Actual source code: ex2.c
1: /*
2: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
3: SLEPc - Scalable Library for Eigenvalue Problem Computations
4: Copyright (c) 2002-2010, Universidad Politecnica de Valencia, Spain
6: This file is part of SLEPc.
7:
8: SLEPc is free software: you can redistribute it and/or modify it under the
9: terms of version 3 of the GNU Lesser General Public License as published by
10: the Free Software Foundation.
12: SLEPc is distributed in the hope that it will be useful, but WITHOUT ANY
13: WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
14: FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
15: more details.
17: You should have received a copy of the GNU Lesser General Public License
18: along with SLEPc. If not, see <http://www.gnu.org/licenses/>.
19: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
20: */
22: static char help[] = "Standard symmetric eigenproblem corresponding to the Laplacian operator in 2 dimensions.\n\n"
23: "The command line options are:\n"
24: " -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
25: " -m <m>, where <m> = number of grid subdivisions in y dimension.\n\n";
27: #include slepceps.h
31: int main( int argc, char **argv )
32: {
33: Mat A; /* operator matrix */
34: EPS eps; /* eigenproblem solver context */
35: const EPSType type;
36: PetscReal error, tol, re, im;
37: PetscScalar kr, ki;
39: PetscInt N, n=10, m, Istart, Iend, II, nev, maxit, i, j, its, nconv;
40: PetscTruth flag;
42: SlepcInitialize(&argc,&argv,(char*)0,help);
44: PetscOptionsGetInt(PETSC_NULL,"-n",&n,PETSC_NULL);
45: PetscOptionsGetInt(PETSC_NULL,"-m",&m,&flag);
46: if(!flag) m=n;
47: N = n*m;
48: PetscPrintf(PETSC_COMM_WORLD,"\n2-D Laplacian Eigenproblem, N=%d (%dx%d grid)\n\n",N,n,m);
50: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
51: Compute the operator matrix that defines the eigensystem, Ax=kx
52: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
54: MatCreate(PETSC_COMM_WORLD,&A);
55: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
56: MatSetFromOptions(A);
57:
58: MatGetOwnershipRange(A,&Istart,&Iend);
59: for( II=Istart; II<Iend; II++ ) {
60: i = II/n; j = II-i*n;
61: if(i>0) { MatSetValue(A,II,II-n,-1.0,INSERT_VALUES); }
62: if(i<m-1) { MatSetValue(A,II,II+n,-1.0,INSERT_VALUES); }
63: if(j>0) { MatSetValue(A,II,II-1,-1.0,INSERT_VALUES); }
64: if(j<n-1) { MatSetValue(A,II,II+1,-1.0,INSERT_VALUES); }
65: MatSetValue(A,II,II,4.0,INSERT_VALUES);
66: }
68: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
69: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
71: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
72: Create the eigensolver and set various options
73: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
75: /*
76: Create eigensolver context
77: */
78: EPSCreate(PETSC_COMM_WORLD,&eps);
80: /*
81: Set operators. In this case, it is a standard eigenvalue problem
82: */
83: EPSSetOperators(eps,A,PETSC_NULL);
84: EPSSetProblemType(eps,EPS_HEP);
86: /*
87: Set solver parameters at runtime
88: */
89: EPSSetFromOptions(eps);
91: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
92: Solve the eigensystem
93: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
95: EPSSolve(eps);
96: EPSGetIterationNumber(eps, &its);
97: PetscPrintf(PETSC_COMM_WORLD," Number of iterations of the method: %d\n",its);
99: /*
100: Optional: Get some information from the solver and display it
101: */
102: EPSGetType(eps,&type);
103: PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
104: EPSGetDimensions(eps,&nev,PETSC_NULL,PETSC_NULL);
105: PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %d\n",nev);
106: EPSGetTolerances(eps,&tol,&maxit);
107: PetscPrintf(PETSC_COMM_WORLD," Stopping condition: tol=%.4g, maxit=%d\n",tol,maxit);
109: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
110: Display solution and clean up
111: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
113: /*
114: Get number of converged approximate eigenpairs
115: */
116: EPSGetConverged(eps,&nconv);
117: PetscPrintf(PETSC_COMM_WORLD," Number of converged approximate eigenpairs: %d\n\n",nconv);
118:
120: if (nconv>0) {
121: /*
122: Display eigenvalues and relative errors
123: */
124: PetscPrintf(PETSC_COMM_WORLD,
125: " k ||Ax-kx||/||kx||\n"
126: " ----------------- ------------------\n" );
128: for( i=0; i<nconv; i++ ) {
129: /*
130: Get converged eigenpairs: i-th eigenvalue is stored in kr (real part) and
131: ki (imaginary part)
132: */
133: EPSGetEigenpair(eps,i,&kr,&ki,PETSC_NULL,PETSC_NULL);
134: /*
135: Compute the relative error associated to each eigenpair
136: */
137: EPSComputeRelativeError(eps,i,&error);
139: #ifdef PETSC_USE_COMPLEX
140: re = PetscRealPart(kr);
141: im = PetscImaginaryPart(kr);
142: #else
143: re = kr;
144: im = ki;
145: #endif
146: if (im!=0.0) {
147: PetscPrintf(PETSC_COMM_WORLD," %9f%+9f j %12g\n",re,im,error);
148: } else {
149: PetscPrintf(PETSC_COMM_WORLD," %12f %12g\n",re,error);
150: }
151: }
152: PetscPrintf(PETSC_COMM_WORLD,"\n" );
153: }
154:
155: /*
156: Free work space
157: */
158: EPSDestroy(eps);
159: MatDestroy(A);
160: SlepcFinalize();
161: return 0;
162: }