Actual source code: ex2.c
1: /*
2: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
3: SLEPc - Scalable Library for Eigenvalue Problem Computations
4: Copyright (c) 2002-2009, 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, J, nev, maxit, i, j, its, nconv;
40: PetscScalar v;
41: PetscTruth flag;
43: SlepcInitialize(&argc,&argv,(char*)0,help);
45: PetscOptionsGetInt(PETSC_NULL,"-n",&n,PETSC_NULL);
46: PetscOptionsGetInt(PETSC_NULL,"-m",&m,&flag);
47: if( flag==PETSC_FALSE ) m=n;
48: N = n*m;
49: PetscPrintf(PETSC_COMM_WORLD,"\n2-D Laplacian Eigenproblem, N=%d (%dx%d grid)\n\n",N,n,m);
51: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
52: Compute the operator matrix that defines the eigensystem, Ax=kx
53: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
55: MatCreate(PETSC_COMM_WORLD,&A);
56: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
57: MatSetFromOptions(A);
58:
59: MatGetOwnershipRange(A,&Istart,&Iend);
60: for( II=Istart; II<Iend; II++ ) {
61: v = -1.0; i = II/n; j = II-i*n;
62: if(i>0) { J=II-n; MatSetValues(A,1,&II,1,&J,&v,INSERT_VALUES); }
63: if(i<m-1) { J=II+n; MatSetValues(A,1,&II,1,&J,&v,INSERT_VALUES); }
64: if(j>0) { J=II-1; MatSetValues(A,1,&II,1,&J,&v,INSERT_VALUES); }
65: if(j<n-1) { J=II+1; MatSetValues(A,1,&II,1,&J,&v,INSERT_VALUES); }
66: v=4.0; MatSetValues(A,1,&II,1,&II,&v,INSERT_VALUES);
67: }
69: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
70: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
72: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
73: Create the eigensolver and set various options
74: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
76: /*
77: Create eigensolver context
78: */
79: EPSCreate(PETSC_COMM_WORLD,&eps);
81: /*
82: Set operators. In this case, it is a standard eigenvalue problem
83: */
84: EPSSetOperators(eps,A,PETSC_NULL);
85: EPSSetProblemType(eps,EPS_HEP);
87: /*
88: Set solver parameters at runtime
89: */
90: EPSSetFromOptions(eps);
92: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
93: Solve the eigensystem
94: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
96: EPSSolve(eps);
97: EPSGetIterationNumber(eps, &its);
98: PetscPrintf(PETSC_COMM_WORLD," Number of iterations of the method: %d\n",its);
100: /*
101: Optional: Get some information from the solver and display it
102: */
103: EPSGetType(eps,&type);
104: PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
105: EPSGetDimensions(eps,&nev,PETSC_NULL,PETSC_NULL);
106: PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %d\n",nev);
107: EPSGetTolerances(eps,&tol,&maxit);
108: PetscPrintf(PETSC_COMM_WORLD," Stopping condition: tol=%.4g, maxit=%d\n",tol,maxit);
110: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
111: Display solution and clean up
112: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
114: /*
115: Get number of converged approximate eigenpairs
116: */
117: EPSGetConverged(eps,&nconv);
118: PetscPrintf(PETSC_COMM_WORLD," Number of converged approximate eigenpairs: %d\n\n",nconv);
119:
121: if (nconv>0) {
122: /*
123: Display eigenvalues and relative errors
124: */
125: PetscPrintf(PETSC_COMM_WORLD,
126: " k ||Ax-kx||/||kx||\n"
127: " ----------------- ------------------\n" );
129: for( i=0; i<nconv; i++ ) {
130: /*
131: Get converged eigenpairs: i-th eigenvalue is stored in kr (real part) and
132: ki (imaginary part)
133: */
134: EPSGetEigenpair(eps,i,&kr,&ki,PETSC_NULL,PETSC_NULL);
135: /*
136: Compute the relative error associated to each eigenpair
137: */
138: EPSComputeRelativeError(eps,i,&error);
140: #ifdef PETSC_USE_COMPLEX
141: re = PetscRealPart(kr);
142: im = PetscImaginaryPart(kr);
143: #else
144: re = kr;
145: im = ki;
146: #endif
147: if (im!=0.0) {
148: PetscPrintf(PETSC_COMM_WORLD," %9f%+9f j %12g\n",re,im,error);
149: } else {
150: PetscPrintf(PETSC_COMM_WORLD," %12f %12g\n",re,error);
151: }
152: }
153: PetscPrintf(PETSC_COMM_WORLD,"\n" );
154: }
155:
156: /*
157: Free work space
158: */
159: EPSDestroy(eps);
160: MatDestroy(A);
161: SlepcFinalize();
162: return 0;
163: }