void fft2x(Complex a[], int n, int nmax, int flag)
{
int i, iter, j, k;
Complex *p, *w;
if(n < 2)
{
fprintf(stderr, "Error : Illegal parameter in fft2()\n");
return;
}
iter = 0;
i = n;
while((i /= 2) != 0) iter++;
j = 1;
for(i = 1; i <= iter; i++) j *= 2;
if(n != j)
{
fprintf(stderr, "Error : n != 2 ^ k in fft2x()\n");
return;
}
w = (Complex *)malloc(n * sizeof(Complex));
if(w == NULL)
{
fprintf(stderr, "Error : Out of memory in fft2x()\n");
return;
}
for(j = 0; j < n; j++, k += nmax)
{
for(i = 0, p = a + j; i < n; i++, p += nmax) *(w + i) = *p;
fft1x(w, n, iter, flag);
for(i = 0, p = a + j; i < n; i++, p += nmax) *p = *(w + i);
}
for(i = k = 0; i < n; i++, k += nmax)
{
for(j = 0, p = a + k; j < n; j++) *(w + j) = *p++;
fft1x(w, n, iter, flag);
for(j = 0, p = a + k; j < n; j++) *p++ = *(w + j);
}
free((char *)w);
return;
}
int main(void)
{
static double ar[8] = { 0., 0., 0., 1., 1., 0., 0., 0.};
static double ai[8] = { 0., 0., 0., 0., 0., 0., 0., 0.};
static double ar2[16] = { 0., 0., 0., 0., 0., 1., 1., 0.,
0., 1., 1., 0., 0., 0., 0., 0.};
static double ai2[16] = { 0., 0., 0., 0., 0., 0., 0., 0.,
0., 0., 0., 0., 0., 0., 0., 0.};
Complex a[8], a2[16];
int flag, i, iter, j, k, n, nmax;
iter = 0;
n = 8;
#ifndef CPX
for(i = 0; i < n; i++)
a[i] = tocomplex(ar[i], ai[i]);
print(ar, ai, n);
#else
printx(a, n);
#endif
/* forward FFT */
flag = 0;
#ifndef CPX
fft1(ar, ai, n, iter, flag);
print(ar, ai, n);
#else
fft1x(a, n, iter, flag);
printx(a, n);
#endif
/* reverse FFT */
flag = 1;
#ifndef CPX
fft1(ar, ai, n, iter, flag);
print(ar, ai, n);
#else
fft1x(a, n, iter, flag);
printx(a, n);
#endif
n = nmax = 4;
for(i = k = 0; i < n; i++)
for(j = 0; j < n; j++, k++)
a2[k] = tocomplex(ar2[k], ai2[k]);
#ifndef CPX
print2(ar2, ai2, n, nmax);
#else
print2x(a2, n, nmax);
#endif
flag = 0;
#ifndef CPX
fft2(ar2, ai2, n, nmax, flag);
print2(ar2, ai2, n, nmax);
#else
fft2x(a2, n, nmax, flag);
print2x(a2, n, nmax);
#endif
flag = 1;
#ifndef CPX
fft2(ar2, ai2, n, nmax, flag);
print2(ar2, ai2, n, nmax);
#else
fft2x(a2, n, nmax, flag);
print2x(a2, n, nmax);
#endif
return 1;
}
