1 static char help[] = "Demonstrates the use of fast Richardson for SOR. And\n\
2 also tests the MatSOR() routines. Input parameters are:\n\
3 -n <n> : problem dimension\n\n";
4
5 #include <petscksp.h>
6 #include <petscpc.h>
7
main(int argc,char ** args)8 int main(int argc, char **args)
9 {
10 Mat mat; /* matrix */
11 Vec b, ustar, u; /* vectors (RHS, exact solution, approx solution) */
12 PC pc; /* PC context */
13 KSP ksp; /* KSP context */
14 PetscInt n = 10, i, its, col[3];
15 PetscScalar value[3];
16 KSPType kspname;
17 PCType pcname;
18
19 PetscFunctionBeginUser;
20 PetscCall(PetscInitialize(&argc, &args, NULL, help));
21 PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL));
22
23 /* Create and initialize vectors */
24 PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &b));
25 PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &ustar));
26 PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &u));
27 PetscCall(VecSet(ustar, 1.0));
28 PetscCall(VecSet(u, 0.0));
29
30 /* Create and assemble matrix */
31 PetscCall(MatCreate(PETSC_COMM_SELF, &mat));
32 PetscCall(MatSetType(mat, MATSEQAIJ));
33 PetscCall(MatSetSizes(mat, n, n, n, n));
34 PetscCall(MatSetFromOptions(mat));
35 PetscCall(MatSeqAIJSetPreallocation(mat, 3, NULL));
36 PetscCall(MatSeqBAIJSetPreallocation(mat, 1, 3, NULL));
37 PetscCall(MatSeqSBAIJSetPreallocation(mat, 1, 3, NULL));
38 PetscCall(MatSeqSELLSetPreallocation(mat, 3, NULL));
39 value[0] = -1.0;
40 value[1] = 2.0;
41 value[2] = -1.0;
42 for (i = 1; i < n - 1; i++) {
43 col[0] = i - 1;
44 col[1] = i;
45 col[2] = i + 1;
46 PetscCall(MatSetValues(mat, 1, &i, 3, col, value, INSERT_VALUES));
47 }
48 i = n - 1;
49 col[0] = n - 2;
50 col[1] = n - 1;
51 PetscCall(MatSetValues(mat, 1, &i, 2, col, value, INSERT_VALUES));
52 i = 0;
53 col[0] = 0;
54 col[1] = 1;
55 value[0] = 2.0;
56 value[1] = -1.0;
57 PetscCall(MatSetValues(mat, 1, &i, 2, col, value, INSERT_VALUES));
58 PetscCall(MatAssemblyBegin(mat, MAT_FINAL_ASSEMBLY));
59 PetscCall(MatAssemblyEnd(mat, MAT_FINAL_ASSEMBLY));
60
61 /* Compute right-hand-side vector */
62 PetscCall(MatMult(mat, ustar, b));
63
64 /* Create PC context and set up data structures */
65 PetscCall(PCCreate(PETSC_COMM_WORLD, &pc));
66 PetscCall(PCSetType(pc, PCNONE));
67 PetscCall(PCSetFromOptions(pc));
68 PetscCall(PCSetOperators(pc, mat, mat));
69 PetscCall(PCSetUp(pc));
70
71 /* Create KSP context and set up data structures */
72 PetscCall(KSPCreate(PETSC_COMM_WORLD, &ksp));
73 PetscCall(KSPSetType(ksp, KSPRICHARDSON));
74 PetscCall(KSPSetFromOptions(ksp));
75 PetscCall(PCSetOperators(pc, mat, mat));
76 PetscCall(KSPSetPC(ksp, pc));
77 PetscCall(KSPSetUp(ksp));
78
79 /* Solve the problem */
80 PetscCall(KSPGetType(ksp, &kspname));
81 PetscCall(PCGetType(pc, &pcname));
82 PetscCall(PetscPrintf(PETSC_COMM_SELF, "Running %s with %s preconditioning\n", kspname, pcname));
83 PetscCall(KSPSolve(ksp, b, u));
84 PetscCall(KSPGetIterationNumber(ksp, &its));
85 PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Number of iterations %" PetscInt_FMT "\n", its));
86
87 /* Free data structures */
88 PetscCall(KSPDestroy(&ksp));
89 PetscCall(VecDestroy(&u));
90 PetscCall(VecDestroy(&ustar));
91 PetscCall(VecDestroy(&b));
92 PetscCall(MatDestroy(&mat));
93 PetscCall(PCDestroy(&pc));
94 PetscCall(PetscFinalize());
95 return 0;
96 }
97
98 /*TEST
99
100 testset:
101 args: -ksp_type gmres -ksp_monitor_short -pc_type sor -pc_sor_symmetric
102 output_file: output/ex3_1.out
103 test:
104 suffix: sor_aij
105 test:
106 suffix: sor_seqbaij
107 args: -mat_type seqbaij
108 test:
109 suffix: sor_seqsbaij
110 args: -mat_type seqbaij
111 test:
112 suffix: sor_seqsell
113 args: -mat_type seqsell
114
115 TEST*/
116