I want to realize IFFT function by cuda. Input data is compelx. The real number is import from “phase_init_befroe_R.csv”, and imaginary number is import from “phase_init_before_C.csv”.Then run cufftExecC2C or cufftExecZ2Z function. The result is save in “out_R.csv” and “out_C.csv”. “out_R.csv” is what I want.
When macro SINGLE is defined, all the data will be signle-precision.Here is the result draw by matlab command imagesc(csvread(“out_R.csv”)
enter image description here
When macro SINGLE is not defined, all the data will be double-precision. Draw by matlab command imagesc(csvread(“out_R.csv”))
enter image description here

I varify the result by matlab. Whether the data is signle or double in matlab, the reult is same. And it is similar to the second image.

So my problem is why single-precision data will lead to wrong our_R.csv?

#include <iostream>
#include <cufft.h>
#include <fstream>

#pragma comment(lib,"cufft.lib")

#define ROW 120
#define COL 160

using namespace std;

// change precision between single and double
//#define SINGLE

#ifdef SINGLE
#define REAL cufftReal
#define COMPLEX cufftComplex
#else
#define REAL cufftDoubleReal
#define COMPLEX cufftDoubleComplex
#endif


// read file csv file
template <typename T>
void readData(T* inputData, const char* fileName)
{
    ifstream file;
    file.open(fileName);
    if(file.is_open())
    {
        for(int i = 0; i<ROW*COL; ++i)
        {
                file>>*inputData++;
                file.get();
        }
        file.close();
    }
    else{
        printf("Can not open file %s", fileName);
    }
}

// save to csv file
template<typename T>
void saveData(T* inputData, const char* fileName, bool realOrImag)
{
    ofstream file;
    file.open(fileName);
    if(file.is_open())
    {
        for(int i = 0; i<ROW; ++i)
        {
            for(int j=0; j<COL; ++j)
            {
                int index = i*COL+j;
                if(j<COL-1)
                {
                    if(realOrImag)
                    {
                        file<<(*inputData).x<<",";
                    }
                    else{
                        file<<(*inputData).y<<",";
                    }

                    inputData++;
                }
                else
                {
                    if(realOrImag)
                    {
                        file<<(*inputData).x<<"n";

                    }
                    else{
                        file<<(*inputData).y<<",";
                    }
                    inputData++;
                }
            }
        }
    }
}

template<typename T>
void showData(T* inputData)
{
    for(int i=0; i<6; ++i)
    {
        for(int j = 0; j<3; ++j)
        {
            printf("(%.3f, %.3f)t", inputData[i*COL+j].x, inputData[i*COL+j].y);
        }
        printf("n");
    }
}

int main() {

    // read data from csv file
    REAL *real, *imag;
    real = (REAL*)malloc(ROW*COL*sizeof(REAL));
    imag = (REAL*)malloc(ROW*COL*sizeof(REAL));
    readData(real, R"(C:UsersadminDocumentsMATLABphase_init_before_R.csv)");
    readData(imag, R"(C:UsersadminDocumentsMATLABphase_init_before_C.csv)");

    COMPLEX *in;
    in = (COMPLEX*)malloc(ROW*COL*sizeof(COMPLEX));
    for(int m = 0; m<ROW*COL; ++m)
    {
        in[m] = {real[m], imag[m]};
    }

    // copy form host to device
    COMPLEX *in_dev;
    cudaMalloc(&in_dev, ROW*COL*sizeof(COMPLEX));
    cudaMemcpy(in_dev, in, ROW*COL*sizeof(COMPLEX), cudaMemcpyHostToDevice);

    // IFFT
#ifdef SINGLE
    cufftHandle handle;
    cufftPlan2d(&handle, ROW, COL, CUFFT_C2C);
    cufftExecC2C(handle, in_dev, in_dev, CUFFT_INVERSE);
#else
    cufftHandle handle;
    cufftPlan2d(&handle, ROW, COL, CUFFT_Z2Z);
    cufftExecZ2Z(handle, in_dev, in_dev, CUFFT_INVERSE);
#endif

    // copy from device to host
    COMPLEX *out;
    out = (COMPLEX*)malloc(ROW*COL*sizeof(COMPLEX));
    cudaMemcpy(out, in_dev, ROW*COL*sizeof(COMPLEX), cudaMemcpyDeviceToHost);

    // save to csv file
    saveData(out, R"(C:UsersadminDocumentsMATLABout_R.csv)", true);
    saveData(out, R"(C:UsersadminDocumentsMATLABout_C.csv)", false);

    cudaFree(in_dev);
    free(in);
    free(out);
    free(real);
    free(imag);
    cufftDestroy(handle);

    return 0;
}

At first, to make it work fast, all data is signle precision. But result is wrong. I check the syntax it is all right. So I tried to change data type from single precision to double precision. It happend to get the right answer.