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

  3: #include <petscmat.h>

  5: int main(int argc, char **args)
  6: {
  7:   Mat             A;
  8:   MatPartitioning part;
  9:   IS              is;
 10:   PetscInt        i,m,N,rstart,rend,nemptyranks,*emptyranks,nbigranks,*bigranks;
 11:   PetscMPIInt     rank,size;
 12:   PetscErrorCode  ierr;

 14:   PetscInitialize(&argc,&args,(char*)0,help);
 15:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 16:   MPI_Comm_size(PETSC_COMM_WORLD,&size);

 18:   nemptyranks = 10;
 19:   nbigranks   = 10;
 20:   PetscMalloc2(nemptyranks,&emptyranks,nbigranks,&bigranks);

 22:   PetscOptionsBegin(PETSC_COMM_WORLD,NULL,"Partitioning example options",NULL);
 23:   PetscOptionsIntArray("-emptyranks","Ranks to be skipped by partition","",emptyranks,&nemptyranks,NULL);
 24:   PetscOptionsIntArray("-bigranks","Ranks to be overloaded","",bigranks,&nbigranks,NULL);
 25:   PetscOptionsEnd();

 27:   m = 1;
 28:   for (i=0; i<nemptyranks; i++) if (rank == emptyranks[i]) m = 0;
 29:   for (i=0; i<nbigranks; i++) if (rank == bigranks[i]) m = 5;

 31:   MatCreate(PETSC_COMM_WORLD,&A);
 32:   MatSetSizes(A,m,m,PETSC_DECIDE,PETSC_DECIDE);
 33:   MatSetFromOptions(A);
 34:   MatSeqAIJSetPreallocation(A,3,NULL);
 35:   MatMPIAIJSetPreallocation(A,3,NULL,2,NULL);
 36:   MatSeqBAIJSetPreallocation(A,1,3,NULL);
 37:   MatMPIBAIJSetPreallocation(A,1,3,NULL,2,NULL);
 38:   MatSeqSBAIJSetPreallocation(A,1,2,NULL);
 39:   MatMPISBAIJSetPreallocation(A,1,2,NULL,1,NULL);

 41:   MatGetSize(A,NULL,&N);
 42:   MatGetOwnershipRange(A,&rstart,&rend);
 43:   for (i=rstart; i<rend; i++) {
 44:     const PetscInt    cols[] = {(i+N-1)%N,i,(i+1)%N};
 45:     const PetscScalar vals[] = {1,1,1};
 46:     MatSetValues(A,1,&i,3,cols,vals,INSERT_VALUES);
 47:   }
 48:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 49:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
 50:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

 52:   MatPartitioningCreate(PETSC_COMM_WORLD,&part);
 53:   MatPartitioningSetAdjacency(part,A);
 54:   MatPartitioningSetFromOptions(part);
 55:   MatPartitioningApply(part,&is);
 56:   ISView(is,PETSC_VIEWER_STDOUT_WORLD);
 57:   ISDestroy(&is);
 58:   MatPartitioningDestroy(&part);
 59:   MatDestroy(&A);
 60:   PetscFree2(emptyranks,bigranks);
 61:   PetscFinalize();
 62:   return 0;
 63: }

 65: /*TEST

 67:    test:
 68:       nsize: 8
 69:       args: -emptyranks 0,2,4 -bigranks 1,3,7 -mat_partitioning_type average
 70:       # cannot test with external package partitioners since they produce different results on different systems

 72: TEST*/