int main(int argc, char ** argv)
{
int n, np, npm, n2, i, j, nruns;
double enp, t, y, z, zr, zi, zm, a;
double * xr, * xi, * pxr, * pxi;
if (argc >= 2) n = atoi(argv[1]); else n = 18;
np = 1 << n;
enp = np;
npm = np / 2 - 1;
t = PI / enp;
xr = calloc(np, sizeof(double));
xi = calloc(np, sizeof(double));
pxr = xr;
pxi = xi;
for (nruns = 0; nruns < NRUNS; nruns++) {
*pxr = (enp - 1.0) * 0.5;
*pxi = 0.0;
n2 = np / 2;
*(pxr+n2) = -0.5;
*(pxi+n2) = 0.0;
for (i = 1; i <= npm; i++) {
j = np - i;
*(pxr+i) = -0.5;
*(pxr+j) = -0.5;
z = t * (double)i;
y = -0.5*(cos(z)/sin(z));
*(pxi+i) = y;
*(pxi+j) = -y;
}
dfft(xr,xi,np);
}
zr = 0.0;
zi = 0.0;
npm = np-1;
for (i = 0; i <= npm; i++ ) {
a = fabs(pxr[i] - i);
if (zr < a) zr = a;
a = fabs(pxi[i]);
if (zi < a) zi = a;
}
zm = zr;
if (zr < zi) zm = zi;
printf("%d points, %s\n", np, zm < 1e-9 ? "result OK" : "WRONG result");
return 0;
}
int main(int argc, char* argv[])
{
int i,j,np,npm,lp,n2,kr,ki;
double *pxr,*pxi;
double a,enp,t,y,zr,zi,zm;
np = 8;
pxr = xr;
pxi = xi;
printf("\nFFT benchmark - Double Precision - V1.0 - 05 Jan 1993\n\n");
printf("FFT size max error\n");
for (lp = 1; lp <= 15; lp++ )
{
np = np * 2;
printf(" %7d ",np);
enp = np;
npm = np / 2 - 1;
t = PI / enp;
pxr[0] = (enp - 1.0) * 0.5;
pxi[0] = 0.0;
n2 = np / 2;
pxr[n2] = -0.5;
pxi[n2] = 0.0;
for (i = 1; i <= npm; i++)
{
j = np - i;
pxr[i] = -0.5;
pxr[j] = -0.5;
y = t * (double)i;
y = -0.5*(cos(y)/sin(y));
pxi[i] = y;
pxi[j] = -y;
}
dfft(xr,xi,np);
/*
for (i=0; i<=15; i++) printf("%d %g %g\n",i,xr[i],xi[i]);
*/
zr = 0.0;
zi = 0.0;
kr = 0;
ki = 0;
npm = np-1;
for (i = 0; i <= npm; i++ )
{
a = fabs( xr[i] - i );
if (zr < a)
{
zr = a;
kr = i;
}
a = fabs(xi[i]);
if (zi < a)
{
zi = a;
ki = i;
}
}
zm = zr;
if ( fabs(zr) < fabs(zi) ) zm = zi;
printf(" %10.2g\n",zm);
/*
printf("re %7d %10.2g im %7d %10.2g\n",kr,zr,ki,zi);
*/
}
return 0;
}
