[petsc-dev] plans for preconditioners for SeqSELL

[Matthew Knepley]

On Sun, Mar 4, 2018 at 6:57 PM, Jed Brown <jed at jedbrown.org> wrote:

> "Zhang, Hong" <hongzhang at anl.gov> writes:
>
> > We have thought about subclassing long before. As Barry suggested, an
> > ideal solution is to make a base class (XAIJ ?) for AIJ, BAIJ, SBAIJ,
> > and SELL. The base class will have diagonal and off diagonal parts
> > without binding their storage format to CSR-type. This requires a lot
> > of efforts to refactor the current AIJ. But I think we should
> > eventually do it.
>
> It sounds like we're mixing the concerns of parallel decomposition (for
> which "Seq*" isn't relevant) with the sequential format as some CSR-like
> variant.  And apart from a couple abstraction-breaking performance
> optimizations (that may not be necessary and could be done differently),
> they are nearly independent.
>
> Now there are some good reasons why we might want SeqAIJ to run inside a
> different parallel decomposition.  MATIS is one such format.  If we're
> serious about working with irregular problems, we'll eventually need a
> 2D sparse decomposition.  We could get it from an existing package such
> as CombBLAS, but if we do preconditioners that depend on matrix format,
> we'll likely want it to work on some native format.
>
> Also, we need a better way to do small-size specialization.  I
> personally like doing it via inline functions instead of macros and
> copy-pasta, though the XL compiler can be offensively negligent.
>

I have missed the larger point. What do you think should be done?

   Matt

-- 
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.caam.rice.edu/~mk51/>
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