0;
    int  ai, aj, ak, al, i, type, t1, t2, t3;
    real phi0A, phi0B, dphiA, dphiB, kfacA, kfacB, phi0, dphi, kfac;
    real phi, ddphi, ddp, ddp2, dp, d2r, L1;
    rvec r_ij, r_kj, r_kl, m, n;

    L1 = 1.0 - lambda;

    d2r = gmx::c_deg2Rad;

    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];
        al   = forceatoms[i++];

        phi0A = forceparams[type].dihres.phiA * d2r;
        dphiA = forceparams[type].dihres.dphiA * d2r;
        kfacA = forceparams[type].dihres.kfacA;

        phi0B = forceparams[type].dihres.phiB * d2r;
        dphiB = forceparams[type].dihres.dphiB * d2r;
        kfacB = forceparams[type].dihres.kfacB;

        phi0 = L1 * phi0A + lambda * phi0B;
        dphi = L1 * dphiA + lambda * dphiB;
        kfac = L1 * kfacA + lambda * kfacB;

        phi = dih_angle(x[ai], x[aj], x[ak], x[al], pbc, r_ij, r_kj, r_kl, m, n, &t1, &t2, &t3);
        /* 84 flops */

        /* phi can jump if phi0 is close to Pi/-Pi, which will cause huge
         * force changes if we just apply a normal harmonic.
         * Instead, we first calculate phi-phi0 and take it modulo (-Pi,Pi).
         * This means we will never have the periodicity problem, unless
         * the dihedral is Pi away from phiO, which is very unlikely due to
         * the potential.
         */
        dp = phi - phi0;
        make_dp_periodic(&dp);

        if (dp > dphi)
        {
            ddp = dp - dphi;
        }
        else if (dp < -dphi)
        {
            ddp = dp + dphi;
        }
        else
        {
            ddp = 0;
        }

        if (ddp != 0.0)
        {
            ddp2 = ddp * ddp;
            vtot += 0.5 * kfac * ddp2;
            ddphi = kfac * ddp;

            *dvdlambda += 0.5 * (kfacB - kfacA) * ddp2;
            /* lambda dependence from changing restraint distances */
            if (ddp > 0)
            {
                *dvdlambda -= kfac * ddp * ((dphiB - dphiA) + (phi0B - phi0A));
            }
            else if (ddp < 0)
            {
                *dvdlambda += kfac * ddp * ((dphiB - dphiA) - (phi0B - phi0A));
            }
            do_dih_fup<flavor>(
                    ai, aj, ak, al, ddphi, r_ij, r_kj, r_kl, m, n, f, fshift, pbc, x, t1, t2, t3); /* 112		*/
        }
    }
    return vtot;
}


real unimplemented(int gmx_unused             nbonds,
                   const t_iatom gmx_unused   forceatoms[],
                   const t_iparams gmx_unused forceparams[],
                   const rvec gmx_unused      x[],
                   rvec4 gmx_unused           f[],
                   rvec gmx_unused            fshift[],
                   const t_pbc gmx_unused* pbc,
                   real gmx_unused         lambda,
                   real gmx_unused* dvdlambda,
                   gmx::ArrayRef<const real> /*charge*/,
                   t_fcdata gmx_unused* fcd,
                   t_disresdata gmx_unused* disresdata,
                   t_oriresdata gmx_unused* oriresdata,
                   int gmx_unused* global_atom_index)
{
    gmx_impl("*** you are using a not implemented function");
}

template<BondedKernelFlavor flavor>
real restrangles(int             nbonds,
                 const t_iatom   forceatoms[],
                 const t_iparams forceparams[],
                 const rvec      x[],
                 rvec4           f[],
                 rvec            fshift[],
                 const t_pbc*    pbc,
                 real gmx_unused lambda,
                 real gmx_unused* dvdlambda,
                 gmx::ArrayRef<const real> /*charge*/,
                 t_fcdata gmx_unused* fcd,
                 t_disresdata gmx_unused* disresdata,
                 t_oriresdata gmx_unused* oriresdata,
                 int gmx_unused* global_atom_index)
{
    int    i, d, ai, aj, ak, type, m;
    int    t1, t2;
    real   v, vtot;
    rvec   f_i, f_j, f_k;
    double prefactor, ratio_ante, ratio_post;
    rvec   delta_ante, delta_post, vec_temp;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];

        t1 = pbc_rvec_sub(pbc, x[ai], x[aj], vec_temp);
        pbc_rvec_sub(pbc, x[aj], x[ai], delta_ante);
        t2 = pbc_rvec_sub(pbc, x[ak], x[aj], delta_post);


        /* This function computes factors needed for restricted angle potential.
         * The restricted angle potential is used in coarse-grained simulations to avoid singularities
         * when three particles align and the dihedral angle and dihedral potential
         * cannot be calculated. This potential is calculated using the formula:
           real restrangles(int nbonds,
            const t_iatom forceatoms[],const t_iparams forceparams[],
            const rvec x[],rvec4 f[],rvec fshift[],
            const t_pbc *pbc,
            real gmx_unused lambda,real gmx_unused *dvdlambda,
            const t_mdatoms gmx_unused *md,t_fcdata gmx_unused *fcd,
            int gmx_unused *global_atom_index)
           {
           int  i, d, ai, aj, ak, type, m;
           int t1, t2;
           rvec r_ij,r_kj;
           real v, vtot;
           rvec f_i, f_j, f_k;
           real prefactor, ratio_ante, ratio_post;
           rvec delta_ante, delta_post, vec_temp;

           vtot = 0.0;
           for(i=0; (i<nbonds); )
           {
           type = forceatoms[i++];
           ai   = forceatoms[i++];
           aj   = forceatoms[i++];
           ak   = forceatoms[i++];

         * \f[V_{\rm ReB}(\theta_i) = \frac{1}{2} k_{\theta} \frac{(\cos\theta_i - \cos\theta_0)^2}
         * {\sin^2\theta_i}\f] ({eq:ReB} and ref \cite{MonicaGoga2013} from the manual).
         * For more explanations see comments file "restcbt.h". */

        compute_factors_restangles(
                type, forceparams, delta_ante, delta_post, &prefactor, &ratio_ante, &ratio_post, &v);

        /*   Forces are computed per component */
        for (d = 0; d < DIM; d++)
        {
            f_i[d] = prefactor * (ratio_ante * delta_ante[d] - delta_post[d]);
            f_j[d] = prefactor
                     * ((ratio_post + 1.0) * delta_post[d] - (ratio_ante + 1.0) * delta_ante[d]);
            f_k[d] = prefactor * (delta_ante[d] - ratio_post * delta_post[d]);
        }

        /*   Computation of potential energy   */

        vtot += v;

        /*   Update forces */

        for (m = 0; (m < DIM); m++)
        {
            f[ai][m] += f_i[m];
            f[aj][m] += f_j[m];
            f[ak][m] += f_k[m];
        }

        if (computeVirial(flavor))
        {
            rvec_inc(fshift[t1], f_i);
            rvec_inc(fshift[c_centralShiftIndex], f_j);
            rvec_inc(fshift[t2], f_k);
        }
    }
    return vtot;
}


template<BondedKernelFlavor flavor>
real restrdihs(int             nbonds,
               const t_iatom   forceatoms[],
               const t_iparams forceparams[],
               const rvec      x[],
               rvec4           f[],
               rvec            fshift[],
               const t_pbc*    pbc,
               real gmx_unused lambda,
               real gmx_unused* dvlambda,
               gmx::ArrayRef<const real> /*charge*/,
               t_fcdata gmx_unused* fcd,
               t_disresdata gmx_unused* disresdata,
               t_oriresdata gmx_unused* oriresdata,
               int gmx_unused* global_atom_index)
{
    int  i, d, type, ai, aj, ak, al;
    rvec f_i, f_j, f_k, f_l;
    rvec dx_jl;
    int  t1, t2, t3;
    real v, vtot;
    rvec delta_ante, delta_crnt, delta_post, vec_temp;
    real factor_phi_ai_ante, factor_phi_ai_crnt, factor_phi_ai_post;
    real factor_phi_aj_ante, factor_phi_aj_crnt, factor_phi_aj_post;
    real factor_phi_ak_ante, factor_phi_ak_crnt, factor_phi_ak_post;
    real factor_phi_al_ante, factor_phi_al_crnt, factor_phi_al_post;
    real prefactor_phi;


    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];
        al   = forceatoms[i++];

        t1 = pbc_rvec_sub(pbc, x[ai], x[aj], vec_temp);
        pbc_rvec_sub(pbc, x[aj], x[ai], delta_ante);
        t2 = pbc_rvec_sub(pbc, x[ak], x[aj], delta_crnt);
        pbc_rvec_sub(pbc, x[ak], x[al], vec_temp);
        pbc_rvec_sub(pbc, x[al], x[ak], delta_post);

        /* This function computes factors needed for restricted angle potential.
         * The restricted angle potential is used in coarse-grained simulations to avoid singularities
         * when three particles align and the dihedral angle and dihedral potential cannot be calculated.
         * This potential is calculated using the formula:
         * \f[V_{\rm ReB}(\theta_i) = \frac{1}{2} k_{\theta}
         * \frac{(\cos\theta_i - \cos\theta_0)^2}{\sin^2\theta_i}\f]
         * ({eq:ReB} and ref \cite{MonicaGoga2013} from the manual).
         * For more explanations see comments file "restcbt.h" */

        compute_factors_restrdihs(type,
                                  forceparams,
                                  delta_ante,
                                  delta_crnt,
                                  delta_post,
                                  &factor_phi_ai_ante,
                                  &factor_phi_ai_crnt,
                                  &factor_phi_ai_post,
                                  &factor_phi_aj_ante,
                                  &factor_phi_aj_crnt,
                                  &factor_phi_aj_post,
                                  &factor_phi_ak_ante,
                                  &factor_phi_ak_crnt,
                                  &factor_phi_ak_post,
                                  &factor_phi_al_ante,
                                  &factor_phi_al_crnt,
                                  &factor_phi_al_post,
                                  &prefactor_phi,
                                  &v);


        /*      Computation of forces per component */
        for (d = 0; d < DIM; d++)
        {
            f_i[d] = prefactor_phi
                     * (factor_phi_ai_ante * delta_ante[d] + factor_phi_ai_crnt * delta_crnt[d]
                        + factor_phi_ai_post * delta_post[d]);
            f_j[d] = prefactor_phi
                     * (factor_phi_aj_ante * delta_ante[d] + factor_phi_aj_crnt * delta_crnt[d]
                        + factor_phi_aj_post * delta_post[d]);
            f_k[d] = prefactor_phi
                     * (factor_phi_ak_ante * delta_ante[d] + factor_phi_ak_crnt * delta_crnt[d]
                        + factor_phi_ak_post * delta_post[d]);
            f_l[d] = prefactor_phi
                     * (factor_phi_al_ante * delta_ante[d] + factor_phi_al_crnt * delta_crnt[d]
                        + factor_phi_al_post * delta_post[d]);
        }
        /*      Computation of the energy */

        vtot += v;


        /*    Updating the forces */

        rvec_inc(f[ai], f_i);
        rvec_inc(f[aj], f_j);
        rvec_inc(f[ak], f_k);
        rvec_inc(f[al], f_l);

        if (computeVirial(flavor))
        {
            if (pbc)
            {
                t3 = pbc_rvec_sub(pbc, x[al], x[aj], dx_jl);
            }
            else
            {
                t3 = c_centralShiftIndex;
            }

            rvec_inc(fshift[t1], f_i);
            rvec_inc(fshift[c_centralShiftIndex], f_j);
            rvec_inc(fshift[t2], f_k);
            rvec_inc(fshift[t3], f_l);
        }
    }

    return vtot;
}


template<BondedKernelFlavor flavor>
real cbtdihs(int             nbonds,
             const t_iatom   forceatoms[],
             const t_iparams forceparams[],
             const rvec      x[],
             rvec4           f[],
             rvec            fshift[],
             const t_pbc*    pbc,
             real gmx_unused lambda,
             real gmx_unused* dvdlambda,
             gmx::ArrayRef<const real> /*charge*/,
             t_fcdata gmx_unused* fcd,
             t_disresdata gmx_unused* disresdata,
             t_oriresdata gmx_unused* oriresdata,
             int gmx_unused* global_atom_index)
{
    int  type, ai, aj, ak, al, i, d;
    int  t1, t2, t3;
    real v, vtot;
    rvec vec_temp;
    rvec f_i, f_j, f_k, f_l;
    rvec dx_jl;
    rvec delta_ante, delta_crnt, delta_post;
    rvec f_phi_ai, f_phi_aj, f_phi_ak, f_phi_al;
    rvec f_theta_ante_ai, f_theta_ante_aj, f_theta_ante_ak;
    rvec f_theta_post_aj, f_theta_post_ak, f_theta_post_al;


    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];
        al   = forceatoms[i++];


        t1 = pbc_rvec_sub(pbc, x[ai], x[aj], vec_temp);
        pbc_rvec_sub(pbc, x[aj], x[ai], delta_ante);
        t2 = pbc_rvec_sub(pbc, x[ak], x[aj], vec_temp);
        pbc_rvec_sub(pbc, x[ak], x[aj], delta_crnt);
        pbc_rvec_sub(pbc, x[ak], x[al], vec_temp);
        pbc_rvec_sub(pbc, x[al], x[ak], delta_post);

        /* \brief Compute factors for CBT potential
         * The combined bending-torsion potential goes to zero in a very smooth manner, eliminating the numerical
         * instabilities, when three coarse-grained particles align and the dihedral angle and standard
         * dihedral potentials cannot be calculated. The CBT potential is calculated using the formula:
         * \f[V_{\rm CBT}(\theta_{i-1}, \theta_i, \phi_i) = k_{\phi} \sin^3\theta_{i-1} \sin^3\theta_{i}
         * \sum_{n=0}^4 { a_n \cos^n\phi_i}\f] ({eq:CBT} and ref \cite{MonicaGoga2013} from the manual).
         * It contains in its expression not only the dihedral angle \f$\phi\f$
         * but also \f[\theta_{i-1}\f] (theta_ante bellow) and \f[\theta_{i}\f] (theta_post bellow)
         * --- the adjacent bending angles.
         * For more explanations see comments file "restcbt.h". */

        compute_factors_cbtdihs(type,
                                forceparams,
                                delta_ante,
                                delta_crnt,
                                delta_post,
                                f_phi_ai,
                                f_phi_aj,
                                f_phi_ak,
                                f_phi_al,
                                f_theta_ante_ai,
                                f_theta_ante_aj,
                                f_theta_ante_ak,
                                f_theta_post_aj,
                                f_theta_post_ak,
                                f_theta_post_al,
                                &v);


        /*      Acumulate the resuts per beads */
        for (d = 0; d < DIM; d++)
        {
            f_i[d] = f_phi_ai[d] + f_theta_ante_ai[d];
            f_j[d] = f_phi_aj[d] + f_theta_ante_aj[d] + f_theta_post_aj[d];
            f_k[d] = f_phi_ak[d] + f_theta_ante_ak[d] + f_theta_post_ak[d];
            f_l[d] = f_phi_al[d] + f_theta_post_al[d];
        }

        /*      Compute the potential energy */

        vtot += v;


