[SciPy-user] 2 more sparse questions

Ed Schofield schofield at ftw.at
Tue Aug 1 04:05:25 CDT 2006

[CC to list]

William Hunter wrote:
> Ed;
> I'm still chipping away at this, ... <snip>
> Thought I'd respond off-list as it might be too specific, but I'll add
> it to the scipy wiki once I've figured it out.
> System: {U} = [K]{F}
> Q1) For a sparse symmetric banded K, and an extremely sparse F (one to
> five entries in a vector of length > 1200), what is the best solver to
> use?
I don't know. SciPy only has wrappers for SuperLU and UMFPACK, so I
suggest you read the documentation for those (e.g.
to find out what cases the routines are designed to handle. If you need
something more specialized, try Roman Geus's PySparse. It's not yet been
ported from Numeric to NumPy, although I did port the basic matrix
objects a while ago (in the SciPy sandbox), and that went fine. And
there's Tim Davis's CSparse
(http://www.cise.ufl.edu/research/sparse/CSparse/), which could be
wrapped with ctypes ...

Perhaps Robert Cimrman can give you more specific advice ... he wrote
the UMFPACK wrapper and knows more about sparse solvers than I do.

> Q2) At the moment I'm just using linsolve.spsolve, but I also see that
> there is a linsolve.splu. No docstring, obviously LU factorisation, but
> what does one use then?
> I'll create an example 3 demonstrating the use.

Yeah, we need a docstring for this. I've never used it before either.
But it's a wrapper for the SuperLU factorization functions like
dgstrf(), and you could figure it out by reading the source and the
SuperLU docs. If you could contribute a docstring I'd be very happy to
commit it :)

-- Ed

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