Actual source code: ex22.c

  1: /*$Id: ex22.c,v 1.24 2001/09/11 16:32:10 bsmith 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:   PetscScalar   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:   VecCreate(PETSC_COMM_WORLD,&y);
 24:   VecSetSizes(y,PETSC_DECIDE,N);
 25:   VecSetFromOptions(y);
 26:   VecCreate(PETSC_COMM_WORLD,&x);
 27:   VecSetSizes(x,PETSC_DECIDE,N);
 28:   VecSetFromOptions(x);
 29:   /* create two index sets */
 30:   ISCreateStride(PETSC_COMM_WORLD,n,n*rank,1,&is1);
 31:   ISCreateStride(PETSC_COMM_WORLD,n,(n*(rank+1))%N,1,&is2);

 33:   value = (PetscScalar)(rank+1);
 34:   VecSet(&value,x);
 35:   VecSet(&zero,y);

 37:   VecScatterCreate(x,is1,y,is2,&ctx);
 38:   VecScatterBegin(x,y,ADD_VALUES,SCATTER_FORWARD,ctx);
 39:   VecScatterEnd(x,y,ADD_VALUES,SCATTER_FORWARD,ctx);
 40:   VecScatterDestroy(ctx);
 41: 
 42:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);

 44:   VecDestroy(x);
 45:   VecDestroy(y);
 46:   ISDestroy(is1);
 47:   ISDestroy(is2);

 49:   PetscFinalize();
 50:   return 0;
 51: }
 52: