[petsc-dev] plans for preconditioners for SeqSELL

[Richard Tran Mills]

On Wed, Feb 14, 2018 at 6:15 PM, Jed Brown <jed at jedbrown.org> wrote:

> Richard Tran Mills <rtmills at anl.gov> writes:
>
> > On Tue, Feb 13, 2018 at 8:48 PM, Jed Brown <jed at jedbrown.org> wrote:
> >
> >> Richard Tran Mills <rtmills at anl.gov> writes:
> >>
> >> > I haven't experimented very thoroughly with it (hmm... should
> probably do
> >> > such experiments), but I believe that, once matrix rows become
> >> sufficiently
> >> > long, then SELL doesn't provide an advantage over AIJ.
> >>
> >> What is the performance model that explains why SELL doesn't benefit
> >> from long rows?  It's clear for large blocks where BAIJ can be compiled
> >> to vectorized loads and stores, but much less clear when AIJ is
> >> producing basically scalar code.
> >>
> >
> > Hmm. I may be mistaken in my statements about long rows and AIJ -- I
> think
> > it might be the case that every matrix with long rows for which I've seen
> > the decent performance with AIJ was something that uses and benefits from
> > the Inode versions of the routines.
>
> Have you tested that Inodes are an improvement?  I've seen the opposite
> (by about 5%) on some recent Intel.
>

I have not tested this. I should give this a try and look into what is
going on, either way.

--Richard
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