Actual source code: ex17.c
petsc-3.5.4 2015-05-23
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>
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: VecCreateSeq(PETSC_COMM_SELF,N,&x);
30: /* create two index sets */
31: ISCreateStride(PETSC_COMM_SELF,N,0,1,&is1);
32: ISCreateStride(PETSC_COMM_SELF,N,0,1,&is2);
34: VecSet(x,zero);
35: VecGetOwnershipRange(y,&low,&high);
36: for (i=0; i<n; i++) {
37: iglobal = i + low; value = (PetscScalar) (i + 10*rank);
38: VecSetValues(y,1,&iglobal,&value,INSERT_VALUES);
39: }
40: VecAssemblyBegin(y);
41: VecAssemblyEnd(y);
42: VecView(y,PETSC_VIEWER_STDOUT_WORLD);
44: VecScatterCreate(y,is2,x,is1,&ctx);
45: VecScatterBegin(ctx,y,x,ADD_VALUES,SCATTER_FORWARD);
46: VecScatterEnd(ctx,y,x,ADD_VALUES,SCATTER_FORWARD);
47: VecScatterDestroy(&ctx);
49: if (!rank) {
50: printf("----\n");
51: VecView(x,PETSC_VIEWER_STDOUT_SELF);
52: }
54: VecDestroy(&x);
55: VecDestroy(&y);
56: ISDestroy(&is1);
57: ISDestroy(&is2);
59: PetscFinalize();
60: return 0;
61: }