[petsc-dev] Performance of Petsc Cholesky vs LU

[Matthew Knepley]

On Wed, Nov 30, 2011 at 3:10 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> On Nov 30, 2011, at 2:07 PM, Jed Brown wrote:
>
> > On Wed, Nov 30, 2011 at 14:04, Barry Smith <bsmith at mcs.anl.gov> wrote:
> > Ok, so how can we resolve this? The problem is that the default ordering
> is set when the PCCreate_Cholesky() and is set to be natural in order "to
> be safe" if sbaij matrix is used. We could change it to default to ND and
> then when PCSetUp_Cholesky() is called simply set the ordering to natural
> if it is a sbaij matrix. Kind of a hack but what do you suggest that
> doesn't involve tracking some other variable indicating if the user has set
> the ordering type to something else ...
> >
> > Why the hell set it so soon? This is like choosing which side/norm to
> use in a Krylov method. Make the decision lazily (when it is requested or
> needed to do something), otherwise leave it undefined.
>
>   There is currently no MatOrdering object nor MatColoring object one
> simply calls MatGetOrdering with an MatOrderingType and MatGetColoring with
> a MatColoringType.
>
>   These should both be totally refactored to match the paradigm of other
> PETSc objects; for example KSP  or MatPartitioning. Make a ticket in your
> cumbersome ticketing web interface :-)


Piling on: Make a ticket to make the DMDA HDF5 function respect timesteps
like the regular HDF5 output.

   Matt


>
>   Barry
>
>
>
>


-- 
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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