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Re: [ts-7000] FFT very slow on TS-7260

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Subject: Re: [ts-7000] FFT very slow on TS-7260
From: "Daniel Serpell" <>
Date: Fri, 30 Nov 2007 15:21:02 -0300
Hi!

On Nov 30, 2007 6:36 AM, kurmannthomas <> wrote:
>
[...]
> Im going to check with another floating point FFT next week to see if
> its an FFTW3 problem, or really the TS-7260. My goal is to be able to
> calculate (up to) 9 FFTs with (up to) 16384 points in less than 1 or
> 2 seconds...a DSP would have no problem with this...

I made some benchmarks on this board, using a mix of 50% multiplications,
50% additions, and I'm getting:

Double precision, emulated float:  0.23 mega-ops/second (~870 cycles per op)
Double precision, soft-float:  2.0 mega-ops/second (~104 cycles per op)
Single precision, soft-float: 3.7 mega-ops/second (~54 cycles per op)

A split-radix FFT implementation uses 4N*log2(N)-6N+8 muls and adds,
so an 16384 point FFT will take a total of 1.6*10^6 operations, 50% muls
and 50% adds.

So, using single-precision, soft-float, you should get about two FFTs per
second, not counting filling the arrays, converting from int, etc.

I think you need a fixed-point implementation of the FFT.

    Daniel.


 
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