[Pkg-octave-devel] Bug#295395: [OctDev] [dnj@x.dtu.dk: octave-forge: Replacing a submatrix of a sparse matrix results in a full matrix]

[David Bateman <David.Bateman@motorola.com>]

Rafael Laboissiere wrote:

> package octave-forge
> tags 295395 upstream
> forwarded 295395 octave-dev@lists.sourceforge.net
> thanks
>
> ----- Forwarded message from Dennis Jørgensen <dnj@x.dtu.dk> -----
>
> From: Dennis Jørgensen <dnj@x.dtu.dk>
> Subject: octave-forge: Replacing a submatrix of a sparse matrix results in a full
> matrix
> Date: Tue, 15 Feb 2005 16:28:50 +0100
> To: Debian Bug Tracking System <submit@bugs.debian.org>
>
> Package: octave-forge
> Version: 2004.11.16-3
> Severity: normal
>
>
> With the following commands, I would have expected matrix A to
> stay sparse:
>
> octave:1> A = sparse(4,4);
> octave:2> A([1 2 4],[1 2 4]) = sprand(3,3,0.2);
> octave:3> issparse(A)
> ans = 0
>
>
> Same commands in Matlab:
>
>
>  
>
> > > A = sparse(4,4);     
> > > A([1 2 4],[1 2 4]) = sprand(3,3,0.2);
> > > issparse(A)
> > >      
>
> ans =
>
>     1
>
>
> Replacing sprand() with something returning a full matrix yields
> the same results: sparse 'A' in Matlab, full in Octave.
>
>
>
> Regards,
>
>
>  Dennis J??rgensen
>  

Yes, I know. This is what made me start writing the sparse matrix patch 
that is currently in the unstable CVS of octave. I started to write a 
patch to the assign functions for the sparse matrix code and quickly 
found myself with 2,000 lines of code, and felt if I was going to do 
that, that I might as well replace the whole thing. The good news is as 
this was the problem that made me start writing this code, the assign 
behaviour of the sparse matrices in the unstable octave CVS work as you 
would expect.... Downside, is that I don't expect a patch for the 
octave-forge version of the sparse matrix code, as it is completely 
superseded by the version in octave itself..

D.