Actual source code: ex24.c
1: /*$Id: ex24.c,v 1.13 2001/08/07 21:30:50 bsmith Exp $*/
3: static char help[] = "Tests CG, MINRES and SYMMLQ on symmetric matrices with SBAIJ format. The preconditioner ICC only works on sequential SBAIJ format. nn";
5: #include petscsles.h
8: int main(int argc,char **args)
9: {
10: Mat C;
11: PetscScalar v,none = -1.0;
12: int i,j,I,J,ierr,Istart,Iend,N,m = 4,n = 4,rank,size,its,k;
13: PetscReal err_norm,res_norm;
14: Vec x,b,u,u_tmp;
15: PetscRandom r;
16: SLES sles;
17: PC pc;
18: KSP ksp;
20: PetscInitialize(&argc,&args,(char *)0,help);
21: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
22: MPI_Comm_size(PETSC_COMM_WORLD,&size);
23: PetscOptionsGetInt(PETSC_NULL,"-m",&m,PETSC_NULL);
24: PetscOptionsGetInt(PETSC_NULL,"-n",&n,PETSC_NULL);
25: N = m*n;
28: /* Generate matrix */
29: MatCreate(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,N,N,&C);
30: MatSetFromOptions(C);
31: MatGetOwnershipRange(C,&Istart,&Iend);
32: for (I=Istart; I<Iend; I++) {
33: v = -1.0; i = I/n; j = I - i*n;
34: if (i>0) {J = I - n; MatSetValues(C,1,&I,1,&J,&v,ADD_VALUES);}
35: if (i<m-1) {J = I + n; MatSetValues(C,1,&I,1,&J,&v,ADD_VALUES);}
36: if (j>0) {J = I - 1; MatSetValues(C,1,&I,1,&J,&v,ADD_VALUES);}
37: if (j<n-1) {J = I + 1; MatSetValues(C,1,&I,1,&J,&v,ADD_VALUES);}
38: v = 4.0; MatSetValues(C,1,&I,1,&I,&v,ADD_VALUES);
39: }
40: MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
41: MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
43: /* a shift can make C indefinite. Preconditioners LU, ILU (for BAIJ format) and ICC may fail */
44: /* MatShift(&alpha, C); */
45: /* MatView(C,PETSC_VIEWER_STDOUT_WORLD); */
47: /* Setup and solve for system */
48:
49: /* Create vectors. */
50: VecCreate(PETSC_COMM_WORLD,&x);
51: VecSetSizes(x,PETSC_DECIDE,N);
52: VecSetFromOptions(x);
53: VecDuplicate(x,&b);
54: VecDuplicate(x,&u);
55: VecDuplicate(x,&u_tmp);
57: /* Set exact solution u; then compute right-hand-side vector b. */
58: PetscRandomCreate(PETSC_COMM_SELF,RANDOM_DEFAULT,&r);
59: VecSetRandom(r,u);
60: PetscRandomDestroy(r);
61:
62: MatMult(C,u,b);
64: for (k=0; k<3; k++){
65: if (k == 0){ /* CG */
66: SLESCreate(PETSC_COMM_WORLD,&sles);
67: SLESSetOperators(sles,C,C,DIFFERENT_NONZERO_PATTERN);
68: SLESGetKSP(sles,&ksp);
69: PetscPrintf(PETSC_COMM_WORLD,"n CG: n");
70: KSPSetType(ksp,KSPCG);
71: } else if (k == 1){ /* MINRES */
72: SLESCreate(PETSC_COMM_WORLD,&sles);
73: SLESSetOperators(sles,C,C,DIFFERENT_NONZERO_PATTERN);
74: SLESGetKSP(sles,&ksp);
75: PetscPrintf(PETSC_COMM_WORLD,"n MINRES: n");
76: KSPSetType(ksp,KSPMINRES);
77: } else { /* SYMMLQ */
78: SLESCreate(PETSC_COMM_WORLD,&sles);
79: SLESSetOperators(sles,C,C,DIFFERENT_NONZERO_PATTERN);
80: SLESGetKSP(sles,&ksp);
81: PetscPrintf(PETSC_COMM_WORLD,"n SYMMLQ: n");
82: KSPSetType(ksp,KSPSYMMLQ);
83: }
85: SLESGetPC(sles,&pc);
86: /* PCSetType(pc,PCICC); */
87: PCSetType(pc,PCJACOBI);
88: KSPSetTolerances(ksp,1.e-7,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);
90: /*
91: Set runtime options, e.g.,
92: -ksp_type <type> -pc_type <type> -ksp_monitor -ksp_rtol <rtol>
93: These options will override those specified above as long as
94: SLESSetFromOptions() is called _after_ any other customization
95: routines.
96: */
97: SLESSetFromOptions(sles);
99: /* Solve linear system; */
100: SLESSolve(sles,b,x,&its);
101:
102: /* Check error */
103: VecCopy(u,u_tmp);
104: VecAXPY(&none,x,u_tmp);
105: VecNorm(u_tmp,NORM_2,&err_norm);
106: MatMult(C,x,u_tmp);
107: VecAXPY(&none,b,u_tmp);
108: VecNorm(u_tmp,NORM_2,&res_norm);
109:
110: PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %3dn",its);
111: PetscPrintf(PETSC_COMM_WORLD,"Residual norm %A;",res_norm);
112: PetscPrintf(PETSC_COMM_WORLD," Error norm %A.n",err_norm);
114: SLESDestroy(sles);
115: }
116:
117: /*
118: Free work space. All PETSc objects should be destroyed when they
119: are no longer needed.
120: */
121: VecDestroy(b);
122: VecDestroy(u);
123: VecDestroy(x);
124: VecDestroy(u_tmp);
125: MatDestroy(C);
127: PetscFinalize();
128: return 0;
129: }