[871] | 1 | /* -*- C++ -*- |
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| 2 | * |
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| 3 | * This file is a part of LEMON, a generic C++ optimization library |
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| 4 | * |
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| 5 | * Copyright (C) 2003-2008 |
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| 6 | * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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| 7 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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| 8 | * |
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| 9 | * Permission to use, modify and distribute this software is granted |
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| 10 | * provided that this copyright notice appears in all copies. For |
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| 11 | * precise terms see the accompanying LICENSE file. |
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| 12 | * |
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| 13 | * This software is provided "AS IS" with no warranty of any kind, |
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| 14 | * express or implied, and with no claim as to its suitability for any |
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| 15 | * purpose. |
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| 16 | * |
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| 17 | */ |
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| 18 | |
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| 19 | #ifndef LEMON_CAPACITY_SCALING_H |
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| 20 | #define LEMON_CAPACITY_SCALING_H |
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| 21 | |
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| 22 | /// \ingroup min_cost_flow |
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| 23 | /// |
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| 24 | /// \file |
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| 25 | /// \brief Capacity scaling algorithm for finding a minimum cost flow. |
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| 26 | |
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| 27 | #include <vector> |
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| 28 | #include <lemon/bin_heap.h> |
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| 29 | |
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| 30 | namespace lemon { |
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| 31 | |
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| 32 | /// \addtogroup min_cost_flow |
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| 33 | /// @{ |
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| 34 | |
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| 35 | /// \brief Implementation of the capacity scaling algorithm for |
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| 36 | /// finding a minimum cost flow. |
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| 37 | /// |
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| 38 | /// \ref CapacityScaling implements the capacity scaling version |
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| 39 | /// of the successive shortest path algorithm for finding a minimum |
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| 40 | /// cost flow. |
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| 41 | /// |
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| 42 | /// \tparam Digraph The digraph type the algorithm runs on. |
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| 43 | /// \tparam LowerMap The type of the lower bound map. |
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| 44 | /// \tparam CapacityMap The type of the capacity (upper bound) map. |
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| 45 | /// \tparam CostMap The type of the cost (length) map. |
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| 46 | /// \tparam SupplyMap The type of the supply map. |
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| 47 | /// |
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| 48 | /// \warning |
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| 49 | /// - Arc capacities and costs should be \e non-negative \e integers. |
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| 50 | /// - Supply values should be \e signed \e integers. |
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| 51 | /// - The value types of the maps should be convertible to each other. |
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| 52 | /// - \c CostMap::Value must be signed type. |
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| 53 | /// |
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| 54 | /// \author Peter Kovacs |
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| 55 | template < typename Digraph, |
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| 56 | typename LowerMap = typename Digraph::template ArcMap<int>, |
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| 57 | typename CapacityMap = typename Digraph::template ArcMap<int>, |
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| 58 | typename CostMap = typename Digraph::template ArcMap<int>, |
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| 59 | typename SupplyMap = typename Digraph::template NodeMap<int> > |
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| 60 | class CapacityScaling |
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| 61 | { |
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| 62 | TEMPLATE_DIGRAPH_TYPEDEFS(Digraph); |
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| 63 | |
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| 64 | typedef typename CapacityMap::Value Capacity; |
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| 65 | typedef typename CostMap::Value Cost; |
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| 66 | typedef typename SupplyMap::Value Supply; |
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| 67 | typedef typename Digraph::template ArcMap<Capacity> CapacityArcMap; |
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| 68 | typedef typename Digraph::template NodeMap<Supply> SupplyNodeMap; |
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| 69 | typedef typename Digraph::template NodeMap<Arc> PredMap; |
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| 70 | |
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| 71 | public: |
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| 72 | |
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| 73 | /// The type of the flow map. |
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| 74 | typedef typename Digraph::template ArcMap<Capacity> FlowMap; |
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| 75 | /// The type of the potential map. |
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| 76 | typedef typename Digraph::template NodeMap<Cost> PotentialMap; |
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| 77 | |
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| 78 | private: |
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| 79 | |
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| 80 | /// \brief Special implementation of the \ref Dijkstra algorithm |
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| 81 | /// for finding shortest paths in the residual network. |
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| 82 | /// |
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| 83 | /// \ref ResidualDijkstra is a special implementation of the |
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| 84 | /// \ref Dijkstra algorithm for finding shortest paths in the |
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| 85 | /// residual network of the digraph with respect to the reduced arc |
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| 86 | /// costs and modifying the node potentials according to the |
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| 87 | /// distance of the nodes. |
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| 88 | class ResidualDijkstra |
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| 89 | { |
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| 90 | typedef typename Digraph::template NodeMap<int> HeapCrossRef; |
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| 91 | typedef BinHeap<Cost, HeapCrossRef> Heap; |
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| 92 | |
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| 93 | private: |
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| 94 | |
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| 95 | // The digraph the algorithm runs on |
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| 96 | const Digraph &_graph; |
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| 97 | |
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| 98 | // The main maps |
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| 99 | const FlowMap &_flow; |
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| 100 | const CapacityArcMap &_res_cap; |
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| 101 | const CostMap &_cost; |
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| 102 | const SupplyNodeMap &_excess; |
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| 103 | PotentialMap &_potential; |
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| 104 | |
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| 105 | // The distance map |
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| 106 | PotentialMap _dist; |
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| 107 | // The pred arc map |
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| 108 | PredMap &_pred; |
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| 109 | // The processed (i.e. permanently labeled) nodes |
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| 110 | std::vector<Node> _proc_nodes; |
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| 111 | |
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| 112 | public: |
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| 113 | |
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| 114 | /// Constructor. |
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| 115 | ResidualDijkstra( const Digraph &digraph, |
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| 116 | const FlowMap &flow, |
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| 117 | const CapacityArcMap &res_cap, |
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| 118 | const CostMap &cost, |
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| 119 | const SupplyMap &excess, |
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| 120 | PotentialMap &potential, |
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| 121 | PredMap &pred ) : |
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| 122 | _graph(digraph), _flow(flow), _res_cap(res_cap), _cost(cost), |
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| 123 | _excess(excess), _potential(potential), _dist(digraph), |
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| 124 | _pred(pred) |
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| 125 | {} |
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| 126 | |
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| 127 | /// Run the algorithm from the given source node. |
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| 128 | Node run(Node s, Capacity delta = 1) { |
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| 129 | HeapCrossRef heap_cross_ref(_graph, Heap::PRE_HEAP); |
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| 130 | Heap heap(heap_cross_ref); |
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| 131 | heap.push(s, 0); |
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| 132 | _pred[s] = INVALID; |
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| 133 | _proc_nodes.clear(); |
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| 134 | |
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| 135 | // Processing nodes |
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| 136 | while (!heap.empty() && _excess[heap.top()] > -delta) { |
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| 137 | Node u = heap.top(), v; |
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| 138 | Cost d = heap.prio() + _potential[u], nd; |
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| 139 | _dist[u] = heap.prio(); |
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| 140 | heap.pop(); |
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| 141 | _proc_nodes.push_back(u); |
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| 142 | |
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| 143 | // Traversing outgoing arcs |
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| 144 | for (OutArcIt e(_graph, u); e != INVALID; ++e) { |
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| 145 | if (_res_cap[e] >= delta) { |
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| 146 | v = _graph.target(e); |
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| 147 | switch(heap.state(v)) { |
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| 148 | case Heap::PRE_HEAP: |
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| 149 | heap.push(v, d + _cost[e] - _potential[v]); |
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| 150 | _pred[v] = e; |
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| 151 | break; |
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| 152 | case Heap::IN_HEAP: |
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| 153 | nd = d + _cost[e] - _potential[v]; |
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| 154 | if (nd < heap[v]) { |
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| 155 | heap.decrease(v, nd); |
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| 156 | _pred[v] = e; |
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| 157 | } |
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| 158 | break; |
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| 159 | case Heap::POST_HEAP: |
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| 160 | break; |
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| 161 | } |
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| 162 | } |
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| 163 | } |
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| 164 | |
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| 165 | // Traversing incoming arcs |
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| 166 | for (InArcIt e(_graph, u); e != INVALID; ++e) { |
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| 167 | if (_flow[e] >= delta) { |
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| 168 | v = _graph.source(e); |
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| 169 | switch(heap.state(v)) { |
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| 170 | case Heap::PRE_HEAP: |
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| 171 | heap.push(v, d - _cost[e] - _potential[v]); |
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| 172 | _pred[v] = e; |
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| 173 | break; |
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| 174 | case Heap::IN_HEAP: |
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| 175 | nd = d - _cost[e] - _potential[v]; |
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| 176 | if (nd < heap[v]) { |
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| 177 | heap.decrease(v, nd); |
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| 178 | _pred[v] = e; |
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| 179 | } |
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| 180 | break; |
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| 181 | case Heap::POST_HEAP: |
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| 182 | break; |
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| 183 | } |
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| 184 | } |
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| 185 | } |
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| 186 | } |
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| 187 | if (heap.empty()) return INVALID; |
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| 188 | |
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| 189 | // Updating potentials of processed nodes |
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| 190 | Node t = heap.top(); |
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| 191 | Cost t_dist = heap.prio(); |
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| 192 | for (int i = 0; i < int(_proc_nodes.size()); ++i) |
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| 193 | _potential[_proc_nodes[i]] += _dist[_proc_nodes[i]] - t_dist; |
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| 194 | |
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| 195 | return t; |
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| 196 | } |
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| 197 | |
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| 198 | }; //class ResidualDijkstra |
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| 199 | |
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| 200 | private: |
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| 201 | |
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| 202 | // The digraph the algorithm runs on |
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| 203 | const Digraph &_graph; |
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| 204 | // The original lower bound map |
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| 205 | const LowerMap *_lower; |
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| 206 | // The modified capacity map |
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| 207 | CapacityArcMap _capacity; |
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| 208 | // The original cost map |
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| 209 | const CostMap &_cost; |
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| 210 | // The modified supply map |
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| 211 | SupplyNodeMap _supply; |
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| 212 | bool _valid_supply; |
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| 213 | |
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| 214 | // Arc map of the current flow |
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| 215 | FlowMap *_flow; |
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| 216 | bool _local_flow; |
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| 217 | // Node map of the current potentials |
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| 218 | PotentialMap *_potential; |
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| 219 | bool _local_potential; |
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| 220 | |
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| 221 | // The residual capacity map |
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| 222 | CapacityArcMap _res_cap; |
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| 223 | // The excess map |
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| 224 | SupplyNodeMap _excess; |
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| 225 | // The excess nodes (i.e. nodes with positive excess) |
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| 226 | std::vector<Node> _excess_nodes; |
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| 227 | // The deficit nodes (i.e. nodes with negative excess) |
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| 228 | std::vector<Node> _deficit_nodes; |
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| 229 | |
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| 230 | // The delta parameter used for capacity scaling |
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| 231 | Capacity _delta; |
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| 232 | // The maximum number of phases |
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| 233 | int _phase_num; |
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| 234 | |
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| 235 | // The pred arc map |
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| 236 | PredMap _pred; |
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| 237 | // Implementation of the Dijkstra algorithm for finding augmenting |
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| 238 | // shortest paths in the residual network |
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| 239 | ResidualDijkstra *_dijkstra; |
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| 240 | |
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| 241 | public: |
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| 242 | |
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| 243 | /// \brief General constructor (with lower bounds). |
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| 244 | /// |
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| 245 | /// General constructor (with lower bounds). |
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| 246 | /// |
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| 247 | /// \param digraph The digraph the algorithm runs on. |
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| 248 | /// \param lower The lower bounds of the arcs. |
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| 249 | /// \param capacity The capacities (upper bounds) of the arcs. |
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| 250 | /// \param cost The cost (length) values of the arcs. |
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| 251 | /// \param supply The supply values of the nodes (signed). |
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| 252 | CapacityScaling( const Digraph &digraph, |
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| 253 | const LowerMap &lower, |
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| 254 | const CapacityMap &capacity, |
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| 255 | const CostMap &cost, |
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| 256 | const SupplyMap &supply ) : |
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| 257 | _graph(digraph), _lower(&lower), _capacity(digraph), _cost(cost), |
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| 258 | _supply(digraph), _flow(NULL), _local_flow(false), |
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| 259 | _potential(NULL), _local_potential(false), |
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| 260 | _res_cap(digraph), _excess(digraph), _pred(digraph), _dijkstra(NULL) |
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| 261 | { |
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| 262 | Supply sum = 0; |
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| 263 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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| 264 | _supply[n] = supply[n]; |
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| 265 | _excess[n] = supply[n]; |
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| 266 | sum += supply[n]; |
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| 267 | } |
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| 268 | _valid_supply = sum == 0; |
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| 269 | for (ArcIt a(_graph); a != INVALID; ++a) { |
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| 270 | _capacity[a] = capacity[a]; |
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| 271 | _res_cap[a] = capacity[a]; |
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| 272 | } |
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| 273 | |
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| 274 | // Remove non-zero lower bounds |
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| 275 | typename LowerMap::Value lcap; |
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| 276 | for (ArcIt e(_graph); e != INVALID; ++e) { |
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| 277 | if ((lcap = lower[e]) != 0) { |
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| 278 | _capacity[e] -= lcap; |
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| 279 | _res_cap[e] -= lcap; |
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| 280 | _supply[_graph.source(e)] -= lcap; |
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| 281 | _supply[_graph.target(e)] += lcap; |
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| 282 | _excess[_graph.source(e)] -= lcap; |
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| 283 | _excess[_graph.target(e)] += lcap; |
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| 284 | } |
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| 285 | } |
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| 286 | } |
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| 287 | /* |
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| 288 | /// \brief General constructor (without lower bounds). |
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| 289 | /// |
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| 290 | /// General constructor (without lower bounds). |
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| 291 | /// |
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| 292 | /// \param digraph The digraph the algorithm runs on. |
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| 293 | /// \param capacity The capacities (upper bounds) of the arcs. |
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| 294 | /// \param cost The cost (length) values of the arcs. |
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| 295 | /// \param supply The supply values of the nodes (signed). |
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| 296 | CapacityScaling( const Digraph &digraph, |
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| 297 | const CapacityMap &capacity, |
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| 298 | const CostMap &cost, |
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| 299 | const SupplyMap &supply ) : |
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| 300 | _graph(digraph), _lower(NULL), _capacity(capacity), _cost(cost), |
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| 301 | _supply(supply), _flow(NULL), _local_flow(false), |
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| 302 | _potential(NULL), _local_potential(false), |
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| 303 | _res_cap(capacity), _excess(supply), _pred(digraph), _dijkstra(NULL) |
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| 304 | { |
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| 305 | // Check the sum of supply values |
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| 306 | Supply sum = 0; |
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| 307 | for (NodeIt n(_graph); n != INVALID; ++n) sum += _supply[n]; |
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| 308 | _valid_supply = sum == 0; |
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| 309 | } |
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| 310 | |
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| 311 | /// \brief Simple constructor (with lower bounds). |
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| 312 | /// |
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| 313 | /// Simple constructor (with lower bounds). |
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| 314 | /// |
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| 315 | /// \param digraph The digraph the algorithm runs on. |
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| 316 | /// \param lower The lower bounds of the arcs. |
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| 317 | /// \param capacity The capacities (upper bounds) of the arcs. |
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| 318 | /// \param cost The cost (length) values of the arcs. |
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| 319 | /// \param s The source node. |
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| 320 | /// \param t The target node. |
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| 321 | /// \param flow_value The required amount of flow from node \c s |
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| 322 | /// to node \c t (i.e. the supply of \c s and the demand of \c t). |
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| 323 | CapacityScaling( const Digraph &digraph, |
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| 324 | const LowerMap &lower, |
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| 325 | const CapacityMap &capacity, |
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| 326 | const CostMap &cost, |
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| 327 | Node s, Node t, |
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| 328 | Supply flow_value ) : |
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| 329 | _graph(digraph), _lower(&lower), _capacity(capacity), _cost(cost), |
