Actual source code: ex1.c
1: /*
2: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
3: SLEPc - Scalable Library for Eigenvalue Problem Computations
4: Copyright (c) 2002-2007, Universidad Politecnica de Valencia, Spain
6: This file is part of SLEPc. See the README file for conditions of use
7: and additional information.
8: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
9: */
11: static char help[] = "Standard symmetric eigenproblem corresponding to the Laplacian operator in 1 dimension.\n\n"
12: "The command line options are:\n"
13: " -n <n>, where <n> = number of grid subdivisions = matrix dimension.\n\n";
15: #include slepceps.h
19: int main( int argc, char **argv )
20: {
21: Mat A; /* operator matrix */
22: EPS eps; /* eigenproblem solver context */
23: EPSType type;
24: PetscReal error, tol,re, im;
25: PetscScalar kr, ki;
26: Vec xr, xi;
28: PetscInt n=30, i, Istart, Iend, col[3];
29: int nev, maxit,its, nconv;
30: PetscTruth FirstBlock=PETSC_FALSE, LastBlock=PETSC_FALSE;
31: PetscScalar value[3];
33: SlepcInitialize(&argc,&argv,(char*)0,help);
35: PetscOptionsGetInt(PETSC_NULL,"-n",&n,PETSC_NULL);
36: PetscPrintf(PETSC_COMM_WORLD,"\n1-D Laplacian Eigenproblem, n=%d\n\n",n);
38: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
39: Compute the operator matrix that defines the eigensystem, Ax=kx
40: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
42: MatCreate(PETSC_COMM_WORLD,&A);
43: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n);
44: MatSetFromOptions(A);
45:
46: MatGetOwnershipRange(A,&Istart,&Iend);
47: if (Istart==0) FirstBlock=PETSC_TRUE;
48: if (Iend==n) LastBlock=PETSC_TRUE;
49: value[0]=-1.0; value[1]=2.0; value[2]=-1.0;
50: for( i=(FirstBlock? Istart+1: Istart); i<(LastBlock? Iend-1: Iend); i++ ) {
51: col[0]=i-1; col[1]=i; col[2]=i+1;
52: MatSetValues(A,1,&i,3,col,value,INSERT_VALUES);
53: }
54: if (LastBlock) {
55: i=n-1; col[0]=n-2; col[1]=n-1;
56: MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);
57: }
58: if (FirstBlock) {
59: i=0; col[0]=0; col[1]=1; value[0]=2.0; value[1]=-1.0;
60: MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);
61: }
63: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
64: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
66: MatGetVecs(A,PETSC_NULL,&xr);
67: MatGetVecs(A,PETSC_NULL,&xi);
69: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
70: Create the eigensolver and set various options
71: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
72: /*
73: Create eigensolver context
74: */
75: EPSCreate(PETSC_COMM_WORLD,&eps);
77: /*
78: Set operators. In this case, it is a standard eigenvalue problem
79: */
80: EPSSetOperators(eps,A,PETSC_NULL);
81: EPSSetProblemType(eps,EPS_HEP);
83: /*
84: Set solver parameters at runtime
85: */
86: EPSSetFromOptions(eps);
88: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
89: Solve the eigensystem
90: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
92: EPSSolve(eps);
93: EPSGetIterationNumber(eps, &its);
94: PetscPrintf(PETSC_COMM_WORLD," Number of iterations of the method: %d\n",its);
95: /*
96: Optional: Get some information from the solver and display it
97: */
98: EPSGetType(eps,&type);
99: PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
100: EPSGetDimensions(eps,&nev,PETSC_NULL);
101: PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %d\n",nev);
102: EPSGetTolerances(eps,&tol,&maxit);
103: PetscPrintf(PETSC_COMM_WORLD," Stopping condition: tol=%.4g, maxit=%d\n",tol,maxit);
105: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
106: Display solution and clean up
107: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
108: /*
109: Get number of converged approximate eigenpairs
110: */
111: EPSGetConverged(eps,&nconv);
112: PetscPrintf(PETSC_COMM_WORLD," Number of converged eigenpairs: %d\n\n",nconv);
114: if (nconv>0) {
115: /*
116: Display eigenvalues and relative errors
117: */
118: PetscPrintf(PETSC_COMM_WORLD,
119: " k ||Ax-kx||/||kx||\n"
120: " ----------------- ------------------\n" );
122: for( i=0; i<nconv; i++ ) {
123: /*
124: Get converged eigenpairs: i-th eigenvalue is stored in kr (real part) and
125: ki (imaginary part)
126: */
127: EPSGetEigenpair(eps,i,&kr,&ki,xr,xi);
128: /*
129: Compute the relative error associated to each eigenpair
130: */
131: EPSComputeRelativeError(eps,i,&error);
133: #ifdef PETSC_USE_COMPLEX
134: re = PetscRealPart(kr);
135: im = PetscImaginaryPart(kr);
136: #else
137: re = kr;
138: im = ki;
139: #endif
140: if (im!=0.0) {
141: PetscPrintf(PETSC_COMM_WORLD," %9f%+9f j %12g\n",re,im,error);
142: } else {
143: PetscPrintf(PETSC_COMM_WORLD," %12f %12g\n",re,error);
144: }
145: }
146: PetscPrintf(PETSC_COMM_WORLD,"\n" );
147: }
148:
149: /*
150: Free work space
151: */
152: EPSDestroy(eps);
153: MatDestroy(A);
154: VecDestroy(xr);
155: VecDestroy(xi);
156: SlepcFinalize();
157: return 0;
158: }