linbox
examples/graph-charpoly.C

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 <iostream>
#include <linbox/blackbox/zero-one.h>
#include <givaro/zring.h>
#include <linbox/solutions/charpoly.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;
for (int i=0;i<n;++i)
cout<<P[(size_t)i]<<" ";
cout<<endl;
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 <matrix-file-in-SMS-format>" <<endl;
return -1;
}
ifstream input (argv[1]);
if (!input) {
cerr << "Error opening matrix file " << argv[1] << endl;
return -1;
}
//Givaro::ZRing<integer> ZZ;
Givaro::ZRing<Integer> ZZ;
Matrix A(ZZ);
A.read (input);
commentator().report(1, BRIEF_REPORT)<< "A is " << A.rowdim() << " by " << A.coldim() << endl;
IntPolRing::Element c_A;
charpoly (c_A, A, Method::Blackbox(Method::Wiedemann( Specifier::SYMMETRIC)));
cout<< "Characteristic Polynomial is ";
printPolynomial (ZZ, c_A);
return 0;
}
// vim:sts=8:sw=8:ts=8:noet:sr:cino=>s,f0,{0,g0,(0,:0,t0,+0,=s
// Local Variables:
// mode: C++
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// indent-tabs-mode: nil
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