[SciPy-dev] petsc - UMFPACK and scipy

Nils Wagner nwagner@iam.uni-stuttgart...
Fri Apr 13 07:36:48 CDT 2007


Robert Cimrman wrote:
> Ondrej Certik wrote:
>   
>> On 4/13/07, Robert Cimrman <cimrman3@ntc.zcu.cz> wrote:
>>     
>>> Nils Wagner wrote:
>>>       
>>>> Please can you show me an example where petsc solvers are "better" than
>>>> UMFPACK.
>>>>         
>>> Petsc is really a superpackage providing many parallel linear solvers
>>> (iterative, direct, preconditioners, ...) together with nonlinear
>>> solvers, time steppers, etc. The solvers can be both petsc-native or
>>> external packages, nevertheless all are accessed via a uniform
>>> interface. IMHO UMFPACK is one of the optional external solvers petsc
>>> can use, so to answer your question, petsc can do anything that UMFPACK
>>> does and much more.
>>>       
>> Yes, it's exactly like this. Thus, there is a question whether SciPy
>> should support sparse solvers (my answer is yes) and if so, then it
>> should support petsc, otherwise, for example me, I am not going to use
>> it, as I want to try several solvers according to the problem.
>>     
>
> My problems tend to be such that only a direct solvers work :)
>
>   
>> What I am trying to say is that I don't want to write two versions of
>> my code - one for petsc and second one for SciPy. And from the zen of
>> python:
>>
>> There should be one-- and preferably only one --obvious way to do it.
>>     
>
> Well, you can use very well both petsc and scipy/numpy together. afaik
> petsc4py depends on numpy, so this you need in any case, and scipy is a
> set of very useful modules built on top of numpy (particularly its
> multidimensional array data type), addressing different fields of
> (scientific) computation, not just solving linear systems. It is true
> that the sparse matrix support in scipy is not as mature as some users
> need, but this can change :). So for now, you can use petsc (or <put
> your favourite sparse matrix package here>) for sparse stuff if you
> like, and scipy for other things that are not in petsc.
> There is no contradiction, imho.
>
> Just my 2kc,
>
> r.
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>   
Unfortunately petsc4py has no tutorial.
http://www.cimec.org.ar/python/petsc4py.html#tutorial

I guess that many users prefer well documented packages.

Nils
 


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