[petsc-users] general VecScatter from MPI to MPI

[Matthew Knepley]

On Thu, Feb 17, 2011 at 10:06 AM, Ethan Coon <ecoon at lanl.gov> wrote:

> So I thought I understood how VecScatters worked, but apparently not.
> Is it possible to create a general VecScatter from an arbitrarily
> partitioned (MPI) Vec to another arbitrarily partitioned (MPI) Vec with
> the same global sizes (or same global IS sizes) but different local
> sizes?  Shouldn't this just be a matter of relying upon the implied
> LocalToGlobalMapping?
>

No, the way you have to do this is to map a global Vec to a bunch of
sequential local Vecs with the sizes you want. This is also how we map
to overlapping arrays.

   Matt


> See below snippet (and its errors):
>
> Ethan
>
>
>
> Vec vA
> Vec vB
> VecScatter scatter_AB
>
> PetscInt np
> PetscInt rank
> PetscErrorCode ierr
>
> if (rank.eq.0) np = 3
> if (rank.eq.1) np = 1
>
> call VecCreateMPI(PETSC_COMM_WORLD, 2, PETSC_DETERMINE, vA, ierr)
> call VecCreateMPI(PETSC_COMM_WORLD, np, PETSC_DETERMINE, vB, ierr)
>
> call VecScatterCreate(vA, PETSC_NULL_OBJECT, vB, PETSC_NULL_OBJECT,
>        scatter_AB, ierr)
>
> ...
>
> $> mpiexec -n 2 ./test
>
> [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [0]PETSC ERROR: Nonconforming object sizes!
> [0]PETSC ERROR: Local scatter sizes don't match!
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [1]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [1]PETSC ERROR: Nonconforming object sizes!
> [1]PETSC ERROR: Local scatter sizes don't match!
> [0]PETSC ERROR: Petsc Development HG revision:
> 5dbe1264252fb9cb5d8e033d620d18f7b0e9111f  HG Date: Fri Feb 11 15:44:04
> 2011 -0600
> [0]PETSC ERROR: See docs/changes/index.html for recent updates.
> [0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
> [0]PETSC ERROR: See docs/index.html for manual pages.
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: ./test on a linux-gnu named tama1 by ecoon Thu Feb 17
> 08:14:57 2011
> [0]PETSC ERROR: Libraries linked
> from /packages/petsc/petsc-dev3.0-mpich2-local-gcc-4.3.3/debug-shared/lib
> [0]PETSC ERROR: Configure run at Fri Feb 11 16:15:14 2011
> [0]PETSC ERROR: Configure options --with-debugging=1
> --prefix=/packages/petsc/petsc-dev3.0-mpich2-local-gcc-4.3.3/debug-shared
> --download-mpich=1 --download-ml=1 --download-umfpack=1
> --with-blas-lapack-dir=/usr/lib --download-parmetis=yes
> PETSC_ARCH=linux-gnu-c-debug-shared --with-clanguage=c --download-hypre=1
> --with-shared-libraries=1 --download-hdf5=1
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: VecScatterCreate() line 1432 in
> src/vec/vec/utils/vscat.c
> application called MPI_Abort(MPI_COMM_WORLD, 60) - process 0
> [cli_0]: aborting job:
> application called MPI_Abort(MPI_COMM_WORLD, 60) - process 0
> [1]PETSC ERROR: APPLICATION TERMINATED WITH THE EXIT STRING: Hangup
> (signal 1)
>
>
>
>
> --
> ------------------------------------
> Ethan Coon
> Post-Doctoral Researcher
> Applied Mathematics - T-5
> Los Alamos National Laboratory
> 505-665-8289
>
> http://www.ldeo.columbia.edu/~ecoon/
> ------------------------------------
>
>


-- 
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
-- Norbert Wiener
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