/* -*- mode: C++; indent-tabs-mode: nil; -*- * * This file is a part of LEMON, a generic C++ optimization library. * * Copyright (C) 2003-2009 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport * (Egervary Research Group on Combinatorial Optimization, EGRES). * * Permission to use, modify and distribute this software is granted * provided that this copyright notice appears in all copies. For * precise terms see the accompanying LICENSE file. * * This software is provided "AS IS" with no warranty of any kind, * express or implied, and with no claim as to its suitability for any * purpose. * */ namespace lemon { /** @defgroup datas Data Structures This group contains the several data structures implemented in LEMON. */ /** @defgroup graphs Graph Structures @ingroup datas \brief Graph structures implemented in LEMON. The implementation of combinatorial algorithms heavily relies on efficient graph implementations. LEMON offers data structures which are planned to be easily used in an experimental phase of implementation studies, and thereafter the program code can be made efficient by small modifications. The most efficient implementation of diverse applications require the usage of different physical graph implementations. These differences appear in the size of graph we require to handle, memory or time usage limitations or in the set of operations through which the graph can be accessed. LEMON provides several physical graph structures to meet the diverging requirements of the possible users. In order to save on running time or on memory usage, some structures may fail to provide some graph features like arc/edge or node deletion. Alteration of standard containers need a very limited number of operations, these together satisfy the everyday requirements. In the case of graph structures, different operations are needed which do not alter the physical graph, but gives another view. If some nodes or arcs have to be hidden or the reverse oriented graph have to be used, then this is the case. It also may happen that in a flow implementation the residual graph can be accessed by another algorithm, or a node-set is to be shrunk for another algorithm. LEMON also provides a variety of graphs for these requirements called \ref graph_adaptors "graph adaptors". Adaptors cannot be used alone but only in conjunction with other graph representations. You are free to use the graph structure that fit your requirements the best, most graph algorithms and auxiliary data structures can be used with any graph structure. See also: \ref graph_concepts "Graph Structure Concepts". */ /** @defgroup graph_adaptors Adaptor Classes for Graphs @ingroup graphs \brief Adaptor classes for digraphs and graphs This group contains several useful adaptor classes for digraphs and graphs. The main parts of LEMON are the different graph structures, generic graph algorithms, graph concepts, which couple them, and graph adaptors. While the previous notions are more or less clear, the latter one needs further explanation. Graph adaptors are graph classes which serve for considering graph structures in different ways. A short example makes this much clearer. Suppose that we have an instance \c g of a directed graph type, say ListDigraph and an algorithm \code template int algorithm(const Digraph&); \endcode is needed to run on the reverse oriented graph. It may be expensive (in time or in memory usage) to copy \c g with the reversed arcs. In this case, an adaptor class is used, which (according to LEMON \ref concepts::Digraph "digraph concepts") works as a digraph. The adaptor uses the original digraph structure and digraph operations when methods of the reversed oriented graph are called. This means that the adaptor have minor memory usage, and do not perform sophisticated algorithmic actions. The purpose of it is to give a tool for the cases when a graph have to be used in a specific alteration. If this alteration is obtained by a usual construction like filtering the node or the arc set or considering a new orientation, then an adaptor is worthwhile to use. To come back to the reverse oriented graph, in this situation \code template class ReverseDigraph; \endcode template class can be used. The code looks as follows \code ListDigraph g; ReverseDigraph rg(g); int result = algorithm(rg); \endcode