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>

 19: int main(int argc,char **args)
 20: {
 21:   Mat             A;
 22:   PetscErrorCode  ierr;
 23:   PetscMPIInt     rank,size;
 24:   PetscInt        *ia,*ja;
 25:   MatPartitioning part;
 26:   IS              is,isn,isrows;
 27:   IS              coarseparts,fineparts;
 28:   MPI_Comm        comm;

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

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