/usr/include/linbox/blackbox/companion.h is in liblinbox-dev 1.4.2-3.
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* Copyright(c) LinBox
*
* Written by David Saunders <saunders@cis.udel.edu>
* ========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========
*/
#ifndef __LINBOX_companion_H
#define __LINBOX_companion_H
#include "linbox/blackbox/blackbox-interface.h"
// #include "linbox/blackbox/triplesbb.h"
#include "linbox/matrix/sparse-matrix.h"
#include <vector>
namespace LinBox
{
/** \ingroup blackbox
* \brief %Companion matrix of a monic polynomial.
*
* @warning companion would be faster if built direct, using one axpy per entry: y_i = x_i-1 + p_i*x_n
*/
template<class Field_>
struct Companion: public SparseMatrix<Field_,SparseMatrixFormat::CSR> {
typedef Field_ Field;
typedef SparseMatrix<Field,SparseMatrixFormat::CSR> Father_t;
/// This is the n by n companion matrix of a given polynomial of degree n.
template<class Polynomial>
Companion(const Field& F , const Polynomial& P ) :
Father_t(F, P.size()-1, P.size()-1)
{
size_t n = P.size() - 1;
for (size_t i = 1; i < n; ++i)
this->setEntry(i, i-1, F.one);
for (size_t i = 0; i < n; ++i) {
typename Field::Element x;
F.neg(x, P[i]);
this->setEntry(i, n-1, x);
}
}// Companion cstor
/// zero matrix
Companion(const Field& F) :
Father_t(F)
{}
/**
* \brief This constructs a random companion matrix.
*
* Builds n by n matrix from degree n monic poly with other coefficients random.
*
* @warning should it be a constructor ?
*/
Companion(const Field& F, size_t n,
typename Field::RandIter r ) :
Father_t(F, n, n)
{
std::vector<typename Field::Element> p(n+1);
for (typename std::vector<typename Field::Element>::iterator i = p.begin(); i != p.end(); ++i)
r.random(*i); // we'll pretend p[n] == 1, ok?
for (size_t i = 1; i < n; ++i) this->setEntry(i, i-1, F.one);
for (size_t i = 0; i < n; ++i)
{ typename Field::Element x;
F.neg(x, p[i]);
this->setEntry(i, n-1, x);
}
}
/**
* \brief This constructs a random companion matrix.
*
* Builds n by n matrix from degree n monic poly with other coefficients random.
*
* @warning should it be a constructor ?
*/
Companion(const Field& F, size_t n) :
Father_t(F,n,n)
{
typename Field::RandIter r(F);
std::vector<typename Field::Element> p(n+1);
for (typename std::vector<typename Field::Element>::iterator i = p.begin(); i != p.end(); ++i)
r.random(*i); // we'll pretend p[n] == 1, ok?
// const size_t indexbase = 1;
for (size_t i = 1; i < n; ++i)
this->setEntry(i, i-1, F.one);
for (size_t i = 0; i < n; ++i)
{ typename Field::Element x;
F.neg(x, p[i]);
this->setEntry(i, n-1, x);
}
}
template<typename _Tp1>
struct rebind {
typedef Companion<_Tp1> other;
};
using Father_t::write;
}; //Companion class
} //LinBox
#endif //__LINBOX_companion_H
// Local Variables:
// mode: C++
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