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RE: Octave 3.0
From: |
Schloegl Alois |
Subject: |
RE: Octave 3.0 |
Date: |
Fri, 28 Feb 2003 05:40:53 -0600 |
User-agent: |
Internet Messaging Program (IMP) 4.0-cvs |
Zitat von Andy Adler <address@hidden>:
> On Wed, 26 Feb 2003, Schloegl Alois wrote:
> > * Sparse matrices:
> > An important issue is the matrix multiplication of full and sparse
> matrices.
> > See the following example:
> >
> > x = [-inf, -1, 0, 1, inf,nan];
> > sx= sparse(x);
> > full(x'*x)
> > full(sx'*sx)
> >
> > The point is that under some circumstances (0*inf, 0*-inf, 0*nan), matrix
> > multiplications of full and sparse matrices give different results.
> > SPARSE can be used to control the desired behavior. Therefore, SPARSE is
> > important and, currently, there is no workaround. IMHO, SPARSE has top
> > priority.
>
> Have you looked at the sparse matrix functions in octave-forge?
> Are there any specific features lacking in that package?
>
> Andy
Andy,
I was referring to John's priority list. IMO, it is a good thing, if sparse
arrays become part of core octave.
Unfortunately, I've only access to some outdated versions of Octave (2.1.40),
without a recent version of octave-forge. Hence, I can not say whether I miss a
specific feature in your sparse package. Only, the following example should
return the result below:
x = [-inf, -1, 0, 1, inf,nan];
sx= sparse(x);
full(x'*x)
full(sx'*sx)
ans =
Inf Inf NaN -Inf -Inf NaN
Inf 1 0 -1 -Inf NaN
NaN 0 0 0 NaN NaN
-Inf -1 0 1 Inf NaN
-Inf -Inf NaN Inf Inf NaN
NaN NaN NaN NaN NaN NaN
ans =
Inf Inf 0 -Inf -Inf NaN
Inf 1 0 -1 -Inf NaN
0 0 0 0 0 0
-Inf -1 0 1 Inf NaN
-Inf -Inf 0 Inf Inf NaN
NaN NaN 0 NaN NaN NaN
Alois
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