Re: indexed assignment for sparse matrices in ov-2.9.4

[David Bateman]

Thomas Kasper a écrit :

> Hi,
>
> I have a problem with indexed assignment for sparse matrices in
> octave-2.9.4. See below for an example:
>
> octave:1> version
> ans = 2.9.4
> octave:2> a = sparse(eye(3))
> a =
>
> Compressed Column Sparse (rows = 3, cols = 3, nnz = 3)
>
>   (1, 1) -> 1
>   (2, 2) -> 1
>   (3, 3) -> 1
>
> octave:3> a(:,[3,2,1]) = a
> a =
>
> Compressed Column Sparse (rows = 3, cols = 3, nnz = 3)
>
>   (1, 1) -> 1
>   (2, 2) -> 1
>   (3, 3) -> 1
Firstly, you should use speye(n) rather than sparse(eye(n)) as the full 
n-by-n matrix is created and then destroyed with the second form and 
this poses memory issues with large sparse matrices..

Yes this is a bug, and it has already been fixed in the CVS. With the 
current CVS I get

octave:4> a = speye(3)
a =

Compressed Column Sparse (rows = 3, cols = 3, nnz = 3)

 (1, 1) -> 1
 (2, 2) -> 1
 (3, 3) -> 1

octave:5> a(:,[3,2,1])
ans =

Compressed Column Sparse (rows = 3, cols = 3, nnz = 3)

 (3, 1) -> 1
 (2, 2) -> 1
 (1, 3) -> 1

Cheers
David



-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
-------------------------------------------------------------