Actual source code: ex17.c
2: static char help[] = "Scatters from a parallel vector to a sequential vector. In\n\
3: this case each local vector is as long as the entire parallel vector.\n\n";
5: #include <petscvec.h>
7: int main(int argc,char **argv)
8: {
9: PetscInt n = 5,N,low,high,iglobal,i;
10: PetscMPIInt size,rank;
11: PetscScalar value,zero = 0.0;
12: Vec x,y;
13: IS is1,is2;
14: VecScatter ctx;
16: PetscInitialize(&argc,&argv,(char*)0,help);
17: MPI_Comm_size(PETSC_COMM_WORLD,&size);
18: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
20: /* create two vectors */
21: N = size*n;
22: VecCreate(PETSC_COMM_WORLD,&y);
23: VecSetSizes(y,PETSC_DECIDE,N);
24: VecSetFromOptions(y);
25: VecCreateSeq(PETSC_COMM_SELF,N,&x);
27: /* create two index sets */
28: ISCreateStride(PETSC_COMM_SELF,N,0,1,&is1);
29: ISCreateStride(PETSC_COMM_SELF,N,0,1,&is2);
31: VecSet(x,zero);
32: VecGetOwnershipRange(y,&low,&high);
33: for (i=0; i<n; i++) {
34: iglobal = i + low; value = (PetscScalar) (i + 10*rank);
35: VecSetValues(y,1,&iglobal,&value,INSERT_VALUES);
36: }
37: VecAssemblyBegin(y);
38: VecAssemblyEnd(y);
39: VecView(y,PETSC_VIEWER_STDOUT_WORLD);
41: VecScatterCreate(y,is2,x,is1,&ctx);
42: VecScatterBegin(ctx,y,x,ADD_VALUES,SCATTER_FORWARD);
43: VecScatterEnd(ctx,y,x,ADD_VALUES,SCATTER_FORWARD);
44: VecScatterDestroy(&ctx);
46: if (rank == 0) {
47: PetscPrintf(PETSC_COMM_SELF,"----\n");
48: VecView(x,PETSC_VIEWER_STDOUT_SELF);
49: }
51: VecDestroy(&x);
52: VecDestroy(&y);
53: ISDestroy(&is1);
54: ISDestroy(&is2);
56: PetscFinalize();
57: return 0;
58: }
60: /*TEST
62: test:
63: nsize: 2
65: TEST*/