Actual source code: ex11.c
2: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\n";
4: #include <petscvec.h>
6: int main(int argc,char **argv)
7: {
8: PetscMPIInt size,rank;
9: PetscInt i,N;
10: PetscScalar value;
11: Vec x,y;
12: IS is1,is2;
13: VecScatter ctx = 0;
15: PetscInitialize(&argc,&argv,(char*)0,help);
16: MPI_Comm_size(PETSC_COMM_WORLD,&size);
17: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
19: /* create two vectors */
20: VecCreate(PETSC_COMM_WORLD,&x);
21: VecSetSizes(x,rank+1,PETSC_DECIDE);
22: VecSetFromOptions(x);
23: VecGetSize(x,&N);
24: VecCreateSeq(PETSC_COMM_SELF,N-rank,&y);
26: /* create two index sets */
27: ISCreateStride(PETSC_COMM_SELF,N-rank,rank,1,&is1);
28: ISCreateStride(PETSC_COMM_SELF,N-rank,0,1,&is2);
30: /* fill parallel vector: note this is not efficient way*/
31: for (i=0; i<N; i++) {
32: value = (PetscScalar) i;
33: VecSetValues(x,1,&i,&value,INSERT_VALUES);
34: }
35: VecAssemblyBegin(x);
36: VecAssemblyEnd(x);
37: VecSet(y,-1.0);
39: VecView(x,PETSC_VIEWER_STDOUT_WORLD);
41: VecScatterCreate(x,is1,y,is2,&ctx);
42: VecScatterBegin(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
43: VecScatterEnd(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
44: VecScatterDestroy(&ctx);
46: if (rank == 0) {
47: PetscPrintf(PETSC_COMM_SELF,"----\n");
48: VecView(y,PETSC_VIEWER_STDOUT_SELF);
49: }
51: ISDestroy(&is1);
52: ISDestroy(&is2);
53: VecDestroy(&x);
54: VecDestroy(&y);
56: PetscFinalize();
57: return 0;
58: }
60: /*TEST
62: test:
63: nsize: 2
65: test:
66: suffix: bts
67: nsize: 2
68: args: -vec_assembly_legacy
69: output_file: output/ex11_1.out
71: TEST*/