[petsc-dev] plans for preconditioners for SeqSELL

[Smith, Barry F.]

> On Feb 12, 2018, at 10:25 AM, Stefano Zampini <stefano.zampini at gmail.com> wrote:
> 
> Barry,
> 
> for sure Amat,Pmat is the right approach; however, with complicated user codes, we are not always in control of having a different Jacobian matrix.
> Since Mat*SELL does not currently support any preconditioning except PCSOR and PCJACOBI, we ask the user to put codes like 
> 
> if (type is SELL)
>  create two matrices (and maybe modify the code in many other parts)
> else
>   ok with the previous code

   I don't disagree with what you are saying and am not opposed to the proposed work.

   Perhaps we need to do a better job with making the mat,pmat approach simpler or better documented so more people use it naturally in their applications.

    Barry

> 
> Just my two cents.
> 
> 
> 2018-02-12 19:10 GMT+03:00 Smith, Barry F. <bsmith at mcs.anl.gov>:
> 
> 
> > On Feb 12, 2018, at 9:59 AM, Stefano Zampini <stefano.zampini at gmail.com> wrote:
> >
> > FYI, I just checked and MatSOR_*SELL does not use any vectorized instruction.
> > Why just not converting to SeqAIJ, factor and then use the AIJ implementation for MatSolve for the moment?
> 
>   Why not use the mat, pmat feature of the solvers to pass in both matrices and have the solvers handle using two formats simultaneously instead of burdening the MatSELL code with tons of special code for automatically converting to AIJ for solvers etc?
> 
> 
> >
> > 2018-02-12 18:06 GMT+03:00 Stefano Zampini <stefano.zampini at gmail.com>:
> >
> >
> > 2018-02-12 17:36 GMT+03:00 Jed Brown <jed at jedbrown.org>:
> > Karl Rupp <rupp at iue.tuwien.ac.at> writes:
> >
> > > Hi Stefano,
> > >
> > >> Is there any plan to write code for native ILU/ICC etc for SeqSELL, at least to have BJACOBI in parallel?
> > >
> > > (imho) ILU/ICC is a pain to do with SeqSELL. Point-Jacobi should be
> > > possible, yes. SELL is really just tailored to MatMults and a pain for
> > > anything that is not very similar to a MatMult...
> >
> > There is already MatSOR_*SELL.  MatSolve_SeqSELL wouldn't be any harder.
> > I think it would be acceptable to convert to SeqAIJ, factor, and convert
> > the factors back to SELL.
> >
> > Yes, this was my idea. Today I have started coding something. I'll push the branch whenever I have anything working
> >
> >
> >
> > --
> > Stefano
> >
> >
> >
> > --
> > Stefano
> 
> 
> 
> 
> -- 
> Stefano