Actual source code: ex12.c

  1: /*$Id: ex12.c,v 1.48 2001/03/23 23:21:30 balay Exp $*/

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

  7: #include "petscvec.h"
  8: #include "petscsys.h"

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

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

 20:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 21:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 23:   /* create two vectors */
 24:   VecCreateMPI(PETSC_COMM_WORLD,PETSC_DECIDE,size*n,&x);
 25:   VecCreateSeq(PETSC_COMM_SELF,n,&y);

 27:   /* create two index sets */
 28:   ISCreateStride(PETSC_COMM_SELF,n,n*rank,1,&is1);
 29:   ISCreateStride(PETSC_COMM_SELF,n,0,1,&is2);

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

 40:   VecScatterCreate(y,is2,x,is1,&ctx);
 41:   VecScatterBegin(y,x,INSERT_VALUES,SCATTER_FORWARD,ctx);
 42:   VecScatterEnd(y,x,INSERT_VALUES,SCATTER_FORWARD,ctx);
 43:   VecScatterDestroy(ctx);
 44: 
 45:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

 47:   VecDestroy(x);
 48:   VecDestroy(y);
 49:   ISDestroy(is1);
 50:   ISDestroy(is2);

 52:   PetscFinalize();
 53:   return 0;
 54: }
 55: