[petsc-users] Matrix format mpiaij does not have a built-in PETSc XXX!

[Matthew Knepley]

On Sun, Feb 26, 2012 at 10:48 AM, Max Rudolph <maxwellr at gmail.com> wrote:

> MPIAIJ and SEQQIJ matrices are subtypes of the AIJ matrix type. Looking at
> that table, you should be able to use any of the PCs that supports AIJ and
> has an X under 'parallel'.


Max is correct. For instance, the most popular general purpose parallel
solver is ASM (Additive Schwarz Method), which then
has a sequential subsolver for each block, which defaults to ILU.

   Matt


> Max
>
>
> On Sun, Feb 26, 2012 at 8:16 AM, Aron Roland <aaronroland at gmx.de> wrote:
>
>> Dear All,
>>
>> I hope somebody can help us on this or give at least some clearance.
>>
>> We have just included PETSc as an solver for our sparse matrix evolving
>> from an unstructured mesh advection scheme.
>>
>> The problem is that we are using the mpiaij matrix type, since our matrix
>> is naturally sparse. However it seems that PETSc has no PC for this, except
>> the PCSOR, which showed to be not very effective for our problem.
>>
>> All others give the error msg. of the mail subject, where XXX are the
>> different PC tried.
>>
>> The manual is a bit diffuse on this e.g.
>>
>> http://www.mcs.anl.gov/petsc/**documentation/**linearsolvertable.html<http://www.mcs.anl.gov/petsc/documentation/linearsolvertable.html>
>>
>> it is claimed that certain PC's are running on aij matrices ... but these
>> are to be defined either as seq. or parallel (mpiaij) matrices. Moreover in
>> the above mentioned list are two columns parallel/seriel, what is the
>> intention of parallel capability when not applicable to matrices stored
>> within the parallel mpiaij framework.
>>
>> I guess we just not understanding the concept or have some other
>> difficulties of understanding of all this.
>>
>> Any comments help is welcome
>>
>> Aron
>>
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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