Actual source code: ex4.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[] = "Solves a standard eigensystem Ax=kx with the matrix loaded from a file.\n"
 23:   "This example works for both real and complex numbers.\n\n"
 24:   "The command line options are:\n"
 25:   "  -file <filename>, where <filename> = matrix file in PETSc binary form.\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             nev, maxit, i, its, nconv;
 40:   char                 filename[256];
 41:   PetscViewer          viewer;
 42:   PetscTruth           flg;


 45:   SlepcInitialize(&argc,&argv,(char*)0,help);

 47:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 48:         Load the operator matrix that defines the eigensystem, Ax=kx
 49:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 51:   PetscPrintf(PETSC_COMM_WORLD,"\nEigenproblem stored in file.\n\n");
 52:   PetscOptionsGetString(PETSC_NULL,"-file",filename,256,&flg);
 53:   if (!flg) {
 54:     SETERRQ(1,"Must indicate a file name with the -file option.");
 55:   }

 57: #if defined(PETSC_USE_COMPLEX)
 58:   PetscPrintf(PETSC_COMM_WORLD," Reading COMPLEX matrix from a binary file...\n");
 59: #else
 60:   PetscPrintf(PETSC_COMM_WORLD," Reading REAL matrix from a binary file...\n");
 61: #endif
 62:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,filename,FILE_MODE_READ,&viewer);
 63:   MatLoad(viewer,MATAIJ,&A);
 64:   PetscViewerDestroy(viewer);

 66:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 67:                 Create the eigensolver and set various options
 68:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 70:   /* 
 71:      Create eigensolver context
 72:   */
 73:   EPSCreate(PETSC_COMM_WORLD,&eps);

 75:   /* 
 76:      Set operators. In this case, it is a standard eigenvalue problem
 77:   */
 78:   EPSSetOperators(eps,A,PETSC_NULL);

 80:   /*
 81:      Set solver parameters at runtime
 82:   */
 83:   EPSSetFromOptions(eps);

 85:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 86:                       Solve the eigensystem
 87:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 89:   EPSSolve(eps);
 90:   EPSGetIterationNumber(eps, &its);
 91:   PetscPrintf(PETSC_COMM_WORLD," Number of iterations of the method: %d\n",its);

 93:   /*
 94:      Optional: Get some information from the solver and display it
 95:   */
 96:   EPSGetType(eps,&type);
 97:   PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
 98:   EPSGetDimensions(eps,&nev,PETSC_NULL,PETSC_NULL);
 99:   PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %d\n",nev);
100:   EPSGetTolerances(eps,&tol,&maxit);
101:   PetscPrintf(PETSC_COMM_WORLD," Stopping condition: tol=%.4g, maxit=%d\n",tol,maxit);

103:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
104:                     Display solution and clean up
105:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

107:   /* 
108:      Get number of converged eigenpairs
109:   */
110:   EPSGetConverged(eps,&nconv);
111:   PetscPrintf(PETSC_COMM_WORLD," Number of converged approximate eigenpairs: %d\n\n",nconv);

113:   if (nconv>0) {
114:     /*
115:        Display eigenvalues and relative errors
116:     */
117:     PetscPrintf(PETSC_COMM_WORLD,
118:          "           k             ||Ax-kx||/||kx||\n"
119:          "  --------------------- ------------------\n" );
120:     for( i=0; i<nconv; i++ ) {
121:       /* 
122:          Get converged eigenpairs: i-th eigenvalue is stored in kr (real part) and
123:          ki (imaginary part)
124:       */
125:       EPSGetEigenpair(eps,i,&kr,&ki,PETSC_NULL,PETSC_NULL);

127:       /*
128:          Compute the relative error associated to each eigenpair
129:       */
130:       EPSComputeRelativeError(eps,i,&error);

132: #if defined(PETSC_USE_COMPLEX)
133:       re = PetscRealPart(kr);
134:       im = PetscImaginaryPart(kr);
135: #else
136:       re = kr;
137:       im = ki;
138: #endif
139:       if( im != 0.0 ) {
140:         PetscPrintf(PETSC_COMM_WORLD," % 6f %+6f i",re,im);
141:       } else {
142:         PetscPrintf(PETSC_COMM_WORLD,"       % 6f      ",re);
143:       }
144:       PetscPrintf(PETSC_COMM_WORLD," % 12g\n",error);
145:     }
146:     PetscPrintf(PETSC_COMM_WORLD,"\n" );
147:   }
148: 
149:   /* 
150:      Free work space
151:   */
152:   EPSDestroy(eps);
153:   MatDestroy(A);
154:   SlepcFinalize();
155:   return 0;
156: }