Après beaucoup de temps et l'introduction de la fonctionnalité de rappel de cuFFT, je peux fournir une réponse significative à ma propre question. Ci-dessus, je proposais une «solution peut-être meilleure».Après quelques tests, je me suis rendu compte que, sans utiliser la fonction de rappel callback, cette solution est plus lente car elle utilise pow
. Puis, je l'ai exploré deux alternatives à l'utilisation de pow
, quelque chose comme
float a = (float)(1-2*((int)offset%2));
float2 out = ((float2*)d_in)[offset];
out.x = out.x * a;
out.y = out.y * a;
et
float2 out = ((float2*)d_in)[offset];
if ((int)offset&1) {
out.x = -out.x;
out.y = -out.y;
}
Mais, avec cuFFT standard, toutes les solutions ci-dessus nécessitent deux appels noyau distincts, l'un pour la fftshift et un pour l'appel d'exécution cuFFT. Cependant, avec la nouvelle fonction de rappel de cuFFT, les solutions alternatives ci-dessus peuvent être intégrées dans le code sous la forme __device__
.
Donc, finalement je fini avec le dessous du code de comparaison
#include "cuda_runtime.h"
#include "device_launch_parameters.h"
#include <stdio.h>
#include <assert.h>
#include <cufft.h>
#include <cufftXt.h>
//#define DEBUG
#define BLOCKSIZE 256
/**********/
/* iDivUp */
/**********/
int iDivUp(int a, int b) { return ((a % b) != 0) ? (a/b + 1) : (a/b); }
/********************/
/* CUDA ERROR CHECK */
/********************/
#define gpuErrchk(ans) { gpuAssert((ans), __FILE__, __LINE__); }
inline void gpuAssert(cudaError_t code, const char *file, int line, bool abort=true)
{
if (code != cudaSuccess)
{
fprintf(stderr,"GPUassert: %s %s %d\n", cudaGetErrorString(code), file, line);
if (abort) exit(code);
}
}
/*********************/
/* CUFFT ERROR CHECK */
/*********************/
// See http://stackoverflow.com/questions/16267149/cufft-error-handling
#ifdef _CUFFT_H_
// cuFFT API errors
static const char *_cudaGetErrorEnum(cufftResult error)
{
switch (error)
{
case CUFFT_SUCCESS:
return "CUFFT_SUCCESS";
case CUFFT_INVALID_PLAN:
return "CUFFT_INVALID_PLAN";
case CUFFT_ALLOC_FAILED:
return "CUFFT_ALLOC_FAILED";
case CUFFT_INVALID_TYPE:
return "CUFFT_INVALID_TYPE";
case CUFFT_INVALID_VALUE:
return "CUFFT_INVALID_VALUE";
case CUFFT_INTERNAL_ERROR:
return "CUFFT_INTERNAL_ERROR";
case CUFFT_EXEC_FAILED:
return "CUFFT_EXEC_FAILED";
case CUFFT_SETUP_FAILED:
return "CUFFT_SETUP_FAILED";
case CUFFT_INVALID_SIZE:
return "CUFFT_INVALID_SIZE";
case CUFFT_UNALIGNED_DATA:
return "CUFFT_UNALIGNED_DATA";
}
return "<unknown>";
}
#endif
#define cufftSafeCall(err) __cufftSafeCall(err, __FILE__, __LINE__)
inline void __cufftSafeCall(cufftResult err, const char *file, const int line)
{
if(CUFFT_SUCCESS != err) {
fprintf(stderr, "CUFFT error in file '%s', line %d\n %s\nerror %d: %s\nterminating!\n",__FILE__, __LINE__,err, \
_cudaGetErrorEnum(err)); \
cudaDeviceReset(); assert(0); \
}
}
/****************************************/
/* FFTSHIFT 1D INPLACE MEMORY MOVEMENTS */
/****************************************/
__global__ void fftshift_1D_inplace_memory_movements(float2 *d_inout, unsigned int N)
{
unsigned int tid = threadIdx.x + blockIdx.x * blockDim.x;
if (tid < N/2)
{
float2 temp = d_inout[tid];
d_inout[tid] = d_inout[tid + (N/2)];
d_inout[tid + (N/2)] = temp;
}
}
/**********************************************/
/* FFTSHIFT 1D INPLACE CHESSBOARD - VERSION 1 */
/**********************************************/
__device__ float2 fftshift_1D_chessboard_callback_v1(void *d_in, size_t offset, void *callerInfo, void *sharedPtr) {
float a = (float)(1-2*((int)offset%2));
float2 out = ((float2*)d_in)[offset];
out.x = out.x * a;
out.y = out.y * a;
return out;
}
__device__ cufftCallbackLoadC fftshift_1D_chessboard_callback_v1_Ptr = fftshift_1D_chessboard_callback_v1;
/**********************************************/
/* FFTSHIFT 1D INPLACE CHESSBOARD - VERSION 2 */
/**********************************************/
__device__ float2 fftshift_1D_chessboard_callback_v2(void *d_in, size_t offset, void *callerInfo, void *sharedPtr) {
float a = pow(-1.,(double)(offset&1));
float2 out = ((float2*)d_in)[offset];
out.x = out.x * a;
out.y = out.y * a;
return out;
}
__device__ cufftCallbackLoadC fftshift_1D_chessboard_callback_v2_Ptr = fftshift_1D_chessboard_callback_v2;
/**********************************************/
/* FFTSHIFT 1D INPLACE CHESSBOARD - VERSION 3 */
/**********************************************/
__device__ float2 fftshift_1D_chessboard_callback_v3(void *d_in, size_t offset, void *callerInfo, void *sharedPtr) {
float2 out = ((float2*)d_in)[offset];
if ((int)offset&1) {
out.x = -out.x;
out.y = -out.y;
}
return out;
}
__device__ cufftCallbackLoadC fftshift_1D_chessboard_callback_v3_Ptr = fftshift_1D_chessboard_callback_v3;
/********/
/* MAIN */
/********/
int main()
{
const int N = 131072;
printf("N = %d\n", N);
// --- Host side input array
float2 *h_vect = (float2 *)malloc(N*sizeof(float2));
for (int i=0; i<N; i++) {
h_vect[i].x = (float)rand()/(float)RAND_MAX;
h_vect[i].y = (float)rand()/(float)RAND_MAX;
}
// --- Host side output arrays
float2 *h_out1 = (float2 *)malloc(N*sizeof(float2));
float2 *h_out2 = (float2 *)malloc(N*sizeof(float2));
float2 *h_out3 = (float2 *)malloc(N*sizeof(float2));
float2 *h_out4 = (float2 *)malloc(N*sizeof(float2));
// --- Device side input arrays
float2 *d_vect1; gpuErrchk(cudaMalloc((void**)&d_vect1, N*sizeof(float2)));
float2 *d_vect2; gpuErrchk(cudaMalloc((void**)&d_vect2, N*sizeof(float2)));
float2 *d_vect3; gpuErrchk(cudaMalloc((void**)&d_vect3, N*sizeof(float2)));
float2 *d_vect4; gpuErrchk(cudaMalloc((void**)&d_vect4, N*sizeof(float2)));
gpuErrchk(cudaMemcpy(d_vect1, h_vect, N*sizeof(float2), cudaMemcpyHostToDevice));
gpuErrchk(cudaMemcpy(d_vect2, h_vect, N*sizeof(float2), cudaMemcpyHostToDevice));
gpuErrchk(cudaMemcpy(d_vect3, h_vect, N*sizeof(float2), cudaMemcpyHostToDevice));
gpuErrchk(cudaMemcpy(d_vect4, h_vect, N*sizeof(float2), cudaMemcpyHostToDevice));
// --- Device side output arrays
float2 *d_out1; gpuErrchk(cudaMalloc((void**)&d_out1, N*sizeof(float2)));
float2 *d_out2; gpuErrchk(cudaMalloc((void**)&d_out2, N*sizeof(float2)));
float2 *d_out3; gpuErrchk(cudaMalloc((void**)&d_out3, N*sizeof(float2)));
float2 *d_out4; gpuErrchk(cudaMalloc((void**)&d_out4, N*sizeof(float2)));
