examples/graph-charpoly.C

Compute the integer characteristic polynomial of symetric matrices with (0,1) coefficients.

Compute the integer characteristic polynomial of symetric matrices with (0,1) coefficients.Example for Pr G. Royle.

/*
 * examples/graph-charpoly.C
 *
 * Copyright (C) 2005, 2007, 2010 C. Pernet
  ========LICENCE========
 * This file is part of the library LinBox.
 *
 * LinBox 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * ========LICENCE========
 */

 
#include <linbox/linbox-config.h>
 
#include <iostream>
 
#include <linbox/blackbox/zero-one.h>
#include <givaro/zring.h>
#include <linbox/solutions/charpoly.h>
#include <linbox/solutions/methods.h>
 
using namespace std;
using namespace LinBox;
 
template <class Field, class Polynomial>
void printPolynomial(const Field& F, const Polynomial& P)
{
    int n= (int) P.size()-1;
    if (n==1){
        cout<<"X";
        if ( P[0] != 0)
            F.write(cout<<((P[0]>0)?"+":""),P[0]);
    }
    else{
        cout<<"X^"<<n;
        for ( int i=n-1; i>1; --i)
            if (!F.isZero(P[(size_t)i]))
                F.write(cout<<((P[(size_t)i]>0)?"+":""),P[(size_t)i])<<"*X^"<<i;
        if ( P[1] != 0)
            F.write(cout<<((P[1]>0)?"+":""),P[1])<<"*X";
        if ( P[0] != 0)
            F.write(cout<<((P[0]>0)?"+":""),P[0]);
    }
}
 
 
int main (int argc, char **argv)
{
    commentator().getMessageClass (BRIEF_REPORT).setMaxDepth (2);
    commentator().getMessageClass (BRIEF_REPORT).setMaxDetailLevel (Commentator::LEVEL_UNIMPORTANT);
 
 
    if (argc != 2) {
        cerr << "Usage: graph-charpoly <0/1-symmetric-matrix-file-in-SMS-format>" <<endl;
        return -1;
    }
 
    ifstream input (argv[1]);
    if (!input) {
        cerr << "Error opening matrix file " << argv[1] << endl;
        return -1;
    }
 
    typedef Givaro::ZRing<Integer> IRing_t;
 
    IRing_t ZZ;
    ZeroOne<IRing_t > A(ZZ);
    A.read (input);
    commentator().report(1, BRIEF_REPORT)<< "A is " << A.rowdim() << " by " << A.coldim() << endl;
 
    DensePolynomial<IRing_t> c_A(ZZ);
 
    charpoly (c_A, A, Method::Blackbox(Method::Wiedemann(Shape::Symmetric)));
 
    PolynomialRing<IRing_t>(ZZ,'X').write(
        cout<< "Characteristic Polynomial is ", c_A) << std::endl;
 
 
    return 0;
}
 
// Local Variables:
// mode: C++
// tab-width: 4
// indent-tabs-mode: nil
// c-basic-offset: 4
// End:
// vim:sts=4:sw=4:ts=4:et:sr:cino=>s,f0,{0,g0,(0,\:0,t0,+0,=s