Actual source code: ex22.c
2: static char help[] = "Scatters from a parallel vector to a parallel vector.\n\n";
4: #include petscvec.h
5: #include petscsys.h
9: int main(int argc,char **argv)
10: {
12: PetscInt n = 5,N,i;
13: PetscMPIInt size,rank;
14: PetscScalar value,zero = 0.0;
15: Vec x,y;
16: IS is1,is2;
17: VecScatter ctx = 0;
19: PetscInitialize(&argc,&argv,(char*)0,help);
20: MPI_Comm_size(PETSC_COMM_WORLD,&size);
21: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
23: /* create two vectors */
24: N = size*n;
25: VecCreate(PETSC_COMM_WORLD,&y);
26: VecSetSizes(y,n,PETSC_DECIDE);CHKERRQ(ierr)
27: VecSetFromOptions(y);
29: VecCreate(PETSC_COMM_WORLD,&x);
30: VecSetSizes(x,n,PETSC_DECIDE);
31: VecSetFromOptions(x);
33: /* create two index sets */
34: ISCreateStride(PETSC_COMM_WORLD,n,n*rank,1,&is1);
35: ISCreateStride(PETSC_COMM_WORLD,n,(n*(rank+1))%N,1,&is2);
37: /* fill local part of parallel vector x */
38: value = (PetscScalar)(rank+1);
39: for (i=n*rank; i<n*(rank+1); i++) {
40: VecSetValues(x,1,&i,&value,INSERT_VALUES);
41: }
42: VecAssemblyBegin(x);
43: VecAssemblyEnd(x);
45: VecSet(y,zero);
47: VecScatterCreate(x,is1,y,is2,&ctx);
48: VecScatterBegin(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
49: VecScatterEnd(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
50: VecScatterDestroy(ctx);
51:
52: VecView(y,PETSC_VIEWER_STDOUT_WORLD);
54: VecDestroy(x);
55: VecDestroy(y);
56: ISDestroy(is1);
57: ISDestroy(is2);
59: PetscFinalize();
60: return 0;
61: }
62: