Actual source code: ex9.c
2: static char help[]= "Scatters from a parallel vector to a sequential vector.\n\n";
4: #include petscvec.h
8: int main(int argc,char **argv)
9: {
11: PetscInt n = 5,i,idx2[3] = {0,2,3},idx1[3] = {0,1,2};
12: PetscMPIInt size,rank;
13: PetscScalar value;
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: VecCreate(PETSC_COMM_WORLD,&x);
24: VecSetSizes(x,PETSC_DECIDE,size*n);
25: VecSetFromOptions(x);
26: VecCreateSeq(PETSC_COMM_SELF,n,&y);
28: /* create two index sets */
29: ISCreateGeneral(PETSC_COMM_SELF,3,idx1,&is1);
30: ISCreateGeneral(PETSC_COMM_SELF,3,idx2,&is2);
32: /* fill local part of parallel vector */
33: for (i=n*rank; i<n*(rank+1); i++) {
34: value = (PetscScalar) i;
35: VecSetValues(x,1,&i,&value,INSERT_VALUES);
36: }
37: VecAssemblyBegin(x);
38: VecAssemblyEnd(x);
40: VecView(x,PETSC_VIEWER_STDOUT_WORLD);
42: VecSet(y,-1.0);
44: VecScatterCreate(x,is1,y,is2,&ctx);
45: VecScatterBegin(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
46: VecScatterEnd(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
47: VecScatterDestroy(ctx);
49: if (!rank) {
50: PetscPrintf(PETSC_COMM_SELF,"scattered vector\n");
51: VecView(y,PETSC_VIEWER_STDOUT_SELF);
52: }
53: ISDestroy(is1);
54: ISDestroy(is2);
55: VecDestroy(x);
56: VecDestroy(y);
58: PetscFinalize();
59: return 0;
60: }
61: