Actual source code: ex2.c
2: static char help[] = "Standard symmetric eigenproblem corresponding to the Laplacian operator in 2 dimensions.\n\n"
3: "The command line options are:\n"
4: " -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
5: " -m <m>, where <m> = number of grid subdivisions in y dimension.\n\n";
7: #include slepceps.h
11: int main( int argc, char **argv )
12: {
13: Mat A; /* operator matrix */
14: EPS eps; /* eigenproblem solver context */
15: EPSType type;
16: PetscReal error, tol, re, im;
17: PetscScalar kr, ki;
19: PetscInt N, n=10, m, Istart, Iend, II, J;
20: int nev, maxit, i, j, its, nconv;
21: PetscScalar v;
22: PetscTruth flag;
24: SlepcInitialize(&argc,&argv,(char*)0,help);
26: PetscOptionsGetInt(PETSC_NULL,"-n",&n,PETSC_NULL);
27: PetscOptionsGetInt(PETSC_NULL,"-m",&m,&flag);
28: if( flag==PETSC_FALSE ) m=n;
29: N = n*m;
30: PetscPrintf(PETSC_COMM_WORLD,"\n2-D Laplacian Eigenproblem, N=%d (%dx%d grid)\n\n",N,n,m);
32: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
33: Compute the operator matrix that defines the eigensystem, Ax=kx
34: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
36: MatCreate(PETSC_COMM_WORLD,&A);
37: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
38: MatSetFromOptions(A);
39:
40: MatGetOwnershipRange(A,&Istart,&Iend);
41: for( II=Istart; II<Iend; II++ ) {
42: v = -1.0; i = II/n; j = II-i*n;
43: if(i>0) { J=II-n; MatSetValues(A,1,&II,1,&J,&v,INSERT_VALUES); }
44: if(i<m-1) { J=II+n; MatSetValues(A,1,&II,1,&J,&v,INSERT_VALUES); }
45: if(j>0) { J=II-1; MatSetValues(A,1,&II,1,&J,&v,INSERT_VALUES); }
46: if(j<n-1) { J=II+1; MatSetValues(A,1,&II,1,&J,&v,INSERT_VALUES); }
47: v=4.0; MatSetValues(A,1,&II,1,&II,&v,INSERT_VALUES);
48: }
50: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
51: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
53: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
54: Create the eigensolver and set various options
55: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
57: /*
58: Create eigensolver context
59: */
60: EPSCreate(PETSC_COMM_WORLD,&eps);
62: /*
63: Set operators. In this case, it is a standard eigenvalue problem
64: */
65: EPSSetOperators(eps,A,PETSC_NULL);
66: EPSSetProblemType(eps,EPS_HEP);
68: /*
69: Set solver parameters at runtime
70: */
71: EPSSetFromOptions(eps);
73: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
74: Solve the eigensystem
75: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
77: EPSSolve(eps);
78: EPSGetIterationNumber(eps, &its);
79: PetscPrintf(PETSC_COMM_WORLD," Number of iterations of the method: %d\n",its);
81: /*
82: Optional: Get some information from the solver and display it
83: */
84: EPSGetType(eps,&type);
85: PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
86: EPSGetDimensions(eps,&nev,PETSC_NULL);
87: PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %d\n",nev);
88: EPSGetTolerances(eps,&tol,&maxit);
89: PetscPrintf(PETSC_COMM_WORLD," Stopping condition: tol=%.4g, maxit=%d\n",tol,maxit);
91: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
92: Display solution and clean up
93: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
95: /*
96: Get number of converged approximate eigenpairs
97: */
98: EPSGetConverged(eps,&nconv);
99: PetscPrintf(PETSC_COMM_WORLD," Number of converged approximate eigenpairs: %d\n\n",nconv);
100:
102: if (nconv>0) {
103: /*
104: Display eigenvalues and relative errors
105: */
106: PetscPrintf(PETSC_COMM_WORLD,
107: " k ||Ax-kx||/||kx||\n"
108: " ----------------- ------------------\n" );
110: for( i=0; i<nconv; i++ ) {
111: /*
112: Get converged eigenpairs: i-th eigenvalue is stored in kr (real part) and
113: ki (imaginary part)
114: */
115: EPSGetEigenpair(eps,i,&kr,&ki,PETSC_NULL,PETSC_NULL);
116: /*
117: Compute the relative error associated to each eigenpair
118: */
119: EPSComputeRelativeError(eps,i,&error);
121: #ifdef PETSC_USE_COMPLEX
122: re = PetscRealPart(kr);
123: im = PetscImaginaryPart(kr);
124: #else
125: re = kr;
126: im = ki;
127: #endif
128: if (im!=0.0) {
129: PetscPrintf(PETSC_COMM_WORLD," %9f%+9f j %12g\n",re,im,error);
130: } else {
131: PetscPrintf(PETSC_COMM_WORLD," %12f %12g\n",re,error);
132: }
133: }
134: PetscPrintf(PETSC_COMM_WORLD,"\n" );
135: }
136:
137: /*
138: Free work space
139: */
140: EPSDestroy(eps);
141: MatDestroy(A);
142: SlepcFinalize();
143: return 0;
144: }