Actual source code: ex1.c
1: /*
2: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
3: SLEPc - Scalable Library for Eigenvalue Problem Computations
4: Copyright (c) 2002-2011, Universitat 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 1 dimension.\n\n"
23: "The command line options are:\n"
24: " -n <n>, where <n> = number of grid subdivisions = matrix dimension.\n\n";
26: #include <slepceps.h>
30: int main(int argc,char **argv)
31: {
32: Mat A; /* problem matrix */
33: EPS eps; /* eigenproblem solver context */
34: const EPSType type;
35: PetscReal error,tol,re,im;
36: PetscScalar kr,ki,value[3];
37: Vec xr,xi;
38: PetscInt n=30,i,Istart,Iend,col[3],nev,maxit,its,nconv;
39: PetscBool FirstBlock=PETSC_FALSE,LastBlock=PETSC_FALSE;
42: SlepcInitialize(&argc,&argv,(char*)0,help);
44: PetscOptionsGetInt(PETSC_NULL,"-n",&n,PETSC_NULL);
45: PetscPrintf(PETSC_COMM_WORLD,"\n1-D Laplacian Eigenproblem, n=%d\n\n",n);
47: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
48: Compute the operator matrix that defines the eigensystem, Ax=kx
49: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
51: MatCreate(PETSC_COMM_WORLD,&A);
52: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n);
53: MatSetFromOptions(A);
54:
55: MatGetOwnershipRange(A,&Istart,&Iend);
56: if (Istart==0) FirstBlock=PETSC_TRUE;
57: if (Iend==n) LastBlock=PETSC_TRUE;
58: value[0]=-1.0; value[1]=2.0; value[2]=-1.0;
59: for (i=(FirstBlock? Istart+1: Istart); i<(LastBlock? Iend-1: Iend); i++) {
60: col[0]=i-1; col[1]=i; col[2]=i+1;
61: MatSetValues(A,1,&i,3,col,value,INSERT_VALUES);
62: }
63: if (LastBlock) {
64: i=n-1; col[0]=n-2; col[1]=n-1;
65: MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);
66: }
67: if (FirstBlock) {
68: i=0; col[0]=0; col[1]=1; value[0]=2.0; value[1]=-1.0;
69: MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);
70: }
72: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
73: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
75: MatGetVecs(A,PETSC_NULL,&xr);
76: MatGetVecs(A,PETSC_NULL,&xi);
78: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
79: Create the eigensolver and set various options
80: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
81: /*
82: Create eigensolver context
83: */
84: EPSCreate(PETSC_COMM_WORLD,&eps);
86: /*
87: Set operators. In this case, it is a standard eigenvalue problem
88: */
89: EPSSetOperators(eps,A,PETSC_NULL);
90: EPSSetProblemType(eps,EPS_HEP);
92: /*
93: Set solver parameters at runtime
94: */
95: EPSSetFromOptions(eps);
97: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
98: Solve the eigensystem
99: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
101: EPSSolve(eps);
102: /*
103: Optional: Get some information from the solver and display it
104: */
105: EPSGetIterationNumber(eps,&its);
106: PetscPrintf(PETSC_COMM_WORLD," Number of iterations of the method: %D\n",its);
107: EPSGetType(eps,&type);
108: PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
109: EPSGetDimensions(eps,&nev,PETSC_NULL,PETSC_NULL);
110: PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %D\n",nev);
111: EPSGetTolerances(eps,&tol,&maxit);
112: PetscPrintf(PETSC_COMM_WORLD," Stopping condition: tol=%.4G, maxit=%D\n",tol,maxit);
114: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
115: Display solution and clean up
116: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
117: /*
118: Get number of converged approximate eigenpairs
119: */
120: EPSGetConverged(eps,&nconv);
121: PetscPrintf(PETSC_COMM_WORLD," Number of converged eigenpairs: %D\n\n",nconv);
123: if (nconv>0) {
124: /*
125: Display eigenvalues and relative errors
126: */
127: PetscPrintf(PETSC_COMM_WORLD,
128: " k ||Ax-kx||/||kx||\n"
129: " ----------------- ------------------\n");
131: for (i=0;i<nconv;i++) {
132: /*
133: Get converged eigenpairs: i-th eigenvalue is stored in kr (real part) and
134: ki (imaginary part)
135: */
136: EPSGetEigenpair(eps,i,&kr,&ki,xr,xi);
137: /*
138: Compute the relative error associated to each eigenpair
139: */
140: EPSComputeRelativeError(eps,i,&error);
142: #if defined(PETSC_USE_COMPLEX)
143: re = PetscRealPart(kr);
144: im = PetscImaginaryPart(kr);
145: #else
146: re = kr;
147: im = ki;
148: #endif
149: if (im!=0.0) {
150: PetscPrintf(PETSC_COMM_WORLD," %9F%+9F j %12G\n",re,im,error);
151: } else {
152: PetscPrintf(PETSC_COMM_WORLD," %12F %12G\n",re,error);
153: }
154: }
155: PetscPrintf(PETSC_COMM_WORLD,"\n");
156: }
157:
158: /*
159: Free work space
160: */
161: EPSDestroy(&eps);
162: MatDestroy(&A);
163: VecDestroy(&xr);
164: VecDestroy(&xi);
165: SlepcFinalize();
166: return 0;
167: }