Path: news.mathworks.com!not-for-mail
From: "Bruno Luong" <b.luong@fogale.findmycountry>
Newsgroups: comp.soft-sys.matlab
Subject: Re: overdetermenied system
Date: Tue, 13 Jan 2009 14:40:20 +0000 (UTC)
Organization: FOGALE nanotech
Lines: 10
Message-ID: <gki94k$3qh$1@fred.mathworks.com>
References: <gkhurv$nv1$1@fred.mathworks.com> <gki4hq$1b9$1@fred.mathworks.com> <gki6bu$6j$1@fred.mathworks.com> <gki89q$85e$1@fred.mathworks.com>
Reply-To: "Bruno Luong" <b.luong@fogale.findmycountry>
NNTP-Posting-Host: webapp-02-blr.mathworks.com
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 8bit
X-Trace: fred.mathworks.com 1231857620 3921 172.30.248.37 (13 Jan 2009 14:40:20 GMT)
X-Complaints-To: news@mathworks.com
NNTP-Posting-Date: Tue, 13 Jan 2009 14:40:20 +0000 (UTC)
X-Newsreader: MATLAB Central Newsreader 390839
Xref: news.mathworks.com comp.soft-sys.matlab:511190

"Roger Stafford" <ellieandrogerxyzzy@mindspring.com.invalid> wrote in message <gki89q$85e$1@fred.mathworks.com>...

> 
>   I'm not so sure about its efficiency, though, as opposed to 512*384 individual 4x2 backslashes.  The single block diagonal backslash would have to be smart enough not to waste significant overhead time on all the implied zero "off-diagonals".  The solution to a single 4x2 problem should be very fast, especially if one writes it out as an explicit vectorized expression in terms of the four basic arithmetic operations without using matlab's backslash operator itself.

Roger,

Yes, "\" is smart enough. It is slighly faster than for-loop, see this thread that use the same trick: http://www.mathworks.de/matlabcentral/newsreader/view_thread/235989

Bruno