Actual source code: ex5.c
2: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\
3: This does case when we are merely selecting the local part of the\n\
4: parallel vector.\n\n";
6: #include petscvec.h
7: #include petscsys.h
11: int main(int argc,char **argv)
12: {
14: PetscMPIInt size,rank;
15: PetscInt n = 5,i;
16: PetscScalar value;
17: Vec x,y;
18: IS is1,is2;
19: VecScatter ctx = 0;
21: PetscInitialize(&argc,&argv,(char*)0,help);
22: MPI_Comm_size(PETSC_COMM_WORLD,&size);
23: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
25: /* create two vectors */
26: VecCreate(PETSC_COMM_WORLD,&x);
27: VecSetSizes(x,PETSC_DECIDE,size*n);
28: VecSetFromOptions(x);
29: VecCreateSeq(PETSC_COMM_SELF,n,&y);
31: /* create two index sets */
32: ISCreateStride(PETSC_COMM_SELF,n,n*rank,1,&is1);
33: ISCreateStride(PETSC_COMM_SELF,n,0,1,&is2);
35: /* each processor inserts the entire vector */
36: /* this is redundant but tests assembly */
37: for (i=0; i<n*size; i++) {
38: value = (PetscScalar) i;
39: VecSetValues(x,1,&i,&value,INSERT_VALUES);
40: }
41: VecAssemblyBegin(x);
42: VecAssemblyEnd(x);
43: VecView(x,PETSC_VIEWER_STDOUT_WORLD);
45: VecScatterCreate(x,is1,y,is2,&ctx);
46: VecScatterBegin(x,y,INSERT_VALUES,SCATTER_FORWARD,ctx);
47: VecScatterEnd(x,y,INSERT_VALUES,SCATTER_FORWARD,ctx);
48: VecScatterDestroy(ctx);
49:
50: if (!rank)
51: {printf("----\n"); VecView(y,PETSC_VIEWER_STDOUT_SELF);}
53: VecDestroy(x);
54: VecDestroy(y);
55: ISDestroy(is1);
56: ISDestroy(is2);
58: PetscFinalize();
59: return 0;
60: }
61: