[petsc-dev] MatComputeExplicitOperator

[Matthew Knepley]

On Fri, Apr 19, 2019 at 5:58 PM Smith, Barry F. via petsc-dev <
petsc-dev at mcs.anl.gov> wrote:

>
>
>    I think MPIAIJ was selected because it provided the most parallel
> functionality compared to MPIDENSE for which more operations were not
> written.
>    This may not be relevant any more.
>
>     Definitely the code needs to be fixed. Fixing MatConvert_Shell(); it
> should just assume
> the matrices are dense and preallocate for them.
>

We should restore preallocation. It should be easy to do with Preallocator.

  Matt


>    Barry
>
> > On Apr 19, 2019, at 3:07 PM, Stefano Zampini via petsc-dev <
> petsc-dev at mcs.anl.gov> wrote:
> >
> > What is the rationale behind MatComputeExplicitOperator returning
> SEQDENSE in sequential and MPIAIJ in parallel?
> >
> > Also, before commit
> https://bitbucket.org/petsc/petsc/commits/b3d09e869df0e6ebcb615ca876706bfed4fcf1cd
> full preallocation of the MPIAIJ matrix was happening. Now, if we have a
> very dense operator that we want to sample just for testing purposes
> (inspecting entries, etc..) we have to pay the price of reallocating over
> and over.
> >
> > What is the proper fix? 1) Use MPIDENSE? 2) Restore full preallocation
> for MPIAIJ? 3) Have MatComputeExplicitOperator to accept more arguments ?
> >
> > I'm in favor of 1
> >
> > --
> > Stefano
>
>

-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20190420/54583ffc/attachment.html>