1 | /* -*- C++ -*- |
---|
2 | * src/lemon/tight_edge_filter_map.h - Part of LEMON, a generic C++ optimization library |
---|
3 | * |
---|
4 | * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
---|
5 | * (Egervary Combinatorial Optimization Research Group, EGRES). |
---|
6 | * |
---|
7 | * Permission to use, modify and distribute this software is granted |
---|
8 | * provided that this copyright notice appears in all copies. For |
---|
9 | * precise terms see the accompanying LICENSE file. |
---|
10 | * |
---|
11 | * This software is provided "AS IS" with no warranty of any kind, |
---|
12 | * express or implied, and with no claim as to its suitability for any |
---|
13 | * purpose. |
---|
14 | * |
---|
15 | */ |
---|
16 | |
---|
17 | #ifndef LEMON_TIGHT_EDGE_FILTER_MAP_H |
---|
18 | #define LEMON_TIGHT_EDGE_FILTER_MAP_H |
---|
19 | |
---|
20 | #include <lemon/maps.h> |
---|
21 | |
---|
22 | // /// \file |
---|
23 | // /// \brief Maximum flow algorithms. |
---|
24 | // /// \ingroup galgs |
---|
25 | |
---|
26 | namespace lemon { |
---|
27 | |
---|
28 | /*! |
---|
29 | \brief A map for filtering the edge-set to those edges |
---|
30 | which are tight w.r.t. a node-potential and |
---|
31 | edge-distance. |
---|
32 | |
---|
33 | Let \f$G=(V,A)\f$ be a directed graph (graph for short) and |
---|
34 | let \f$\mathbb{F}\f$ be a number type. |
---|
35 | Given a distance function |
---|
36 | \f$d:E\to\mathbb{F}\f$, |
---|
37 | \f$\pi:V\to\mathbb{F}\f$ is said to be a potetial |
---|
38 | w.r.t. \f$d\f$ |
---|
39 | if and only if |
---|
40 | \f$\pi(v)\le d(uv)+\pi(u)\f$ holds for each edge \f$uv\in E\f$ |
---|
41 | (or the reverse inequality holds for each edge). |
---|
42 | An edge is said to be tight if this inequality holds with equality, |
---|
43 | and the map returns \c true exactly for those edges. |
---|
44 | To avoid rounding errors, it is recommended to use this class with exact |
---|
45 | number types, e.g. with \c int. |
---|
46 | */ |
---|
47 | template<typename Graph, |
---|
48 | typename NodePotentialMap, typename EdgeDistanceMap> |
---|
49 | class TightEdgeFilterMap : public MapBase<typename Graph::Edge, bool> { |
---|
50 | protected: |
---|
51 | const Graph* g; |
---|
52 | NodePotentialMap* node_potential; |
---|
53 | EdgeDistanceMap* edge_distance; |
---|
54 | public: |
---|
55 | TightEdgeFilterMap(Graph& _g, NodePotentialMap& _node_potential, |
---|
56 | EdgeDistanceMap& _edge_distance) : |
---|
57 | g(&_g), node_potential(&_node_potential), |
---|
58 | edge_distance(&_edge_distance) { } |
---|
59 | bool operator[](const typename Graph::Edge& e) const { |
---|
60 | return ((*node_potential)[g->target(e)] == |
---|
61 | (*edge_distance)[e]+(*node_potential)[g->source(e)]); |
---|
62 | } |
---|
63 | }; |
---|
64 | |
---|
65 | } //namespace lemon |
---|
66 | |
---|
67 | #endif //LEMON_TIGHT_EDGE_FILTER_MAP_H |
---|