From octave-maintainers-request at bevo dot che dot wisc dot edu Tue Jan 27 04:38:32 2004 Subject: Re: benchmarks From: David Bateman To: "Dmitri A. Sergatskov" Cc: octave-maintainers at bevo dot che dot wisc dot edu Date: Tue, 27 Jan 2004 11:34:28 +0100 > So Octave faster than Matlab for complex numbers, but slower > than Matlab for real numbers. > It may be that Matlab is using rfftw for real input, and > octave always assumes complex input. > I have a vague recollection that this issue was discussed on > octave list eons ago, but could not find this thread in > archive... Looking at the sources of 2.1.53, octave does use complex transforms at all times. In fact the reason the real transform is slower, is that as well as the transform there is an additional copy of the matrix to a compelx matrix, before calling the tranform. This needs seperate plans for the real transforms, and some code rewriting. However, octave currectly using the FFTw 2.1.x API, and if someone is going to tackle this problem, then we should probably update, or at least offer as an alternative the newer (but incompatiable) FFT 3.x API. There is a bonus in this in that there are also significant sppedup in FFTW 3.x for SSE, SSE2 and 3dNow... It doesn't seem that hard to do this, and in fact someone tried a while back http://www.octave.org/mailing-lists/octave-sources/2003/63 http://www.octave.org/mailing-lists/help-octave/2003/1262 Cheers David -- David Bateman David dot Bateman at motorola dot com Motorola CRM +33 1 69 35 48 04 (Ph) Parc Les Algorithmes, Commune de St Aubin +33 1 69 35 77 01 (Fax) 91193 Gif-Sur-Yvette FRANCE The information contained in this communication has been classified as: [x] General Business Information [ ] Motorola Internal Use Only [ ] Motorola Confidential Proprietary