[petsc-dev] future pull request about multipreconditioned solvers

[Pierre Gosselet]

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