Actual source code: ex22.c

  2: static char help[] = "Scatters from a parallel vector to a parallel vector.\n\n";

 4:  #include petscvec.h

  8: int main(int argc,char **argv)
  9: {
 11:   PetscInt       n = 5,N,i;
 12:   PetscMPIInt    size,rank;
 13:   PetscScalar    value,zero = 0.0;
 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:   N = size*n;
 24:   VecCreate(PETSC_COMM_WORLD,&y);
 25:   VecSetSizes(y,n,PETSC_DECIDE);CHKERRQ(ierr)
 26:   VecSetFromOptions(y);

 28:   VecCreate(PETSC_COMM_WORLD,&x);
 29:   VecSetSizes(x,n,PETSC_DECIDE);
 30:   VecSetFromOptions(x);

 32:   /* create two index sets */
 33:   ISCreateStride(PETSC_COMM_WORLD,n,n*rank,1,&is1);
 34:   ISCreateStride(PETSC_COMM_WORLD,n,(n*(rank+1))%N,1,&is2);

 36:   /* fill local part of parallel vector x */
 37:   value = (PetscScalar)(rank+1);
 38:   for (i=n*rank; i<n*(rank+1); i++) {
 39:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 40:   }
 41:   VecAssemblyBegin(x);
 42:   VecAssemblyEnd(x);

 44:   VecSet(y,zero);

 46:   VecScatterCreate(x,is1,y,is2,&ctx);
 47:   VecScatterBegin(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
 48:   VecScatterEnd(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
 49:   VecScatterDestroy(ctx);
 50: 
 51:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);

 53:   VecDestroy(x);
 54:   VecDestroy(y);
 55:   ISDestroy(is1);
 56:   ISDestroy(is2);

 58:   PetscFinalize();
 59:   return 0;
 60: }
 61: