How to: CUDA IFFT

How to: CUDA IFFT

本文关键字:IFFT CUDA to How      更新时间:2023-10-16

在matlab中,当我输入一个数量的一个维数阵列时,我的数量数量具有相同大小和相同尺寸的数字。试图在CUDA C中重复此操作,但输出不同。你能帮忙吗?在MATLAB中,当我输入ifft(array)

我的arrayofcomplexnmbers:

[4.6500 + 0.0000i   0.5964 - 1.4325i   0.4905 - 0.5637i   0.4286 - 0.2976i   0.4345 - 0.1512i   0.4500 + 0.0000i   0.4345 + 0.1512i  0.4286 + 0.2976i   0.4905 + 0.5637i   0.5964 + 1.4325i]

我的arrayofrealnumbers:

[ 0.9000    0.8000    0.7000    0.6000    0.5000    0.4000    0.3000    0.2000    0.1500    0.1000]

当我在MATLAB中输入ifft(arrayOfComplexNmbers)时,我的输出是arrayOfRealNumbers。谢谢你!这是我的CUDA代码:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <cuda_runtime.h>
#include <cufft.h>
#include "device_launch_parameters.h"
#include "device_functions.h"
#define NX 256
#define NY 128
#define NRANK 2
#define BATCH 1
#define SIGNAL_SIZE 10
typedef float2 Complex;
__global__ void printCUDAVariables_1(cufftComplex *cudaSignal){
int index = threadIdx.x + blockIdx.x*blockDim.x;    
printf("COMPLEX CUDA %d %f %f n", index, cudaSignal[index].x, cudaSignal[index].y);
}
__global__ void printCUDAVariables_2(cufftReal *cudaSignal){
int index = threadIdx.x + blockIdx.x*blockDim.x;
printf("REAL CUDA %d %f n", index, cudaSignal);
}

int main() {
cufftHandle plan;
//int n[NRANK] = { NX, NY };
Complex *h_signal = (Complex *)malloc(sizeof(Complex)* SIGNAL_SIZE);
float *r_signal = 0;
if (r_signal != 0){
    r_signal = (float*)realloc(r_signal, SIGNAL_SIZE * sizeof(float));
}
else{
    r_signal = (float*)malloc(SIGNAL_SIZE * sizeof(float));
}
int mem_size = sizeof(Complex)* SIGNAL_SIZE * 2;
h_signal[0].x = (float)4.65;
h_signal[0].y = (float)0;
h_signal[1].x = (float)0.5964;
h_signal[1].y = (float)0;
h_signal[2].x = (float)4.65;
h_signal[2].y = (float)-1.4325;
h_signal[3].x = (float)0.4905;
h_signal[3].y = (float)0.5637;
h_signal[4].x = (float)0.4286;
h_signal[4].y = (float)-0.2976;
h_signal[5].x = (float)0.4345;
h_signal[5].y = (float)-0.1512;
h_signal[6].x = (float)0.45;
h_signal[6].y = (float)0;
h_signal[7].x = (float)0.4345;
h_signal[7].y = (float)-0.1512;
h_signal[8].x = (float)0.4286;
h_signal[8].y = (float)0.2976;
h_signal[9].x = (float)0.4905;
h_signal[9].y = (float)-0.5637;
h_signal[10].x = (float)0.5964;
h_signal[10].y = (float)1.4325;
//for (int i = 0; i < SIGNAL_SIZE; i++){
//  printf("RAW %f %fn", h_signal[i].x, h_signal[i].y);
//}
//allocate device memory for signal
cufftComplex *d_signal, *d_signal_out;
cudaMalloc(&d_signal, mem_size);    
cudaMalloc(&d_signal_out, mem_size);
cudaMemcpy(d_signal, h_signal, mem_size, cudaMemcpyHostToDevice);
printCUDAVariables_1 << <10, 1 >> >(d_signal);
//cufftReal *odata;
//cudaMalloc((void **)&odata, sizeof(cufftReal)*NX*(NY / 2 + 1));
//cufftPlan1d(&plan, SIGNAL_SIZE, CUFFT_C2R, BATCH);    
cufftPlan1d(&plan, NX, CUFFT_C2C, BATCH);
cufftExecC2C(plan, d_signal, d_signal_out, CUFFT_INVERSE);
//cufftExecC2R(plan, d_signal, odata);
cudaDeviceSynchronize();
printCUDAVariables_1 << <10, 1 >> >(d_signal_out);
//printCUDAVariables_2 << <10, 1 >> >(odata);
//cudaMemcpy(h_signal, d_signal_out, SIGNAL_SIZE*2*sizeof(float), cudaMemcpyDeviceToHost);
cufftDestroy(plan);
cudaFree(d_signal);
cudaFree(d_signal_out);
return 0;
}

用MATLAB计算ifft时,默认行为如下:

