Trying to do cross correlation in C - c

Question

I am doing a project which is locating a sound source. I am using three microphones to capture data and then do cross correlation to find the time difference. The time difference is then used to locate the sound source. The issue I think am having is with the cross correlation of my code. I am doing this in C and from my understanding FFT needs to be done and so I am using the FFTW library to do this. The result of my cross correlation is always 0. The microphones are capturing data by sampling them, and then after a loud sound it captures data for half a buffer and then writes the data to a text file. I am using a circular buffer for storing the data. After the trigger event occurs, the data is reordered and then fast fourier transformed. Then multiplied and then inverse transformed. I then determine when the peak occurs from the output of the IFFT. Most of the time it is 0 but I am not sure why. So I wrote the data into a text file where I then imported the data into MATLAB. This was to test the xcorr function with my data. The results of this match my cross correlation code in C. So I am now not sure of where the issue lies with my code.
I have added a link to the data I acquired in a text file.1 Then for my cross correlation in C I have the following code.
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <math.h>
#include <complex.h> /* Standard Library of Complex Numbers */
#include <fftw3.h>
int i,size = 8; //defining the size of the buffer and FFT
int peak_detec(double);
void reverse(double a[]);
int peak_detec(double a) // function which calculates the maximum value of an array
{
int b= 0;
double Largest;
int Position;
Largest = a;
for(b=1; b<10; b++)
{
if(Largest<a)
{
Largest=a;
Position = b;
}
}
return Position;
}
void reverse(double a[]) // function which reverses the order of the array send to the function
{
int i;
double temp[size];
for(i = 1; i < size+1; i++)
{
temp[i-1] = a[size-i];
}
for (i=0; i< size;i++)
{
a[i]=temp[i];
}
}
int main(void)
{
double array[] = {0.7,0.1,0.1,0.1,0.1,0.1,0.1,0.1}; //my two arrays for FFT
double array2[] = {0.1,0.1,0.1,0.1,0.1,0.1,0.7,0.1};
double *out,*out2,*out3; //pointer for the output
double *err,*err2; //pointer for errors
double *double_array;
double *double_array2;
//****pointer for complex arrays****//
double complex *out_cpx;
double complex *out_cpx2;
double complex *out_cpx3;
//****defining all the plans for fft****//
fftw_plan fft;
fftw_plan ifft;
fftw_plan fft2;
fftw_plan ifft2;
fftw_plan ifft3;
//****allocating memory****//
out_cpx = (double complex*) fftw_malloc(sizeof(double complex)*(2*size));
out = (double *) malloc((2*size)*sizeof(double));
err = (double *) malloc((2*size)*sizeof(double));
out_cpx2 = (double complex*) fftw_malloc(sizeof(double complex)*(2*size));
out2 = (double *) malloc((2*size)*sizeof(double));
err2 = (double *) malloc((2*size)*sizeof(double));
out_cpx3 = (double complex*) fftw_malloc(sizeof(double complex)*(2*size));
out3 = (double *) malloc((2*size)*sizeof(double));
double_array = (double*) malloc(sizeof(double)*(2*size));
double_array2 = (double*) malloc(sizeof(double)*(2*size));
//****setting up fftw and ifft plans****//
fft = fftw_plan_dft_r2c_1d((2*size), double_array, out_cpx, FFTW_ESTIMATE); //Setup fftw plan for fft
ifft = fftw_plan_dft_c2r_1d((2*size), out_cpx, out, FFTW_ESTIMATE); //Setup fftw plan for ifft
fft2 = fftw_plan_dft_r2c_1d((2*size), double_array2, out_cpx2, FFTW_ESTIMATE); //Setup fftw plan for fft
ifft2 = fftw_plan_dft_c2r_1d((2*size), out_cpx2, out2, FFTW_ESTIMATE); //Setup fftw plan for ifft
ifft3 = fftw_plan_dft_c2r_1d((2*size), out_cpx3, out3, FFTW_ESTIMATE); //Setup fftw plan for ifft
//reverse(array2);
memcpy (double_array, array, sizeof(double)*(size));
memset (double_array + size+1, 0, sizeof(double) * (size-1));
memcpy (double_array2, array2, sizeof(double)*(size));
memset (double_array2 + size+1, 0, sizeof(double) * (size-1));
//****executing fft****//
fftw_execute(fft);
fftw_execute(fft2);
double complex scale = 1.0/(2 * size);
for (i=0;i<2*size;i++) //loop which multiplies the FFT arrays
{
out_cpx3[i] = out_cpx[i]*out_cpx2[i]*scale;
}
//****executing ifft****//
fftw_execute(ifft);
fftw_execute(ifft2);
fftw_execute(ifft3);
//****for loop which finds the largest value of the array****//
int Position =0;
double Largest;
Largest = out3[0];
for(i=1; i<2*size; i++)
{
if(Largest<=out3[i])
{
Largest=out3[i];
Position = i ;
}
}
printf("Position of peak value: %d\n",Position);
//****frees the memory****//
fftw_destroy_plan(fft);
fftw_destroy_plan(fft2);
fftw_destroy_plan(ifft);
fftw_destroy_plan(ifft2);
fftw_destroy_plan(ifft3);
fftw_free(out_cpx);
fftw_free(out_cpx2);
fftw_free(out_cpx3);
free(double_array);
free(double_array2);
free(err);
free(out);
free(err2);
free(out2);
free(out3);
return 0;
}
Can anyone help with my issue? I am trying to do cross correlation and with the data in the shared link but does not seem to work.
It is my first time asking a question on here, I think I have given enough information but if not then I can try provide more if something does not make sense.