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Diffstat (limited to 'Source/Utils/Algorithms/UpperBound.H')
-rw-r--r-- | Source/Utils/Algorithms/UpperBound.H | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/Source/Utils/Algorithms/UpperBound.H b/Source/Utils/Algorithms/UpperBound.H new file mode 100644 index 000000000..8a528971a --- /dev/null +++ b/Source/Utils/Algorithms/UpperBound.H @@ -0,0 +1,49 @@ +/* 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_ |