During running the algorithm, the original digraph \c g is untouched. This techniques give rise to an elegant code, and based on stable graph adaptors, complex algorithms can be implemented easily. In flow, circulation and matching problems, the residual graph is of particular importance. Combining an adaptor implementing this with shortest path algorithms or minimum mean cycle algorithms, a range of weighted and cardinality optimization algorithms can be obtained. For other examples, the interested user is referred to the detailed documentation of particular adaptors. The behavior of graph adaptors can be very different. Some of them keep capabilities of the original graph while in other cases this would be meaningless. This means that the concepts that they meet depend on the graph adaptor, and the wrapped graph. For example, if an arc of a reversed digraph is deleted, this is carried out by deleting the corresponding arc of the original digraph, thus the adaptor modifies the original digraph. However in case of a residual digraph, this operation has no sense. Let us stand one more example here to simplify your work. ReverseDigraph has constructor \code ReverseDigraph(Digraph& digraph); \endcode This means that in a situation, when a const %ListDigraph& reference to a graph is given, then it have to be instantiated with Digraph=const %ListDigraph. \code int algorithm1(const ListDigraph& g) { ReverseDigraph rg(g); return algorithm2(rg); } \endcode */ /** @defgroup maps Maps @ingroup datas \brief Map structures implemented in LEMON. This group contains the map structures implemented in LEMON. LEMON provides several special purpose maps and map adaptors that e.g. combine new maps from existing ones. See also: \ref map_concepts "Map Concepts". */ /** @defgroup graph_maps Graph Maps @ingroup maps \brief Special graph-related maps. This group contains maps that are specifically designed to assign values to the nodes and arcs/edges of graphs. If you are looking for the standard graph maps (\c NodeMap, \c ArcMap, \c EdgeMap), see the \ref graph_concepts "Graph Structure Concepts". */ /** \defgroup map_adaptors Map Adaptors \ingroup maps \brief Tools to create new maps from existing ones This group contains map adaptors that are used to create "implicit" maps from other maps. Most of them are \ref concepts::ReadMap "read-only maps". They can make arithmetic and logical operations between one or two maps (negation, shifting, addition, multiplication, logical 'and', 'or', 'not' etc.) or e.g. convert a map to another one of different Value type. The typical usage of this classes is passing implicit maps to algorithms. If a function type algorithm is called then the function type map adaptors can be used comfortable. For example let's see the usage of map adaptors with the \c graphToEps() function. \code Color nodeColor(int deg) { if (deg >= 2) { return Color(0.5, 0.0, 0.5); } else if (deg == 1) { return Color(1.0, 0.5, 1.0); } else { return Color(0.0, 0.0, 0.0); } } Digraph::NodeMap degree_map(graph); graphToEps(graph, "graph.eps") .coords(coords).scaleToA4().undirected() .nodeColors(composeMap(functorToMap(nodeColor), degree_map)) .run(); \endcode The \c functorToMap() function makes an \c int to \c Color map from the \c nodeColor() function. The \c composeMap() compose the \c degree_map and the previously created map. The composed map is a proper function to get the color of each node. The usage with class type algorithms is little bit harder. In this case the function type map adaptors can not be used, because the function map adaptors give back temporary objects. \code Digraph graph; typedef Digraph::ArcMap DoubleArcMap; DoubleArcMap length(graph); DoubleArcMap speed(graph); typedef DivMap TimeMap; TimeMap time(length, speed); Dijkstra dijkstra(graph, time); dijkstra.run(source, target); \endcode We have a length map and a maximum speed map on the arcs of a digraph. The minimum time to pass the arc can be calculated as the division of the two maps which can be done implicitly with the \c DivMap template class. We use the implicit minimum time map as the length map of the \c Dijkstra algorithm. */ /** @defgroup matrices Matrices @ingroup datas \brief Two dimensional data storages implemented in LEMON. This group contains two dimensional data storages implemented