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| 330 | _supply(digraph, 0), _flow(NULL), _local_flow(false), |
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| 331 | _potential(NULL), _local_potential(false), |
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| 332 | _res_cap(capacity), _excess(digraph, 0), _pred(digraph), _dijkstra(NULL) |
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| 333 | { |
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| 334 | // Remove non-zero lower bounds |
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| 335 | _supply[s] = _excess[s] = flow_value; |
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| 336 | _supply[t] = _excess[t] = -flow_value; |
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| 337 | typename LowerMap::Value lcap; |
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| 338 | for (ArcIt e(_graph); e != INVALID; ++e) { |
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| 339 | if ((lcap = lower[e]) != 0) { |
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| 340 | _capacity[e] -= lcap; |
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| 341 | _res_cap[e] -= lcap; |
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| 342 | _supply[_graph.source(e)] -= lcap; |
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| 343 | _supply[_graph.target(e)] += lcap; |
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| 344 | _excess[_graph.source(e)] -= lcap; |
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| 345 | _excess[_graph.target(e)] += lcap; |
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| 346 | } |
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| 347 | } |
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| 348 | _valid_supply = true; |
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| 349 | } |
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| 350 | |
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| 351 | /// \brief Simple constructor (without lower bounds). |
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| 352 | /// |
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| 353 | /// Simple constructor (without lower bounds). |
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| 354 | /// |
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| 355 | /// \param digraph The digraph the algorithm runs on. |
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| 356 | /// \param capacity The capacities (upper bounds) of the arcs. |
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| 357 | /// \param cost The cost (length) values of the arcs. |
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| 358 | /// \param s The source node. |
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| 359 | /// \param t The target node. |
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| 360 | /// \param flow_value The required amount of flow from node \c s |
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| 361 | /// to node \c t (i.e. the supply of \c s and the demand of \c t). |
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| 362 | CapacityScaling( const Digraph &digraph, |
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| 363 | const CapacityMap &capacity, |
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| 364 | const CostMap &cost, |
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| 365 | Node s, Node t, |
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| 366 | Supply flow_value ) : |
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| 367 | _graph(digraph), _lower(NULL), _capacity(capacity), _cost(cost), |
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| 368 | _supply(digraph, 0), _flow(NULL), _local_flow(false), |
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| 369 | _potential(NULL), _local_potential(false), |
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| 370 | _res_cap(capacity), _excess(digraph, 0), _pred(digraph), _dijkstra(NULL) |
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| 371 | { |
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| 372 | _supply[s] = _excess[s] = flow_value; |
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| 373 | _supply[t] = _excess[t] = -flow_value; |
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| 374 | _valid_supply = true; |
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| 375 | } |
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| 376 | */ |
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| 377 | /// Destructor. |
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| 378 | ~CapacityScaling() { |
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| 379 | if (_local_flow) delete _flow; |
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| 380 | if (_local_potential) delete _potential; |
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| 381 | delete _dijkstra; |
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| 382 | } |
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| 383 | |
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| 384 | /// \brief Set the flow map. |
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| 385 | /// |
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| 386 | /// Set the flow map. |
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| 387 | /// |
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| 388 | /// \return \c (*this) |
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| 389 | CapacityScaling& flowMap(FlowMap &map) { |
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| 390 | if (_local_flow) { |
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| 391 | delete _flow; |
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| 392 | _local_flow = false; |
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| 393 | } |
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| 394 | _flow = ↦ |
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| 395 | return *this; |
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| 396 | } |
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| 397 | |
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| 398 | /// \brief Set the potential map. |
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| 399 | /// |
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| 400 | /// Set the potential map. |
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| 401 | /// |
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| 402 | /// \return \c (*this) |
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| 403 | CapacityScaling& potentialMap(PotentialMap &map) { |
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| 404 | if (_local_potential) { |
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| 405 | delete _potential; |
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| 406 | _local_potential = false; |
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| 407 | } |
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| 408 | _potential = ↦ |
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| 409 | return *this; |
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| 410 | } |
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| 411 | |
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| 412 | /// \name Execution control |
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| 413 | |
