Re: ASCII file format for sparse matrices?

[Rui Maciel]

On 05/12/2011 09:50 PM, Jordi Gutiérrez Hermoso wrote:
> On 12 May 2011 15:33, Rui Maciel<address@hidden>  wrote:
> > Does Octave support any ASCII file format to import/export sparse matrices?
> Yes, it's the default format. Try
>
>       x = sprand(5,5,0.2)
>       save x x
>
> and you can now inspect in an editor file named "x" to see how Octave saved it

Thanks for the help, Jordi.  I've ran your example and a file was saved 
in a "dictionary of keys" sort of format.  Nice.

Yet, I've stumbled on what appears to be a problem.  Although the file 
format appears to follow the "dictionary of keys" format, the input 
routine fails to successfully import any matrix whose coefficients 
aren't ordered according to the compressed column format.  So, for 
example, considering the following random matrix generated by octave:

# Created by Octave 3.2.4, Fri May 13 02:09:48 2011 WEST <address@hidden>
# name: K
# type: sparse matrix
# nnz: 6
# rows: 5
# columns: 5
2 1 0.6120845834944717
2 2 0.5161747681939882
4 2 0.9411864619881111
2 3 0.5464955826864553
2 5 0.6005530554138011
4 5 0.8149565265346684

And now, if the fields are reordered in the compressed row order:

# Created by Octave 3.2.4, Fri May 13 02:09:48 2011 WEST <address@hidden>
# name: K
# type: sparse matrix
# nnz: 6
# rows: 5
# columns: 5
2 1 0.6120845834944717
2 2 0.5161747681939882
2 3 0.5464955826864553
2 5 0.6005530554138011
4 2 0.9411864619881111
4 5 0.8149565265346684



If that file is loaded into octave, octave only manages to generate the 
following matrix.

# Created by Octave 3.2.4, Fri May 13 02:12:02 2011 WEST <address@hidden>
# name: K
# type: sparse matrix
# nnz: 6
# rows: 5
# columns: 5
2 1 0.6120845834944717
2 2 0.5161747681939882
2 2 0.5464955826864553
2 2 0.6005530554138011
4 2 0.9411864619881111
4 5 0.8149565265346684


So, does this file format only support compressed-column format ordering 
or is there a bug with the file importing routine?


Thanks in advance,
Rui Maciel