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: