Actual source code: ex25.c
2: static char help[] = "Scatters from a parallel vector to a sequential vector. In\n\
3: this case processor zero is as long as the entire parallel vector; rest are zero length.\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: if (rank == 0) {
26: VecCreateSeq(PETSC_COMM_SELF,N,&x);
27: } else {
28: VecCreateSeq(PETSC_COMM_SELF,0,&x);
29: }
31: /* create two index sets */
32: if (rank == 0) {
33: ISCreateStride(PETSC_COMM_SELF,N,0,1,&is1);
34: ISCreateStride(PETSC_COMM_SELF,N,0,1,&is2);
35: } else {
36: ISCreateStride(PETSC_COMM_SELF,0,0,1,&is1);
37: ISCreateStride(PETSC_COMM_SELF,0,0,1,&is2);
38: }
40: VecSet(x,zero);
41: VecGetOwnershipRange(y,&low,&high);
42: for (i=0; i<n; i++) {
43: iglobal = i + low; value = (PetscScalar) (i + 10*rank);
44: VecSetValues(y,1,&iglobal,&value,INSERT_VALUES);
45: }
46: VecAssemblyBegin(y);
47: VecAssemblyEnd(y);
48: VecView(y,PETSC_VIEWER_STDOUT_WORLD);
50: VecScatterCreate(y,is2,x,is1,&ctx);
51: VecScatterBegin(ctx,y,x,ADD_VALUES,SCATTER_FORWARD);
52: VecScatterEnd(ctx,y,x,ADD_VALUES,SCATTER_FORWARD);
53: VecScatterDestroy(&ctx);
55: if (rank == 0) {
56: PetscPrintf(PETSC_COMM_SELF,"----\n");
57: VecView(x,PETSC_VIEWER_STDOUT_SELF);
58: }
60: VecDestroy(&x);
61: VecDestroy(&y);
62: ISDestroy(&is1);
63: ISDestroy(&is2);
65: PetscFinalize();
66: return 0;
67: }
69: /*TEST
71: test:
72: nsize: 3
74: TEST*/