ifp_Precon.cc

/*@HEADER
// ***********************************************************************
// 
//       Ifpack: Object-Oriented Algebraic Preconditioner Package
//                 Copyright (2002) Sandia Corporation
// 
// Under terms of Contract DE-AC04-94AL85000, there is a non-exclusive
// license for use of this work by or on behalf of the U.S. Government.
// 
// This library is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; either version 2.1 of the
// License, or (at your option) any later version.
//  
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//  
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
// USA
// Questions? Contact Michael A. Heroux (maherou@sandia.gov) 
// 
// ***********************************************************************
//@HEADER
*/

#include "ifp_Matrix.h"
#include "ifp_Precon.h"
#include "ifp_ifpack.h"

double ifp_Precon::condest()
{
  // This routine computes a  bound of the infinity-norm condition number 
  // of the preconditioner.
  // It is equal to infinity-norm of M^-1 e, where e is the vector of all
  // ones.

  int i;

  int m = dimrow(); // Object is a matrix, so it has row/col dimensions.
  int n = dimcol();
  double *u = new double[n];
  double *v = new double[m];

    for (i=0; i<n; i++) u[i] = 1.0;

    apply(n, 1, u, n, v, n);

    double cond_number = 0.0;
    for (i=0; i<m; i++)
        if (ABS(v[i]) > cond_number)
           cond_number = ABS(v[i]);

    delete [] u;
    delete [] v;

    return(cond_number);
}

---