/usr/include/linbox/algorithms/gauss/gauss-pivot.inl is in liblinbox-dev 1.3.2-1.1build2.
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* Copyright (C) 2009,2010 The LinBox group
* Written by JG Dumas <Jean-Guillaume.Dumas@imag.fr>
*
*
* ========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========
*.
*
* SparseElimination search for pivots
*/
#ifndef __LINBOX_gauss_pivot_INL
#define __LINBOX_gauss_pivot_INL
namespace LinBox
{
template <class _Field>
template <class Vector, class D> inline void
GaussDomain<_Field>::SparseFindPivot (Vector &lignepivot,
unsigned long &indcol,
long &indpermut,
D &columns,
Element &determinant) const
{
// std::cerr << "SFP BEG : lignepivot: [";
// for(typename Vector::const_iterator refs = lignepivot.begin();
// refs != lignepivot.end() ;
// ++refs )
// std::cerr << '(' << refs->first << ';' << refs->second << ')';
// std::cerr << "]" << std::endl;
typedef typename Vector::value_type E;
long nj = lignepivot.size ();
bool pivoting = false;
if (nj > 0) {
indpermut = lignepivot[0].first;
long ds = --columns[indpermut], dl, p = 0;
for (long j = 1; j < nj; ++j) {
if ((dl = --columns[lignepivot[j].first]) < ds) {
ds = dl;
p = j;
}
}
if (p != 0) {
pivoting = true;
if (indpermut == static_cast<long>(indcol)) {
indpermut = lignepivot[p].first;
std::swap( lignepivot[p].second, lignepivot[0].second);
}
else {
E ttm = lignepivot[p];
indpermut = ttm.first;
for (long m = p; m; --m)
lignepivot[m] = lignepivot[m-1];
lignepivot[0] = ttm;
}
}
_field.mulin(determinant, lignepivot[0].second);
if (indpermut != static_cast<long>(indcol)) {
// std::cerr << "Permuting col: " << indpermut << " <--> " << indcol << std::endl;
// no need to decrement/increment, already done during the search
lignepivot[0].first = (unsigned)indcol;
pivoting = true;
}
if (pivoting) _field.negin(determinant);
++indcol;
}
else
indpermut = -1;
// std::cerr << "SFP END : lignepivot: [";
// for(typename Vector::const_iterator refs = lignepivot.begin();
// refs != lignepivot.end() ;
// ++refs )
// std::cerr << '(' << refs->first << ';' << refs->second << ')';
// std::cerr << "]" << std::endl;
}
template <class _Field>
template <class Vector> inline void
GaussDomain<_Field>::SparseFindPivot (Vector &lignepivot,
unsigned long &indcol,
long &indpermut,
Element& determinant) const
{
long nj = lignepivot.size ();
if (nj > 0) {
indpermut = lignepivot[0].first;
_field.mulin(determinant, lignepivot[0].second);
if (indpermut != static_cast<long>(indcol)){
// std::cerr << "Permuting col: " << lignepivot[0].first << " <--> " << indcol << std::endl;
lignepivot[0].first = (unsigned)indcol;
_field.negin(determinant);
}
++indcol;
}
else
indpermut = -1;
}
template <class _Field>
template <class Vector> inline void
GaussDomain<_Field>::FindPivot (Vector &lignepivot,
unsigned long &k,
long &indpermut) const
{
// Dense lignepivot
long n = lignepivot.size ();
long j = (long)k;
for (; j < n ; ++j )
if (!_field.isZero (lignepivot[j])) break ;
if (j == n )
indpermut = -1 ;
else {
indpermut = j ;
if (indpermut != (long)k) {
typename Vector::value_type tmp = lignepivot[k] ;
lignepivot[k] = lignepivot[j] ;
lignepivot[j] = tmp ;
}
++k;
}
}
} // namespace LinBox
#endif // __LINBOX_gauss_pivot_INL
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