Actual source code: ex22.c

  1: /*$Id: ex22.c,v 1.21 2001/03/23 23:21:30 balay Exp $*/

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

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

  8: int main(int argc,char **argv)
  9: {
 10:   int           n = 5,ierr;
 11:   int           size,rank,N;
 12:   Scalar        value,zero = 0.0;
 13:   Vec           x,y;
 14:   IS            is1,is2;
 15:   VecScatter    ctx = 0;

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

 21:   /* create two vectors */
 22:   N = size*n;
 23:   VecCreateMPI(PETSC_COMM_WORLD,PETSC_DECIDE,N,&y);
 24:   VecCreateMPI(PETSC_COMM_WORLD,PETSC_DECIDE,N,&x);

 26:   /* create two index sets */
 27:   ISCreateStride(PETSC_COMM_WORLD,n,n*rank,1,&is1);
 28:   ISCreateStride(PETSC_COMM_WORLD,n,(n*(rank+1))%N,1,&is2);

 30:   value = (Scalar)(rank+1);
 31:   VecSet(&value,x);
 32:   VecSet(&zero,y);

 34:   VecScatterCreate(x,is1,y,is2,&ctx);
 35:   VecScatterBegin(x,y,ADD_VALUES,SCATTER_FORWARD,ctx);
 36:   VecScatterEnd(x,y,ADD_VALUES,SCATTER_FORWARD,ctx);
 37:   VecScatterDestroy(ctx);
 38: 
 39:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);

 41:   VecDestroy(x);
 42:   VecDestroy(y);
 43:   ISDestroy(is1);
 44:   ISDestroy(is2);

 46:   PetscFinalize();
 47:   return 0;
 48: }
 49: