C_Code.c

#include <stdio.h>
#include <math.h>
#include <complex.h>
#include <xtime_l.h>

double PI;
typedef double complex cplx;

void _fft(cplx buf[], cplx out[], int n, int step)
{
	if (step < n) {
		_fft(out, buf, n, step * 2);
		_fft(out + step, buf + step, n, step * 2);

		for (int i = 0; i < n; i += 2 * step) {
			cplx t = cexp(-I * PI * i / n) * out[i + step];
			buf[i / 2]     = out[i] + t;
			buf[(i + n)/2] = out[i] - t;
		}
	}
}

void fft(cplx buf[], int n)
{
	cplx out[n];
	for (int i = 0; i < n; i++) out[i] = buf[i];

	_fft(buf, out, n, 1);
}


void show(const char * s, cplx buf[]) {
	printf("%s", s);
	for (int i = 0; i < 8; i++){
		if (!cimag(buf[i]))
			printf("%g  ", creal(buf[i]));
		else
			printf("(%g, %g)  ", creal(buf[i]), cimag(buf[i]));
	}
}

int main()
{
	XTime start, end;
	PI = atan2(1, 1) * 4;
	cplx inOut[] = {1, 1, 1, 1, -1, -1, -1, -1};

	show("Data: ", inOut);
	XTime_GetTime(&start);
	fft(inOut, 8);
	XTime_GetTime(&end);
	show("\nFFT: ", inOut);
        printf("\nExecution Time: %f",(end-start)*1000000.0/COUNTS_PER_SECOND);
	return 0;
}