float time;
cudaEvent_t start, stop;
cudaEventCreate(&start);
cudaEventCreate(&stop);
/*******************************************/
/* cuFFT + MEMORY MOVEMENTS BASED FFTSHIFT */
/*******************************************/
cufftHandle planinverse; cufftSafeCall(cufftPlan1d(&planinverse, N, CUFFT_C2C, 1));
cudaEventRecord(start, 0);
cufftSafeCall(cufftExecC2C(planinverse, d_vect1, d_vect1, CUFFT_INVERSE));
fftshift_1D_inplace_memory_movements<<<iDivUp(N/2, BLOCKSIZE), BLOCKSIZE>>>(d_vect1, N);
#ifdef DEBUG
gpuErrchk(cudaPeekAtLastError());
gpuErrchk(cudaDeviceSynchronize());
#endif
cudaEventRecord(stop, 0);
cudaEventSynchronize(stop);
cudaEventElapsedTime(&time, start, stop);
printf("Memory movements elapsed time: %3.3f ms \n", time);
gpuErrchk(cudaMemcpy(h_out1, d_vect1, N*sizeof(float2), cudaMemcpyDeviceToHost));
/****************************************/
/* CHESSBOARD MULTIPLICATION V1 + cuFFT */
/****************************************/
cufftCallbackLoadC hfftshift_1D_chessboard_callback_v1_Ptr;
gpuErrchk(cudaMemcpyFromSymbol(&hfftshift_1D_chessboard_callback_v1_Ptr, fftshift_1D_chessboard_callback_v1_Ptr, sizeof(hfftshift_1D_chessboard_callback_v1_Ptr)));
cufftHandle planinverse_v1; cufftSafeCall(cufftPlan1d(&planinverse_v1, N, CUFFT_C2C, 1));
cufftResult status = cufftXtSetCallback(planinverse_v1, (void **)&hfftshift_1D_chessboard_callback_v1_Ptr, CUFFT_CB_LD_COMPLEX, 0);
if (status == CUFFT_LICENSE_ERROR) {
printf("This sample requires a valid license file.\n");
printf("The file was either not found, out of date, or otherwise invalid.\n");
exit(EXIT_FAILURE);
} else {
cufftSafeCall(status);
}
cudaEventRecord(start, 0);
cufftSafeCall(cufftExecC2C(planinverse_v1, d_vect2, d_out2, CUFFT_INVERSE));
cudaEventRecord(stop, 0);
cudaEventSynchronize(stop);
cudaEventElapsedTime(&time, start, stop);
printf("Chessboard v1 elapsed time: %3.3f ms \n", time);
gpuErrchk(cudaMemcpy(h_out2, d_out2, N*sizeof(float2), cudaMemcpyDeviceToHost));
// --- Checking the results
for (int i=0; i<N; i++) if ((h_out1[i].x != h_out2[i].x)||(h_out1[i].y != h_out2[i].y)) { printf("Chessboard v1 test failed!\n"); return 0; }
printf("Chessboard v1 test passed!\n");
/****************************************/
/* CHESSBOARD MULTIPLICATION V2 + cuFFT */
/****************************************/
cufftCallbackLoadC hfftshift_1D_chessboard_callback_v2_Ptr;
gpuErrchk(cudaMemcpyFromSymbol(&hfftshift_1D_chessboard_callback_v2_Ptr, fftshift_1D_chessboard_callback_v2_Ptr, sizeof(hfftshift_1D_chessboard_callback_v2_Ptr)));
cufftHandle planinverse_v2; cufftSafeCall(cufftPlan1d(&planinverse_v2, N, CUFFT_C2C, 1));
status = cufftXtSetCallback(planinverse_v2, (void **)&hfftshift_1D_chessboard_callback_v2_Ptr, CUFFT_CB_LD_COMPLEX, 0);
if (status == CUFFT_LICENSE_ERROR) {
printf("This sample requires a valid license file.\n");
printf("The file was either not found, out of date, or otherwise invalid.\n");
exit(EXIT_FAILURE);
} else {
cufftSafeCall(status);
}
cudaEventRecord(start, 0);
cufftSafeCall(cufftExecC2C(planinverse_v2, d_vect3, d_out3, CUFFT_INVERSE));
cudaEventRecord(stop, 0);
cudaEventSynchronize(stop);
