Date: 2022-08-02T03:14:09+00:00

Actual source code: ex17.c

      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*/