  • 没有输入信号的零填充
  • 没有输出信号的缩放

您的袖扣代码的流程正确,但是与MATLAB相比有些不同的参数正在引起当前输出。

  • NX常数要具体导致输入信号为零盖的长度为256。为了实现MATLAB的行为,保持NX等于SIGNAL_SIZE
  • cufft将输出信号值与输入信号的长度相连。您必须将输出值与SIGNAL_SIZE分开以获取实际值。
  • 另一个重要的问题是,在初始化输入信号时,您正在执行越野访问。信号长度为10,但是您正在初始化第10个索引的值,该索引不超约束。我认为这可能是由于MATLAB的1个基索引引起的混乱。输入信号必须仅在0SIGNAL_SIZE-1索引初始化。
  • 不建议使用cuda内核可视化信号,因为打印可能会过失。您应该将结果复制回主机并串行打印。

这是固定的代码,它提供了与MATLAB相同的输出。

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <cuda_runtime.h>
#include <cufft.h>
#include "device_launch_parameters.h"
#include "device_functions.h"
#define NX 10
#define NY 1
#define NRANK 1
#define BATCH 1
#define SIGNAL_SIZE 10
typedef float2 Complex;  
int main() 
{
cufftHandle plan;
//int n[NRANK] = { NX, NY };
Complex *h_signal = (Complex *)malloc(sizeof(Complex)* SIGNAL_SIZE);
float *r_signal = 0;
if (r_signal != 0)
{
    r_signal = (float*)realloc(r_signal, SIGNAL_SIZE * sizeof(float));
}
else
{
    r_signal = (float*)malloc(SIGNAL_SIZE * sizeof(float));
}
int mem_size = sizeof(Complex)* SIGNAL_SIZE;
h_signal[0].x = (float)4.65;
h_signal[0].y = (float)0;
h_signal[1].x = (float)0.5964;
h_signal[1].y = (float)-1.4325;
h_signal[2].x = (float)0.4905;
h_signal[2].y = (float)-0.5637;
h_signal[3].x = (float)0.4286;
h_signal[3].y = (float)-0.2976;
h_signal[4].x = (float)0.4345;
h_signal[4].y = (float)-0.1512;
h_signal[5].x = (float)0.45;
h_signal[5].y = (float)0.0;
h_signal[6].x = (float)0.4345;
h_signal[6].y = (float)0.1512;
h_signal[7].x = (float)0.4286;
h_signal[7].y = (float)0.2976;
h_signal[8].x = (float)0.4905;
h_signal[8].y = (float)0.5637;
h_signal[9].x = (float)0.5964;
h_signal[9].y = (float)1.4325;
printf("nInput:n");
for(int i=0; i<SIGNAL_SIZE; i++)
{
    char op = h_signal[i].y < 0 ? '-' : '+';
    printf("%f %c %fin", h_signal[i].x/SIGNAL_SIZE, op, fabsf(h_signal[i].y/SIGNAL_SIZE ) );
}
//allocate device memory for signal
cufftComplex *d_signal, *d_signal_out;
cudaMalloc(&d_signal, mem_size);    
cudaMalloc(&d_signal_out, mem_size);
cudaMemcpy(d_signal, h_signal, mem_size, cudaMemcpyHostToDevice);

//cufftPlan1d(&plan, SIGNAL_SIZE, CUFFT_C2R, BATCH);    
cufftPlan1d(&plan, NX, CUFFT_C2C, BATCH);
cufftExecC2C(plan, d_signal, d_signal_out, CUFFT_INVERSE);
cudaDeviceSynchronize();
cudaMemcpy(h_signal, d_signal_out, SIGNAL_SIZE*sizeof(Complex), cudaMemcpyDeviceToHost);

printf("nn-------------------------------nn");
printf("Output:n");
for(int i=0; i<SIGNAL_SIZE; i++)
{
    char op = h_signal[i].y < 0 ? '-' : '+';
    printf("%f %c %fin", h_signal[i].x/SIGNAL_SIZE, op, fabsf(h_signal[i].y/SIGNAL_SIZE ) );
}
cufftDestroy(plan);
cudaFree(d_signal);
cudaFree(d_signal_out);
return 0;
}

输出仍处于复杂形式,但假想组件接近零。同样,实际组件的精度差异是因为MATLAB默认使用双精度,而此代码基于单个精度值。


在Ubuntu 14.04,Cuda 8.0上进行了编译和测试。

nvcc -o ifft ifft.cu -ark = sm_61 -lcufft

将输出与Matlab 2017a进行了比较。

程序输出:

Input:
0.465000 + 0.000000i
0.059640 - 0.143250i
0.049050 - 0.056370i
0.042860 - 0.029760i
0.043450 - 0.015120i
0.045000 + 0.000000i
0.043450 + 0.015120i
0.042860 + 0.029760i
0.049050 + 0.056370i
0.059640 + 0.143250i

-------------------------------
Output:
0.900000 - 0.000000i
0.800026 - 0.000000i
0.699999 - 0.000000i
0.599964 - 0.000000i
0.500011 + 0.000000i
0.400000 + 0.000000i
0.299990 + 0.000000i
0.199993 + 0.000000i
0.150000 + 0.000000i
0.100018 - 0.000000i