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+/* $Id: CoinPresolveImpliedFree.hpp 1694 2014-04-29 02:08:35Z tkr $ */
+// 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 CoinPresolveImpliedFree_H
+#define CoinPresolveImpliedFree_H
+
+/*!
+ \file
+*/
+
+#define IMPLIED_FREE 9
+
+/*! \class implied_free_action
+ \brief Detect and process implied free variables
+
+ Consider a singleton variable x (<i>i.e.</i>, a variable involved in only
+ one constraint). Suppose that the bounds on that constraint, combined with
+ the bounds on the other variables involved in the constraint, are such that
+ even the worst case values of the other variables still imply bounds for x
+ which are tighter than the variable's original bounds. Since x can never
+ reach its upper or lower bounds, it is an implied free variable. Both x and
+ the constraint can be deleted from the problem.
+
+ A similar transform for the case where the variable is not a natural column
+ singleton is handled by #subst_constraint_action.
+*/
+class implied_free_action : public CoinPresolveAction {
+ struct action {
+ int row, col;
+ double clo, cup;
+ double rlo, rup;
+ const double *rowels;
+ const double *costs;
+ int ninrow;
+ };
+
+ const int nactions_;
+ const action *const actions_;
+
+ implied_free_action(int nactions,
+ const action *actions,
+ const CoinPresolveAction *next) :
+ CoinPresolveAction(next),
+ nactions_(nactions), actions_(actions) {}
+
+ public:
+ const char *name() const;
+
+ static const CoinPresolveAction *presolve(CoinPresolveMatrix * prob,
+ const CoinPresolveAction *next,
+ int & fillLevel);
+
+ void postsolve(CoinPostsolveMatrix *prob) const;
+
+ virtual ~implied_free_action();
+};
+
+#endif