cuda-samples/Samples/sortingNetworks/bitonicSort.cu
2021-10-21 16:34:49 +05:30

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/* Copyright (c) 2021, NVIDIA CORPORATION. All rights reserved.
*
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//Based on http://www.iti.fh-flensburg.de/lang/algorithmen/sortieren/bitonic/bitonicen.htm
#include <assert.h>
#include <cooperative_groups.h>
namespace cg = cooperative_groups;
#include <helper_cuda.h>
#include "sortingNetworks_common.h"
#include "sortingNetworks_common.cuh"
////////////////////////////////////////////////////////////////////////////////
// Monolithic bitonic sort kernel for short arrays fitting into shared memory
////////////////////////////////////////////////////////////////////////////////
__global__ void bitonicSortShared(uint *d_DstKey, uint *d_DstVal,
uint *d_SrcKey, uint *d_SrcVal,
uint arrayLength, uint dir) {
// Handle to thread block group
cg::thread_block cta = cg::this_thread_block();
// Shared memory storage for one or more short vectors
__shared__ uint s_key[SHARED_SIZE_LIMIT];
__shared__ uint s_val[SHARED_SIZE_LIMIT];
// Offset to the beginning of subbatch and load data
d_SrcKey += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
d_SrcVal += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
d_DstKey += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
d_DstVal += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
s_key[threadIdx.x + 0] = d_SrcKey[0];
s_val[threadIdx.x + 0] = d_SrcVal[0];
s_key[threadIdx.x + (SHARED_SIZE_LIMIT / 2)] =
d_SrcKey[(SHARED_SIZE_LIMIT / 2)];
s_val[threadIdx.x + (SHARED_SIZE_LIMIT / 2)] =
d_SrcVal[(SHARED_SIZE_LIMIT / 2)];
for (uint size = 2; size < arrayLength; size <<= 1) {
// Bitonic merge
uint ddd = dir ^ ((threadIdx.x & (size / 2)) != 0);
for (uint stride = size / 2; stride > 0; stride >>= 1) {
cg::sync(cta);
uint pos = 2 * threadIdx.x - (threadIdx.x & (stride - 1));
Comparator(s_key[pos + 0], s_val[pos + 0], s_key[pos + stride],
s_val[pos + stride], ddd);
}
}
// ddd == dir for the last bitonic merge step
{
for (uint stride = arrayLength / 2; stride > 0; stride >>= 1) {
cg::sync(cta);
uint pos = 2 * threadIdx.x - (threadIdx.x & (stride - 1));
Comparator(s_key[pos + 0], s_val[pos + 0], s_key[pos + stride],
s_val[pos + stride], dir);
}
}
cg::sync(cta);
d_DstKey[0] = s_key[threadIdx.x + 0];
d_DstVal[0] = s_val[threadIdx.x + 0];
d_DstKey[(SHARED_SIZE_LIMIT / 2)] =
s_key[threadIdx.x + (SHARED_SIZE_LIMIT / 2)];
d_DstVal[(SHARED_SIZE_LIMIT / 2)] =
s_val[threadIdx.x + (SHARED_SIZE_LIMIT / 2)];
}
////////////////////////////////////////////////////////////////////////////////
// Bitonic sort kernel for large arrays (not fitting into shared memory)
////////////////////////////////////////////////////////////////////////////////
// Bottom-level bitonic sort
// Almost the same as bitonicSortShared with the exception of
// even / odd subarrays being sorted in opposite directions
// Bitonic merge accepts both
