[SciPy-user] Obtaining factors of sparse matrices
Thu Apr 2 23:24:45 CDT 2009
On Fri, Apr 3, 2009 at 12:15 AM, <firstname.lastname@example.org> wrote:
> On Thu, Apr 2, 2009 at 11:02 PM, Bill Cochran <email@example.com> wrote:
>> I am new to scipy. I would like to compare fill-in between a standard GEPP and
>> one that I have developed to schedule pivoting in parallel codes. My matrices
>> are large and sparse. In MATLAB code, I need this:
>> [L,U] = lu ( A )
>> I have looked at the scipy documentation and I believe the function I am looking
>> for is sparse.linalg.splu (...). I do not know what permc_spec means. Neither
>> I nor Google know what a "factored_lu" object is. And I don't understand the
>> instruction: "See scipy.sparse.linalg.dsolve._superlu.dgstrf for more info."
>> Neither does Google.
> I'm just looking up the source, I don't know this part of scipy:
> the above means that the only documentation of the details is in the c source
> 144 permc_spec specifies the matrix ordering used for the
> 145 0: natural ordering\n\
> 146 1: MMD applied to the structure of A^T * A\n\
> 147 2: MMD applied to the structure of A^T + A\n\
> 148 3: COLAMD, approximate minimum degree column ordering\n\
> 149 (default: 2)\n\
> splu is just a thin wrapper around dgrstrf (for double), see
> if umfpack (scikits) is installed, than LU is calculated using umfpack
> That's browsing the source, for more info you need someone who knows
> this part. The return type of functions, I usually just inspect for an
> example dir(result), ...
>> Any help would be appreciated. I am kind of crunched for time and thought I'd
>> see if scipy lived up to the hype. Please help scipy live up to the hype.
just one more reference, I think this part of sparse linalg came from pysparse:
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