Actual source code: ex12.c

  2: static char help[] = "Scatters from a sequential vector to a parallel vector.\n\
  3: This does case when we are merely selecting the local part of the\n\
  4: parallel vector.\n";

 6:  #include petscvec.h

 10: int main(int argc,char **argv)
 11: {
 13:   PetscMPIInt    size,rank;
 14:   PetscInt       n = 5,i;
 15:   PetscScalar    value;
 16:   Vec            x,y;
 17:   IS             is1,is2;
 18:   VecScatter     ctx = 0;

 20:   PetscInitialize(&argc,&argv,(char*)0,help);

 22:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 23:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 25:   /* create two vectors */
 26:   VecCreate(PETSC_COMM_WORLD,&x);
 27:   VecSetSizes(x,PETSC_DECIDE,size*n);
 28:   VecSetFromOptions(x);
 29:   VecCreateSeq(PETSC_COMM_SELF,n,&y);

 31:   /* create two index sets */
 32:   ISCreateStride(PETSC_COMM_SELF,n,n*rank,1,&is1);
 33:   ISCreateStride(PETSC_COMM_SELF,n,0,1,&is2);

 35:   /* each processor inserts the entire vector */
 36:   /* this is redundant but tests assembly */
 37:   for (i=0; i<n; i++) {
 38:     value = (PetscScalar) (i + 10*rank);
 39:     VecSetValues(y,1,&i,&value,INSERT_VALUES);
 40:   }
 41:   VecAssemblyBegin(y);
 42:   VecAssemblyEnd(y);

 44:   VecScatterCreate(y,is2,x,is1,&ctx);
 45:   VecScatterBegin(ctx,y,x,INSERT_VALUES,SCATTER_FORWARD);
 46:   VecScatterEnd(ctx,y,x,INSERT_VALUES,SCATTER_FORWARD);
 47:   VecScatterDestroy(ctx);
 48: 
 49:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

 51:   VecDestroy(x);
 52:   VecDestroy(y);
 53:   ISDestroy(is1);
 54:   ISDestroy(is2);

 56:   PetscFinalize();
 57:   return 0;
 58: }
 59: