Actual source code: ex11.c

  1: /*$Id: ex11.c,v 1.52 2001/09/11 16:32:10 bsmith Exp $*/

  3: static char help[] = "Scatters from a parallel vector to a sequential vector.nn";

 5:  #include petscvec.h
 6:  #include petscsys.h

  8: int main(int argc,char **argv)
  9: {
 10:   int           ierr,size,rank,i,N;
 11:   PetscScalar   mone = -1.0,value;
 12:   Vec           x,y;
 13:   IS            is1,is2;
 14:   VecScatter    ctx = 0;

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

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

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

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

 40:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

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

 47:   if (!rank)
 48:     {printf("----n"); VecView(y,PETSC_VIEWER_STDOUT_SELF);}

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

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