Actual source code: ex17.c
petsc-3.12.1 2019-10-22
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: {
10: PetscInt n = 5,N,low,high,iglobal,i;
11: PetscMPIInt size,rank;
12: PetscScalar value,zero = 0.0;
13: Vec x,y;
14: IS is1,is2;
15: VecScatter ctx;
17: PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
18: MPI_Comm_size(PETSC_COMM_WORLD,&size);
19: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
21: /* create two vectors */
22: N = size*n;
23: VecCreate(PETSC_COMM_WORLD,&y);
24: VecSetSizes(y,PETSC_DECIDE,N);
25: VecSetFromOptions(y);
26: VecCreateSeq(PETSC_COMM_SELF,N,&x);
28: /* create two index sets */
29: ISCreateStride(PETSC_COMM_SELF,N,0,1,&is1);
30: ISCreateStride(PETSC_COMM_SELF,N,0,1,&is2);
32: VecSet(x,zero);
33: VecGetOwnershipRange(y,&low,&high);
34: for (i=0; i<n; i++) {
35: iglobal = i + low; value = (PetscScalar) (i + 10*rank);
36: VecSetValues(y,1,&iglobal,&value,INSERT_VALUES);
37: }
38: VecAssemblyBegin(y);
39: VecAssemblyEnd(y);
40: VecView(y,PETSC_VIEWER_STDOUT_WORLD);
42: VecScatterCreate(y,is2,x,is1,&ctx);
43: VecScatterBegin(ctx,y,x,ADD_VALUES,SCATTER_FORWARD);
44: VecScatterEnd(ctx,y,x,ADD_VALUES,SCATTER_FORWARD);
45: VecScatterDestroy(&ctx);
47: if (!rank) {
48: printf("----\n");
49: VecView(x,PETSC_VIEWER_STDOUT_SELF);
50: }
52: VecDestroy(&x);
53: VecDestroy(&y);
54: ISDestroy(&is1);
55: ISDestroy(&is2);
57: PetscFinalize();
58: return ierr;
59: }
63: /*TEST
65: test:
66: nsize: 2
68: TEST*/