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/* Copyright 2022 Luca Fedeli
*
* This file is part of WarpX.
*
* License: BSD-3-Clause-LBNL
*/
#ifndef WARPX_UTILS_ALGORITHMS_UPPER_BOUND_H_
#define WARPX_UTILS_ALGORITHMS_UPPER_BOUND_H_
#include <AMReX_Extension.H>
#include <AMReX_GpuQualifiers.H>
namespace utils::algorithms
{
/** \brief Returns a pointer to the first element in the range [first, last) that is greater than val
*
* A re-implementation of the upper_bound algorithm suitable for GPU kernels.
*
* @param first: pointer to left limit of the range to consider
* @param last: pointer to right limit of the range to consider
* @param val: value to compare the elements of [first, last) to
*/
template<typename T> AMREX_GPU_DEVICE AMREX_FORCE_INLINE
const T* upper_bound(const T* first, const T* last, const T& val)
{
const T* it;
size_t count, step;
count = last-first;
while(count>0){
it = first;
step = count/2;
it += step;
if (!(val<*it)){
first = ++it;
count -= step + 1;
}
else{
count = step;
}
}
return first;
}
}
#endif //WARPX_UTILS_ALGORITHMS_UPPER_BOUND_H_
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