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From: "Andreas Sprenger" <sprenger_a@yahoo.de>
Newsgroups: comp.soft-sys.matlab
Subject: Re: conv2 in R2008b very slow
Date: Fri, 26 Dec 2008 15:55:03 +0000 (UTC)
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ImageAnalyst <imageanalyst@mailinator.com> wrote in message <64571b05-b09d-4d55-a8b5-a4921d84398e@s24g2000vbp.googlegroups.com>...
> On Dec 26, 9:04=A0am, "Matt" <mjacobson.removet...@xorantech.com> wrote:
> > > Andreas:
> > > Interesting question. =A0here are my times:
> > > % in R2008b: 21.170 seconds.
> > > % in R2008a: =A0 0.018 seconds.
> >
> > Did you check quantitative agreement between the results of each?
> > I just can't believe it's possible to do a convolution that size in 0.018=
>  sec.
> >
> > But if so, what kind of machine are you using?
> 
> ---------------------------------------------------------------------------=
> ------------
> Matt:
> I didn't.  I simply copied and pasted and didn't do much analysis or
> interpretation of results, other than simply noting the elapsed time
> in the command window.  I ran it on a Dell M90 notebook computer with
> a Intel Centrino Duo CPU and 4 GB of RAM.  Checking agreement would be
> the next step. I could write the array out to a mat file and then read
> it back in and subtract.  I haven't done this.  If you want, you can
> simply copy and paste this code into test.m (the customgauss from the
> fileexchange is included):

Ok, I calculated the two matrizes by 2008a and 2008b and subtracted them. The sum is zero, so the calculation is the same - but the computation time in 2008b is about 1000 times longer. Again: why?

Andreas

BTW: the calculation times were 0.019018 s in 2008a and 17.730552 in 2008b on a conventional PC with a Core2Duo Intel Processor, WinXP Prof, 2GB RAM, NVIDIA 7600 GS and Quadro NVS 290 graphic cards.