Actual source code: ex5.c

  1: /*$Id: ex5.c,v 1.53 2001/09/11 16:32:10 bsmith Exp $*/

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

 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:   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,PETSC_DECIDE,size*n);
 25:   VecSetFromOptions(x);
 26:   VecCreateSeq(PETSC_COMM_SELF,n,&y);

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

 32:   /* each processor inserts the entire vector */
 33:   /* this is redundant but tests assembly */
 34:   for (i=0; i<n*size; i++) {
 35:     value = (PetscScalar) i;
 36:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 37:   }
 38:   VecAssemblyBegin(x);
 39:   VecAssemblyEnd(x);
 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);
 46: 
 47:   if (!rank)
 48:    {printf("----n"); VecView(y,PETSC_VIEWER_STDOUT_SELF);}

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

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