/* *****************************************************
** in-place Radix-2 inverse FFT for real values
** (by the so-called "packing method")
** data: array of doubles:
** re(0),re(size/2),re(1),im(1),re(2),im(2),...,re(size/2-1),im(size/2-1)
**
** output:
** re(0),re(1),re(2),...,re(size-1)
** NOT normalized by array length
**
** Source: see the routines it calls ...
******************************************************* */
void irealfft_packed(MYFLT *data, MYFLT *outdata, int size, MYFLT *twiddle) {
int i;
size >>= 1;
unrealize(data, size);
unshuffle(data, size);
inverse_dit_butterfly(data, size, twiddle);
size <<= 1;
for (i=0; i<size; i++)
outdata[i] = data[i] * 2;
}
/*
in-place Radix-2 inverse FFT for complex values
data: (array of float, below order)
re(0),im(0),re(1),im(1),...,re(size-1),im(size-1)
means size=array_length/2 !!
output is in similar order, NOT normalized by array length
*/
void fa_ifft(uintptr_t handle, float* data)
{
int i, bit;
fa_fft_ctx_t *f = (fa_fft_ctx_t *)handle;
float *temp = f->fft_work;
int size = f->length;
int *bit_rvs = f->bit_rvs;
float *cos_ang = f->cos_ang;
float *sin_ang = f->sin_ang;
for (i = 0 ; i < size ; i++) {
bit = bit_rvs[i];
temp[i+i] = data[bit+bit]; temp[i+i+1] = data[bit+bit+1];
}
for (i = 0; i < size ; i++) {
data[i+i] = temp[i+i]/size;
data[i+i+1] = temp[i+i+1]/size;
}
inverse_dit_butterfly(data, size, cos_ang, sin_ang);
}
/*
in-place Radix-2 inverse FFT for complex values
data: (array of double, below order)
re(0),im(0),re(1),im(1),...,re(size-1),im(size-1)
means size=array_length/2 !!
output is in similar order, NOT normalized by array length
*/
void llz_ifft(unsigned long handle, double* data)
{
int i, bit;
llz_fft_ctx_t *f = (llz_fft_ctx_t *)handle;
double *temp = f->fft_work;
int size = f->length;
int *bit_rvs = f->bit_rvs;
double *cos_ang = f->cos_ang;
double *sin_ang = f->sin_ang;
for (i = 0 ; i < size ; i++) {
bit = bit_rvs[i];
temp[i+i] = data[bit+bit]; temp[i+i+1] = data[bit+bit+1];
}
for (i = 0; i < size ; i++) {
data[i+i] = temp[i+i]/size;
data[i+i+1] = temp[i+i+1]/size;
}
inverse_dit_butterfly(data, size, cos_ang, sin_ang);
}
