Actual source code: ex5.c
petsc-3.12.0 2019-09-29
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>
8: int main(int argc,char **argv)
9: {
11: PetscMPIInt size,rank;
12: PetscInt n = 5,i;
13: PetscScalar value;
14: Vec x,y;
15: IS is1,is2;
16: VecScatter ctx = 0;
18: PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
19: MPI_Comm_size(PETSC_COMM_WORLD,&size);
20: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
22: /* create two vectors */
23: VecCreate(PETSC_COMM_WORLD,&x);
24: VecSetSizes(x,PETSC_DECIDE,size*n);
25: VecSetFromOptions(x);
26: VecCreateSeq(PETSC_COMM_SELF,n,&y);
28: /* create two index sets */
29: ISCreateStride(PETSC_COMM_SELF,n,n*rank,1,&is1);
30: ISCreateStride(PETSC_COMM_SELF,n,0,1,&is2);
32: /* each processor inserts the entire vector */
33: /* this is redundant but tests assembly */
34: for (i=0; i<n*size; i++) {
35: value = (PetscScalar) i;
36: VecSetValues(x,1,&i,&value,INSERT_VALUES);
37: }
38: VecAssemblyBegin(x);
39: VecAssemblyEnd(x);
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: PetscPrintf(PETSC_COMM_SELF,"----\n");
49: VecView(y,PETSC_VIEWER_STDOUT_SELF);
50: }
52: VecDestroy(&x);
53: VecDestroy(&y);
54: ISDestroy(&is1);
55: ISDestroy(&is2);
57: PetscFinalize();
58: return ierr;
59: }
61: /*TEST
63: test:
64: nsize: 2
66: TEST*/