        /*  Updating the forces */
        rvec_inc(f[ai], f_i);
        rvec_inc(f[aj], f_j);
        rvec_inc(f[ak], f_k);
        rvec_inc(f[al], f_l);


        if (computeVirial(flavor))
        {
            if (pbc)
            {
                t3 = pbc_rvec_sub(pbc, x[al], x[aj], dx_jl);
            }
            else
            {
                t3 = c_centralShiftIndex;
            }

            rvec_inc(fshift[t1], f_i);
            rvec_inc(fshift[c_centralShiftIndex], f_j);
            rvec_inc(fshift[t2], f_k);
            rvec_inc(fshift[t3], f_l);
        }
    }

    return vtot;
}

template<BondedKernelFlavor flavor>
std::enable_if_t<flavor != BondedKernelFlavor::ForcesSimdWhenAvailable || !GMX_SIMD_HAVE_REAL, real>
rbdihs(int             nbonds,
       const t_iatom   forceatoms[],
       const t_iparams forceparams[],
       const rvec      x[],
       rvec4           f[],
       rvec            fshift[],
       const t_pbc*    pbc,
       real            lambda,
       real*           dvdlambda,
       gmx::ArrayRef<const real> /*charge*/,
       t_fcdata gmx_unused* fcd,
       t_disresdata gmx_unused* disresdata,
       t_oriresdata gmx_unused* oriresdata,
       int gmx_unused* global_atom_index)
{
    const real c0 = 0.0, c1 = 1.0, c2 = 2.0, c3 = 3.0, c4 = 4.0, c5 = 5.0;
    int        type, ai, aj, ak, al, i, j;
    int        t1, t2, t3;
    rvec       r_ij, r_kj, r_kl, m, n;
    real       parmA[NR_RBDIHS];
    real       parmB[NR_RBDIHS];
    real       parm[NR_RBDIHS];
    real       cos_phi, phi, rbp, rbpBA;
    real       v, ddphi, sin_phi;
    real       cosfac, vtot;
    real       L1        = 1.0 - lambda;
    real       dvdl_term = 0;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];
        al   = forceatoms[i++];

        phi = dih_angle(x[ai], x[aj], x[ak], x[al], pbc, r_ij, r_kj, r_kl, m, n, &t1, &t2, &t3); /*  84		*/

        /* Change to polymer convention */
        if (phi < c0)
        {
            phi += M_PI;
        }
        else
        {
            phi -= M_PI; /*   1		*/
        }
        cos_phi = std::cos(phi);
        /* Beware of accuracy loss, cannot use 1-sqrt(cos^2) ! */
        sin_phi = std::sin(phi);

        for (j = 0; (j < NR_RBDIHS); j++)
        {
            parmA[j] = forceparams[type].rbdihs.rbcA[j];
            parmB[j] = forceparams[type].rbdihs.rbcB[j];
            parm[j]  = L1 * parmA[j] + lambda * parmB[j];
        }
        /* Calculate cosine powers */
        /* Calculate the energy */
        /* Calculate the derivative */

        v = parm[0];
        dvdl_term += (parmB[0] - parmA[0]);
        ddphi  = c0;
        cosfac = c1;

        rbp   = parm[1];
        rbpBA = parmB[1] - parmA[1];
        ddphi += rbp * cosfac;
        cosfac *= cos_phi;
        v += cosfac * rbp;
        dvdl_term += cosfac * rbpBA;
        rbp   = parm[2];
        rbpBA = parmB[2] - parmA[2];
        ddphi += c2 * rbp * cosfac;
        cosfac *= cos_phi;
        v += cosfac * rbp;
        dvdl_term += cosfac * rbpBA;
        rbp   = parm[3];
        rbpBA = parmB[3] - parmA[3];
        ddphi += c3 * rbp * cosfac;
        cosfac *= cos_phi;
        v += cosfac * rbp;
        dvdl_term += cosfac * rbpBA;
        rbp   = parm[4];
        rbpBA = parmB[4] - parmA[4];
        ddphi += c4 * rbp * cosfac;
        cosfac *= cos_phi;
        v += cosfac * rbp;
        dvdl_term += cosfac * rbpBA;
        rbp   = parm[5];
        rbpBA = parmB[5] - parmA[5];
        ddphi += c5 * rbp * cosfac;
        cosfac *= cos_phi;
        v += cosfac * rbp;
        dvdl_term += cosfac * rbpBA;

        ddphi = -ddphi * sin_phi; /*  11		*/

        do_dih_fup<flavor>(ai, aj, ak, al, ddphi, r_ij, r_kj, r_kl, m, n, f, fshift, pbc, x, t1, t2, t3); /* 112		*/
        vtot += v;
    }
    *dvdlambda += dvdl_term;

    return vtot;
}

//! \endcond

/*! \brief Mysterious undocumented function */
int cmap_setup_grid_index(int ip, int grid_spacing, int* ipm1, int* ipp1, int* ipp2)
{
    int im1, ip1, ip2;

    if (ip < 0)
    {
        ip = ip + grid_spacing - 1;
    }
    else if (ip > grid_spacing)
    {
        ip = ip - grid_spacing - 1;
    }

    im1 = ip - 1;
    ip1 = ip + 1;
    ip2 = ip + 2;

    if (ip == 0)
    {
        im1 = grid_spacing - 1;
    }
    else if (ip == grid_spacing - 2)
    {
        ip2 = 0;
    }
    else if (ip == grid_spacing - 1)
    {
        ip1 = 0;
        ip2 = 1;
    }

    *ipm1 = im1;
    *ipp1 = ip1;
    *ipp2 = ip2;

    return ip;
}

using CmapForceStructure = std::array<real, 4>;

gmx::RVec processCmapForceComponent(const gmx::RVec a,
                                    const gmx::RVec b,
                                    const real      df,
                                    const real      gaa,
                                    const real      fga,
                                    const real      gbb,
                                    const real      hgb,
                                    const int       dim)
{
    gmx::RVec result; // mapping XX <-> f, YY <-> g, ZZ <-> h
    result[XX] = gaa * a[dim];
    result[YY] = fga * a[dim] - hgb * b[dim];
    result[ZZ] = gbb * b[dim];
    return result * df;
}

CmapForceStructure applyCmapForceComponent(const gmx::RVec forceComponent)
{
    // forceComponent mapping is XX <-> f, YY <-> g, ZZ <-> h
    CmapForceStructure forces;
    forces[0] = forceComponent[XX];
    forces[1] = -forceComponent[XX] - forceComponent[YY];
    forces[2] = forceComponent[ZZ] + forceComponent[YY];
    forces[3] = -forceComponent[ZZ];
    return forces;
}

void accumulateCmapForces(const rvec      x[],
                          rvec4           f[],
                          rvec            fshift[],
                          const t_pbc*    pbc,
                          const gmx::RVec r_ij,
                          const gmx::RVec r_kj,
                          const gmx::RVec r_kl,
                          const gmx::RVec a,
                          const gmx::RVec b,
                          gmx::RVec       h,
                          const real      ra2r,
                          const real      rb2r,
                          const real      rgr,
                          const real      rg,
                          const int       ai,
                          const int       aj,
                          const int       ak,
                          const int       al,
                          const real      df,
                          const int       t1,
                          const int       t2)
{
    const real fg  = iprod(r_ij, r_kj);
    const real hg  = iprod(r_kl, r_kj);
    const real fga = fg * ra2r * rgr;
    const real hgb = hg * rb2r * rgr;
    const real gaa = -ra2r * rg;
    const real gbb = rb2r * rg;

    gmx::RVec f_i, f_j, f_k, f_l;
    for (int i = 0; i < DIM; i++)
    {
        CmapForceStructure forces =
                applyCmapForceComponent(processCmapForceComponent(a, b, df, gaa, fga, gbb, hgb, i));
        f_i[i] = forces[0];
        f_j[i] = forces[1];
        f_k[i] = forces[2];
        f_l[i] = forces[3];
    }
    rvec_inc(f[ai], f_i);
    rvec_inc(f[aj], f_j);
    rvec_inc(f[ak], f_k);
    rvec_inc(f[al], f_l);