// Ascending | descending or descending | ascending sorted pairs
__global__ void bitonicSortShared1(uint *d_DstKey, uint *d_DstVal,
uint *d_SrcKey, uint *d_SrcVal) {
// Handle to thread block group
cg::thread_block cta = cg::this_thread_block();
// Shared memory storage for current subarray
__shared__ uint s_key[SHARED_SIZE_LIMIT];
__shared__ uint s_val[SHARED_SIZE_LIMIT];
// Offset to the beginning of subarray and load data
d_SrcKey += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
d_SrcVal += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
d_DstKey += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
d_DstVal += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
s_key[threadIdx.x + 0] = d_SrcKey[0];
s_val[threadIdx.x + 0] = d_SrcVal[0];
s_key[threadIdx.x + (SHARED_SIZE_LIMIT / 2)] =
d_SrcKey[(SHARED_SIZE_LIMIT / 2)];
s_val[threadIdx.x + (SHARED_SIZE_LIMIT / 2)] =
d_SrcVal[(SHARED_SIZE_LIMIT / 2)];
for (uint size = 2; size < SHARED_SIZE_LIMIT; size <<= 1) {
// Bitonic merge
uint ddd = (threadIdx.x & (size / 2)) != 0;
for (uint stride = size / 2; stride > 0; stride >>= 1) {
cg::sync(cta);
uint pos = 2 * threadIdx.x - (threadIdx.x & (stride - 1));
Comparator(s_key[pos + 0], s_val[pos + 0], s_key[pos + stride],
s_val[pos + stride], ddd);
}
}
// Odd / even arrays of SHARED_SIZE_LIMIT elements
// sorted in opposite directions
uint ddd = blockIdx.x & 1;
{
for (uint stride = SHARED_SIZE_LIMIT / 2; stride > 0; stride >>= 1) {
cg::sync(cta);
uint pos = 2 * threadIdx.x - (threadIdx.x & (stride - 1));
Comparator(s_key[pos + 0], s_val[pos + 0], s_key[pos + stride],
s_val[pos + stride], ddd);
}
}
cg::sync(cta);
d_DstKey[0] = s_key[threadIdx.x + 0];
d_DstVal[0] = s_val[threadIdx.x + 0];
d_DstKey[(SHARED_SIZE_LIMIT / 2)] =
s_key[threadIdx.x + (SHARED_SIZE_LIMIT / 2)];
d_DstVal[(SHARED_SIZE_LIMIT / 2)] =
s_val[threadIdx.x + (SHARED_SIZE_LIMIT / 2)];
}
// Bitonic merge iteration for stride >= SHARED_SIZE_LIMIT
__global__ void bitonicMergeGlobal(uint *d_DstKey, uint *d_DstVal,
uint *d_SrcKey, uint *d_SrcVal,
uint arrayLength, uint size, uint stride,
uint dir) {
uint global_comparatorI = blockIdx.x * blockDim.x + threadIdx.x;
uint comparatorI = global_comparatorI & (arrayLength / 2 - 1);
// Bitonic merge
uint ddd = dir ^ ((comparatorI & (size / 2)) != 0);
uint pos = 2 * global_comparatorI - (global_comparatorI & (stride - 1));
uint keyA = d_SrcKey[pos + 0];
uint valA = d_SrcVal[pos + 0];
uint keyB = d_SrcKey[pos + stride];
uint valB = d_SrcVal[pos + stride];
Comparator(keyA, valA, keyB, valB, ddd);
d_DstKey[pos + 0] = keyA;
d_DstVal[pos + 0] = valA;
d_DstKey[pos + stride] = keyB;
d_DstVal[pos + stride] = valB;
}
// Combined bitonic merge steps for
// size > SHARED_SIZE_LIMIT and stride = [1 .. SHARED_SIZE_LIMIT / 2]
__global__ void bitonicMergeShared(uint *d_DstKey, uint *d_DstVal,
uint *d_SrcKey, uint *d_SrcVal,
uint arrayLength, uint size, uint dir) {
// Handle to thread block group
