/*
 * This file is part of the GROMACS molecular simulation package.
 *
 * Copyright 2019- 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
 * Declares the PairlistType enum and PairlistParams class
 *
 * \author Berk Hess <hess@kth.se>
 * \ingroup module_nbnxm
 */

#ifndef GMX_NBNXM_PAIRLISTPARAMS_H
#define GMX_NBNXM_PAIRLISTPARAMS_H

#include "config.h"

#include "gromacs/mdtypes/locality.h"
#include "gromacs/utility/enumerationhelpers.h"
#include "gromacs/utility/real.h"

namespace Nbnxm
{
enum class KernelType;
}

//! The i-cluster size for CPU kernels, always 4 atoms
static constexpr int c_nbnxnCpuIClusterSize = 4;

//! The i- and j-cluster size for GPU lists, 8 atoms for CUDA, set at configure time for OpenCL and SYCL
#if GMX_GPU_OPENCL || GMX_GPU_SYCL
static constexpr int c_nbnxnGpuClusterSize = GMX_GPU_NB_CLUSTER_SIZE;
#else
static constexpr int c_nbnxnGpuClusterSize      = 8;
#endif

/*! \brief The number of clusters along a direction in a pair-search grid cell for GPU lists
 *
 * Typically all 2, but X can be 1 when targeting Intel Ponte Vecchio */
//! \{
static constexpr int c_gpuNumClusterPerCellZ = GMX_GPU_NB_NUM_CLUSTER_PER_CELL_Z;
static constexpr int c_gpuNumClusterPerCellY = GMX_GPU_NB_NUM_CLUSTER_PER_CELL_Y;
static constexpr int c_gpuNumClusterPerCellX = GMX_GPU_NB_NUM_CLUSTER_PER_CELL_X;
//! \}
//! The number of clusters in a pair-search grid cell for GPU lists
static constexpr int c_gpuNumClusterPerCell =
        c_gpuNumClusterPerCellZ * c_gpuNumClusterPerCellY * c_gpuNumClusterPerCellX;


/*! \brief The number of sub-parts used for data storage for a GPU cluster pair
 *
 * In CUDA the number of threads in a warp is 32 and we have cluster pairs
 * of 8*8=64 atoms, so it's convenient to store data for cluster pair halves,
 * i.e. split in 2.
 *
 * On architectures with 64-wide execution however it is better to avoid splitting
 * (e.g. AMD GCN, CDNA and later).
 */
#if GMX_GPU_NB_DISABLE_CLUSTER_PAIR_SPLIT
static constexpr int c_nbnxnGpuClusterpairSplit = 1;
#else
static constexpr int c_nbnxnGpuClusterpairSplit = 2;
#endif

//! The fixed size of the exclusion mask array for a half GPU cluster pair
static constexpr int c_nbnxnGpuExclSize =
        c_nbnxnGpuClusterSize * c_nbnxnGpuClusterSize / c_nbnxnGpuClusterpairSplit;

//! The available pair list types
enum class PairlistType : int
{
    Simple4x2,
    Simple4x4,
    Simple4x8,
    HierarchicalNxN,
    Count
};

//! Gives the i-cluster size for each pairlist type
static constexpr gmx::EnumerationArray<PairlistType, int> IClusterSizePerListType = {
    { c_nbnxnCpuIClusterSize, c_nbnxnCpuIClusterSize, c_nbnxnCpuIClusterSize, c_nbnxnGpuClusterSize }
};
//! Gives the j-cluster size for each pairlist type
static constexpr gmx::EnumerationArray<PairlistType, int> JClusterSizePerListType = {
    { 2, 4, 8, c_nbnxnGpuClusterSize }
};
//! True if given pairlist type is used on GPU, false if on CPU.
static constexpr gmx::EnumerationArray<PairlistType, bool> sc_isGpuPairListType = {
    { false, false, false, true }
};

/*! \internal
 * \brief The setup for generating and pruning the nbnxn pair list.
 *
 * Without dynamic pruning rlistOuter=rlistInner.
 */
struct PairlistParams
{
    /*! \brief Constructor producing a struct with dynamic pruning disabled
     */
    PairlistParams(Nbnxm::KernelType kernelType, bool haveFep, real rlist, bool haveMultipleDomains);

    //! The type of cluster-pair list
    PairlistType pairlistType;
    //! Tells whether we have perturbed interactions
    bool haveFep;
    //! Cut-off of the larger, outer pair-list
    real rlistOuter;
    //! Cut-off of the smaller, inner pair-list
    real rlistInner;
    //! True when using DD with multiple domains
    bool haveMultipleDomains;
    //! Are we using dynamic pair-list pruning
    bool useDynamicPruning;
    //! The interval in steps for computing non-bonded interactions, =1 without MTS
    int mtsFactor;
    //! Pair-list dynamic pruning interval
    int nstlistPrune;
    //! The number parts to divide the pair-list into for rolling pruning, a value of 1 gives no rolling pruning
    int numRollingPruningParts;
    //! Lifetime in steps of the pair-list
    int lifetime;
};

#endif