    /* Shift forces */
    if (fshift != nullptr)
    {
        const int t3 = pbc ? pbc_rvec_sub(pbc, x[al], x[aj], h) : c_centralShiftIndex;
        rvec_inc(fshift[t1], f_i);
        rvec_inc(fshift[c_centralShiftIndex], f_j);
        rvec_inc(fshift[t2], f_k);
        rvec_inc(fshift[t3], f_l);
    }
}


} // namespace

real cmap_dihs(int                 nbonds,
               const t_iatom       forceatoms[],
               const t_iparams     forceparams[],
               const gmx_cmap_t*   cmap_grid,
               const rvec          x[],
               rvec4               f[],
               rvec                fshift[],
               const struct t_pbc* pbc,
               real gmx_unused     lambda,
               real gmx_unused* dvdlambda,
               gmx::ArrayRef<const real> /*charge*/,
               t_fcdata gmx_unused* fcd,
               t_disresdata gmx_unused* disresdata,
               t_oriresdata gmx_unused* oriresdata,
               int gmx_unused* global_atom_index)
{
    int t11, t21, t31, t12, t22, t32;
    int ip1m1, ip1p1, ip1p2;
    int ip2m1, ip2p1, ip2p2;
    int l1, l2, l3;

    real ty[4], ty1[4], ty2[4], ty12[4], tx[16];

    rvec r1_ij, r1_kj, r1_kl, m1, n1;
    rvec r2_ij, r2_kj, r2_kl, m2, n2;

    int loop_index[4][4] = { { 0, 4, 8, 12 }, { 1, 5, 9, 13 }, { 2, 6, 10, 14 }, { 3, 7, 11, 15 } };

    /* Total CMAP energy */
    real vtot = 0;

    for (int n = 0; n < nbonds;)
    {
        /* Five atoms are involved in the two torsions */
        const int type = forceatoms[n++];
        const int ai   = forceatoms[n++];
        const int aj   = forceatoms[n++];
        const int ak   = forceatoms[n++];
        const int al   = forceatoms[n++];
        const int am   = forceatoms[n++];

        /* Which CMAP type is this */
        const int                 cmapA = forceparams[type].cmap.cmapA;
        gmx::ArrayRef<const real> cmapd = cmap_grid->cmapdata[cmapA].cmap;

        /* First torsion */
        const int a1i = ai;
        const int a1j = aj;
        const int a1k = ak;
        const int a1l = al;

        real phi1 = dih_angle(
                x[a1i], x[a1j], x[a1k], x[a1l], pbc, r1_ij, r1_kj, r1_kl, m1, n1, &t11, &t21, &t31); /* 84 */

        const real cos_phi1 = std::cos(phi1);

        gmx::RVec a1, b1, h1;
        cprod(r1_ij, r1_kj, a1); /* 9 */
        cprod(r1_kl, r1_kj, b1); /* 9 */

        pbc_rvec_sub(pbc, x[a1l], x[a1k], h1);

        const real ra21 = iprod(a1, a1);       /* 5 */
        const real rb21 = iprod(b1, b1);       /* 5 */
        const real rg21 = iprod(r1_kj, r1_kj); /* 5 */
        const real rg1  = sqrt(rg21);

        const real rgr1  = 1.0 / rg1;
        const real ra2r1 = 1.0 / ra21;
        const real rb2r1 = 1.0 / rb21;
        const real rabr1 = sqrt(ra2r1 * rb2r1);

        const real sin_phi1 = rg1 * rabr1 * iprod(a1, h1) * (-1);

        if (cos_phi1 < -0.5 || cos_phi1 > 0.5)
        {
            phi1 = std::asin(sin_phi1);

            if (cos_phi1 < 0)
            {
                if (phi1 > 0)
                {
                    phi1 = M_PI - phi1;
                }
                else
                {
                    phi1 = -M_PI - phi1;
                }
            }
        }
        else
        {
            phi1 = std::acos(cos_phi1);

            if (sin_phi1 < 0)
            {
                phi1 = -phi1;
            }
        }

        real xphi1 = phi1 + M_PI; /* 1 */

        /* Second torsion */
        const int a2i = aj;
        const int a2j = ak;
        const int a2k = al;
        const int a2l = am;

        real phi2 = dih_angle(
                x[a2i], x[a2j], x[a2k], x[a2l], pbc, r2_ij, r2_kj, r2_kl, m2, n2, &t12, &t22, &t32); /* 84 */

        const real cos_phi2 = std::cos(phi2);

        gmx::RVec a2, b2, h2;
        cprod(r2_ij, r2_kj, a2); /* 9 */
        cprod(r2_kl, r2_kj, b2); /* 9 */

        pbc_rvec_sub(pbc, x[a2l], x[a2k], h2);

        const real ra22 = iprod(a2, a2);       /* 5 */
        const real rb22 = iprod(b2, b2);       /* 5 */
        const real rg22 = iprod(r2_kj, r2_kj); /* 5 */
        const real rg2  = sqrt(rg22);

        const real rgr2  = 1.0 / rg2;
        const real ra2r2 = 1.0 / ra22;
        const real rb2r2 = 1.0 / rb22;
        const real rabr2 = sqrt(ra2r2 * rb2r2);

        const real sin_phi2 = rg2 * rabr2 * iprod(a2, h2) * (-1);

        if (cos_phi2 < -0.5 || cos_phi2 > 0.5)
        {
            phi2 = std::asin(sin_phi2);

            if (cos_phi2 < 0)
            {
                if (phi2 > 0)
                {
                    phi2 = M_PI - phi2;
                }
                else
                {
                    phi2 = -M_PI - phi2;
                }
            }
        }
        else
        {
            phi2 = std::acos(cos_phi2);

            if (sin_phi2 < 0)
            {
                phi2 = -phi2;
            }
        }

        real xphi2 = phi2 + M_PI; /* 1 */

        /* Range mangling */
        if (xphi1 < 0)
        {
            xphi1 = xphi1 + 2 * M_PI;
        }
        else if (xphi1 >= 2 * M_PI)
        {
            xphi1 = xphi1 - 2 * M_PI;
        }

        if (xphi2 < 0)
        {
            xphi2 = xphi2 + 2 * M_PI;
        }
        else if (xphi2 >= 2 * M_PI)
        {
            xphi2 = xphi2 - 2 * M_PI;
        }

        /* Number of grid points */
        real dx = 2 * M_PI / cmap_grid->grid_spacing;

        /* Where on the grid are we */
        int iphi1 = static_cast<int>(xphi1 / dx);
        int iphi2 = static_cast<int>(xphi2 / dx);

        iphi1 = cmap_setup_grid_index(iphi1, cmap_grid->grid_spacing, &ip1m1, &ip1p1, &ip1p2);
        iphi2 = cmap_setup_grid_index(iphi2, cmap_grid->grid_spacing, &ip2m1, &ip2p1, &ip2p2);

        const int pos1 = iphi1 * cmap_grid->grid_spacing + iphi2;
        const int pos2 = ip1p1 * cmap_grid->grid_spacing + iphi2;
        const int pos3 = ip1p1 * cmap_grid->grid_spacing + ip2p1;
        const int pos4 = iphi1 * cmap_grid->grid_spacing + ip2p1;

        ty[0] = cmapd[pos1 * 4];
        ty[1] = cmapd[pos2 * 4];
        ty[2] = cmapd[pos3 * 4];
        ty[3] = cmapd[pos4 * 4];

        ty1[0] = cmapd[pos1 * 4 + 1];
        ty1[1] = cmapd[pos2 * 4 + 1];
        ty1[2] = cmapd[pos3 * 4 + 1];
        ty1[3] = cmapd[pos4 * 4 + 1];

        ty2[0] = cmapd[pos1 * 4 + 2];
        ty2[1] = cmapd[pos2 * 4 + 2];
        ty2[2] = cmapd[pos3 * 4 + 2];
        ty2[3] = cmapd[pos4 * 4 + 2];

        ty12[0] = cmapd[pos1 * 4 + 3];
        ty12[1] = cmapd[pos2 * 4 + 3];
        ty12[2] = cmapd[pos3 * 4 + 3];
        ty12[3] = cmapd[pos4 * 4 + 3];