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| 414 | /// @{ |
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| 415 | |
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| 416 | /// \brief Run the algorithm. |
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| 417 | /// |
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| 418 | /// This function runs the algorithm. |
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| 419 | /// |
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| 420 | /// \param scaling Enable or disable capacity scaling. |
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| 421 | /// If the maximum arc capacity and/or the amount of total supply |
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| 422 | /// is rather small, the algorithm could be slightly faster without |
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| 423 | /// scaling. |
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| 424 | /// |
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| 425 | /// \return \c true if a feasible flow can be found. |
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| 426 | bool run(bool scaling = true) { |
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| 427 | return init(scaling) && start(); |
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| 428 | } |
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| 429 | |
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| 430 | /// @} |
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| 431 | |
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| 432 | /// \name Query Functions |
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| 433 | /// The results of the algorithm can be obtained using these |
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| 434 | /// functions.\n |
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| 435 | /// \ref lemon::CapacityScaling::run() "run()" must be called before |
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| 436 | /// using them. |
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| 437 | |
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| 438 | /// @{ |
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| 439 | |
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| 440 | /// \brief Return a const reference to the arc map storing the |
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| 441 | /// found flow. |
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| 442 | /// |
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| 443 | /// Return a const reference to the arc map storing the found flow. |
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| 444 | /// |
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| 445 | /// \pre \ref run() must be called before using this function. |
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| 446 | const FlowMap& flowMap() const { |
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| 447 | return *_flow; |
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| 448 | } |
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| 449 | |
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| 450 | /// \brief Return a const reference to the node map storing the |
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| 451 | /// found potentials (the dual solution). |
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| 452 | /// |
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| 453 | /// Return a const reference to the node map storing the found |
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| 454 | /// potentials (the dual solution). |
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| 455 | /// |
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| 456 | /// \pre \ref run() must be called before using this function. |
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| 457 | const PotentialMap& potentialMap() const { |
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| 458 | return *_potential; |
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| 459 | } |
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| 460 | |
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| 461 | /// \brief Return the flow on the given arc. |
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| 462 | /// |
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| 463 | /// Return the flow on the given arc. |
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| 464 | /// |
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| 465 | /// \pre \ref run() must be called before using this function. |
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| 466 | Capacity flow(const Arc& arc) const { |
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| 467 | return (*_flow)[arc]; |
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| 468 | } |
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| 469 | |
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| 470 | /// \brief Return the potential of the given node. |
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| 471 | /// |
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| 472 | /// Return the potential of the given node. |
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| 473 | /// |
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| 474 | /// \pre \ref run() must be called before using this function. |
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| 475 | Cost potential(const Node& node) const { |
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| 476 | return (*_potential)[node]; |
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| 477 | } |
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| 478 | |
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| 479 | /// \brief Return the total cost of the found flow. |
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| 480 | /// |
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| 481 | /// Return the total cost of the found flow. The complexity of the |
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| 482 | /// function is \f$ O(e) \f$. |
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| 483 | /// |
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| 484 | /// \pre \ref run() must be called before using this function. |
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| 485 | Cost totalCost() const { |
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| 486 | Cost c = 0; |
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| 487 | for (ArcIt e(_graph); e != INVALID; ++e) |
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| 488 | c += (*_flow)[e] * _cost[e]; |
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| 489 | return c; |
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| 490 | } |
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| 491 | |
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| 492 | /// @} |
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| 493 | |
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| 494 | private: |
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| 495 | |
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| 496 | /// Initialize the algorithm. |
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| 497 | bool init(bool scaling) { |
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| 498 | if (!_valid_supply) return false; |
