FFT support libraries

Greg Lindahl lindahl at conservativecomputer.com
Thu Jul 26 14:42:13 PDT 2001

On Thu, Jul 26, 2001 at 10:10:03PM +0200, Steffen Persvold wrote:

> I'm trying to port a fortran application using SGI FFT functions
> (complib.sgimath) to Linux. The only FFT functions that are used are
> zfft1di and zfft1d. I understand that these are double complex
> functions and I've downloaded the double precision fftpack from
> netlib.org (dfftpack). However, the dfftpack routines zffti and
> zfft{f,b} doesn't seem to match the SGI functions.

Welcome to Fourier Transform Hell. No 2 libraries are the same, for
no good reason.

> Now, here I guess that the direction parameter to ZFFT1D is just a
> way to decide wether to use a forward or a backward FFT, but what is
> the parameter after E_SLICE ??.

The manpage says that the parameter after E_SLICE is the stride of the
array, which will be undoubtedly 1 in your code. This is a fairly
unusual feature in a fft library.


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