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Re: Zero or not?
From: |
Miroslaw Kwasniak |
Subject: |
Re: Zero or not? |
Date: |
Mon, 23 Jul 2007 23:10:53 +0200 |
User-agent: |
Mutt/1.5.9i |
On Mon, Jul 23, 2007 at 12:22:33PM -0400, James Sherman Jr. wrote:
> You asked for the maximum error that could happen. And if you actually
> compare Francesco's estimate and mine, his is actually lower (I am not
> saying that mine is correct, again I am not an expert). Also note that what
> Przemek says in his mail. This really isn't an Octave thing, but floating
> point calculations in general.
... and octave (I assume) does sum in standard, quickest way.
> Stuff like sorting numbers by absolute value
> can help reduce the error of the operations.
This is one of methods of improvment in precission. But is very costly :(
I made this method in one program twenty years ago ;)
I can be done in octave in a simplest way:
[i,i]=sort(abs(x)); s=sum(x(i));
But last year I read one article (title&author forgotten) that there isn't
one method that wins in FP sum precission :(
I've read either that typical FFT gives (statistically) smaller error then
simple DFT - it's an effect of its butterfly summation.
- Zero or not?, Matthias Brennwald, 2007/07/21
- Re: Zero or not?, Jordi GutiƩrrez Hermoso, 2007/07/21
- Re: Zero or not?, Matthias Brennwald, 2007/07/21
- Re: Zero or not?, Ben Abbott, 2007/07/21
- Re: Zero or not?, Matthias Brennwald, 2007/07/22
- Re: Zero or not?, James Sherman Jr., 2007/07/22
- Re: Zero or not?, Matthias Brennwald, 2007/07/23
- Re: Zero or not?, Francesco Potorti`, 2007/07/23
- Re: Zero or not?, James Sherman Jr., 2007/07/23
- Re: Zero or not?,
Miroslaw Kwasniak <=
- Re: Zero or not?, Francesco Potorti`, 2007/07/24
- Re: Zero or not?, kensmith, 2007/07/24
- Re: Zero or not?, Przemek Klosowski, 2007/07/24
- Re: Zero or not?, kensmith, 2007/07/24
- Re: Zero or not?, Francesco Potorti`, 2007/07/22
- Re: Zero or not?, Miroslaw Kwasniak, 2007/07/23
- Re: Zero or not?, Francesco Potorti`, 2007/07/23
- Re: Zero or not?, kensmith, 2007/07/23
- Re: Zero or not?, Przemek Klosowski, 2007/07/23
- Re: Zero or not?, Robert A. Macy, 2007/07/21