        /* Switch to degrees */
        dx    = 360.0 / cmap_grid->grid_spacing;
        xphi1 = xphi1 * gmx::c_rad2Deg;
        xphi2 = xphi2 * gmx::c_rad2Deg;

        for (int i = 0; i < 4; i++) /* 16 */
        {
            tx[i]      = ty[i];
            tx[i + 4]  = ty1[i] * dx;
            tx[i + 8]  = ty2[i] * dx;
            tx[i + 12] = ty12[i] * dx * dx;
        }

        std::array<real, 16> tc = { 0 };
        for (int idx = 0; idx < 16; idx++) /* 1056 */
        {
            for (int k = 0; k < 16; k++)
            {
                tc[idx] += cmap_coeff_matrix[k * 16 + idx] * tx[k];
            }
        }

        const real tt = (xphi1 - iphi1 * dx) / dx;
        const real tu = (xphi2 - iphi2 * dx) / dx;

        real e   = 0;
        real df1 = 0;
        real df2 = 0;

        for (int i = 3; i >= 0; i--)
        {
            l1 = loop_index[i][3];
            l2 = loop_index[i][2];
            l3 = loop_index[i][1];

            e = tt * e + ((tc[i * 4 + 3] * tu + tc[i * 4 + 2]) * tu + tc[i * 4 + 1]) * tu + tc[i * 4];
            df1 = tu * df1 + (3.0 * tc[l1] * tt + 2.0 * tc[l2]) * tt + tc[l3];
            df2 = tt * df2 + (3.0 * tc[i * 4 + 3] * tu + 2.0 * tc[i * 4 + 2]) * tu + tc[i * 4 + 1];
        }

        const real fac = gmx::c_rad2Deg / dx;
        df1            = df1 * fac;
        df2            = df2 * fac;

        /* CMAP energy */
        vtot += e;

        /* Do forces - first torsion */
        accumulateCmapForces(
                x, f, fshift, pbc, r1_ij, r1_kj, r1_kl, a1, b1, h1, ra2r1, rb2r1, rgr1, rg1, a1i, a1j, a1k, a1l, df1, t11, t21);

        /* Do forces - second torsion */
        accumulateCmapForces(
                x, f, fshift, pbc, r2_ij, r2_kj, r2_kl, a2, b2, h2, ra2r2, rb2r2, rgr2, rg2, a2i, a2j, a2k, a2l, df2, t12, t22);
    }
    return vtot;
}

namespace
{

//! \cond
/***********************************************************
 *
 *   G R O M O S  9 6   F U N C T I O N S
 *
 ***********************************************************/
real g96harmonic(real kA, real kB, real xA, real xB, real x, real lambda, real* V, real* F)
{
    const real half = 0.5;
    real       L1, kk, x0, dx, dx2;
    real       v, f, dvdlambda;

    L1 = 1.0 - lambda;
    kk = L1 * kA + lambda * kB;
    x0 = L1 * xA + lambda * xB;

    dx  = x - x0;
    dx2 = dx * dx;

    f         = -kk * dx;
    v         = half * kk * dx2;
    dvdlambda = half * (kB - kA) * dx2 + (xA - xB) * kk * dx;

    *F = f;
    *V = v;

    return dvdlambda;

    /* That was 21 flops */
}

template<BondedKernelFlavor flavor>
real g96bonds(int             nbonds,
              const t_iatom   forceatoms[],
              const t_iparams forceparams[],
              const rvec      x[],
              rvec4           f[],
              rvec            fshift[],
              const t_pbc*    pbc,
              real            lambda,
              real*           dvdlambda,
              gmx::ArrayRef<const real> /*charge*/,
              t_fcdata gmx_unused* fcd,
              t_disresdata gmx_unused* disresdata,
              t_oriresdata gmx_unused* oriresdata,
              int gmx_unused* global_atom_index)
{
    int  i, ki, ai, aj, type;
    real dr2, fbond, vbond, vtot;
    rvec dx;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];

        ki  = pbc_rvec_sub(pbc, x[ai], x[aj], dx); /*   3      */
        dr2 = iprod(dx, dx);                       /*   5		*/

        *dvdlambda += g96harmonic(forceparams[type].harmonic.krA,
                                  forceparams[type].harmonic.krB,
                                  forceparams[type].harmonic.rA,
                                  forceparams[type].harmonic.rB,
                                  dr2,
                                  lambda,
                                  &vbond,
                                  &fbond);

        vtot += 0.5 * vbond; /* 1*/

        spreadBondForces<flavor>(fbond, dx, ai, aj, f, ki, fshift); /* 15 */
    }                                                               /* 44 TOTAL	*/
    return vtot;
}

real g96bond_angle(const rvec xi, const rvec xj, const rvec xk, const t_pbc* pbc, rvec r_ij, rvec r_kj, int* t1, int* t2)
/* Return value is the angle between the bonds i-j and j-k */
{
    real costh;

    *t1 = pbc_rvec_sub(pbc, xi, xj, r_ij); /*  3		*/
    *t2 = pbc_rvec_sub(pbc, xk, xj, r_kj); /*  3		*/

    costh = cos_angle(r_ij, r_kj); /* 25		*/
    /* 41 TOTAL	*/
    return costh;
}

template<BondedKernelFlavor flavor>
real g96angles(int             nbonds,
               const t_iatom   forceatoms[],
               const t_iparams forceparams[],
               const rvec      x[],
               rvec4           f[],
               rvec            fshift[],
               const t_pbc*    pbc,
               real            lambda,
               real*           dvdlambda,
               gmx::ArrayRef<const real> /*charge*/,
               t_fcdata gmx_unused* fcd,
               t_disresdata gmx_unused* disresdata,
               t_oriresdata gmx_unused* oriresdata,
               int gmx_unused* global_atom_index)
{
    int  i, ai, aj, ak, type, m, t1, t2;
    rvec r_ij, r_kj;
    real cos_theta, dVdt, va, vtot;
    real rij_1, rij_2, rkj_1, rkj_2, rijrkj_1;
    rvec f_i, f_j, f_k;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];

        cos_theta = g96bond_angle(x[ai], x[aj], x[ak], pbc, r_ij, r_kj, &t1, &t2);

        *dvdlambda += g96harmonic(forceparams[type].harmonic.krA,
                                  forceparams[type].harmonic.krB,
                                  forceparams[type].harmonic.rA,
                                  forceparams[type].harmonic.rB,
                                  cos_theta,
                                  lambda,
                                  &va,
                                  &dVdt);
        vtot += va;

        rij_1    = gmx::invsqrt(iprod(r_ij, r_ij));
        rkj_1    = gmx::invsqrt(iprod(r_kj, r_kj));
        rij_2    = rij_1 * rij_1;
        rkj_2    = rkj_1 * rkj_1;
        rijrkj_1 = rij_1 * rkj_1; /* 23 */

        for (m = 0; (m < DIM); m++) /*  42	*/
        {
            f_i[m] = dVdt * (r_kj[m] * rijrkj_1 - r_ij[m] * rij_2 * cos_theta);
            f_k[m] = dVdt * (r_ij[m] * rijrkj_1 - r_kj[m] * rkj_2 * cos_theta);
            f_j[m] = -f_i[m] - f_k[m];
            f[ai][m] += f_i[m];
            f[aj][m] += f_j[m];
            f[ak][m] += f_k[m];
        }

        if (computeVirial(flavor))
        {
            rvec_inc(fshift[t1], f_i);
            rvec_inc(fshift[c_centralShiftIndex], f_j);
            rvec_inc(fshift[t2], f_k); /* 9 */
        }
        /* 163 TOTAL	*/
    }
    return vtot;
}

template<BondedKernelFlavor flavor>
real cross_bond_bond(int             nbonds,
                     const t_iatom   forceatoms[],
                     const t_iparams forceparams[],
                     const rvec      x[],
                     rvec4           f[],
                     rvec            fshift[],
                     const t_pbc*    pbc,
                     real gmx_unused lambda,
                     real gmx_unused* dvdlambda,
                     gmx::ArrayRef<const real> /*charge*/,
                     t_fcdata gmx_unused* fcd,
                     t_disresdata gmx_unused* disresdata,
                     t_oriresdata gmx_unused* oriresdata,
                     int gmx_unused* global_atom_index)
{
    /* Potential from Lawrence and Skimmer, Chem. Phys. Lett. 372 (2003)
     * pp. 842-847
     */
    int  i, ai, aj, ak, type, m, t1, t2;
    rvec r_ij, r_kj;
    real vtot, vrr, s1, s2, r1, r2, r1e, r2e, krr;
    rvec f_i, f_j, f_k;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];
        r1e  = forceparams[type].cross_bb.r1e;
        r2e  = forceparams[type].cross_bb.r2e;
        krr  = forceparams[type].cross_bb.krr;

