1 | /* -*- C++ -*- |
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2 | * src/lemon/tight_edge_filter_map.h - Part of LEMON, a generic C++ optimization library |
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3 | * |
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4 | * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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5 | * (Egervary Combinatorial Optimization Research Group, EGRES). |
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6 | * |
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7 | * Permission to use, modify and distribute this software is granted |
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8 | * provided that this copyright notice appears in all copies. For |
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9 | * precise terms see the accompanying LICENSE file. |
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10 | * |
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11 | * This software is provided "AS IS" with no warranty of any kind, |
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12 | * express or implied, and with no claim as to its suitability for any |
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13 | * purpose. |
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14 | * |
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15 | */ |
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16 | |
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17 | #ifndef LEMON_TIGHT_EDGE_FILTER_MAP_H |
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18 | #define LEMON_TIGHT_EDGE_FILTER_MAP_H |
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19 | |
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20 | #include <lemon/maps.h> |
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21 | |
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22 | // /// \file |
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23 | // /// \brief Maximum flow algorithms. |
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24 | // /// \ingroup galgs |
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25 | |
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26 | namespace lemon { |
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27 | |
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28 | /// \brief A map for filtering the edge-set to those edges |
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29 | /// which are tight w.r.t. some node_potential map and |
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30 | /// edge_distance map. |
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31 | /// |
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32 | /// A node-map node_potential is said to be a potential w.r.t. |
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33 | /// an edge-map edge_distance |
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34 | /// if and only if for each edge e, node_potential[g.head(e)] |
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35 | /// <= edge_distance[e]+node_potential[g.tail(e)] |
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36 | /// (or the reverse inequality holds for each edge). |
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37 | /// An edge is said to be tight if this inequality holds with equality, |
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38 | /// and the map returns true exactly for those edges. |
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39 | /// To avoid rounding errors, it is recommended to use this class with exact |
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40 | /// types, e.g. with int. |
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41 | template<typename Graph, |
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42 | typename NodePotentialMap, typename EdgeDistanceMap> |
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43 | class TightEdgeFilterMap : public MapBase<typename Graph::Edge, bool> { |
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44 | protected: |
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45 | const Graph* g; |
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46 | NodePotentialMap* node_potential; |
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47 | EdgeDistanceMap* edge_distance; |
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48 | public: |
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49 | TightEdgeFilterMap(Graph& _g, NodePotentialMap& _node_potential, |
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50 | EdgeDistanceMap& _edge_distance) : |
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51 | g(&_g), node_potential(&_node_potential), |
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52 | edge_distance(&_edge_distance) { } |
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53 | bool operator[](const typename Graph::Edge& e) const { |
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54 | return ((*node_potential)[g->head(e)] == |
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55 | (*edge_distance)[e]+(*node_potential)[g->tail(e)]); |
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56 | } |
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57 | }; |
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58 | |
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59 | } //namespace lemon |
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60 | |
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61 | #endif //LEMON_TIGHT_EDGE_FILTER_MAP_H |
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62 | |
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63 | |
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