Actual source code: ex22.c
petsc-3.9.2 2018-05-20
2: static char help[] = "Scatters from a parallel vector to a parallel vector.\n\n";
4: /*T
5: requires: x
6: T*/
8: #include <petscvec.h>
10: int main(int argc,char **argv)
11: {
13: PetscInt n = 5,N,i;
14: PetscMPIInt size,rank;
15: PetscScalar value,zero = 0.0;
16: Vec x,y;
17: IS is1,is2;
18: VecScatter ctx = 0;
20: PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
21: MPI_Comm_size(PETSC_COMM_WORLD,&size);
22: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
24: /* create two vectors */
25: N = size*n;
26: VecCreate(PETSC_COMM_WORLD,&y);
27: VecSetSizes(y,n,PETSC_DECIDE);
28: VecSetFromOptions(y);
30: VecCreate(PETSC_COMM_WORLD,&x);
31: VecSetSizes(x,n,PETSC_DECIDE);
32: VecSetFromOptions(x);
34: /* create two index sets */
35: ISCreateStride(PETSC_COMM_WORLD,n,n*rank,1,&is1);
36: ISCreateStride(PETSC_COMM_WORLD,n,(n*(rank+1))%N,1,&is2);
38: /* fill local part of parallel vector x */
39: value = (PetscScalar)(rank+1);
40: for (i=n*rank; i<n*(rank+1); i++) {
41: VecSetValues(x,1,&i,&value,INSERT_VALUES);
42: }
43: VecAssemblyBegin(x);
44: VecAssemblyEnd(x);
46: VecSet(y,zero);
48: VecScatterCreate(x,is1,y,is2,&ctx);
49: VecScatterBegin(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
50: VecScatterEnd(ctx,x,y,ADD_VALUES,SCATTER_FORWARD);
51: VecScatterDestroy(&ctx);
53: VecView(y,PETSC_VIEWER_STDOUT_WORLD);
55: VecDestroy(&x);
56: VecDestroy(&y);
57: ISDestroy(&is1);
58: ISDestroy(&is2);
60: PetscFinalize();
61: return ierr;
62: }
66: /*TEST
68: test:
69: nsize: 4
71: TEST*/