Actual source code: ex11.c
petsc-3.12.2 2019-11-22
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: {
9: PetscMPIInt size,rank;
10: PetscInt i,N;
11: PetscScalar value;
12: Vec x,y;
13: IS is1,is2;
14: VecScatter ctx = 0;
16: PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
17: MPI_Comm_size(PETSC_COMM_WORLD,&size);
18: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
20: /* create two vectors */
21: VecCreate(PETSC_COMM_WORLD,&x);
22: VecSetSizes(x,rank+1,PETSC_DECIDE);
23: VecSetFromOptions(x);
24: VecGetSize(x,&N);
25: VecCreateSeq(PETSC_COMM_SELF,N-rank,&y);
27: /* create two index sets */
28: ISCreateStride(PETSC_COMM_SELF,N-rank,rank,1,&is1);
29: ISCreateStride(PETSC_COMM_SELF,N-rank,0,1,&is2);
31: /* fill parallel vector: note this is not efficient way*/
32: for (i=0; i<N; i++) {
33: value = (PetscScalar) i;
34: VecSetValues(x,1,&i,&value,INSERT_VALUES);
35: }
36: VecAssemblyBegin(x);
37: VecAssemblyEnd(x);
38: VecSet(y,-1.0);
40: VecView(x,PETSC_VIEWER_STDOUT_WORLD);
42: VecScatterCreate(x,is1,y,is2,&ctx);
43: VecScatterBegin(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
44: VecScatterEnd(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
45: VecScatterDestroy(&ctx);
47: if (!rank) {
48: printf("----\n");
49: VecView(y,PETSC_VIEWER_STDOUT_SELF);
50: }
52: ISDestroy(&is1);
53: ISDestroy(&is2);
54: VecDestroy(&x);
55: VecDestroy(&y);
57: PetscFinalize();
58: return ierr;
59: }
63: /*TEST
65: test:
66: nsize: 2
68: test:
69: suffix: bts
70: nsize: 2
71: args: -vec_assembly_legacy
72: output_file: output/ex11_1.out
74: TEST*/