        /* Compute distance vectors ... */
        t1 = pbc_rvec_sub(pbc, x[ai], x[aj], r_ij);
        t2 = pbc_rvec_sub(pbc, x[ak], x[aj], r_kj);

        /* ... and their lengths */
        r1 = norm(r_ij);
        r2 = norm(r_kj);

        /* Deviations from ideality */
        s1 = r1 - r1e;
        s2 = r2 - r2e;

        /* Energy (can be negative!) */
        vrr = krr * s1 * s2;
        vtot += vrr;

        /* Forces */
        svmul(-krr * s2 / r1, r_ij, f_i);
        svmul(-krr * s1 / r2, r_kj, f_k);

        for (m = 0; (m < DIM); m++) /*  12	*/
        {
            f_j[m] = -f_i[m] - f_k[m];
            f[ai][m] += f_i[m];
            f[aj][m] += f_j[m];
            f[ak][m] += f_k[m];
        }

        if (computeVirial(flavor))
        {
            rvec_inc(fshift[t1], f_i);
            rvec_inc(fshift[c_centralShiftIndex], f_j);
            rvec_inc(fshift[t2], f_k); /* 9 */
        }
        /* 163 TOTAL	*/
    }
    return vtot;
}

template<BondedKernelFlavor flavor>
real cross_bond_angle(int             nbonds,
                      const t_iatom   forceatoms[],
                      const t_iparams forceparams[],
                      const rvec      x[],
                      rvec4           f[],
                      rvec            fshift[],
                      const t_pbc*    pbc,
                      real gmx_unused lambda,
                      real gmx_unused* dvdlambda,
                      gmx::ArrayRef<const real> /*charge*/,
                      t_fcdata gmx_unused* fcd,
                      t_disresdata gmx_unused* disresdata,
                      t_oriresdata gmx_unused* oriresdata,
                      int gmx_unused* global_atom_index)
{
    /* Potential from Lawrence and Skimmer, Chem. Phys. Lett. 372 (2003)
     * pp. 842-847
     */
    int  i, ai, aj, ak, type, m, t1, t2;
    rvec r_ij, r_kj, r_ik;
    real vtot, vrt, s1, s2, s3, r1, r2, r3, r1e, r2e, r3e, krt, k1, k2, k3;
    rvec f_i, f_j, f_k;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];
        r1e  = forceparams[type].cross_ba.r1e;
        r2e  = forceparams[type].cross_ba.r2e;
        r3e  = forceparams[type].cross_ba.r3e;
        krt  = forceparams[type].cross_ba.krt;

        /* Compute distance vectors ... */
        t1 = pbc_rvec_sub(pbc, x[ai], x[aj], r_ij);
        t2 = pbc_rvec_sub(pbc, x[ak], x[aj], r_kj);
        pbc_rvec_sub(pbc, x[ai], x[ak], r_ik);

        /* ... and their lengths */
        r1 = norm(r_ij);
        r2 = norm(r_kj);
        r3 = norm(r_ik);

        /* Deviations from ideality */
        s1 = r1 - r1e;
        s2 = r2 - r2e;
        s3 = r3 - r3e;

        /* Energy (can be negative!) */
        vrt = krt * s3 * (s1 + s2);
        vtot += vrt;

        /* Forces */
        k1 = -krt * (s3 / r1);
        k2 = -krt * (s3 / r2);
        k3 = -krt * (s1 + s2) / r3;
        for (m = 0; (m < DIM); m++)
        {
            f_i[m] = k1 * r_ij[m] + k3 * r_ik[m];
            f_k[m] = k2 * r_kj[m] - k3 * r_ik[m];
            f_j[m] = -f_i[m] - f_k[m];
        }

        for (m = 0; (m < DIM); m++) /*  12	*/
        {
            f[ai][m] += f_i[m];
            f[aj][m] += f_j[m];
            f[ak][m] += f_k[m];
        }

        if (computeVirial(flavor))
        {
            rvec_inc(fshift[t1], f_i);
            rvec_inc(fshift[c_centralShiftIndex], f_j);
            rvec_inc(fshift[t2], f_k); /* 9 */
        }
        /* 163 TOTAL	*/
    }
    return vtot;
}

/*! \brief Computes the potential and force for a tabulated potential */
real bonded_tab(const char*          type,
                int                  table_nr,
                const bondedtable_t* table,
                real                 kA,
                real                 kB,
                real                 r,
                real                 lambda,
                real*                V,
                real*                F)
{
    real k, tabscale, rt, eps, eps2, Yt, Ft, Geps, Heps2, Fp, VV, FF;
    int  n0, nnn;
    real dvdlambda;

    k = (1.0 - lambda) * kA + lambda * kB;

    tabscale          = table->scale;
    const real* VFtab = table->data.data();

    rt = r * tabscale;
    n0 = static_cast<int>(rt);
    if (n0 >= table->n)
    {
        gmx_fatal(FARGS,
                  "A tabulated %s interaction table number %d is out of the table range: r %f, "
                  "between table indices %d and %d, table length %d",
                  type,
                  table_nr,
                  r,
                  n0,
                  n0 + 1,
                  table->n);
    }
    eps   = rt - n0;
    eps2  = eps * eps;
    nnn   = 4 * n0;
    Yt    = VFtab[nnn];
    Ft    = VFtab[nnn + 1];
    Geps  = VFtab[nnn + 2] * eps;
    Heps2 = VFtab[nnn + 3] * eps2;
    Fp    = Ft + Geps + Heps2;
    VV    = Yt + Fp * eps;
    FF    = Fp + Geps + 2.0 * Heps2;

    *F        = -k * FF * tabscale;
    *V        = k * VV;
    dvdlambda = (kB - kA) * VV;

    return dvdlambda;

    /* That was 22 flops */
}

template<BondedKernelFlavor flavor>
real tab_bonds(int             nbonds,
               const t_iatom   forceatoms[],
               const t_iparams forceparams[],
               const rvec      x[],
               rvec4           f[],
               rvec            fshift[],
               const t_pbc*    pbc,
               real            lambda,
               real*           dvdlambda,
               gmx::ArrayRef<const real> /*charge*/,
               t_fcdata*    fcd,
               t_disresdata gmx_unused* disresdata,
               t_oriresdata gmx_unused* oriresdata,
               int gmx_unused* global_atom_index)
{
    int  i, ki, ai, aj, type, table;
    real dr, dr2, fbond, vbond, vtot;
    rvec dx;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];

        ki  = pbc_rvec_sub(pbc, x[ai], x[aj], dx); /*   3      */
        dr2 = iprod(dx, dx);                       /*   5		*/
        dr  = dr2 * gmx::invsqrt(dr2);             /*  10		*/

        table = forceparams[type].tab.table;

