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/* $Id: CoinPresolveDoubleton.hpp 1498 2011-11-02 15:25:35Z mjs $ */
// Copyright (C) 2002, International Business Machines
// Corporation and others. All Rights Reserved.
// This code is licensed under the terms of the Eclipse Public License (EPL).
#ifndef CoinPresolveDoubleton_H
#define CoinPresolveDoubleton_H
#define DOUBLETON 5
/*! \class doubleton_action
\brief Solve ax+by=c for y and substitute y out of the problem.
This moves the bounds information for y onto x, making y free and allowing
us to substitute it away.
\verbatim
a x + b y = c
l1 <= x <= u1
l2 <= y <= u2 ==>
l2 <= (c - a x) / b <= u2
b/-a > 0 ==> (b l2 - c) / -a <= x <= (b u2 - c) / -a
b/-a < 0 ==> (b u2 - c) / -a <= x <= (b l2 - c) / -a
\endverbatim
*/
class doubleton_action : public CoinPresolveAction {
public:
struct action {
double clox;
double cupx;
double costx;
double costy;
double rlo;
double coeffx;
double coeffy;
double *colel;
int icolx;
int icoly;
int row;
int ncolx;
int ncoly;
};
const int nactions_;
const action *const actions_;
private:
doubleton_action(int nactions,
const action *actions,
const CoinPresolveAction *next) :
CoinPresolveAction(next),
nactions_(nactions), actions_(actions)
{}
public:
const char *name() const { return ("doubleton_action"); }
static const CoinPresolveAction *presolve(CoinPresolveMatrix *,
const CoinPresolveAction *next);
void postsolve(CoinPostsolveMatrix *prob) const;
virtual ~doubleton_action();
};
#endif
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