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From: "Bruno Luong" <b.luong@fogale.findmycountry>
Newsgroups: comp.soft-sys.matlab
Subject: Re: size(sparse matrix) > size(full matrix)
Date: Thu, 17 Sep 2009 11:10:03 +0000 (UTC)
Organization: FOGALE nanotech
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Rune Allnor <allnor@tele.ntnu.no> wrote in message <a56978d9-99f2-4ff6-8073-a77ab61bb6d6@o21g2000vbl.googlegroups.com>...

> 
> Sparse matrices are not used to gain speed, but to save
> space. 

Wrong, many linear algebra algorithms are designed to gain speed with sparse matrix since Matrix-vector product is much faster than for full matrix. That lead to the class of iterative method (gradient conjugate, GMRES, Lanczos, etc...) that is suitable when working with sparse matrix. The full matrix is not even competitive, even for speed.

Bruno