Actual source code: ex55.c
1: static const char help[]="Example demonstrating PCCOMPOSITE where one of the inner PCs uses a different operator\n\
2: \n";
4: /*T
5: Concepts: KSP^using nested solves
6: Concepts: PC^using composite PCs
7: Processors: n
8: T*/
9: #include <petscksp.h>
11: int main(int argc, char **argv)
12: {
13: PetscInt n=10,i,col[3];
14: Vec x,b;
15: Mat A,B;
16: KSP ksp;
17: PC pc,subpc;
18: PetscScalar value[3];
20: PetscInitialize(&argc,&argv,(char*)0,help);
22: /* Create a diagonal matrix with a given distribution of diagonal elements */
23: MatCreate(PETSC_COMM_WORLD,&A);
24: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n);
25: MatSetFromOptions(A);
26: MatSetUp(A);
27: /*
28: Assemble matrix
29: */
30: value[0] = -1.0; value[1] = 2.0; value[2] = -1.0;
31: for (i=1; i<n-1; i++) {
32: col[0] = i-1; col[1] = i; col[2] = i+1;
33: MatSetValues(A,1,&i,3,col,value,INSERT_VALUES);
34: }
35: i = n - 1; col[0] = n - 2; col[1] = n - 1;
36: MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);
37: i = 0; col[0] = 0; col[1] = 1; value[0] = 2.0; value[1] = -1.0;
38: MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);
39: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
40: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
42: MatCreateVecs(A,&x,&b);
44: /* Create a KSP object */
45: KSPCreate(PETSC_COMM_WORLD,&ksp);
46: KSPSetOperators(ksp,A,A);
48: /* Set up a composite preconditioner */
49: KSPGetPC(ksp,&pc);
50: PCSetType(pc,PCCOMPOSITE); /* default composite with single Identity PC */
51: PCCompositeSetType(pc,PC_COMPOSITE_ADDITIVE);
52: PCCompositeAddPCType(pc,PCLU);
53: PCCompositeGetPC(pc,0,&subpc);
54: /* B is set to the diagonal of A; this demonstrates that setting the operator for a subpc changes the preconditioning */
55: MatDuplicate(A,MAT_DO_NOT_COPY_VALUES,&B);
56: MatGetDiagonal(A,b);
57: MatDiagonalSet(B,b,ADD_VALUES);
58: PCSetOperators(subpc,B,B);
59: PCCompositeAddPCType(pc,PCNONE);
61: KSPSetFromOptions(ksp);
62: KSPSolve(ksp,b,x);
64: KSPDestroy(&ksp);
65: MatDestroy(&A);
66: MatDestroy(&B);
67: VecDestroy(&x);
68: VecDestroy(&b);
69: PetscFinalize();
70: return 0;
71: }
73: /*TEST
75: test:
76: args: -ksp_monitor -pc_composite_type multiplicative
78: TEST*/