Actual source code: ex17.c
petsc-3.4.2 2013-07-02

      1: static char help[] = "Example of using graph partitioning with a matrix in which some procs have empty ownership\n\n";

      3: /*T
      4:    Concepts: Mat^mat partitioning
      5:    Concepts: Mat^image segmentation
      6:    Processors: n
      7: T*/

      9: #include <petscmat.h>

     13: int main(int argc, char **args)
     14: {
     15:   Mat             A;
     16:   MatPartitioning part;
     17:   IS              is;
     18:   PetscInt        i,m,N,rstart,rend,nemptyranks,*emptyranks,nbigranks,*bigranks;
     19:   PetscMPIInt     rank,size;
     20:   PetscErrorCode  ierr;

     22:   PetscInitialize(&argc,&args,(char*)0,help);
     23:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
     24:   MPI_Comm_size(PETSC_COMM_WORLD,&size);

     26:   nemptyranks = 10;
     27:   nbigranks   = 10;
     28:   PetscMalloc2(nemptyranks,PetscInt,&emptyranks,nbigranks,PetscInt,&bigranks);

     30:   PetscOptionsBegin(PETSC_COMM_WORLD,NULL,"Partitioning example options",NULL);
     31:   PetscOptionsIntArray("-emptyranks","Ranks to be skipped by partition","",emptyranks,&nemptyranks,NULL);
     32:   PetscOptionsIntArray("-bigranks","Ranks to be overloaded","",bigranks,&nbigranks,NULL);
     33:   PetscOptionsEnd();

     35:   m = 1;
     36:   for (i=0; i<nemptyranks; i++) if (rank == emptyranks[i]) m = 0;
     37:   for (i=0; i<nbigranks; i++) if (rank == bigranks[i]) m = 5;

     39:   MatCreate(PETSC_COMM_WORLD,&A);
     40:   MatSetSizes(A,m,m,PETSC_DECIDE,PETSC_DECIDE);
     41:   MatSetFromOptions(A);
     42:   MatSeqAIJSetPreallocation(A,3,NULL);
     43:   MatMPIAIJSetPreallocation(A,3,NULL,2,NULL);
     44:   MatSeqBAIJSetPreallocation(A,1,3,NULL);
     45:   MatMPIBAIJSetPreallocation(A,1,3,NULL,2,NULL);
     46:   MatSeqSBAIJSetPreallocation(A,1,2,NULL);
     47:   MatMPISBAIJSetPreallocation(A,1,2,NULL,1,NULL);

     49:   MatGetSize(A,NULL,&N);
     50:   MatGetOwnershipRange(A,&rstart,&rend);
     51:   for (i=rstart; i<rend; i++) {
     52:     const PetscInt    cols[] = {(i+N-1)%N,i,(i+1)%N};
     53:     const PetscScalar vals[] = {1,1,1};
     54:     MatSetValues(A,1,&i,3,cols,vals,INSERT_VALUES);
     55:   }
     56:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
     57:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
     58:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

     60:   MatPartitioningCreate(PETSC_COMM_WORLD,&part);
     61:   MatPartitioningSetAdjacency(part,A);
     62:   MatPartitioningSetFromOptions(part);
     63:   MatPartitioningApply(part,&is);
     64:   ISView(is,PETSC_VIEWER_STDOUT_WORLD);
     65:   ISDestroy(&is);
     66:   MatPartitioningDestroy(&part);
     67:   MatDestroy(&A);
     68:   PetscFree2(emptyranks,bigranks);
     69:   PetscFinalize();
     70:   return 0;
     71: }