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/*! \internal \file
 * \brief
 * Helper functions and constants for SYCL NBNXM kernels
 *
 * \ingroup module_nbnxm
 */
#ifndef GMX_NBNXM_SYCL_NBNXN_SYCL_KERNEL_UTILS_H
#define GMX_NBNXM_SYCL_NBNXN_SYCL_KERNEL_UTILS_H

#include "gromacs/gpu_utils/sycl_kernel_utils.h"
#include "gromacs/nbnxm/pairlist.h"
#include "gromacs/nbnxm/pairlistparams.h"

namespace Nbnxm
{

#ifndef GMX_NBNXN_PRUNE_KERNEL_JPACKED_CONCURRENCY
//! \brief Default for the prune kernel's jPacked processing concurrency.
#    define GMX_NBNXN_PRUNE_KERNEL_JPACKED_CONCURRENCY 4
#endif

/*! \brief Prune kernel's jPacked processing concurrency.
 *
 *  The \c GMX_NBNXN_PRUNE_KERNEL_JPACKED_CONCURRENCY macro allows compile-time override.
 */
static constexpr int c_syclPruneKernelJPackedConcurrency = GMX_NBNXN_PRUNE_KERNEL_JPACKED_CONCURRENCY;

/* Convenience constants */
/*! \cond */
// cluster size = number of atoms per cluster.
static constexpr int c_clSize = c_nbnxnGpuClusterSize;
// Square of cluster size.
static constexpr int c_clSizeSq = c_clSize * c_clSize;
// j-cluster size after split (4 in the current implementation).
static constexpr int c_splitClSize = c_clSize / c_nbnxnGpuClusterpairSplit;
// i-cluster interaction mask for a super-cluster with all c_nbnxnGpuNumClusterPerSupercluster=8 bits set.
static constexpr unsigned superClInteractionMask = ((1U << c_nbnxnGpuNumClusterPerSupercluster) - 1U);

// 1/sqrt(pi), same value as \c M_FLOAT_1_SQRTPI in other NB kernels.
static constexpr float c_OneOverSqrtPi = 0.564189583547756F;
// 1/6, same value as in other NB kernels.
static constexpr float c_oneSixth = 0.16666667F;
// 1/12, same value as in other NB kernels.
static constexpr float c_oneTwelfth = 0.08333333F;
/*! \endcond */

/*! \brief Explicit uniform load across the warp
 *
 *  Uses the readfirstlane intrinsic to ensure that uniform loads use
 *  scalar registers and subsequent operations on the results generate
 *  scalar instructions.
 *
 *  Note that some ROCm versions' compilers can figure out that the nbnxm
 *  exclusion indices and imasks are uniform and generate the right instructions,
 *  but others (like 4.5 and 5.0.2) do not.
 */
#if defined(__SYCL_DEVICE_ONLY__) && defined(__AMDGCN__) && GMX_GPU_NB_DISABLE_CLUSTER_PAIR_SPLIT
#    define UNIFORM_LOAD_CLUSTER_PAIR_DATA(x) (__builtin_amdgcn_readfirstlane(x))
#else
#    define UNIFORM_LOAD_CLUSTER_PAIR_DATA(x) (x)
#endif

} // namespace Nbnxm

#endif // GMX_NBNXM_SYCL_NBNXN_SYCL_KERNEL_UTILS_H
