Actual source code: ex10.c
petsc-3.9.4 2018-09-11
2: static char help[]= "Scatters from a parallel vector to a sequential vector.\n\
3: uses block index sets\n\n";
5: /*T
6: requires: x
7: T*/
9: #include <petscvec.h>
11: int main(int argc,char **argv)
12: {
14: 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};
15: PetscMPIInt size,rank;
16: PetscScalar value;
17: Vec x,y;
18: IS isx,isy;
19: VecScatter ctx = 0,newctx;
21: PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
22: MPI_Comm_size(PETSC_COMM_WORLD,&size);
23: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
25: if (size != 2) SETERRQ(PETSC_COMM_SELF,1,"Must run with 2 processors");
27: PetscOptionsGetInt(NULL,NULL,"-bs",&bs,NULL);
28: n = bs*n;
30: /* create two vectors */
31: VecCreate(PETSC_COMM_WORLD,&x);
32: VecSetSizes(x,PETSC_DECIDE,size*n);
33: VecSetFromOptions(x);
34: VecCreateSeq(PETSC_COMM_SELF,n,&y);
36: /* create two index sets */
37: if (!rank) {
38: ISCreateBlock(PETSC_COMM_SELF,bs,3,ix0,PETSC_COPY_VALUES,&isx);
39: ISCreateBlock(PETSC_COMM_SELF,bs,3,iy0,PETSC_COPY_VALUES,&isy);
40: } else {
41: ISCreateBlock(PETSC_COMM_SELF,bs,3,ix1,PETSC_COPY_VALUES,&isx);
42: ISCreateBlock(PETSC_COMM_SELF,bs,3,iy1,PETSC_COPY_VALUES,&isy);
43: }
45: /* fill local part of parallel vector */
46: for (i=n*rank; i<n*(rank+1); i++) {
47: value = (PetscScalar) i;
48: VecSetValues(x,1,&i,&value,INSERT_VALUES);
49: }
50: VecAssemblyBegin(x);
51: VecAssemblyEnd(x);
53: VecView(x,PETSC_VIEWER_STDOUT_WORLD);
55: /* fill local part of parallel vector */
56: for (i=0; i<n; i++) {
57: value = -(PetscScalar) (i + 100*rank);
58: VecSetValues(y,1,&i,&value,INSERT_VALUES);
59: }
60: VecAssemblyBegin(y);
61: VecAssemblyEnd(y);
64: VecScatterCreate(x,isx,y,isy,&ctx);
65: VecScatterCopy(ctx,&newctx);
66: VecScatterDestroy(&ctx);
68: VecScatterBegin(newctx,y,x,INSERT_VALUES,SCATTER_REVERSE);
69: VecScatterEnd(newctx,y,x,INSERT_VALUES,SCATTER_REVERSE);
70: VecScatterDestroy(&newctx);
72: VecView(x,PETSC_VIEWER_STDOUT_WORLD);
74: ISDestroy(&isx);
75: ISDestroy(&isy);
76: VecDestroy(&x);
77: VecDestroy(&y);
79: PetscFinalize();
80: return ierr;
81: }
85: /*TEST
87: test:
88: nsize: 2
90: TEST*/