Actual source code: ex5.c
1: /*$Id: ex5.c,v 1.50 2001/03/23 23:21:30 balay Exp $*/
3: static char help[] = "Scatters from a parallel vector to a sequential vector.n
4: This does case when we are merely selecting the local part of then
5: parallel vector.nn";
7: #include "petscvec.h"
8: #include "petscsys.h"
10: int main(int argc,char **argv)
11: {
12: int n = 5,ierr,size,rank,i;
13: Scalar value;
14: Vec x,y;
15: IS is1,is2;
16: VecScatter ctx = 0;
18: PetscInitialize(&argc,&argv,(char*)0,help);
19: MPI_Comm_size(PETSC_COMM_WORLD,&size);
20: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
22: /* create two vectors */
23: VecCreateMPI(PETSC_COMM_WORLD,PETSC_DECIDE,size*n,&x);
24: VecCreateSeq(PETSC_COMM_SELF,n,&y);
26: /* create two index sets */
27: ISCreateStride(PETSC_COMM_SELF,n,n*rank,1,&is1);
28: ISCreateStride(PETSC_COMM_SELF,n,0,1,&is2);
30: /* each processor inserts the entire vector */
31: /* this is redundant but tests assembly */
32: for (i=0; i<n*size; i++) {
33: value = (Scalar) i;
34: VecSetValues(x,1,&i,&value,INSERT_VALUES);
35: }
36: VecAssemblyBegin(x);
37: VecAssemblyEnd(x);
38: VecView(x,PETSC_VIEWER_STDOUT_WORLD);
40: VecScatterCreate(x,is1,y,is2,&ctx);
41: VecScatterBegin(x,y,INSERT_VALUES,SCATTER_FORWARD,ctx);
42: VecScatterEnd(x,y,INSERT_VALUES,SCATTER_FORWARD,ctx);
43: VecScatterDestroy(ctx);
44:
45: if (!rank)
46: {printf("----n"); VecView(y,PETSC_VIEWER_STDOUT_SELF);}
48: VecDestroy(x);
49: VecDestroy(y);
50: ISDestroy(is1);
51: ISDestroy(is2);
53: PetscFinalize();
54: return 0;
55: }
56: