1 2 static char help[] = "Partition tiny grid using hierarchical partitioning and increase overlap using MatIncreaseOverlapSplit.\n\n"; 3 4 /* 5 Include "petscmat.h" so that we can use matrices. Note that this file 6 automatically includes: 7 petscsys.h - base PETSc routines petscvec.h - vectors 8 petscmat.h - matrices 9 petscis.h - index sets 10 petscviewer.h - viewers 11 */ 12 #include <petscmat.h> 13 14 int main(int argc,char **args) 15 { 16 Mat A,B; 17 PetscMPIInt rank,size,membershipKey; 18 PetscInt *ia,*ja,*indices_sc,isrows_localsize; 19 const PetscInt *indices; 20 MatPartitioning part; 21 IS is,isrows,isrows_sc; 22 IS coarseparts,fineparts; 23 MPI_Comm comm,scomm; 24 25 PetscCall(PetscInitialize(&argc,&args,(char*)0,help)); 26 comm = PETSC_COMM_WORLD; 27 PetscCallMPI(MPI_Comm_size(comm,&size)); 28 PetscCheck(size == 4,comm,PETSC_ERR_WRONG_MPI_SIZE,"Must run with 4 processors "); 29 PetscCallMPI(MPI_Comm_rank(comm,&rank)); 30 /*set a small matrix */ 31 PetscCall(PetscMalloc1(5,&ia)); 32 PetscCall(PetscMalloc1(16,&ja)); 33 if (rank == 0) { 34 ja[0] = 1; ja[1] = 4; ja[2] = 0; ja[3] = 2; ja[4] = 5; ja[5] = 1; ja[6] = 3; ja[7] = 6; 35 ja[8] = 2; ja[9] = 7; 36 ia[0] = 0; ia[1] = 2; ia[2] = 5; ia[3] = 8; ia[4] = 10; 37 membershipKey = 0; 38 } else if (rank == 1) { 39 ja[0] = 0; ja[1] = 5; ja[2] = 8; ja[3] = 1; ja[4] = 4; ja[5] = 6; ja[6] = 9; ja[7] = 2; 40 ja[8] = 5; ja[9] = 7; ja[10] = 10; ja[11] = 3; ja[12] = 6; ja[13] = 11; 41 ia[0] = 0; ia[1] = 3; ia[2] = 7; ia[3] = 11; ia[4] = 14; 42 membershipKey = 0; 43 } else if (rank == 2) { 44 ja[0] = 4; ja[1] = 9; ja[2] = 12; ja[3] = 5; ja[4] = 8; ja[5] = 10; ja[6] = 13; ja[7] = 6; 45 ja[8] = 9; ja[9] = 11; ja[10] = 14; ja[11] = 7; ja[12] = 10; ja[13] = 15; 46 ia[0] = 0; ia[1] = 3; ia[2] = 7; ia[3] = 11; ia[4] = 14; 47 membershipKey = 1; 48 } else { 49 ja[0] = 8; ja[1] = 13; ja[2] = 9; ja[3] = 12; ja[4] = 14; ja[5] = 10; ja[6] = 13; ja[7] = 15; 50 ja[8] = 11; ja[9] = 14; 51 ia[0] = 0; ia[1] = 2; ia[2] = 5; ia[3] = 8; ia[4] = 10; 52 membershipKey = 1; 53 } 54 PetscCall(MatCreateMPIAdj(comm,4,16,ia,ja,NULL,&A)); 55 PetscCall(MatView(A,PETSC_VIEWER_STDOUT_WORLD)); 56 /* 57 Partition the graph of the matrix 58 */ 59 PetscCall(MatPartitioningCreate(comm,&part)); 60 PetscCall(MatPartitioningSetAdjacency(part,A)); 61 PetscCall(MatPartitioningSetType(part,MATPARTITIONINGHIERARCH)); 62 PetscCall(MatPartitioningHierarchicalSetNcoarseparts(part,2)); 63 PetscCall(MatPartitioningHierarchicalSetNfineparts(part,2)); 64 PetscCall(MatPartitioningSetFromOptions(part)); 65 /* get new processor owner number of each vertex */ 66 PetscCall(MatPartitioningApply(part,&is)); 67 /* coarse parts */ 68 PetscCall(MatPartitioningHierarchicalGetCoarseparts(part,&coarseparts)); 69 PetscCall(ISView(coarseparts,PETSC_VIEWER_STDOUT_WORLD)); 70 /* fine parts */ 71 PetscCall(MatPartitioningHierarchicalGetFineparts(part,&fineparts)); 72 PetscCall(ISView(fineparts,PETSC_VIEWER_STDOUT_WORLD)); 73 /* partitioning */ 74 PetscCall(ISView(is,PETSC_VIEWER_STDOUT_WORLD)); 75 /* compute coming rows */ 76 PetscCall(ISBuildTwoSided(is,NULL,&isrows)); 77 PetscCall(ISView(isrows,PETSC_VIEWER_STDOUT_WORLD)); 78 /*create a sub-communicator */ 79 PetscCallMPI(MPI_Comm_split(comm, membershipKey,rank,&scomm)); 80 PetscCall(ISGetLocalSize(isrows,&isrows_localsize)); 81 PetscCall(PetscMalloc1(isrows_localsize,&indices_sc)); 82 PetscCall(ISGetIndices(isrows,&indices)); 83 PetscCall(PetscArraycpy(indices_sc,indices,isrows_localsize)); 84 PetscCall(ISRestoreIndices(isrows,&indices)); 85 PetscCall(ISDestroy(&is)); 86 PetscCall(ISDestroy(&coarseparts)); 87 PetscCall(ISDestroy(&fineparts)); 88 PetscCall(ISDestroy(&isrows)); 89 PetscCall(MatPartitioningDestroy(&part)); 90 /*create a sub-IS on the sub communicator */ 91 PetscCall(ISCreateGeneral(scomm,isrows_localsize,indices_sc,PETSC_OWN_POINTER,&isrows_sc)); 92 PetscCall(MatConvert(A,MATMPIAIJ,MAT_INITIAL_MATRIX,&B)); 93 #if 1 94 PetscCall(MatView(B,PETSC_VIEWER_STDOUT_WORLD)); 95 #endif 96 /*increase overlap */ 97 PetscCall(MatIncreaseOverlapSplit(B,1,&isrows_sc,1)); 98 PetscCall(ISView(isrows_sc,NULL)); 99 PetscCall(ISDestroy(&isrows_sc)); 100 /* 101 Free work space. All PETSc objects should be destroyed when they 102 are no longer needed. 103 */ 104 PetscCall(MatDestroy(&A)); 105 PetscCall(MatDestroy(&B)); 106 PetscCall(PetscFinalize()); 107 return 0; 108 } 109