[petsc-users] GPU implementation of serial smoothers

[Mark Lohry]

>
> Is DILU a point-block method? We have -pc_type pbjacobi (and vpbjacobi if
> the node size is not uniform). The are good choices for scale-resolving CFD
> on GPUs.
>

I was hoping you'd know :)  pbjacobi is underperforming ilu by a pretty
wide margin on some of the systems i'm looking at.

We don't have colored smoothers currently in PETSc.
>

So what happens under the hood when I run -mg_levels_pc_type sor on GPU?
Are you actually decomposing the matrix into lower and computing updates
with matrix multiplications? Or is it just the standard serial algorithm
with thread safety ignored?

On Tue, Jan 10, 2023 at 1:52 PM Barry Smith <bsmith at petsc.dev> wrote:

>
>   We don't have colored smoothers currently in PETSc.
>
> > On Jan 10, 2023, at 12:56 PM, Jed Brown <jed at jedbrown.org> wrote:
> >
> > Is DILU a point-block method? We have -pc_type pbjacobi (and vpbjacobi
> if the node size is not uniform). The are good choices for scale-resolving
> CFD on GPUs.
> >
> > Mark Lohry <mlohry at gmail.com> writes:
> >
> >> I'm running GAMG with CUDA, and I'm wondering how the nominally serial
> >> smoother algorithms are implemented on GPU? Specifically SOR/GS and
> ILU(0)
> >> -- in e.g. AMGx these are applied by first creating a coloring, and the
> >> smoother passes are done color by color. Is this how it's done in petsc
> AMG?
> >>
> >> Tangential, AMGx and OpenFOAM offer something called "DILU", diagonal
> ILU.
> >> Is there an equivalent in petsc?
> >>
> >> Thanks,
> >> Mark
>
>
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