        *dvdlambda += bonded_tab("bond",
                                 table,
                                 &fcd->bondtab[table],
                                 forceparams[type].tab.kA,
                                 forceparams[type].tab.kB,
                                 dr,
                                 lambda,
                                 &vbond,
                                 &fbond); /*  22 */

        if (dr2 == 0.0)
        {
            continue;
        }


        vtot += vbond;              /* 1*/
        fbond *= gmx::invsqrt(dr2); /*   6		*/

        spreadBondForces<flavor>(fbond, dx, ai, aj, f, ki, fshift); /* 15 */
    }                                                               /* 62 TOTAL	*/
    return vtot;
}

template<BondedKernelFlavor flavor>
real tab_angles(int             nbonds,
                const t_iatom   forceatoms[],
                const t_iparams forceparams[],
                const rvec      x[],
                rvec4           f[],
                rvec            fshift[],
                const t_pbc*    pbc,
                real            lambda,
                real*           dvdlambda,
                gmx::ArrayRef<const real> /*charge*/,
                t_fcdata*    fcd,
                t_disresdata gmx_unused* disresdata,
                t_oriresdata gmx_unused* oriresdata,
                int gmx_unused* global_atom_index)
{
    int  i, ai, aj, ak, t1, t2, type, table;
    rvec r_ij, r_kj;
    real cos_theta, cos_theta2, theta, dVdt, va, vtot;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];

        theta = bond_angle(x[ai], x[aj], x[ak], pbc, r_ij, r_kj, &cos_theta, &t1, &t2); /*  41 */

        table = forceparams[type].tab.table;

        *dvdlambda += bonded_tab("angle",
                                 table,
                                 &fcd->angletab[table],
                                 forceparams[type].tab.kA,
                                 forceparams[type].tab.kB,
                                 theta,
                                 lambda,
                                 &va,
                                 &dVdt); /*  22  */
        vtot += va;

        cos_theta2 = gmx::square(cos_theta); /*   1		*/
        if (cos_theta2 < 1)
        {
            int  m;
            real st, sth;
            real cik, cii, ckk;
            real nrkj2, nrij2;
            rvec f_i, f_j, f_k;

            st    = dVdt * gmx::invsqrt(1 - cos_theta2); /*  12		*/
            sth   = st * cos_theta;                      /*   1		*/
            nrkj2 = iprod(r_kj, r_kj);                   /*   5		*/
            nrij2 = iprod(r_ij, r_ij);

            cik = st * gmx::invsqrt(nrkj2 * nrij2); /*  12		*/
            cii = sth / nrij2;                      /*  10		*/
            ckk = sth / nrkj2;                      /*  10		*/

            for (m = 0; (m < DIM); m++) /*  39		*/
            {
                f_i[m] = -(cik * r_kj[m] - cii * r_ij[m]);
                f_k[m] = -(cik * r_ij[m] - ckk * r_kj[m]);
                f_j[m] = -f_i[m] - f_k[m];
                f[ai][m] += f_i[m];
                f[aj][m] += f_j[m];
                f[ak][m] += f_k[m];
            }

            if (computeVirial(flavor))
            {
                rvec_inc(fshift[t1], f_i);
                rvec_inc(fshift[c_centralShiftIndex], f_j);
                rvec_inc(fshift[t2], f_k);
            }
        } /* 169 TOTAL	*/
    }
    return vtot;
}

template<BondedKernelFlavor flavor>
real tab_dihs(int             nbonds,
              const t_iatom   forceatoms[],
              const t_iparams forceparams[],
              const rvec      x[],
              rvec4           f[],
              rvec            fshift[],
              const t_pbc*    pbc,
              real            lambda,
              real*           dvdlambda,
              gmx::ArrayRef<const real> /*charge*/,
              t_fcdata*    fcd,
              t_disresdata gmx_unused* disresdata,
              t_oriresdata gmx_unused* oriresdata,
              int gmx_unused* global_atom_index)
{
    int  i, type, ai, aj, ak, al, table;
    int  t1, t2, t3;
    rvec r_ij, r_kj, r_kl, m, n;
    real phi, ddphi, vpd, vtot;

    vtot = 0.0;
    for (i = 0; (i < nbonds);)
    {
        type = forceatoms[i++];
        ai   = forceatoms[i++];
        aj   = forceatoms[i++];
        ak   = forceatoms[i++];
        al   = forceatoms[i++];

        phi = dih_angle(x[ai], x[aj], x[ak], x[al], pbc, r_ij, r_kj, r_kl, m, n, &t1, &t2, &t3); /*  84  */

        table = forceparams[type].tab.table;

        /* Hopefully phi+M_PI never results in values < 0 */
        *dvdlambda += bonded_tab("dihedral",
                                 table,
                                 &fcd->dihtab[table],
                                 forceparams[type].tab.kA,
                                 forceparams[type].tab.kB,
                                 phi + M_PI,
                                 lambda,
                                 &vpd,
                                 &ddphi);

        vtot += vpd;
        do_dih_fup<flavor>(ai, aj, ak, al, -ddphi, r_ij, r_kj, r_kl, m, n, f, fshift, pbc, x, t1, t2, t3); /* 112	*/

    } /* 227 TOTAL  */

    return vtot;
}

struct BondedInteractions
{
    BondedFunction function;
    int            nrnbIndex;
};

