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From: ImageAnalyst <imageanalyst@mailinator.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: conv2 in R2008b very slow
Date: Fri, 26 Dec 2008 09:23:45 -0800 (PST)
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On Dec 26, 11:16=A0am, "Andreas Sprenger" <sprenge...@yahoo.de> wrote:
> "Matt" <mjacobson.removet...@xorantech.com> wrote in message <gj2o8i$pu..=
.@fred.mathworks.com>...
> > > 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 0.0=
18 sec.
>
> > But if so, what kind of machine are you using?
>
> Concerning my computer: Core2Duo E6600 (2x2.4 GHz), 2GB RAM, NVIDIA Gefor=
ce 7600 GS and Quadro NVS 290, WinXP Prof.
>
> I did one more test. On my computer I have three versions currently insta=
lled and got the following calculation times:
>
> Matlab 7.0.0.19920: 0.016000 s
> Matlab 7.6.0.324: 0.019018 s
> Matlab 7.7.0.471: 17.730552 s
>
> I subtracted those three results one another: no differences, all are the=
 same (sum(sum(abs(A - B))). I'm really interested in what's the reason for=
 this big difference in calculation speed.
>
> In the lab we have some older PCs with single user licenses running ML 6.=
0 and 6.5. I could check the calculation times on these machines in a few d=
ays...
>
> Andreas

--------------------------------------------------------
Andreas:
I tried an interesting experiment, after wondering if it had something
to do with the routine checking to see if the kernel were separable
and then trying to make some kind of optimization.  I replaced the
kernel F with just an array of random numbers - the same size 23x180.
Well when I did that:
R2008a: 0.02 seconds
R2008b: 3.46 seconds
Now the latest version is only about 173 times slower.  If I use conv2
with the 'full' option, I get the same times as with the 'same'
option.
Regards,
ImageAnalyst