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| 499 | |
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| 500 | // Initializing maps |
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| 501 | if (!_flow) { |
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| 502 | _flow = new FlowMap(_graph); |
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| 503 | _local_flow = true; |
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| 504 | } |
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| 505 | if (!_potential) { |
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| 506 | _potential = new PotentialMap(_graph); |
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| 507 | _local_potential = true; |
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| 508 | } |
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| 509 | for (ArcIt e(_graph); e != INVALID; ++e) (*_flow)[e] = 0; |
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| 510 | for (NodeIt n(_graph); n != INVALID; ++n) (*_potential)[n] = 0; |
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| 511 | |
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| 512 | _dijkstra = new ResidualDijkstra( _graph, *_flow, _res_cap, _cost, |
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| 513 | _excess, *_potential, _pred ); |
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| 514 | |
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| 515 | // Initializing delta value |
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| 516 | if (scaling) { |
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| 517 | // With scaling |
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| 518 | Supply max_sup = 0, max_dem = 0; |
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| 519 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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| 520 | if ( _supply[n] > max_sup) max_sup = _supply[n]; |
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| 521 | if (-_supply[n] > max_dem) max_dem = -_supply[n]; |
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| 522 | } |
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| 523 | Capacity max_cap = 0; |
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| 524 | for (ArcIt e(_graph); e != INVALID; ++e) { |
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| 525 | if (_capacity[e] > max_cap) max_cap = _capacity[e]; |
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| 526 | } |
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| 527 | max_sup = std::min(std::min(max_sup, max_dem), max_cap); |
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| 528 | _phase_num = 0; |
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| 529 | for (_delta = 1; 2 * _delta <= max_sup; _delta *= 2) |
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| 530 | ++_phase_num; |
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| 531 | } else { |
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| 532 | // Without scaling |
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| 533 | _delta = 1; |
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| 534 | } |
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| 535 | |
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| 536 | return true; |
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| 537 | } |
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| 538 | |
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| 539 | bool start() { |
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| 540 | if (_delta > 1) |
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| 541 | return startWithScaling(); |
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| 542 | else |
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| 543 | return startWithoutScaling(); |
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| 544 | } |
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| 545 | |
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| 546 | /// Execute the capacity scaling algorithm. |
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| 547 | bool startWithScaling() { |
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| 548 | // Processing capacity scaling phases |
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| 549 | Node s, t; |
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| 550 | int phase_cnt = 0; |
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| 551 | int factor = 4; |
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| 552 | while (true) { |
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| 553 | // Saturating all arcs not satisfying the optimality condition |
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| 554 | for (ArcIt e(_graph); e != INVALID; ++e) { |
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| 555 | Node u = _graph.source(e), v = _graph.target(e); |
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| 556 | Cost c = _cost[e] + (*_potential)[u] - (*_potential)[v]; |
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| 557 | if (c < 0 && _res_cap[e] >= _delta) { |
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| 558 | _excess[u] -= _res_cap[e]; |
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| 559 | _excess[v] += _res_cap[e]; |
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| 560 | (*_flow)[e] = _capacity[e]; |
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| 561 | _res_cap[e] = 0; |
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| 562 | } |
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| 563 | else if (c > 0 && (*_flow)[e] >= _delta) { |
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| 564 | _excess[u] += (*_flow)[e]; |
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| 565 | _excess[v] -= (*_flow)[e]; |
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| 566 | (*_flow)[e] = 0; |
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| 567 | _res_cap[e] = _capacity[e]; |
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| 568 | } |
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| 569 | } |
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| 570 | |
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| 571 | // Finding excess nodes and deficit nodes |
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| 572 | _excess_nodes.clear(); |
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| 573 | _deficit_nodes.clear(); |
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| 574 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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| 575 | if (_excess[n] >= _delta) _excess_nodes.push_back(n); |
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| 576 | if (_excess[n] <= -_delta) _deficit_nodes.push_back(n); |
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| 577 | } |
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| 578 | int next_node = 0, next_def_node = 0; |
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| 579 | |
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| 580 | // Finding augmenting shortest paths |
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| 581 | while (next_node < int(_excess_nodes.size())) { |
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| 582 | // Checking deficit nodes |
