Actual source code: ex5.c
petsc-3.6.4 2016-04-12
2: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\
3: This does case when we are merely selecting the local part of the\n\
4: parallel vector.\n\n";
6: #include <petscvec.h>
10: int main(int argc,char **argv)
11: {
13: PetscMPIInt size,rank;
14: PetscInt n = 5,i;
15: PetscScalar value;
16: Vec x,y;
17: IS is1,is2;
18: VecScatter ctx = 0;
20: PetscInitialize(&argc,&argv,(char*)0,help);
21: MPI_Comm_size(PETSC_COMM_WORLD,&size);
22: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
24: /* create two vectors */
25: VecCreate(PETSC_COMM_WORLD,&x);
26: VecSetSizes(x,PETSC_DECIDE,size*n);
27: VecSetFromOptions(x);
28: VecCreateSeq(PETSC_COMM_SELF,n,&y);
30: /* create two index sets */
31: ISCreateStride(PETSC_COMM_SELF,n,n*rank,1,&is1);
32: ISCreateStride(PETSC_COMM_SELF,n,0,1,&is2);
34: /* each processor inserts the entire vector */
35: /* this is redundant but tests assembly */
36: for (i=0; i<n*size; i++) {
37: value = (PetscScalar) i;
38: VecSetValues(x,1,&i,&value,INSERT_VALUES);
39: }
40: VecAssemblyBegin(x);
41: VecAssemblyEnd(x);
42: VecView(x,PETSC_VIEWER_STDOUT_WORLD);
44: VecScatterCreate(x,is1,y,is2,&ctx);
45: VecScatterBegin(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
46: VecScatterEnd(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
47: VecScatterDestroy(&ctx);
49: if (!rank) {
50: printf("----\n");
51: VecView(y,PETSC_VIEWER_STDOUT_SELF);
52: }
54: VecDestroy(&x);
55: VecDestroy(&y);
56: ISDestroy(&is1);
57: ISDestroy(&is2);
59: PetscFinalize();
60: return 0;
61: }