blob: 42259512b0dd897fb5591ecdcfa7e4485ffd2fe2 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
|
/* Copyright 2019 Yinjian Zhao
*
* This file is part of WarpX.
*
* License: BSD-3-Clause-LBNL
*/
#ifndef WARPX_PARTICLES_COLLISION_SHUFFLE_FISHER_YATES_H_
#define WARPX_PARTICLES_COLLISION_SHUFFLE_FISHER_YATES_H_
#include <AMReX_Random.H>
/* \brief Shuffle array according to Fisher-Yates algorithm.
* Only shuffle the part between is <= i < ie, n = ie-is.
* T_index shall be
* amrex::DenseBins<WarpXParticleContainer::ParticleType>::index_type
*/
template <typename T_index>
AMREX_GPU_HOST_DEVICE AMREX_INLINE
void ShuffleFisherYates (T_index *array, T_index const is, T_index const ie,
amrex::RandomEngine const& engine)
{
T_index buf;
for (int i = ie-1; i >= static_cast<int>(is+1); --i)
{
// get random number j: is <= j <= i
const int j = amrex::Random_int(i-is+1, engine) + is;
// swap the ith array element with the jth
buf = array[i];
array[i] = array[j];
array[j] = buf;
}
}
#endif // WARPX_PARTICLES_COLLISION_SHUFFLE_FISHER_YATES_H_
|
