Re: HYPRE with multiple variables

[Shaman Mahmoudi <shma7099@xxxxxxxxxxxxx>]

Hi,

int HYPRE_BOOMERAMGSetNodal(....)

Sets whether to use the nodal systems version. Default is 0, i.e. do  
not.

int HYPRE_BoomerAMGSetNumFunctions (.....)

sets the size of the system of PDEs.

With best regards, Shaman Mahmoudi

On Apr 25, 2007, at 6:35 PM, Barry Smith wrote:

>   Nicolas,
>
> On Wed, 25 Apr 2007, Nicolas Bathfield wrote:
>
> > Dear Barry,
> >
> > Using MatSetBlockSize(A,5) improved my results greatly. Boomemramg  
> > is now
> > solving the system of equations.
>
>    Good
>
> > Still, the equations I solve are coupled, and my discretization  
> > scheme is
> > meant for a non-segregated solver. As a consequence (I believe),  
> > boomeramg
> > still diverges.
>
>   How can "Boomeramg be now solving the system of equations" but also
> diverge? I am so confused.
>
> >  I would therefore like to use the nodal relaxation in
> > boomeramg (the hypre command is HYPRE_BOOMERAMGSetNodal) in order to
> > couple the coarse grid choice for all my variables.
>
>   I can add this this afternoon.
>
>   I have to admit I do not understand the difference between
> HYPRE_BOOMERAMGSetNodal() and hypre_BoomerAMGSetNumFunctions(). Do  
> you?
>
>    Barry
> > How can I achieve this from PETSc?
> >
> > Best regards,
> >
> > Nicolas
> >
> > >   From PETSc MPIAIJ matrices you need to set the block size of  
> > > the matrix
> > > with MatSetBlockSize(A,5) after you have called MatSetType() or
> > > MatCreateMPIAIJ(). Then HYPRE_BoomerAMGSetNumFunctions() is  
> > > automatically
> > > called by PETSc.
> > >
> > >    Barry
> > >
> > > The reason this is done this way instead of as
> > > -pc_hypre_boomeramg_block_size <bs> is the idea that hypre will  
> > > use the
> > > properties of the matrix it is given in building the  
> > > preconditioner so
> > > the user does not have to pass those properties in seperately  
> > > directly
> > > to hypre.
> > >
> > >
> > > On Fri, 13 Apr 2007, Shaman Mahmoudi wrote:
> > >
> > > > Hi,
> > > >
> > > > int HYPRE_BoomerAMGSetNumFunctions (.....)
> > > >
> > > > sets the size of the system of PDEs.
> > > >
> > > > With best regards, Shaman Mahmoudi
> > > >
> > > > On Apr 13, 2007, at 2:04 PM, Shaman Mahmoudi wrote:
> > > >
> > > > > Hi Nicolas,
> > > > >
> > > > > You are right. hypre has changed a lot since the version I used.
> > > > >
> > > > > I found this interesting information:
> > > > >
> > > > > int HYPRE_BOOMERAMGSetNodal(....)
> > > > >
> > > > > Sets whether to use the nodal systems version. Default is 0.
> > > > >
> > > > > Then information about smoothers:
> > > > >
> > > > > One interesting thing there is this,
> > > > >
> > > > > HYPRE_BoomerAMGSetDomainType(....)
> > > > >
> > > > > 0 - each point is a domain (default)
> > > > > 1 each node is a domain (only of interest in systems AMG)
> > > > > 2 ....
> > > > >
> > > > > I could not find how you define the nodal displacement  
> > > > > ordering. But
> > > > it
> > > > > should be there somewhere.
> > > > >
> > > > > I read the reference manual for hypre 2.0
> > > > >
> > > > > With best regards, Shaman Mahmoudi
> > > > >
> > > > >
> > > > > On Apr 13, 2007, at 1:40 PM, Nicolas Bathfield wrote:
> > > > >
> > > > > > Dear Shaman,
> > > > > >
> > > > > > As far as I could understand, there is a BoomerAMG?s systems AMG
> > > > version
> > > > > > available. This seems to be exactly what I am looking for, but I
> > > > just
> > > > > > don't know how to access it, either through PETSc or directly.
> > > > > >
> > > > > > Best regards,
> > > > > >
> > > > > > Nicolas
> > > > > >
> > > > > > > Hi,
> > > > > > >
> > > > > > > You want to exploit the structure of the model?
> > > > > > > As far as I know, boomeramg can not treat a set of rows or  
> > > > > > > blocks
> > > > as
> > > > > > > a molecule,  a so called block-smoother?
> > > > > > > ML 2.0 smoothed aggregation does support it.
> > > > > > >
> > > > > > > With best regards, Shaman Mahmoudi
> > > > > > >
> > > > > > > On Apr 13, 2007, at 10:45 AM, Nicolas Bathfield wrote:
> > > > > > >
> > > > > > > > Hi,
> > > > > > > >
> > > > > > > > I am solving the Navier-stokes equations and try to use  
> > > > > > > > Hypre as
> > > > > > > > preconditioner.
> > > > > > > > Until now, I used PETSc as non-segregated solver and it worked
> > > > > > > > perfectly.
> > > > > > > > Things got worse when I decided to use Boomeramg (Hypre).
> > > > > > > > As I solve a system of PDEs,  each cell is represented by 5  
> > > > > > > > rows
> > > > in my
> > > > > > > > matrix (I solve for 5 variables). PETSc handles that without
> > > > problem
> > > > > > > > apparently, but the coarsening scheme of Boomeramg needs more
> > > > input in
> > > > > > > > order to work properly.
> > > > > > > >
> > > > > > > > Is there an option in PETSc to tell HYPRE that we are dealing
> > > > with a
> > > > > > > > system of PDEs? (something like:  -pc_hypre_boomeramg_...)
> > > > > > > >
> > > > > > > >
> > > > > > > > Thanks for your help.
> > > > > > > >
> > > > > > > > Best regards,
> > > > > > > >
> > > > > > > > Nicolas
> > > > > > > >
> > > > > > > >
> > > > > > > > --
> > > > > > > > Nicolas BATHFIELD
> > > > > > > > Chalmers University of Technology
> > > > > > > > Shipping and Marine Technology
> > > > > > > > phone: +46 (0)31 772 1476
> > > > > > > > fax:   +46 (0)31 772 3699
> > > > > >
> > > > > >
> > > > > > --
> > > > > > Nicolas BATHFIELD
> > > > > > Chalmers University of Technology
> > > > > > Shipping and Marine Technology
> > > > > > phone: +46 (0)31 772 1476
> > > > > > fax:   +46 (0)31 772 3699