Actual source code: ex24.c
2: static char help[] = "Tests CG, MINRES and SYMMLQ on symmetric matrices with SBAIJ format. The preconditioner ICC only works on sequential SBAIJ format. \n\n";
4: #include <petscksp.h>
6: int main(int argc,char **args)
7: {
8: Mat C;
9: PetscScalar v,none = -1.0;
10: PetscInt i,j,Ii,J,Istart,Iend,N,m = 4,n = 4,its,k;
11: PetscMPIInt size,rank;
12: PetscReal err_norm,res_norm;
13: Vec x,b,u,u_tmp;
14: PC pc;
15: KSP ksp;
17: PetscInitialize(&argc,&args,(char*)0,help);
18: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
19: MPI_Comm_size(PETSC_COMM_WORLD,&size);
20: PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);
21: PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
22: N = m*n;
24: /* Generate matrix */
25: MatCreate(PETSC_COMM_WORLD,&C);
26: MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,N,N);
27: MatSetFromOptions(C);
28: MatSetUp(C);
29: MatGetOwnershipRange(C,&Istart,&Iend);
30: for (Ii=Istart; Ii<Iend; Ii++) {
31: v = -1.0; i = Ii/n; j = Ii - i*n;
32: if (i>0) {J = Ii - n; MatSetValues(C,1,&Ii,1,&J,&v,ADD_VALUES);}
33: if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,ADD_VALUES);}
34: if (j>0) {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,ADD_VALUES);}
35: if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,ADD_VALUES);}
36: v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,ADD_VALUES);
37: }
38: MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
39: MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
41: /* a shift can make C indefinite. Preconditioners LU, ILU (for BAIJ format) and ICC may fail */
42: /* MatShift(C,alpha); */
43: /* MatView(C,PETSC_VIEWER_STDOUT_WORLD); */
45: /* Setup and solve for system */
46: /* Create vectors. */
47: VecCreate(PETSC_COMM_WORLD,&x);
48: VecSetSizes(x,PETSC_DECIDE,N);
49: VecSetFromOptions(x);
50: VecDuplicate(x,&b);
51: VecDuplicate(x,&u);
52: VecDuplicate(x,&u_tmp);
53: /* Set exact solution u; then compute right-hand-side vector b. */
54: VecSet(u,1.0);
55: MatMult(C,u,b);
57: for (k=0; k<3; k++) {
58: if (k == 0) { /* CG */
59: KSPCreate(PETSC_COMM_WORLD,&ksp);
60: KSPSetOperators(ksp,C,C);
61: PetscPrintf(PETSC_COMM_WORLD,"\n CG: \n");
62: KSPSetType(ksp,KSPCG);
63: } else if (k == 1) { /* MINRES */
64: KSPCreate(PETSC_COMM_WORLD,&ksp);
65: KSPSetOperators(ksp,C,C);
66: PetscPrintf(PETSC_COMM_WORLD,"\n MINRES: \n");
67: KSPSetType(ksp,KSPMINRES);
68: } else { /* SYMMLQ */
69: KSPCreate(PETSC_COMM_WORLD,&ksp);
70: KSPSetOperators(ksp,C,C);
71: PetscPrintf(PETSC_COMM_WORLD,"\n SYMMLQ: \n");
72: KSPSetType(ksp,KSPSYMMLQ);
73: }
74: KSPGetPC(ksp,&pc);
75: /* PCSetType(pc,PCICC); */
76: PCSetType(pc,PCJACOBI);
77: KSPSetTolerances(ksp,1.e-7,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);
79: /*
80: Set runtime options, e.g.,
81: -ksp_type <type> -pc_type <type> -ksp_monitor -ksp_rtol <rtol>
82: These options will override those specified above as long as
83: KSPSetFromOptions() is called _after_ any other customization
84: routines.
85: */
86: KSPSetFromOptions(ksp);
88: /* Solve linear system; */
89: KSPSetUp(ksp);
90: KSPSolve(ksp,b,x);
92: KSPGetIterationNumber(ksp,&its);
93: /* Check error */
94: VecCopy(u,u_tmp);
95: VecAXPY(u_tmp,none,x);
96: VecNorm(u_tmp,NORM_2,&err_norm);
97: MatMult(C,x,u_tmp);
98: VecAXPY(u_tmp,none,b);
99: VecNorm(u_tmp,NORM_2,&res_norm);
101: PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %3D\n",its);
102: PetscPrintf(PETSC_COMM_WORLD,"Residual norm %g;",(double)res_norm);
103: PetscPrintf(PETSC_COMM_WORLD," Error norm %g.\n",(double)err_norm);
104: KSPDestroy(&ksp);
105: }
107: /*
108: Free work space. All PETSc objects should be destroyed when they
109: are no longer needed.
110: */
111: VecDestroy(&b);
112: VecDestroy(&u);
113: VecDestroy(&x);
114: VecDestroy(&u_tmp);
115: MatDestroy(&C);
117: PetscFinalize();
118: return 0;
119: }
121: /*TEST
123: test:
124: args: -pc_type icc -mat_type seqsbaij -mat_ignore_lower_triangular
126: test:
127: suffix: 2
128: args: -pc_type icc -pc_factor_levels 2 -mat_type seqsbaij -mat_ignore_lower_triangular
130: test:
131: suffix: 3
132: nsize: 2
133: args: -pc_type bjacobi -sub_pc_type icc -mat_type mpisbaij -mat_ignore_lower_triangular -ksp_max_it 8
135: test:
136: suffix: 4
137: nsize: 2
138: args: -pc_type bjacobi -sub_pc_type icc -sub_pc_factor_levels 1 -mat_type mpisbaij -mat_ignore_lower_triangular
140: TEST*/