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/*
* $Revision: 2523 $
*
* last checkin:
* $Author: gutwenger $
* $Date: 2012-07-02 20:59:27 +0200 (Mon, 02 Jul 2012) $
***************************************************************/
/** \file
* \brief Declaration of base class of min-cost-flow algorithms
*
* Includes some useful functions dealing with min-cost flow
* (generater, checker).
*
* \author Carsten Gutwenger
*
* \par License:
* This file is part of the Open Graph Drawing Framework (OGDF).
*
* \par
* Copyright (C)<br>
* See README.txt in the root directory of the OGDF installation for details.
*
* \par
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* Version 2 or 3 as published by the Free Software Foundation;
* see the file LICENSE.txt included in the packaging of this file
* for details.
*
* \par
* This program 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 General Public License for more details.
*
* \par
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
* \see http://www.gnu.org/copyleft/gpl.html
***************************************************************/
#ifdef _MSC_VER
#pragma once
#endif
#ifndef OGDF_MIN_COST_FLOW_MODULE_H
#define OGDF_MIN_COST_FLOW_MODULE_H
#include <ogdf/basic/Graph.h>
namespace ogdf {
/**
* \brief Interface for min-cost flow algorithms.
*/
class OGDF_EXPORT MinCostFlowModule
{
public:
//! Initializes a min-cost flow module.
MinCostFlowModule() { }
// destruction
virtual ~MinCostFlowModule() { }
/**
* \brief Computes a min-cost flow in the directed graph \a G.
*
* \pre \a G must be connected, \a lowerBound[\a e] \f$\leq\f$ \a upperBound[\a e]
* for all edges \a e, and the sum over all supplies must be zero.
*
* @param G is the directed input graph.
* @param lowerBound gives the lower bound for the flow on each edge.
* @param upperBound gives the upper bound for the flow on each edge.
* @param cost gives the costs for each edge.
* @param supply gives the supply (or demand if negative) of each node.
* @param flow is assigned the computed flow on each edge.
* @param dual is assigned the computed dual variables.
* \return true iff a feasible min-cost flow exists.
*/
virtual bool call(
const Graph &G, // directed graph
const EdgeArray<int> &lowerBound, // lower bound for flow
const EdgeArray<int> &upperBound, // upper bound for flow
const EdgeArray<int> &cost, // cost of an edge
const NodeArray<int> &supply, // supply (if neg. demand) of a node
EdgeArray<int> &flow, // computed flow
NodeArray<int> &dual // computed dual variables
) = 0;
//
// static functions
//
/**
* \brief Generates an instance of a min-cost flow problem with \a n nodes and
* \a m+\a n edges.
*/
static void generateProblem(
Graph &G,
int n,
int m,
EdgeArray<int> &lowerBound,
EdgeArray<int> &upperBound,
EdgeArray<int> &cost,
NodeArray<int> &supply);
/**
* \brief Checks if a given min-cost flow problem instance satisfies
* the preconditions.
* The following preconditions are checked:
* - \a lowerBound[\a e] \f$\leq\f$ \a upperBound[\a e] for all edges \a e
* - sum over all \a supply[\a v] = 0
*
* @param G is the input graph.
* @param lowerBound gives the lower bound for the flow on each edge.
* @param upperBound gives the upper bound for the flow on each edge.
* @param supply gives the supply (or demand if negative) of each node.
* \return true iff the problem satisfies the preconditions.
*/
static bool checkProblem(
const Graph &G,
const EdgeArray<int> &lowerBound,
const EdgeArray<int> &upperBound,
const NodeArray<int> &supply);
/**
* \brief checks if a computed flow is a feasible solution to the given problem
* instance.
*
* Checks in particular if:
* - \a lowerBound[\a e] \f$\leq\f$ \a flow[\a e] \f$\leq\f$ \a upperBound[\a e]
* - sum \a flow[\a e], \a e is outgoing edge of \a v minus
* sum \a flow[\a e], \a e is incoming edge of \a v equals \a supply[\a v]
* for each node \a v
*
* @param G is the input graph.
* @param lowerBound gives the lower bound for the flow on each edge.
* @param upperBound gives the upper bound for the flow on each edge.
* @param cost gives the costs for each edge.
* @param supply gives the supply (or demand if negative) of each node.
* @param flow is the flow on each edge.
* @param value is assigned the value of the flow.
* \return true iff the solution is feasible.
*/
static bool checkComputedFlow(
const Graph &G,
EdgeArray<int> &lowerBound,
EdgeArray<int> &upperBound,
EdgeArray<int> &cost,
NodeArray<int> &supply,
EdgeArray<int> &flow,
int &value);
/**
* \brief checks if a computed flow is a feasible solution to the given problem
* instance.
*
* Checks in particular if:
* - \a lowerBound[\a e] \f$\leq\f$ \a flow[\a e] \f$\leq\f$ \a upperBound[\a e]
* - sum \a flow[\a e], \a e is outgoing edge of \a v minus
* sum \a flow[\a e], \a e is incoming edge of \a v equals \a supply[\a v]
* for each node \a v
*
* @param G is the input graph.
* @param lowerBound gives the lower bound for the flow on each edge.
* @param upperBound gives the upper bound for the flow on each edge.
* @param cost gives the costs for each edge.
* @param supply gives the supply (or demand if negative) of each node.
* @param flow is the flow on each edge.
* \return true iff the solution is feasible.
*/
static bool checkComputedFlow(
const Graph &G,
EdgeArray<int> &lowerBound,
EdgeArray<int> &upperBound,
EdgeArray<int> &cost,
NodeArray<int> &supply,
EdgeArray<int> &flow)
{
int value;
return checkComputedFlow(
G,lowerBound,upperBound,cost,supply,flow,value);
}
};
} // end namespace ogdf
#endif
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