[SciPy-dev] Introductions, sparse matrix support

[Ed Schofield]

Robert Cimrman wrote:

>>>I'd be happy to work with Jonathan, Dan, and Robert on sparse matrix 
>>>support in SciPy, integrating PySparse code with Travis and Robert's 
>>>UMFPACK wrapper.  Perhaps we could even find support among other 
>>>PySparse developers.  PySparse currently depends on Numeric, and will 
>>>need porting to SciPy Core eventually...
>>>      
>>>
>PySparse contains umfpack v4.1, right? Then if it is going to go into 
>scipy tree, having me wrapping v4.4 separately would be useless - we (me 
>if you like) could just update what already is in PySparse...
>
>We should settle first on the sparse matrix implementation to use and 
>then care about wrapping related solvers (who almost always use the 
>CSR/CSC format). I am keenly waiting on the benchmark results of 
>Jonathan and Dan... (hoping that some work remains for me on Monday (a 
>trip to Berlin tomorrow)).
>  
>
Yes, you're right, PySparse does contain UMFPACK 4.1.  It seems from the 
UMFPACK 4.4 change log that its API is backwardly compatible with 4.1, 
so perhaps updating PySparse won't require much more than merging the 
new UMFPACK source tree.

I suggest we adopt all three of PySparse's implementations: LL, CSR, and 
SSS.  LL (a simple linked list format) is particularly useful for its 
flexibility, and PySparse's UMFPACK wrapper uses LL matrices currently 
as its input format.  There might be an argument that SSS support isn't 
necessary, but it doesn't really get in the way, and removing it from 
PySparse would be more work than leaving it in.  I like the idea of 
keeping the patch set from upstream PySparse simple, limited to 
improving integration with SciPy (e.g. making dense and sparse matrices 
expose a similar interface for operations like matrix products and as 
iterables.)  And folding our patches back into PySparse will simplify 
the task.