Actual source code: ex17.c

petsc-master 2017-06-21
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  1: static char help[] = "Example of using graph partitioning with a matrix in which some procs have empty ownership\n\n";

  3: /*T
  4:    Concepts: Mat^mat partitioning
  5:    Concepts: Mat^image segmentation
  6:    Processors: n
  7: T*/

  9:  #include <petscmat.h>

 11: int main(int argc, char **args)
 12: {
 13:   Mat             A;
 14:   MatPartitioning part;
 15:   IS              is;
 16:   PetscInt        i,m,N,rstart,rend,nemptyranks,*emptyranks,nbigranks,*bigranks;
 17:   PetscMPIInt     rank,size;
 18:   PetscErrorCode  ierr;

 20:   PetscInitialize(&argc,&args,(char*)0,help);
 21:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 22:   MPI_Comm_size(PETSC_COMM_WORLD,&size);

 24:   nemptyranks = 10;
 25:   nbigranks   = 10;
 26:   PetscMalloc2(nemptyranks,&emptyranks,nbigranks,&bigranks);

 28:   PetscOptionsBegin(PETSC_COMM_WORLD,NULL,"Partitioning example options",NULL);
 29:   PetscOptionsIntArray("-emptyranks","Ranks to be skipped by partition","",emptyranks,&nemptyranks,NULL);
 30:   PetscOptionsIntArray("-bigranks","Ranks to be overloaded","",bigranks,&nbigranks,NULL);
 31:   PetscOptionsEnd();

 33:   m = 1;
 34:   for (i=0; i<nemptyranks; i++) if (rank == emptyranks[i]) m = 0;
 35:   for (i=0; i<nbigranks; i++) if (rank == bigranks[i]) m = 5;

 37:   MatCreate(PETSC_COMM_WORLD,&A);
 38:   MatSetSizes(A,m,m,PETSC_DECIDE,PETSC_DECIDE);
 39:   MatSetFromOptions(A);
 40:   MatSeqAIJSetPreallocation(A,3,NULL);
 41:   MatMPIAIJSetPreallocation(A,3,NULL,2,NULL);
 42:   MatSeqBAIJSetPreallocation(A,1,3,NULL);
 43:   MatMPIBAIJSetPreallocation(A,1,3,NULL,2,NULL);
 44:   MatSeqSBAIJSetPreallocation(A,1,2,NULL);
 45:   MatMPISBAIJSetPreallocation(A,1,2,NULL,1,NULL);

 47:   MatGetSize(A,NULL,&N);
 48:   MatGetOwnershipRange(A,&rstart,&rend);
 49:   for (i=rstart; i<rend; i++) {
 50:     const PetscInt    cols[] = {(i+N-1)%N,i,(i+1)%N};
 51:     const PetscScalar vals[] = {1,1,1};
 52:     MatSetValues(A,1,&i,3,cols,vals,INSERT_VALUES);
 53:   }
 54:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 55:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
 56:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

 58:   MatPartitioningCreate(PETSC_COMM_WORLD,&part);
 59:   MatPartitioningSetAdjacency(part,A);
 60:   MatPartitioningSetFromOptions(part);
 61:   MatPartitioningApply(part,&is);
 62:   ISView(is,PETSC_VIEWER_STDOUT_WORLD);
 63:   ISDestroy(&is);
 64:   MatPartitioningDestroy(&part);
 65:   MatDestroy(&A);
 66:   PetscFree2(emptyranks,bigranks);
 67:   PetscFinalize();
 68:   return ierr;
 69: }