Actual source code: ex2.c
2: static char help[] = "Tests PC and KSP on a tridiagonal matrix. Note that most\n\
3: users should employ the KSP interface instead of using PC directly.\n\n";
5: #include <petscksp.h>
7: int main(int argc, char **args)
8: {
9: Mat mat; /* matrix */
10: Vec b, ustar, u; /* vectors (RHS, exact solution, approx solution) */
11: PC pc; /* PC context */
12: KSP ksp; /* KSP context */
13: PetscInt n = 10, i, its, col[3];
14: PetscScalar value[3];
15: PCType pcname;
16: KSPType kspname;
17: PetscReal norm, tol = 1000. * PETSC_MACHINE_EPSILON;
20: PetscInitialize(&argc, &args, (char *)0, help);
21: /* Create and initialize vectors */
22: VecCreateSeq(PETSC_COMM_SELF, n, &b);
23: VecCreateSeq(PETSC_COMM_SELF, n, &ustar);
24: VecCreateSeq(PETSC_COMM_SELF, n, &u);
25: VecSet(ustar, 1.0);
26: VecSet(u, 0.0);
28: /* Create and assemble matrix */
29: MatCreateSeqAIJ(PETSC_COMM_SELF, n, n, 3, NULL, &mat);
30: value[0] = -1.0;
31: value[1] = 2.0;
32: value[2] = -1.0;
33: for (i = 1; i < n - 1; i++) {
34: col[0] = i - 1;
35: col[1] = i;
36: col[2] = i + 1;
37: MatSetValues(mat, 1, &i, 3, col, value, INSERT_VALUES);
38: }
39: i = n - 1;
40: col[0] = n - 2;
41: col[1] = n - 1;
42: MatSetValues(mat, 1, &i, 2, col, value, INSERT_VALUES);
43: i = 0;
44: col[0] = 0;
45: col[1] = 1;
46: value[0] = 2.0;
47: value[1] = -1.0;
48: MatSetValues(mat, 1, &i, 2, col, value, INSERT_VALUES);
49: MatAssemblyBegin(mat, MAT_FINAL_ASSEMBLY);
50: MatAssemblyEnd(mat, MAT_FINAL_ASSEMBLY);
52: /* Compute right-hand-side vector */
53: MatMult(mat, ustar, b);
55: /* Create PC context and set up data structures */
56: PCCreate(PETSC_COMM_WORLD, &pc);
57: PCSetType(pc, PCNONE);
58: PCSetFromOptions(pc);
59: PCSetOperators(pc, mat, mat);
60: PCSetUp(pc);
62: /* Create KSP context and set up data structures */
63: KSPCreate(PETSC_COMM_WORLD, &ksp);
64: KSPSetType(ksp, KSPRICHARDSON);
65: KSPSetFromOptions(ksp);
66: PCSetOperators(pc, mat, mat);
67: KSPSetPC(ksp, pc);
68: KSPSetUp(ksp);
70: /* Solve the problem */
71: KSPGetType(ksp, &kspname);
72: PCGetType(pc, &pcname);
73: PetscPrintf(PETSC_COMM_SELF, "Running %s with %s preconditioning\n", kspname, pcname);
74: KSPSolve(ksp, b, u);
75: VecAXPY(u, -1.0, ustar);
76: VecNorm(u, NORM_2, &norm);
77: KSPGetIterationNumber(ksp, &its);
78: if (norm > tol) PetscPrintf(PETSC_COMM_SELF, "2 norm of error %g Number of iterations %" PetscInt_FMT "\n", (double)norm, its);
80: /* Free data structures */
81: KSPDestroy(&ksp);
82: VecDestroy(&u);
83: VecDestroy(&ustar);
84: VecDestroy(&b);
85: MatDestroy(&mat);
86: PCDestroy(&pc);
88: PetscFinalize();
89: return 0;
90: }
92: /*TEST
94: test:
95: args: -ksp_type cg -ksp_monitor_short
97: TEST*/