[petsc-users] PC HYPRE BoomerAMG options for nodal

[Bernardo Rocha]

Thanks a lot.
I'm going to change to the interlaced version. It is easier and more
efficient.
Best regards.
Bernardo

On Wed, Feb 15, 2017 at 12:07 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> > On Feb 14, 2017, at 7:57 PM, Bernardo Rocha <bernardomartinsrocha at gmail.
> com> wrote:
> >
> > No particular reason. Let's say it was the first approach I tried in an
> old code.
> >
> > OK, so to get it working I should use the interlaced version for the
> ordering of my dofs.
> > It does not require too much coding on my side.
> >
> > Just to know, if I wanted to insist in the non-interlaced, to keep using
> Hypre/BoomerAMG from PETSc I would need to write some code in PETSc for
> wrapping this feature (AMGSetDofFunc), right?
> >
> > Thanks.
> >
> > On Tue, Feb 14, 2017 at 11:48 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> >
> >   Ahh, thanks for the explanation. What a nutso API: way to general,
> they should just support interlaced and non-interlaced.
> >
> >   Anyways we strongly recommend using the interlaced version; for most
> calculations it gives much better locality for cache lines and cache. We
> always use interlaced. Any particular reason you use non-interlaced?
>
>    Yes, you would have to add a call to HYPRE_BoomerAMGSetDofFunc() with
> the information as you computed. For trying things out the easily way would
> be to just stick it in an appropriate place in hypre.c
>
>   Barry
>
>
>
>
> >
> >   Barry
> >
> > > On Feb 14, 2017, at 7:17 PM, Bernardo Rocha <
> bernardomartinsrocha at gmail.com> wrote:
> > >
> > > Thanks a lot for the reply.
> > >
> > > ​From my understanding and specifically for my problem I would have to
> use the AMGSetDofFunc as follows:​
> > >
> > > ​nsyseq = 3;​
> > > for (i=0; i<nsyseq; i++)
> > > ​    ​for (k=0; k<​N​; k++)​ // N: number of nodes​
> > >     {
> > >     ​    ​eqnIndex[i*​N​+k] = i;
> > >     }
> > > HYPRE_BoomerAMGSetDofFunc(preconditioner, eqnIndex);​
> > >
> > > For a system of 3 PDEs (e.g. linear elasticity in 3D​) the default
> behaviour of the nodal coarsening in BoomerAMG, considers an array that is
> filled with
> > >
> > > eqnIndex = ​0 1 2 0 1 2 0 1 2....0 1 2
> > >
> > >  > HYPRE_BoomerAMGSetDofFunc
> > >
> > >    I could not find an indication of that this is suppose to be
> setting; it is mentioned in the users manual but I don't know what it
> means. It looks like it takes an integer array but I don't even know how
> long that array is.
> > >
> > >    If you figure out what it means and can add support for it we'll
> take it as a pull request.
> > >
> > > ​​OK Barry, I will try to specify the block size of the matrix.
> > > But I'm not sure if the block size would be 3 or N (number of nodes).
> > > This is my ordering of the displacements: [ux1, ux2, ..., uxN, uy1,
> uy2,...uyN, uz1, uz2, ..., uzN]
> > >
> > > > HYPRE_BoomerAMGSetNumFunctions
> > >
> > >    Set the block size of the matrix; this information is then
> transferred automatically to hypre.  Note that you can set a block size
> even for AIJ matrices.
> > > ​
> > > ​Best regards,
> > > Bernardo​
> >
> >
>
>
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