Actual source code: ex11.c

  2: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\n";

 4:  #include petscvec.h

  8: int main(int argc,char **argv)
  9: {
 11:   PetscMPIInt    size,rank;
 12:   PetscInt       i,N;
 13:   PetscScalar    value;
 14:   Vec            x,y;
 15:   IS             is1,is2;
 16:   VecScatter     ctx = 0;

 18:   PetscInitialize(&argc,&argv,(char*)0,help);
 19:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 20:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 22:   /* create two vectors */
 23:   VecCreate(PETSC_COMM_WORLD,&x);
 24:   VecSetSizes(x,rank+1,PETSC_DECIDE);
 25:   VecSetFromOptions(x);
 26:   VecGetSize(x,&N);
 27:   VecCreateSeq(PETSC_COMM_SELF,N-rank,&y);

 29:   /* create two index sets */
 30:   ISCreateStride(PETSC_COMM_SELF,N-rank,rank,1,&is1);
 31:   ISCreateStride(PETSC_COMM_SELF,N-rank,0,1,&is2);

 33:   /* fill parallel vector: note this is not efficient way*/
 34:   for (i=0; i<N; i++) {
 35:     value = (PetscScalar) i;
 36:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 37:   }
 38:   VecAssemblyBegin(x);
 39:   VecAssemblyEnd(x);
 40:   VecSet(y,-1.0);

 42:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

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

 49:   if (!rank)
 50:     {printf("----\n"); VecView(y,PETSC_VIEWER_STDOUT_SELF);}

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

 57:   PetscFinalize();
 58:   return 0;
 59: }
 60: