The first thing I did was to put 3, not 4 : I got an error thrown in
MatCreateIS (see the git diff + stack below). As the error said I used
globalSize = numberOfMPIProcessus * localSize : my understanding is that, when
using MatIS, the global size needs to be the sum of all local sizes. Correct ?
I have a 3x3 global matrix made of two overlapping 2x2 local matrix (= diagonal
with 1.). Each local matrix correspond to one domain (each domain is delegated
to one MPI proc, so, I have 2 MPI procs because I have 2 domains).
This is the simplest possible example: I have two 2x2 (local) diag matrix that
overlap so that the global matrix built from them is 1, 2, 1 on the diagonal
(local contributions add up in the middle).
I need to MatMult this global matrix with a global vector filled with 1.
Franck
Git diff :
--- a/matISLocalMat.cpp
+++ b/matISLocalMat.cpp
@@ -16,7 +16,7 @@ int main(int argc,char **argv) {
int size = 0; MPI_Comm_size(MPI_COMM_WORLD, &size); if (size != 2) return 1;
int rank = 0; MPI_Comm_rank(MPI_COMM_WORLD, &rank);
- PetscInt localSize = 2, globalSize = localSize*2 /*2 MPI*/;
+ PetscInt localSize = 2, globalSize = 3;
PetscInt localIdx[2] = {0, 0};
if (rank == 0) {localIdx[0] = 0; localIdx[1] = 1;}
else {localIdx[0] = 1; localIdx[1] = 2;}
Stack error:
[0]PETSC ERROR: Nonconforming object sizes
[0]PETSC ERROR: Sum of local lengths 4 does not equal global length 3, my local
length 2
[0]PETSC ERROR: [0] ISG2LMapApply line 17
/home/fghoussen/Documents/INRIA/petsc-3.7.6/src/vec/is/utils/isltog.c
[0]PETSC ERROR: [0] MatSetValues_IS line 692
/home/fghoussen/Documents/INRIA/petsc-3.7.6/src/mat/impls/is/matis.c
[0]PETSC ERROR: [0] MatSetValues line 1157
/home/fghoussen/Documents/INRIA/petsc-3.7.6/src/mat/interface/matrix.c
[0]PETSC ERROR: [0] MatISSetPreallocation_IS line 95
/home/fghoussen/Documents/INRIA/petsc-3.7.6/src/mat/impls/is/matis.c
[0]PETSC ERROR: [0] MatISSetPreallocation line 80
/home/fghoussen/Documents/INRIA/petsc-3.7.6/src/mat/impls/is/matis.c
[0]PETSC ERROR: [0] PetscSplitOwnership line 80
/home/fghoussen/Documents/INRIA/petsc-3.7.6/src/sys/utils/psplit.c
[0]PETSC ERROR: [0] PetscLayoutSetUp line 129
/home/fghoussen/Documents/INRIA/petsc-3.7.6/src/vec/is/utils/pmap.c
[0]PETSC ERROR: [0] MatSetLocalToGlobalMapping_IS line 628
/home/fghoussen/Documents/INRIA/petsc-3.7.6/src/mat/impls/is/matis.c
[0]PETSC ERROR: [0] MatSetLocalToGlobalMapping line 1899
/home/fghoussen/Documents/INRIA/petsc-3.7.6/src/mat/interface/matrix.c
[0]PETSC ERROR: [0] MatCreateIS line 986
/home/fghoussen/Documents/INRIA/petsc-3.7.6/src/mat/impls/is/matis.c
----- Mail original -----
> De: "Stefano Zampini" <[email protected]>
> À: "Matthew Knepley" <[email protected]>
> Cc: "Franck Houssen" <[email protected]>, "PETSc"
> <[email protected]>, "PETSc" <[email protected]>
> Envoyé: Dimanche 21 Mai 2017 23:02:37
> Objet: Re: [petsc-dev] Using PETSc MatIS, how to matmult a global IS matrix
> and a global vector ?
> Franck,
> PETSc takes care of doing the matrix-vector multiplication properly using
> MatIS. As Matt said, the layout of the vectors is the usual parallel layout.
> The local sizes of the MatIS matrix (i.e. the local size of the left and
> right vectors used in MatMult) are not the sizes of the local subdomain
> matrices in MatIS.
> > On May 21, 2017, at 6:47 PM, Matthew Knepley < [email protected] > wrote:
>
> > On Sun, May 21, 2017 at 11:26 AM, Franck Houssen < [email protected]
> > >
> > wrote:
>
> > > Using PETSc MatIS, how to matmult a global IS matrix and a global vector
> > > ?
> > > Example is attached : I don't get what I expect that is a vector such
> > > that
> > > proc0 = [1, 2] and proc1 = [2, 1]
> >
>
> > 1) I think the global size of your matrix is wrong. You seem to want 3, not
> > 4
>
> > 2) Global vectors have a non-overlapping row partition. You might be
> > thinking
> > of local vectors
>
> > Thanks,
>
> > Matt
>
> > --
>
> > 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
>
> > http://www.caam.rice.edu/~mk51/
>
----- Mail original -----
> De: "Stefano Zampini" <[email protected]>
> À: "Matthew Knepley" <[email protected]>
> Cc: "Franck Houssen" <[email protected]>, "PETSc"
> <[email protected]>, "PETSc" <[email protected]>
> Envoyé: Dimanche 21 Mai 2017 23:02:37
> Objet: Re: [petsc-dev] Using PETSc MatIS, how to matmult a global IS matrix
> and a global vector ?
> Franck,
> PETSc takes care of doing the matrix-vector multiplication properly using
> MatIS. As Matt said, the layout of the vectors is the usual parallel layout.
> The local sizes of the MatIS matrix (i.e. the local size of the left and
> right vectors used in MatMult) are not the sizes of the local subdomain
> matrices in MatIS.
> > On May 21, 2017, at 6:47 PM, Matthew Knepley < [email protected] > wrote:
>
> > On Sun, May 21, 2017 at 11:26 AM, Franck Houssen < [email protected]
> > >
> > wrote:
>
> > > Using PETSc MatIS, how to matmult a global IS matrix and a global vector
> > > ?
> > > Example is attached : I don't get what I expect that is a vector such
> > > that
> > > proc0 = [1, 2] and proc1 = [2, 1]
> >
>
> > 1) I think the global size of your matrix is wrong. You seem to want 3, not
> > 4
>
> > 2) Global vectors have a non-overlapping row partition. You might be
> > thinking
> > of local vectors
>
> > Thanks,
>
> > Matt
>
> > > Franck
> >
>
> > --
>
> > 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
>
> > http://www.caam.rice.edu/~mk51/
>