cg::thread_block cta = cg::this_thread_block();
// Shared memory storage for current subarray
__shared__ uint s_key[SHARED_SIZE_LIMIT];
__shared__ uint s_val[SHARED_SIZE_LIMIT];
d_SrcKey += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
d_SrcVal += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
d_DstKey += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
d_DstVal += blockIdx.x * SHARED_SIZE_LIMIT + threadIdx.x;
s_key[threadIdx.x + 0] = d_SrcKey[0];
s_val[threadIdx.x + 0] = d_SrcVal[0];
s_key[threadIdx.x + (SHARED_SIZE_LIMIT / 2)] =
d_SrcKey[(SHARED_SIZE_LIMIT / 2)];
s_val[threadIdx.x + (SHARED_SIZE_LIMIT / 2)] =
d_SrcVal[(SHARED_SIZE_LIMIT / 2)];
// Bitonic merge
uint comparatorI =
UMAD(blockIdx.x, blockDim.x, threadIdx.x) & ((arrayLength / 2) - 1);
uint ddd = dir ^ ((comparatorI & (size / 2)) != 0);
for (uint stride = SHARED_SIZE_LIMIT / 2; stride > 0; stride >>= 1) {
cg::sync(cta);
uint pos = 2 * threadIdx.x - (threadIdx.x & (stride - 1));
Comparator(s_key[pos + 0], s_val[pos + 0], s_key[pos + stride],
s_val[pos + stride], ddd);
}
cg::sync(cta);
d_DstKey[0] = s_key[threadIdx.x + 0];
d_DstVal[0] = s_val[threadIdx.x + 0];
d_DstKey[(SHARED_SIZE_LIMIT / 2)] =
s_key[threadIdx.x + (SHARED_SIZE_LIMIT / 2)];
d_DstVal[(SHARED_SIZE_LIMIT / 2)] =
s_val[threadIdx.x + (SHARED_SIZE_LIMIT / 2)];
}
////////////////////////////////////////////////////////////////////////////////
// Interface function
////////////////////////////////////////////////////////////////////////////////
// Helper function (also used by odd-even merge sort)
extern "C" uint factorRadix2(uint *log2L, uint L) {
if (!L) {
*log2L = 0;
return 0;
} else {
for (*log2L = 0; (L & 1) == 0; L >>= 1, *log2L++)
;
return L;
}
}
extern "C" uint bitonicSort(uint *d_DstKey, uint *d_DstVal, uint *d_SrcKey,
uint *d_SrcVal, uint batchSize, uint arrayLength,
uint dir) {
// Nothing to sort
if (arrayLength < 2) return 0;
// Only power-of-two array lengths are supported by this implementation
uint log2L;
uint factorizationRemainder = factorRadix2(&log2L, arrayLength);
assert(factorizationRemainder == 1);
dir = (dir != 0);
uint blockCount = batchSize * arrayLength / SHARED_SIZE_LIMIT;
uint threadCount = SHARED_SIZE_LIMIT / 2;
if (arrayLength <= SHARED_SIZE_LIMIT) {
assert((batchSize * arrayLength) % SHARED_SIZE_LIMIT == 0);
bitonicSortShared<<<blockCount, threadCount>>>(d_DstKey, d_DstVal, d_SrcKey,
d_SrcVal, arrayLength, dir);
} else {
bitonicSortShared1<<<blockCount, threadCount>>>(d_DstKey, d_DstVal,
d_SrcKey, d_SrcVal);
for (uint size = 2 * SHARED_SIZE_LIMIT; size <= arrayLength; size <<= 1)
for (unsigned stride = size / 2; stride > 0; stride >>= 1)
if (stride >= SHARED_SIZE_LIMIT) {
bitonicMergeGlobal<<<(batchSize * arrayLength) / 512, 256>>>(
d_DstKey, d_DstVal, d_DstKey, d_DstVal, arrayLength, size, stride,
dir);
} else {
bitonicMergeShared<<<blockCount, threadCount>>>(
d_DstKey, d_DstVal, d_DstKey, d_DstVal, arrayLength, size, dir);
break;
}
}
return threadCount;
}