AMReX_GpuLaunchFunctsSIMD.H

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#ifndef AMREX_GPU_LAUNCH_FUNCTS_SIMD_H_
#define AMREX_GPU_LAUNCH_FUNCTS_SIMD_H_
 
#include <AMReX_Config.H>
#include <AMReX_Extension.H>
#include <AMReX_SIMD.H>
 
#include <type_traits>
 
 
namespace amrex
{
 
template<int WIDTH, class N=int>
struct SIMDindex
{
    static constexpr int width = WIDTH;
 
    N index = 0;
};
 
template <int WIDTH, std::integral N, typename L >
AMREX_ATTRIBUTE_FLATTEN_FOR
void ParallelForSIMD (N n, L const& f) noexcept
{
    N i = 0;
    // vectorize full lanes
    for (; i + WIDTH <= n; i+=WIDTH) {
        f(SIMDindex<WIDTH, N>{i});
    }
    // scalar handling of the remainder
    // note: we could make the remainder calls faster, by repeatedly
    //       decreasing the SIMD width by 2 until we reach 1
    for (; i < n; ++i) {
        f(SIMDindex<1, N>{i});
    }
}
 
template <typename T, std::integral N, typename L >
AMREX_ATTRIBUTE_FLATTEN_FOR
void ParallelForSIMD (N n, L && f) noexcept
{
#ifdef AMREX_USE_SIMD
    if constexpr (amrex::simd::is_vectorized<T>) {
        amrex::ParallelForSIMD<T::simd_width>(n, std::forward<L>(f));
    } else
#endif
    {
        amrex::ParallelFor(n, std::forward<L>(f));
    }
}
 
} // namespace amrex
 
#endif