in LEMON. */ /** @defgroup paths Path Structures @ingroup datas \brief %Path structures implemented in LEMON. This group contains the path structures implemented in LEMON. LEMON provides flexible data structures to work with paths. All of them have similar interfaces and they can be copied easily with assignment operators and copy constructors. This makes it easy and efficient to have e.g. the Dijkstra algorithm to store its result in any kind of path structure. \sa lemon::concepts::Path */ /** @defgroup auxdat Auxiliary Data Structures @ingroup datas \brief Auxiliary data structures implemented in LEMON. This group contains some data structures implemented in LEMON in order to make it easier to implement combinatorial algorithms. */ /** @defgroup algs Algorithms \brief This group contains the several algorithms implemented in LEMON. This group contains the several algorithms implemented in LEMON. */ /** @defgroup search Graph Search @ingroup algs \brief Common graph search algorithms. This group contains the common graph search algorithms, namely \e breadth-first \e search (BFS) and \e depth-first \e search (DFS). */ /** @defgroup shortest_path Shortest Path Algorithms @ingroup algs \brief Algorithms for finding shortest paths. This group contains the algorithms for finding shortest paths in digraphs. - \ref Dijkstra algorithm for finding shortest paths from a source node when all arc lengths are non-negative. - \ref BellmanFord "Bellman-Ford" algorithm for finding shortest paths from a source node when arc lenghts can be either positive or negative, but the digraph should not contain directed cycles with negative total length. - \ref FloydWarshall "Floyd-Warshall" and \ref Johnson "Johnson" algorithms for solving the \e all-pairs \e shortest \e paths \e problem when arc lenghts can be either positive or negative, but the digraph should not contain directed cycles with negative total length. - \ref Suurballe A successive shortest path algorithm for finding arc-disjoint paths between two nodes having minimum total length. */ /** @defgroup max_flow Maximum Flow Algorithms @ingroup algs \brief Algorithms for finding maximum flows. This group contains the algorithms for finding maximum flows and feasible circulations. The \e maximum \e flow \e problem is to find a flow of maximum value between a single source and a single target. Formally, there is a \f$G=(V,A)\f$ digraph, a \f$cap: A\rightarrow\mathbf{R}^+_0\f$ capacity function and \f$s, t \in V\f$ source and target nodes. A maximum flow is an \f$f: A\rightarrow\mathbf{R}^+_0\f$ solution of the following optimization problem. \f[ \max\sum_{sv\in A} f(sv) - \sum_{vs\in A} f(vs) \f] \f[ \sum_{uv\in A} f(uv) = \sum_{vu\in A} f(vu) \quad \forall u\in V\setminus\{s,t\} \f] \f[ 0 \leq f(uv) \leq cap(uv) \quad \forall uv\in A \f] LEMON contains several algorithms for solving maximum flow problems: - \ref EdmondsKarp Edmonds-Karp algorithm. - \ref Preflow Goldberg-Tarjan's preflow push-relabel algorithm. - \ref DinitzSleatorTarjan Dinitz's blocking flow algorithm with dynamic trees. - \ref GoldbergTarjan Preflow push-relabel algorithm with dynamic trees. In most cases the \ref Preflow "Preflow" algorithm provides the fastest method for computing a maximum flow. All implementations also provide functions to query the minimum cut, which is the dual problem of maximum flow. \ref Circulation is a preflow push-relabel algorithm implemented directly for finding feasible circulations, which is a somewhat different problem, but it is strongly related to maximum flow. For more information, see \ref Circulation. */ /** @defgroup min_cost_flow Minimum Cost Flow Algorithms @ingroup algs \brief Algorithms for finding minimum cost flows and circulations. This group contains the algorithms for finding minimum cost flows and circulations. The \e minimum \e cost \e flow \e problem is to find a feasible flow of minimum total cost from a set of supply nodes to a set of demand nodes in a network with capacity constraints (lower and upper bounds) and arc costs. Formally, let \f$G=(V,A)\f$ be a digraph, \f$lower: A\rightarrow\mathbf{Z}\f$, \f$upper: A\rightarrow\mathbf{Z}\cup\{+\infty\}\f$ denote the lower and upper bounds for the flow values on the arcs, for which \f$lower(uv) \leq upper(uv)\f$ must hold for all \f$uv\in A\f$, \f$cost: A\rightarrow\mathbf{Z}\f$ denotes the cost per unit flow on the arcs and \f$sup: V\rightarrow\mathbf{Z}\f$ denotes the signed supply values of the nodes. If \f$sup(u)>0\f$, then \f$u\f$ is a supply node with \f$sup(u)\f$ supply, if \f$sup(u)<0\f$, then \f$u\f$ is a demand node with \f$-sup(u)\f$ demand. A minimum cost flow is an \f$f: A\rightarrow\mathbf{Z}\f$ solution of the following optimization problem. \f[ \min\sum_{uv\in A} f(uv) \cdot cost(uv) \f] \f[ \sum_{uv\in A} f(uv) - \sum_{vu\in A} f(vu) \geq sup(u) \quad \forall u\in V \f] \f[ lower(uv) \leq f(uv) \leq upper(uv) \quad \forall uv\in A \f] The sum of the supply values, i.e. \f$\sum_{u\in V} sup(u)\f$ must be zero or negative in order to have a feasible solution (since the sum of the expressions on the left-hand side of the inequalities is zero). It means that the total demand must be greater or equal to the total supply and all the supplies have to be carried out from the supply nodes, but there could be demands that are not satisfied. If \f$\sum_{u\in V} sup(u)\f$ is zero, then all the supply/demand constraints have to be satisfied with equality, i.e. all demands have to be satisfied and all supplies have to be used. If you need the opposite inequalities in the supply/demand constraints (i.e. the total demand is less than the total supply and all the demands have to be satisfied while there could be supplies that are not used), then you could easily transform the problem to the above form by reversing the direction of the arcs and taking the negative of the supply values (e.g. using \ref ReverseDigraph and \ref NegMap adaptors). However \ref NetworkSimplex algorithm also supports this form directly for the sake of convenience. A feasible solution for this problem can be found using \ref Circulation. Note that the above formulation is actually more general than the usual definition of the minimum cost flow problem, in which strict equalities are required in the supply/demand contraints, i.e. \f[ \sum_{uv\in A} f(uv) - \sum_{vu\in A} f(vu) = sup(u) \quad \forall u\in V. \f] However if the sum of the supply values is zero, then these two problems are equivalent. So if you need the equality form, you have to ensure this additional contraint for the algorithms. The dual solution of the minimum cost flow problem is represented by node potentials \f$\pi: V\rightarrow\mathbf{Z}\f$. An \f$f: A\rightarrow\mathbf{Z}\f$ feasible solution of the problem is optimal if and only if for some \f$\pi: V\rightarrow\mathbf{Z}\f$ node potentials the following \e complementary \e slackness optimality conditions hold. - For all \f$uv\in A\f$ arcs: - if \f$cost^\pi(uv)>0\f$, then \f$f(uv)=lower(uv)\f$; - if \f$lower(uv)typedefs etc. an implementation of the %concepts should provide, however completely without implementations and real data structures behind the interface. On the other hand they should provide nothing else. All the algorithms working on a data structure meeting a certain concept should compile with these classes. (Though it will not run properly, of course.) In this way it is easily to check if an algorithm doesn't use any extra feature of a certain implementation. - The concept descriptor classes also provide a checker class that makes it possible to check whether a certain implementation of a concept indeed provides all the required features. - Finally, They can serve as a skeleton of a new implementation of a concept. */ /** @defgroup graph_concepts Graph Structure Concepts @ingroup concept \brief Skeleton and concept checking classes for graph structures This group contains the skeletons and concept checking classes of LEMON's graph structures and helper classes used to implement these. */ /** @defgroup map_concepts Map Concepts @ingroup concept \brief Skeleton and concept checking classes for maps This group contains the skeletons and concept checking classes of maps. */ /** \anchor demoprograms @defgroup demos Demo Programs Some demo programs are listed here. Their full source codes can be found in the \c demo subdirectory of the source tree. In order to compile them, use the make demo or the make check commands. */ /** @defgroup tools Standalone Utility Applications Some utility applications are listed here. The standard compilation procedure (./configure;make) will compile them, as well. */ }