Actual source code: ex10.c
petsc-3.12.0 2019-09-29
2: static char help[]= "Scatters from a parallel vector to a sequential vector.\n\
3: uses block index sets\n\n";
5: #include <petscvec.h>
7: int main(int argc,char **argv)
8: {
10: PetscInt bs = 1,n = 5,ix0[3] = {5,7,9},ix1[3] = {2,3,4},i,iy0[3] = {1,2,4},iy1[3] = {0,1,3};
11: PetscMPIInt size,rank;
12: PetscScalar value;
13: Vec x,y;
14: IS isx,isy;
15: VecScatter ctx = 0,newctx;
17: PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
18: MPI_Comm_size(PETSC_COMM_WORLD,&size);
19: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
21: if (size != 2) SETERRQ(PETSC_COMM_SELF,1,"Must run with 2 processors");
23: PetscOptionsGetInt(NULL,NULL,"-bs",&bs,NULL);
24: n = bs*n;
26: /* create two vectors */
27: VecCreate(PETSC_COMM_WORLD,&x);
28: VecSetSizes(x,PETSC_DECIDE,size*n);
29: VecSetFromOptions(x);
30: VecCreateSeq(PETSC_COMM_SELF,n,&y);
32: /* create two index sets */
33: if (!rank) {
34: ISCreateBlock(PETSC_COMM_SELF,bs,3,ix0,PETSC_COPY_VALUES,&isx);
35: ISCreateBlock(PETSC_COMM_SELF,bs,3,iy0,PETSC_COPY_VALUES,&isy);
36: } else {
37: ISCreateBlock(PETSC_COMM_SELF,bs,3,ix1,PETSC_COPY_VALUES,&isx);
38: ISCreateBlock(PETSC_COMM_SELF,bs,3,iy1,PETSC_COPY_VALUES,&isy);
39: }
41: /* fill local part of parallel vector */
42: for (i=n*rank; i<n*(rank+1); i++) {
43: value = (PetscScalar) i;
44: VecSetValues(x,1,&i,&value,INSERT_VALUES);
45: }
46: VecAssemblyBegin(x);
47: VecAssemblyEnd(x);
49: VecView(x,PETSC_VIEWER_STDOUT_WORLD);
51: /* fill local part of parallel vector */
52: for (i=0; i<n; i++) {
53: value = -(PetscScalar) (i + 100*rank);
54: VecSetValues(y,1,&i,&value,INSERT_VALUES);
55: }
56: VecAssemblyBegin(y);
57: VecAssemblyEnd(y);
60: VecScatterCreate(x,isx,y,isy,&ctx);
61: VecScatterCopy(ctx,&newctx);
62: VecScatterDestroy(&ctx);
64: VecScatterBegin(newctx,y,x,INSERT_VALUES,SCATTER_REVERSE);
65: VecScatterEnd(newctx,y,x,INSERT_VALUES,SCATTER_REVERSE);
66: VecScatterDestroy(&newctx);
68: VecView(x,PETSC_VIEWER_STDOUT_WORLD);
70: ISDestroy(&isx);
71: ISDestroy(&isy);
72: VecDestroy(&x);
73: VecDestroy(&y);
75: PetscFinalize();
76: return ierr;
77: }
81: /*TEST
83: test:
84: nsize: 2
86: TEST*/