WG: [PD] fft algorithms
Krzysztof Czaja
czaja at chopin.edu.pl
Wed Apr 10 15:02:12 CEST 2002
hi Thomas,
it looks like your 2nd requirement is met for rfftw:
``FFTW's one-dimensional real transforms store hermitian arrays as
"halfcomplex" arrays. A halfcomplex array of size n is a
one-dimensional array of n `fftw_real' numbers. A hermitian array
X in stored into a halfcomplex array Y as follows. For all
integers i such that 0 <= i <= n / 2, we have Y[i] = Re(X[i]). For
all integers i such that 0 < i < n / 2, we have Y[n-i] =
Im(X[i]).''
The actual `real2hc' codelets use separate real and imag arrays.
Krzysztof
Thomas Grill wrote:
...
> following properties:
> - in-place (or with a small workspace)
> - separated vectors for real and imaginary data, with stride factors
> - preferably also mixed-radix (for non-power-2 transforms)
>
> Alternatively, as FFTW exists (but doesn't fulfill the 2nd requirement):
> - is there an algorithm that transforms a vector of complex points into
> separated real and imaginary vectors in place?
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