[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Problems with FFT and IFFT
From: |
Dmitri A. Sergatskov |
Subject: |
Re: Problems with FFT and IFFT |
Date: |
Tue, 28 Feb 2006 10:25:11 -0700 |
On 2/28/06, John W. Eaton <address@hidden> wrote:
> On 28-Feb-2006, Keith Goodman wrote:
>
> | Here's what I get (no imaginary part; I get the same result in 2.1.72):
> |
> | $ octave
> | Octave 2.9.4 Forge 20050613
> | >> fs = 0:0.1:10;
> | >> x = sin(2*pi*fs);
> | >> real(x)
>
> What kind of hardware? I see imaginary parts, but all less than eps.
> Perhaps due to extra internal precision of amd64/x86 floating point
> hardware? Also, I am using fftw, are you? Try
>
> octave_config_info ("FFTW_LIBS")
>
> to see.
>
> In any case, while it might be nice to understand where the
> differences are coming from, I don't think this is a bug.
max(imag(x2) on Athlon64 is 2x as big:
octave:6> max(imag(x2))
ans = 2.57566273587379e-16
that is slightly larger than eps
octave:7> eps
eps = 2.22044604925031e-16
Is not Matlab using (hacked) fftw2 (while octave is using fftw3)?
>
> jwe
>
Dmitri.
--
-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.
Octave's home on the web: http://www.octave.org
How to fund new projects: http://www.octave.org/funding.html
Subscription information: http://www.octave.org/archive.html
-------------------------------------------------------------
- Problems with FFT and IFFT, Sascha Berkenkamp, 2006/02/28
- Re: Problems with FFT and IFFT, Keith Goodman, 2006/02/28
- Re: Problems with FFT and IFFT, Keith Goodman, 2006/02/28
- Re: Problems with FFT and IFFT, John W. Eaton, 2006/02/28
- Re: Problems with FFT and IFFT,
Dmitri A. Sergatskov <=
- Re: Problems with FFT and IFFT, Sascha Berkenkamp, 2006/02/28
- Re: Problems with FFT and IFFT, John W. Eaton, 2006/02/28
- Re: Problems with FFT and IFFT, Joe Koski, 2006/02/28
- Re: Problems with FFT and IFFT, Quentin Spencer, 2006/02/28
- Re: Problems with FFT and IFFT, Joe Koski, 2006/02/28
- Re: Problems with FFT and IFFT, Bill Denney, 2006/02/28
- Re: Problems with FFT and IFFT, Steve C. Thompson, 2006/02/28
- RE: Problems with FFT and IFFT, Frank Palazzolo, 2006/02/28
Re: Problems with FFT and IFFT, Joe Koski, 2006/02/28