leave my rows alone

[Satish Balay]

Perhaps the issue is not using MatGetRowOnership() [but some other
scheme] to get the row indices that are used in MatSetValues()

Satish

On Wed, 16 Aug 2006, Matt Funk wrote:

> Hi Thomas.
> 
> I am not sure if the following is what you are looking for, but i don't have 
> PETSc 'redistribute' anything. That is, i tell PETSc exactly how the matrix 
> should be distributed across the procs via the following:
> 
>  m_ierr = MatCreateMPIAIJ(PETSC_COMM_WORLD, 
>                            a_totallocal_numPoints[a_thisproc], 
>                            a_totallocal_numPoints[a_thisproc],
>                            a_totalglobal_numPoints, 
>                            a_totalglobal_numPoints,
>                            PETSC_NULL,
>                            a_NumberOfNZPointsInDiagonalMatrix,
>                            PETSC_NULL,
>                            a_NumberOfNZPointsInOffDiagonalMatrix,
>                            &m_globalMatrix);
> 
> The argument descriptions are found at 
> 'http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MatCreateMPIAIJ.html'
> 
> So anyway, PETSc does not touch this matrix in the sense of redistributing 
> anything. It is just as i want it to be. Hope this helps ...
> 
> mat
> 
> 
> On Wednesday 16 August 2006 10:37, Thomas Geenen wrote:
> > On Wednesday 16 August 2006 18:21, Matthew Knepley wrote:
> > > On 8/16/06, Thomas Geenen <geenen at gmail.com> wrote:
> > > > dear petsc users,
> > > >
> > > > is there a way to prevent Petsc during the assembly phase from
> > > > redistributing matrix rows over cpu's ?? i like the way the rows are
> > > > assigned to the cpu's during the setvalues phase.
> > >
> > > Actually,  the layout of a matrix is fully determined after
> > > MatSetSizes(), or equivalently MatCreate***(). We do not redistribute at
> > > assembly.
> > >
> > > setValues() will take values for any row, and send it to the correct-
> > > process. The
> >
> > send it to the correct process sounds a lot like redistributing but that's
> > probably a matter of semantics
> >
> > > matrix layouts we support all have contiguous row on each proc. You can
> > > set the sizes on creation.
> >
> > pity
> >
> > >   Does this answer your question?
> >
> > yep
> > thanks
> >
> > >   Thanks,
> > >
> > >      Matt
> > >
> > > > apparently petsc assigns the first nrows to cpu0 the second nrows to
> > > > cpu1 etc. I could of course renumber my matrix but I would rather
> > > > convince petsc that it should keep the distribution of the matrix rows.
> > > >
> > > > tia
> > > > Thomas
> 
>