[petsc-users] access to matnest block (0,1) ?

[Klaij, Christiaan]

I have two DMs which I add to a DMComposite and then use MATNEST when getting the corresponding matrix. This gives me block (0,0) and block (1,1). How do I set/get blocks (0,1) and (1,0)? Looking at ex28 I tried MatGetLocalSubMatrix but it gives a null arg...

#include <petscdmda.h>

int main(int argc, char **argv)
{

  DM               da0, da1;
  DMDABoundaryType bx = DMDA_BOUNDARY_PERIODIC, by = DMDA_BOUNDARY_PERIODIC;
  DMDAStencilType  stype = DMDA_STENCIL_STAR;
  PetscInt         Mx = 8, My = 8;

  PetscInitialize(&argc, &argv, PETSC_NULL, PETSC_NULL);

  // create distributed array for Q
  DMDACreate2d(PETSC_COMM_WORLD,bx,by,stype,Mx,My,PETSC_DECIDE,PETSC_DECIDE,2,1,PETSC_NULL,PETSC_NULL,&da0);

  // create distributed array for C
  DMDACreate2d(PETSC_COMM_WORLD,bx,by,stype,Mx,My,PETSC_DECIDE,PETSC_DECIDE,1,1,PETSC_NULL,PETSC_NULL,&da1);

  // mat nest from pack
  DM  pack;
  Mat A;
  Vec X;
  DMCompositeCreate(PETSC_COMM_WORLD,&pack);
  DMCompositeAddDM(pack,da0);
  DMCompositeAddDM(pack,da1);
  DMSetUp(pack);
  DMGetMatrix(pack,MATNEST,&A);
  MatView(A,PETSC_VIEWER_DEFAULT);

  IS *is;
  Mat G;
  PetscInt col[1],ierr;
  PetscScalar vals[1];
  DMCompositeGetLocalISs(pack,&is);
  MatGetLocalSubMatrix(A,is[0],is[1],&G);
  MatView(G,PETSC_VIEWER_DEFAULT);

  PetscFinalize();

  return 0;

}


$ mpiexec -n 1 ./dmda-try3
  Matrix object:
    type=nest, rows=2, cols=2
    MatNest structure:
    (0,0) : type=seqaij, rows=128, cols=128
    (0,1) : PETSC_NULL
    (1,0) : PETSC_NULL
    (1,1) : type=seqaij, rows=64, cols=64
[0]PETSC ERROR: --------------------- Error Message ------------------------------------
[0]PETSC ERROR: Null argument, when expecting valid pointer!
[0]PETSC ERROR: Null Object: Parameter # 1!
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.2.0, Patch 5, Sat Oct 29 13:45:54 CDT 2011
[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: ./dmda-try3 on a linux_64b named lin0133 by cklaij Wed Jan 18 09:00:37 2012
[0]PETSC ERROR: Libraries linked from /opt/refresco/64bit_intelv11.1_openmpi/petsc-3.2-p5/lib
[0]PETSC ERROR: Configure run at Mon Jan 16 14:03:34 2012
[0]PETSC ERROR: Configure options --prefix=/opt/refresco/64bit_intelv11.1_openmpi/petsc-3.2-p5 --with-mpi-dir=/opt/refresco/64bit_intelv11.1_openmpi/openmpi-1.4.4 --with-x=0 --with-mpe=0 --with-debugging=1 --with-hypre-include=/opt/refresco/64bit_intelv11.1_openmpi/hypre-2.7.0b/include --with-hypre-lib=/opt/refresco/64bit_intelv11.1_openmpi/hypre-2.7.0b/lib/libHYPRE.a --with-ml-include=/opt/refresco/64bit_intelv11.1_openmpi/ml-6.2/include --with-ml-lib=/opt/refresco/64bit_intelv11.1_openmpi/ml-6.2/lib/libml.a --with-blas-lapack-dir=/opt/intel/mkl
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: MatView() line 723 in src/mat/interface/matrix.c



dr. ir. Christiaan Klaij
CFD Researcher
Research & Development
E mailto:C.Klaij at marin.nl
T +31 317 49 33 44

MARIN
2, Haagsteeg, P.O. Box 28, 6700 AA Wageningen, The Netherlands
T +31 317 49 39 11, F +31 317 49 32 45, I www.marin.nl