Path: news.mathworks.com!newsfeed-00.mathworks.com!nlpi057.nbdc.sbc.com!prodigy.net!news.glorb.com!news2!postnews.google.com!17g2000vbf.googlegroups.com!not-for-mail
From: ImageAnalyst <imageanalyst@mailinator.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: conv2 in R2008b very slow
Date: Thu, 25 Dec 2008 20:59:07 -0800 (PST)
Organization: http://groups.google.com
Lines: 39
Message-ID: <3762e938-71a0-46a1-9cd4-3a56fd62fe0f@17g2000vbf.googlegroups.com>
References: <gie3tb$qen$1@fred.mathworks.com>
NNTP-Posting-Host: 75.186.70.56
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
X-Trace: posting.google.com 1230267548 5877 127.0.0.1 (26 Dec 2008 04:59:08 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Fri, 26 Dec 2008 04:59:08 +0000 (UTC)
Complaints-To: groups-abuse@google.com
Injection-Info: 17g2000vbf.googlegroups.com; posting-host=75.186.70.56; 
	posting-account=0rLUzAkAAABojYSRC64DkTbtiSCX77HH
User-Agent: G2/1.0
X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET 
	CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 
	3.5.21022),gzip(gfe),gzip(gfe)
Xref: news.mathworks.com comp.soft-sys.matlab:508791


On Dec 18, 1:14=A0pm, "Andreas Sprenger" <sprenge...@yahoo.de> wrote:
> I just realized that conv2 is very slow in 2008b. I created a 2D filter b=
y
>
> GaussWidth =3D [23, 180];
> F =3D customgauss([GaussWidth(2), GaussWidth(2)], GaussWidth(1), GaussWid=
th(1), 0, 0, 1, [0 0]);
> % custumgauss -> see FileExchange
>
> % Array of zeros
> G1 =3D zeros(600, 1000);
>
> % Set one single point
> G1(300, 400) =3D 1.5;
>
> % in R2008a:
> tic; G2 =3D conv2(G1, F, 'same'); toc
>
> >> Elapsed time is 0.014846 seconds.
>
> % in R2008b:
> tic; G2 =3D conv2(G1, F, 'same'); toc
>
> >> Elapsed time is 17.831022 seconds.
>
> Same machine, no background activity, reproducable. Why?
>
> Andreas

-------------------------------------------------------------------------
Andreas:
Interesting question.  here are my times:
% in R2008b: 21.170 seconds.
% in R2008a:   0.018 seconds.
URL for customgauss:
http://www.mathworks.com/matlabcentral/fx_files/9556/1/customgauss.m
Maybe Steve Eddins can give an answer.
Regards,
ImageAnalyst