[petsc-dev] future pull request about multipreconditioned solvers

[Pierre Gosselet]

Thank you Lawrence,
sorry for my mistake.

Maybe the "Pull Request" explanation in 
https://bitbucket.org/petsc/petsc/wiki/pull-request-instructions-git
should not link to https://bitbucket.org/petsc/petsc/pull-request/new

I hope reviewers will find some interest in our proposal.

Best regards
pierre

Le mardi 11 juin 2019 à 15:00 +0100, Lawrence Mitchell a écrit :
> Pierre,
> 
> did you attempt to open the pull request in bitbucket.org/petsc/petsc
> (not allowed unless you have petsc write access), or in your fork
> (allowed, and you can target at petsc/petsc master)?
> 
> Lawrence
> 
> > On 11 Jun 2019, at 14:55, Smith, Barry F. via petsc-dev <
> > petsc-dev at mcs.anl.gov> wrote:
> > 
> > 
> >  Hmm, I can't explain this. Just a guess did you make a new branch
> > with its own name or just work in master? I don't think it should
> > matter but could you try making a branch not called master if yours
> > is called master.
> > 
> > 
> > > On Jun 11, 2019, at 7:39 AM, Pierre Gosselet <
> > > gosselet at lmt.ens-cachan.fr> wrote:
> > > 
> > > Dear Barry, 
> > > I have done all the steps described in 
> > > https://bitbucket.org/petsc/petsc/wiki/pull-request-instructions-git
> > > unfortunately, when I click on "create pull request",
> > > I get a "access denied" page.
> > > 
> > > My branch gosselet/multiprecond can be found here: 
> > > https://bitbucket.org/pierre_gosselet/petscfork/src/master/
> > > 
> > > Best regards
> > > pierre
> > > 
> > > Le vendredi 07 juin 2019 à 17:58 +0000, Smith, Barry F. a écrit :
> > > > Pierre,
> > > > 
> > > >  Thanks for your generous offer. Maybe you could point us to a
> > > > repository with the branch with your additions so we could take
> > > > a
> > > > look at it and see how it could be adopted into PETSc?
> > > > 
> > > >  Barry
> > > > 
> > > > 
> > > > > On Jun 7, 2019, at 11:07 AM, Pierre Gosselet via petsc-dev <
> > > > > petsc-dev at mcs.anl.gov> wrote:
> > > > > 
> > > > > Dear Petsc developers,
> > > > > 
> > > > > I am Pierre Gosselet, researcher in computational mechanics
> > > > > from
> > > > > France
> > > > > (ENS Paris Saclay / Univ. Lille). Lately I have been working
> > > > > on
> > > > > multipreconditioned solvers arising from domain decomposition
> > > > > (DD).
> > > > > I have co-authored some papers with Nicole Spillane whom you
> > > > > probably know.
> > > > > 
> > > > > Together with Nicolas Tardieu from EDF we have done some
> > > > > developments
> > > > > in PetSc and we would be happy to share them. Nicolas told me
> > > > > I had
> > > > > better send you a short notice before making a pull request.
> > > > > 
> > > > > We have implemented a MultiPreconditioned Conjugate Gradients
> > > > > solver
> > > > > for the SPD case and a MultiPreconditioned Orthomin solver
> > > > > for
> > > > > general
> > > > > matrices.
> > > > > 
> > > > > These solvers rely on a method with signature 
> > > > > PCApplyMultiPrecond(PC, Vec in, Mat out) 
> > > > > We proposed an implementation of this method in the
> > > > > (Restrictive)
> > > > > Additive Schwarz (R)ASM framework:
> > > > > PCApplyMultiPrecond_ASM(...). 
> > > > > When preconditioning, each subdomain provides a column which
> > > > > is
> > > > > used to
> > > > > expand the search space. There is an experimental use of the
> > > > > information in NearNullSpace in order to speed up the
> > > > > convergence
> > > > > (ersatz of Nicholaides' two-level (R)ASM).
> > > > > 
> > > > > In practice, there are new files for the solvers (mpcg.c and
> > > > > mpomin.c),
> > > > > some features were added in asm.c, and there are few lines
> > > > > added
> > > > > in  other files in order to declare the solvers. We tried to
> > > > > make a
> > > > > nice implementation and integration, but we would be happy to
> > > > > have
> > > > > our
> > > > > code reviewed for better performance. 
> > > > > 
> > > > > 
> > > > > Unfortunately, from the very limited numerical experiments
> > > > > that we
> > > > > have
> > > > > conducted, we do not have tremendous examples to show, the
> > > > > extra
> > > > > costs
> > > > > associated with multipreconditioning are not always
> > > > > compensated by
> > > > > the
> > > > > improved convergence. In fact, it appears that
> > > > > multipreconditioned
> > > > > solvers do not behave as well in the (R)ASM framework as in
> > > > > other
> > > > > DD
> > > > > frameworks, like FETI(DP) or BDD(C), where the spectrum has a
> > > > > more
> > > > > favorable shape and where adaptive strategies are available.
> > > > > 
> > > > > Anyhow our developments offer opportunities to test mpcg and
> > > > > mpomin, to
> > > > > implement new multipreconditioned solvers and new
> > > > > multipreconditioning
> > > > > frameworks (one just need to implement
> > > > > PCApplyMultiPrecond_???).
> > > > > 
> > > > > I hope you will be interested by these developments,
> > > > > best regards
> > > > > pierre
> > > > > 
> > > > > 
> > > > > -- 
> > > > > Pierre Gosselet
> > > > > CR CNRS (research agent) 
> > > > > LMT -- ENS Paris-Saclay/UMR8535
> > > > > 61 av. du président Wilson, 94235 CACHAN
> > > > > tel: +33 1 47405333
> > > > > 
> > > -- 
> > > Pierre Gosselet
> > > CR CNRS (research agent) 
> > > LMT -- ENS Paris-Saclay/UMR8535
> > > 61 av. du président Wilson, 94235 CACHAN
> > > tel: +33 1 47405333
> > > 
-- 
Pierre Gosselet
CR CNRS (research agent) 
LMT -- ENS Paris-Saclay/UMR8535
61 av. du président Wilson, 94235 CACHAN
tel: +33 1 47405333