cudaEventElapsedTime(&time, start, stop);
printf("Chessboard v2 elapsed time: %3.3f ms \n", time);
gpuErrchk(cudaMemcpy(h_out3, d_out3, N*sizeof(float2), cudaMemcpyDeviceToHost));
// --- Checking the results
for (int i=0; i<N; i++) if ((h_out1[i].x != h_out3[i].x)||(h_out1[i].y != h_out3[i].y)) { printf("Chessboard v2 test failed!\n"); return 0; }
printf("Chessboard v2 test passed!\n");
/****************************************/
/* CHESSBOARD MULTIPLICATION V3 + cuFFT */
/****************************************/
cufftCallbackLoadC hfftshift_1D_chessboard_callback_v3_Ptr;
gpuErrchk(cudaMemcpyFromSymbol(&hfftshift_1D_chessboard_callback_v3_Ptr, fftshift_1D_chessboard_callback_v3_Ptr, sizeof(hfftshift_1D_chessboard_callback_v3_Ptr)));
cufftHandle planinverse_v3; cufftSafeCall(cufftPlan1d(&planinverse_v3, N, CUFFT_C2C, 1));
status = cufftXtSetCallback(planinverse_v3, (void **)&hfftshift_1D_chessboard_callback_v3_Ptr, CUFFT_CB_LD_COMPLEX, 0);
if (status == CUFFT_LICENSE_ERROR) {
printf("This sample requires a valid license file.\n");
printf("The file was either not found, out of date, or otherwise invalid.\n");
exit(EXIT_FAILURE);
} else {
cufftSafeCall(status);
}
cudaEventRecord(start, 0);
cufftSafeCall(cufftExecC2C(planinverse_v3, d_vect4, d_out4, CUFFT_INVERSE));
cudaEventRecord(stop, 0);
cudaEventSynchronize(stop);
cudaEventElapsedTime(&time, start, stop);
printf("Chessboard v3 elapsed time: %3.3f ms \n", time);
gpuErrchk(cudaMemcpy(h_out4, d_out4, N*sizeof(float2), cudaMemcpyDeviceToHost));
// --- Checking the results
for (int i=0; i<N; i++) if ((h_out1[i].x != h_out4[i].x)||(h_out1[i].y != h_out4[i].y)) { printf("Chessboard v3 test failed!\n"); return 0; }
printf("Chessboard v3 test passed!\n");
return 0;
}
RÉSULTATS SUR UN GTX 480
N Mem mov v1 v2 v3
131072 0.552 0.136 0.354 0.183
262144 0.536 0.175 0.451 0.237
524288 0.661 0.283 0.822 0.290
1048576 0.784 0.565 1.548 0.548
2097152 1.298 0.952 2.973 0.944
RÉSULTATS SUR UN TESLA C2050
N Mem mov v1 v2 v3
131072 0.278 0.130 0.236 0.132
262144 0.344 0.202 0.374 0.206
524288 0.544 0.378 0.696 0.387
1048576 0.909 0.695 1.294 0.695
2097152 1.656 1.349 2.531 1.349
RÉSULTATS SUR UN KEPLER K20c
N Mem mov v1 v2 v3
131072 0.077 0.076 0.136 0.076
262144 0.142 0.128 0.202 0.127
524288 0.268 0.229 0.374 0.230
1048576 0.516 0.433 0.717 0.435
2097152 1.019 0.853 1.400 0.855
Nous vous remercions de votre réponse. Fondamentalement, vous déplacez physiquement les premiers éléments 'N/2' à la fin (derniers éléments' N/2') du tableau '1.5N' par un DeviceToDevice cudaMemcpy. Cela semble être intelligent. Mais dans un autre post, voir [CUDA Device To Device transfert coûteux] (http://stackoverflow.com/questions/6063619/cuda-device-to-device-transfer-expensive), vous avez découragé par vous-même un autre utilisateur de cette pratique , étant plus lent que de créer un noyau pour faire les swaps. Aussi, il semble que cette solution occupe plus de mémoire. Pourriez-vous s'il vous plaît commenter davantage sur ce point? – JackOLantern
J'ai probablement trouvé une nouvelle solution. S'il vous plaît, jetez un oeil à la publication révisée. – JackOLantern