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: