Actual source code: ex25.c
petsc-3.7.3 2016-07-24
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>
9: int main(int argc,char **argv)
10: {
12: PetscInt n = 5,N,low,high,iglobal,i;
13: PetscMPIInt size,rank;
14: PetscScalar value,zero = 0.0;
15: Vec x,y;
16: IS is1,is2;
17: VecScatter ctx;
19: PetscInitialize(&argc,&argv,(char*)0,help);
20: MPI_Comm_size(PETSC_COMM_WORLD,&size);
21: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
23: /* create two vectors */
24: N = size*n;
25: VecCreate(PETSC_COMM_WORLD,&y);
26: VecSetSizes(y,PETSC_DECIDE,N);
27: VecSetFromOptions(y);
28: if (!rank) {
29: VecCreateSeq(PETSC_COMM_SELF,N,&x);
30: } else {
31: VecCreateSeq(PETSC_COMM_SELF,0,&x);
32: }
34: /* create two index sets */
35: if (!rank) {
36: ISCreateStride(PETSC_COMM_SELF,N,0,1,&is1);
37: ISCreateStride(PETSC_COMM_SELF,N,0,1,&is2);
38: } else {
39: ISCreateStride(PETSC_COMM_SELF,0,0,1,&is1);
40: ISCreateStride(PETSC_COMM_SELF,0,0,1,&is2);
41: }
43: VecSet(x,zero);
44: VecGetOwnershipRange(y,&low,&high);
45: for (i=0; i<n; i++) {
46: iglobal = i + low; value = (PetscScalar) (i + 10*rank);
47: VecSetValues(y,1,&iglobal,&value,INSERT_VALUES);
48: }
49: VecAssemblyBegin(y);
50: VecAssemblyEnd(y);
51: VecView(y,PETSC_VIEWER_STDOUT_WORLD);
53: VecScatterCreate(y,is2,x,is1,&ctx);
54: VecScatterBegin(ctx,y,x,ADD_VALUES,SCATTER_FORWARD);
55: VecScatterEnd(ctx,y,x,ADD_VALUES,SCATTER_FORWARD);
56: VecScatterDestroy(&ctx);
58: if (!rank) {
59: printf("----\n");
60: VecView(x,PETSC_VIEWER_STDOUT_SELF);
61: }
63: VecDestroy(&x);
64: VecDestroy(&y);
65: ISDestroy(&is1);
66: ISDestroy(&is2);
68: PetscFinalize();
69: return 0;
70: }