2: static char help[] = "Partition tiny grid using hierarchical partitioning and increase overlap using MatIncreaseOverlapSplit.\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,B;
 22:   PetscErrorCode  ierr;
 23:   PetscMPIInt     rank,size,membershipKey;
 24:   PetscInt        *ia,*ja,*indices_sc,isrows_localsize;
 25:   const PetscInt  *indices;
 26:   MatPartitioning part;
 27:   IS              is,isrows,isrows_sc;
 28:   IS              coarseparts,fineparts;
 29:   MPI_Comm        comm,scomm;

 31:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 32:   comm = PETSC_COMM_WORLD;
 33:   MPI_Comm_size(comm,&size);
 34:   if (size != 4) SETERRQ(comm,1,"Must run with 4 processors \n");
 35:   MPI_Comm_rank(comm,&rank);
 36:   /*set a small matrix */
 37:   PetscMalloc1(5,&ia);
 38:   PetscMalloc1(16,&ja);
 39:   if (!rank) {
 40:     ja[0] = 1; ja[1] = 4; ja[2] = 0; ja[3] = 2; ja[4] = 5; ja[5] = 1; ja[6] = 3; ja[7] = 6;
 41:     ja[8] = 2; ja[9] = 7;
 42:     ia[0] = 0; ia[1] = 2; ia[2] = 5; ia[3] = 8; ia[4] = 10;
 43:     membershipKey = 0;
 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:     membershipKey = 0;
 49:   } else if (rank == 2) {
 50:     ja[0] = 4; ja[1] = 9; ja[2] = 12; ja[3] = 5; ja[4] = 8; ja[5] = 10; ja[6] = 13; ja[7] = 6;
 51:     ja[8] = 9; ja[9] = 11; ja[10] = 14; ja[11] = 7; ja[12] = 10; ja[13] = 15;
 52:     ia[0] = 0; ia[1] = 3; ia[2] = 7; ia[3] = 11; ia[4] = 14;
 53:     membershipKey = 1;
 54:   } else {
 55:     ja[0] = 8; ja[1] = 13; ja[2] = 9; ja[3] = 12; ja[4] = 14; ja[5] = 10; ja[6] = 13; ja[7] = 15;
 56:     ja[8] = 11; ja[9] = 14;
 57:     ia[0] = 0; ia[1] = 2; ia[2] = 5; ia[3] = 8; ia[4] = 10;
 58:     membershipKey = 1;
 59:   }
 60:   MatCreateMPIAdj(comm,4,16,ia,ja,NULL,&A);
 61:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
 62:   /*
 63:    Partition the graph of the matrix
 64:   */
 65:   MatPartitioningCreate(comm,&part);
 66:   MatPartitioningSetAdjacency(part,A);
 67:   MatPartitioningSetType(part,MATPARTITIONINGHIERARCH);
 68:   MatPartitioningHierarchicalSetNcoarseparts(part,2);
 69:   MatPartitioningHierarchicalSetNfineparts(part,2);
 70:   MatPartitioningSetFromOptions(part);
 71:   /* get new processor owner number of each vertex */
 72:   MatPartitioningApply(part,&is);
 73:   /* coarse parts */
 74:   MatPartitioningHierarchicalGetCoarseparts(part,&coarseparts);
 75:   ISView(coarseparts,PETSC_VIEWER_STDOUT_WORLD);
 76:   /* fine parts */
 77:   MatPartitioningHierarchicalGetFineparts(part,&fineparts);
 78:   ISView(fineparts,PETSC_VIEWER_STDOUT_WORLD);
 79:   /* partitioning */
 80:   ISView(is,PETSC_VIEWER_STDOUT_WORLD);
 81:   /* compute coming rows */
 82:   ISBuildTwoSided(is,NULL,&isrows);
 83:   ISView(isrows,PETSC_VIEWER_STDOUT_WORLD);
 84:   /*create a sub-communicator */
 85:   MPI_Comm_split(comm, membershipKey,rank,&scomm);
 86:   ISGetLocalSize(isrows,&isrows_localsize);
 87:   PetscMalloc1(isrows_localsize,&indices_sc);
 88:   ISGetIndices(isrows,&indices);
 89:   PetscArraycpy(indices_sc,indices,isrows_localsize);
 90:   ISRestoreIndices(isrows,&indices);
 91:   ISDestroy(&is);
 92:   ISDestroy(&coarseparts);
 93:   ISDestroy(&fineparts);
 94:   ISDestroy(&isrows);
 95:   MatPartitioningDestroy(&part);
 96:   /*create a sub-IS on the sub communicator  */
 97:   ISCreateGeneral(scomm,isrows_localsize,indices_sc,PETSC_OWN_POINTER,&isrows_sc);
 98:   MatConvert(A,MATMPIAIJ,MAT_INITIAL_MATRIX,&B);
 99: #if 1
100:   MatView(B,PETSC_VIEWER_STDOUT_WORLD);
101: #endif
102:   /*increase overlap */
103:   MatIncreaseOverlapSplit(B,1,&isrows_sc,1);
104:   ISView(isrows_sc,NULL);
105:   ISDestroy(&isrows_sc);
106:   /*
107:     Free work space.  All PETSc objects should be destroyed when they
108:     are no longer needed.
109:   */
110:   MatDestroy(&A);
111:   MatDestroy(&B);
112:   PetscFinalize();
113:   return ierr;
114: }