AMReX_ConstexprFor.H

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#ifndef AMREX_CONSTEXPR_FOR_H_
#define AMREX_CONSTEXPR_FOR_H_
#include <AMReX_Config.H>
 
#include <AMReX_GpuQualifiers.H>
#include <AMReX_Extension.H>
 
#include <type_traits>
 
namespace amrex {
 
// Implementation of "constexpr for" based on
// https://artificial-mind.net/blog/2020/10/31/constexpr-for
//
// Approximates what one would get from a compile-time
// unrolling of the loop
// for (int i = 0; i < N; ++i) {
//    f(i);
// }
//
// The mechanism is recursive: we evaluate f(i) at the current
// i and then call the for loop at i+1. f() is a lambda function
// that provides the body of the loop and takes only an integer
// i as its argument.
 
template<auto I, auto N, class F>
AMREX_GPU_HOST_DEVICE AMREX_INLINE
constexpr void constexpr_for (F const& f)
{
    if constexpr (I < N) {
        f(std::integral_constant<decltype(I), I>());
        constexpr_for<I+1, N>(f);
    }
}
 
}
 
#endif