2: static char help[] = "Partition a tiny grid using hierarchical partitioning.\n\n";

  4: /*T
  5:    Concepts: partitioning
  6:    Processors: 4
  7: T*/

  9: /*
 10:   Include "petscmat.h" so that we can use matrices.  Note that this file
 11:   automatically includes:
 12:      petscsys.h       - base PETSc routines   petscvec.h - vectors
 13:      petscmat.h - matrices
 14:      petscis.h     - index sets
 15:      petscviewer.h - viewers
 16: */
 17: #include <petscmat.h>

 21: int main(int argc,char **args)
 22: {
 23:   Mat             A;
 24:   PetscErrorCode  ierr;
 25:   PetscMPIInt     rank,size;
 26:   PetscInt        *ia,*ja;
 27:   MatPartitioning part;
 28:   IS              is,isn,isrows;
 29:   IS              coarseparts,fineparts;
 30:   MPI_Comm        comm;

 32:   PetscInitialize(&argc,&args,(char*)0,help);
 33:   comm = PETSC_COMM_WORLD;
 34:   MPI_Comm_size(comm,&size);
 35:   if (size != 4) SETERRQ(comm,1,"Must run with 4 processors");
 36:   MPI_Comm_rank(comm,&rank);

 38:   PetscMalloc1(5,&ia);
 39:   PetscMalloc1(16,&ja);
 40:   if (!rank) {
 41:     ja[0] = 1; ja[1] = 4; ja[2] = 0; ja[3] = 2; ja[4] = 5; ja[5] = 1; ja[6] = 3; ja[7] = 6;
 42:     ja[8] = 2; ja[9] = 7;
 43:     ia[0] = 0; ia[1] = 2; ia[2] = 5; ia[3] = 8; ia[4] = 10;
 44:   } else if (rank == 1) {
 45:     ja[0] = 0; ja[1] = 5; ja[2] = 8; ja[3] = 1; ja[4] = 4; ja[5] = 6; ja[6] = 9; ja[7] = 2;
 46:     ja[8] = 5; ja[9] = 7; ja[10] = 10; ja[11] = 3; ja[12] = 6; ja[13] = 11;
 47:     ia[0] = 0; ia[1] = 3; ia[2] = 7; ia[3] = 11; ia[4] = 14;
 48:   } else if (rank == 2) {
 49:     ja[0] = 4; ja[1] = 9; ja[2] = 12; ja[3] = 5; ja[4] = 8; ja[5] = 10; ja[6] = 13; ja[7] = 6;
 50:     ja[8] = 9; ja[9] = 11; ja[10] = 14; ja[11] = 7; ja[12] = 10; ja[13] = 15;
 51:     ia[0] = 0; ia[1] = 3; ia[2] = 7; ia[3] = 11; ia[4] = 14;
 52:   } else {
 53:     ja[0] = 8; ja[1] = 13; ja[2] = 9; ja[3] = 12; ja[4] = 14; ja[5] = 10; ja[6] = 13; ja[7] = 15;
 54:     ja[8] = 11; ja[9] = 14;
 55:     ia[0] = 0; ia[1] = 2; ia[2] = 5; ia[3] = 8; ia[4] = 10;
 56:   }
 57:   MatCreateMPIAdj(comm,4,16,ia,ja,NULL,&A);
 58:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
 59:   /*
 60:    Partition the graph of the matrix
 61:   */
 62:   MatPartitioningCreate(comm,&part);
 63:   MatPartitioningSetAdjacency(part,A);
 64:   MatPartitioningSetType(part,MATPARTITIONINGHIERARCH);
 65:   MatPartitioningHierarchicalSetNcoarseparts(part,2);
 66:   MatPartitioningHierarchicalSetNfineparts(part,2);
 67:   MatPartitioningSetFromOptions(part);
 68:   /* get new processor owner number of each vertex */
 69:   MatPartitioningApply(part,&is);
 70:   /* coarse parts */
 71:   MatPartitioningHierarchicalGetCoarseparts(part,&coarseparts);
 72:   ISView(coarseparts,PETSC_VIEWER_STDOUT_WORLD);
 73:   /* fine parts */
 74:   MatPartitioningHierarchicalGetFineparts(part,&fineparts);
 75:   ISView(fineparts,PETSC_VIEWER_STDOUT_WORLD);
 76:   /* partitioning */
 77:   ISView(is,PETSC_VIEWER_STDOUT_WORLD);
 78:   /* get new global number of each old global number */
 79:   ISPartitioningToNumbering(is,&isn);
 80:   ISView(isn,PETSC_VIEWER_STDOUT_WORLD);
 81:   ISBuildTwoSided(is,&isrows);
 82:   ISView(isrows,PETSC_VIEWER_STDOUT_WORLD);
 83:   ISDestroy(&is);
 84:   ISDestroy(&coarseparts);
 85:   ISDestroy(&fineparts);
 86:   ISDestroy(&isrows);
 87:   ISDestroy(&isn);
 88:   MatPartitioningDestroy(&part);
 89:   /*
 90:     Free work space.  All PETSc objects should be destroyed when they
 91:     are no longer needed.
 92:   */
 93:   MatDestroy(&A);
 94:   PetscFinalize();
 95:   return 0;
 96: }