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## Speed concerns with fft

**From**: |
Sébastien Maerten |

**Subject**: |
Speed concerns with fft |

**Date**: |
Fri, 8 Oct 2004 15:15:21 +0200 |

Hello,

`I need to perform fft on "large" sets of data, for that I've used
``octave binary installed by fink on macosx 10.3.5 on an ibook G4 1GHz (
``256 Mo RAM). It turns out that computing fft( my_data ) takes about 15
``sec when my_data is a 500K floats vector (timed by tic() ; fft () ;
``toc() ). With a 1M floats vector, the time jumps to 6000 sec !
``Do anybody know if this is the intended behavior ? ( I don't know a
``word about fft algorythms )
`

`I'm sorry I can't provide more info about octave's build options than
``it's current fink version.
`

`Do anybody know how I can get a "faster" result ? Building octave with
``proper math libraries ? Which one ? It seems to me that building octave
``from source on osx is not trivial (I've failed with fink, darwinports
``and manually with versions 2.1.57 , 2.1.59 and 2.1.60), btw, is it
``worth reporting such build failures ?
`

`I'm in trouble because I *need* those fft's but I can't give the
``computer around 100 x 6000 sec just for tha :( .
`
Any idea / pointer / help would be greatly apreciated. Thanks.
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**Speed concerns with fft**,
*Sébastien Maerten* **<=**