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/* $Id: CoinPresolveUseless.hpp 1566 2012-11-29 19:33:56Z lou $ */
// 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 CoinPresolveUseless_H
#define CoinPresolveUseless_H
#define USELESS 20
class useless_constraint_action : public CoinPresolveAction {
struct action {
double rlo;
double rup;
const int *rowcols;
const double *rowels;
int row;
int ninrow;
};
const int nactions_;
const action *const actions_;
useless_constraint_action(int nactions,
const action *actions,
const CoinPresolveAction *next);
public:
const char *name() const;
// These rows are asserted to be useless,
// that is, given a solution the row activity
// must be in range.
static const CoinPresolveAction *presolve(CoinPresolveMatrix * prob,
const int *useless_rows,
int nuseless_rows,
const CoinPresolveAction *next);
void postsolve(CoinPostsolveMatrix *prob) const;
virtual ~useless_constraint_action();
};
/*! \relates useless_constraint_action
\brief Scan constraints looking for useless constraints
A front end to identify useless constraints and hand them to
useless_constraint_action::presolve() for processing.
In a bit more detail, the routine implements a greedy algorithm that
identifies a set of necessary constraints. A constraint is necessary if it
implies a tighter bound on a variable than the original column bound. These
tighter column bounds are then used to calculate row activity and identify
constraints that are useless given the presence of the necessary
constraints.
*/
const CoinPresolveAction *testRedundant(CoinPresolveMatrix *prob,
const CoinPresolveAction *next) ;
#endif
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