/*! \brief Lookup table of bonded interaction functions
 *
 * This must have as many entries as interaction_function in ifunc.cpp */
template<BondedKernelFlavor flavor>
constexpr std::array<BondedInteractions, F_NRE> c_bondedInteractionFunctions = {
    BondedInteractions{ bonds<flavor>, eNR_BONDS },                       // F_BONDS
    BondedInteractions{ g96bonds<flavor>, eNR_BONDS },                    // F_G96BONDS
    BondedInteractions{ morse_bonds<flavor>, eNR_MORSE },                 // F_MORSE
    BondedInteractions{ cubic_bonds<flavor>, eNR_CUBICBONDS },            // F_CUBICBONDS
    BondedInteractions{ unimplemented, -1 },                              // F_CONNBONDS
    BondedInteractions{ bonds<flavor>, eNR_BONDS },                       // F_HARMONIC
    BondedInteractions{ FENE_bonds<flavor>, eNR_FENEBONDS },              // F_FENEBONDS
    BondedInteractions{ tab_bonds<flavor>, eNR_TABBONDS },                // F_TABBONDS
    BondedInteractions{ tab_bonds<flavor>, eNR_TABBONDS },                // F_TABBONDSNC
    BondedInteractions{ restraint_bonds<flavor>, eNR_RESTRBONDS },        // F_RESTRBONDS
    BondedInteractions{ angles<flavor>, eNR_ANGLES },                     // F_ANGLES
    BondedInteractions{ g96angles<flavor>, eNR_ANGLES },                  // F_G96ANGLES
    BondedInteractions{ restrangles<flavor>, eNR_ANGLES },                // F_RESTRANGLES
    BondedInteractions{ linear_angles<flavor>, eNR_ANGLES },              // F_LINEAR_ANGLES
    BondedInteractions{ cross_bond_bond<flavor>, eNR_CROSS_BOND_BOND },   // F_CROSS_BOND_BONDS
    BondedInteractions{ cross_bond_angle<flavor>, eNR_CROSS_BOND_ANGLE }, // F_CROSS_BOND_ANGLES
    BondedInteractions{ urey_bradley<flavor>, eNR_UREY_BRADLEY },         // F_UREY_BRADLEY
    BondedInteractions{ quartic_angles<flavor>, eNR_QANGLES },            // F_QUARTIC_ANGLES
    BondedInteractions{ tab_angles<flavor>, eNR_TABANGLES },              // F_TABANGLES
    BondedInteractions{ pdihs<flavor>, eNR_PROPER },                      // F_PDIHS
    BondedInteractions{ rbdihs<flavor>, eNR_RB },                         // F_RBDIHS
    BondedInteractions{ restrdihs<flavor>, eNR_PROPER },                  // F_RESTRDIHS
    BondedInteractions{ cbtdihs<flavor>, eNR_RB },                        // F_CBTDIHS
    BondedInteractions{ rbdihs<flavor>, eNR_FOURDIH },                    // F_FOURDIHS
    BondedInteractions{ idihs<flavor>, eNR_IMPROPER },                    // F_IDIHS
    BondedInteractions{ pdihs<flavor>, eNR_IMPROPER },                    // F_PIDIHS
    BondedInteractions{ tab_dihs<flavor>, eNR_TABDIHS },                  // F_TABDIHS
    BondedInteractions{ unimplemented, eNR_CMAP },                        // F_CMAP
    BondedInteractions{ unimplemented, -1 },                              // F_GB12_NOLONGERUSED
    BondedInteractions{ unimplemented, -1 },                              // F_GB13_NOLONGERUSED
    BondedInteractions{ unimplemented, -1 },                              // F_GB14_NOLONGERUSED
    BondedInteractions{ unimplemented, -1 },                              // F_GBPOL_NOLONGERUSED
    BondedInteractions{ unimplemented, -1 },                       // F_NPSOLVATION_NOLONGERUSED
    BondedInteractions{ unimplemented, eNR_NB14 },                 // F_LJ14
    BondedInteractions{ unimplemented, -1 },                       // F_COUL14
    BondedInteractions{ unimplemented, eNR_NB14 },                 // F_LJC14_Q
    BondedInteractions{ unimplemented, eNR_NB14 },                 // F_LJC_PAIRS_NB
    BondedInteractions{ unimplemented, -1 },                       // F_LJ
    BondedInteractions{ unimplemented, -1 },                       // F_BHAM
    BondedInteractions{ unimplemented, -1 },                       // F_LJ_LR_NOLONGERUSED
    BondedInteractions{ unimplemented, -1 },                       // F_BHAM_LR_NOLONGERUSED
    BondedInteractions{ unimplemented, -1 },                       // F_DISPCORR
    BondedInteractions{ unimplemented, -1 },                       // F_COUL_SR
    BondedInteractions{ unimplemented, -1 },                       // F_COUL_LR_NOLONGERUSED
    BondedInteractions{ unimplemented, -1 },                       // F_RF_EXCL
    BondedInteractions{ unimplemented, -1 },                       // F_COUL_RECIP
    BondedInteractions{ unimplemented, -1 },                       // F_LJ_RECIP
    BondedInteractions{ unimplemented, -1 },                       // F_DPD
    BondedInteractions{ polarize<flavor>, eNR_POLARIZE },          // F_POLARIZATION
    BondedInteractions{ water_pol<flavor>, eNR_WPOL },             // F_WATER_POL
    BondedInteractions{ thole_pol<flavor>, eNR_THOLE },            // F_THOLE_POL
    BondedInteractions{ anharm_polarize<flavor>, eNR_ANHARM_POL }, // F_ANHARM_POL
    BondedInteractions{ unimplemented, -1 },                       // F_POSRES
    BondedInteractions{ unimplemented, -1 },                       // F_FBPOSRES
    BondedInteractions{ ta_disres, eNR_DISRES },                   // F_DISRES
    BondedInteractions{ unimplemented, -1 },                       // F_DISRESVIOL
    BondedInteractions{ orires, eNR_ORIRES },                      // F_ORIRES
    BondedInteractions{ unimplemented, -1 },                       // F_ORIRESDEV
    BondedInteractions{ angres<flavor>, eNR_ANGRES },              // F_ANGRES
    BondedInteractions{ angresz<flavor>, eNR_ANGRESZ },            // F_ANGRESZ
    BondedInteractions{ dihres<flavor>, eNR_DIHRES },              // F_DIHRES
    BondedInteractions{ unimplemented, -1 },                       // F_DIHRESVIOL
    BondedInteractions{ unimplemented, -1 },                       // F_CONSTR
    BondedInteractions{ unimplemented, -1 },                       // F_CONSTRNC
    BondedInteractions{ unimplemented, -1 },                       // F_SETTLE
    BondedInteractions{ unimplemented, -1 },                       // F_VSITE2
    BondedInteractions{ unimplemented, -1 },                       // F_VSITE3
    BondedInteractions{ unimplemented, -1 },                       // F_VSITE3FD
    BondedInteractions{ unimplemented, -1 },                       // F_VSITE3FAD
    BondedInteractions{ unimplemented, -1 },                       // F_VSITE3OUT
    BondedInteractions{ unimplemented, -1 },                       // F_VSITE4FD
    BondedInteractions{ unimplemented, -1 },                       // F_VSITE4FDN
    BondedInteractions{ unimplemented, -1 },                       // F_VSITEN
    BondedInteractions{ unimplemented, -1 },                       // F_COM_PULL
    BondedInteractions{ unimplemented, -1 },                       // F_DENSITYFITTING
    BondedInteractions{ unimplemented, -1 },                       // F_EQM
    BondedInteractions{ unimplemented, -1 },                       // F_EPOT
    BondedInteractions{ unimplemented, -1 },                       // F_EKIN
    BondedInteractions{ unimplemented, -1 },                       // F_ETOT
    BondedInteractions{ unimplemented, -1 },                       // F_ECONSERVED
    BondedInteractions{ unimplemented, -1 },                       // F_TEMP
    BondedInteractions{ unimplemented, -1 },                       // F_VTEMP_NOLONGERUSED
    BondedInteractions{ unimplemented, -1 },                       // F_PDISPCORR
    BondedInteractions{ unimplemented, -1 },                       // F_PRES
    BondedInteractions{ unimplemented, -1 },                       // F_DVDL_CONSTR
    BondedInteractions{ unimplemented, -1 },                       // F_DVDL
    BondedInteractions{ unimplemented, -1 },                       // F_DKDL
    BondedInteractions{ unimplemented, -1 },                       // F_DVDL_COUL
    BondedInteractions{ unimplemented, -1 },                       // F_DVDL_VDW
    BondedInteractions{ unimplemented, -1 },                       // F_DVDL_BONDED
    BondedInteractions{ unimplemented, -1 },                       // F_DVDL_RESTRAINT
    BondedInteractions{ unimplemented, -1 },                       // F_DVDL_TEMPERATURE
};

/*! \brief List of instantiated BondedInteractions list */
constexpr gmx::EnumerationArray<BondedKernelFlavor, std::array<BondedInteractions, F_NRE>> c_bondedInteractionFunctionsPerFlavor = {
    c_bondedInteractionFunctions<BondedKernelFlavor::ForcesSimdWhenAvailable>,
    c_bondedInteractionFunctions<BondedKernelFlavor::ForcesNoSimd>,
    c_bondedInteractionFunctions<BondedKernelFlavor::ForcesAndVirialAndEnergy>,
    c_bondedInteractionFunctions<BondedKernelFlavor::ForcesAndEnergy>
};

//! \endcond

} // namespace

real calculateSimpleBond(const int                 ftype,
                         const int                 numForceatoms,
                         const t_iatom             forceatoms[],
                         const t_iparams           forceparams[],
                         const rvec                x[],
                         rvec4                     f[],
                         rvec                      fshift[],
                         const struct t_pbc*       pbc,
                         const real                lambda,
                         real*                     dvdlambda,
                         gmx::ArrayRef<const real> charge,
                         t_fcdata*                 fcd,
                         t_disresdata*             disresdata,
                         t_oriresdata*             oriresdata,
                         int gmx_unused*          global_atom_index,
                         const BondedKernelFlavor bondedKernelFlavor)
{
    const BondedInteractions& bonded = c_bondedInteractionFunctionsPerFlavor[bondedKernelFlavor][ftype];

    real v = bonded.function(
            numForceatoms, forceatoms, forceparams, x, f, fshift, pbc, lambda, dvdlambda, charge, fcd, disresdata, oriresdata, global_atom_index);

    return v;
}

int nrnbIndex(int ftype)
{
    return c_bondedInteractionFunctions<BondedKernelFlavor::ForcesAndVirialAndEnergy>[ftype].nrnbIndex;
}
