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/* $Id: CoinPresolveZeros.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 CoinPresolveZeros_H
#define CoinPresolveZeros_H
/*! \file
Drop/reintroduce explicit zeros.
*/
#define DROP_ZERO 8
/*! \brief Tracking information for an explicit zero coefficient
\todo Why isn't this a nested class in drop_zero_coefficients_action?
That would match the structure of other presolve classes.
*/
struct dropped_zero {
int row;
int col;
};
/*! \brief Removal of explicit zeros
The presolve action for this class removes explicit zeros from the constraint
matrix. The postsolve action puts them back.
*/
class drop_zero_coefficients_action : public CoinPresolveAction {
const int nzeros_;
const dropped_zero *const zeros_;
drop_zero_coefficients_action(int nzeros,
const dropped_zero *zeros,
const CoinPresolveAction *next) :
CoinPresolveAction(next),
nzeros_(nzeros), zeros_(zeros)
{}
public:
const char *name() const { return ("drop_zero_coefficients_action"); }
static const CoinPresolveAction *presolve(CoinPresolveMatrix *prob,
int *checkcols,
int ncheckcols,
const CoinPresolveAction *next);
void postsolve(CoinPostsolveMatrix *prob) const;
virtual ~drop_zero_coefficients_action() { deleteAction(zeros_,dropped_zero*); }
};
const CoinPresolveAction *drop_zero_coefficients(CoinPresolveMatrix *prob,
const CoinPresolveAction *next);
#endif
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