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| 583 | if (_delta > 1) { |
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| 584 | bool delta_deficit = false; |
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| 585 | for ( ; next_def_node < int(_deficit_nodes.size()); |
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| 586 | ++next_def_node ) { |
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| 587 | if (_excess[_deficit_nodes[next_def_node]] <= -_delta) { |
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| 588 | delta_deficit = true; |
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| 589 | break; |
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| 590 | } |
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| 591 | } |
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| 592 | if (!delta_deficit) break; |
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| 593 | } |
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| 594 | |
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| 595 | // Running Dijkstra |
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| 596 | s = _excess_nodes[next_node]; |
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| 597 | if ((t = _dijkstra->run(s, _delta)) == INVALID) { |
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| 598 | if (_delta > 1) { |
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| 599 | ++next_node; |
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| 600 | continue; |
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| 601 | } |
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| 602 | return false; |
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| 603 | } |
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| 604 | |
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| 605 | // Augmenting along a shortest path from s to t. |
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| 606 | Capacity d = std::min(_excess[s], -_excess[t]); |
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| 607 | Node u = t; |
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| 608 | Arc e; |
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| 609 | if (d > _delta) { |
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| 610 | while ((e = _pred[u]) != INVALID) { |
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| 611 | Capacity rc; |
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| 612 | if (u == _graph.target(e)) { |
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| 613 | rc = _res_cap[e]; |
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| 614 | u = _graph.source(e); |
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| 615 | } else { |
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| 616 | rc = (*_flow)[e]; |
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| 617 | u = _graph.target(e); |
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| 618 | } |
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| 619 | if (rc < d) d = rc; |
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| 620 | } |
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| 621 | } |
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| 622 | u = t; |
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| 623 | while ((e = _pred[u]) != INVALID) { |
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| 624 | if (u == _graph.target(e)) { |
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| 625 | (*_flow)[e] += d; |
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| 626 | _res_cap[e] -= d; |
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| 627 | u = _graph.source(e); |
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| 628 | } else { |
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| 629 | (*_flow)[e] -= d; |
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| 630 | _res_cap[e] += d; |
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| 631 | u = _graph.target(e); |
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| 632 | } |
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| 633 | } |
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| 634 | _excess[s] -= d; |
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| 635 | _excess[t] += d; |
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| 636 | |
---|
| 637 | if (_excess[s] < _delta) ++next_node; |
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| 638 | } |
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| 639 | |
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| 640 | if (_delta == 1) break; |
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| 641 | if (++phase_cnt > _phase_num / 4) factor = 2; |
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| 642 | _delta = _delta <= factor ? 1 : _delta / factor; |
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| 643 | } |
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| 644 | |
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| 645 | // Handling non-zero lower bounds |
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| 646 | if (_lower) { |
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| 647 | for (ArcIt e(_graph); e != INVALID; ++e) |
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| 648 | (*_flow)[e] += (*_lower)[e]; |
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| 649 | } |
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| 650 | return true; |
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| 651 | } |
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| 652 | |
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| 653 | /// Execute the successive shortest path algorithm. |
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| 654 | bool startWithoutScaling() { |
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| 655 | // Finding excess nodes |
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| 656 | for (NodeIt n(_graph); n != INVALID; ++n) |
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| 657 | if (_excess[n] > 0) _excess_nodes.push_back(n); |
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| 658 | if (_excess_nodes.size() == 0) return true; |
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| 659 | int next_node = 0; |
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| 660 | |
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| 661 | // Finding shortest paths |
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| 662 | Node s, t; |
---|
| 663 | while ( _excess[_excess_nodes[next_node]] > 0 || |
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| 664 | ++next_node < int(_excess_nodes.size()) ) |
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| 665 | { |
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| 666 | // Running Dijkstra |
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| 667 | s = _excess_nodes[next_node]; |
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| 668 | if ((t = _dijkstra->run(s)) == INVALID) return false; |
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| 669 | |
---|
| 670 | // Augmenting along a shortest path from s to t |
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| 671 | Capacity d = std::min(_excess[s], -_excess[t]); |
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| 672 | Node u = t; |
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| 673 | Arc e; |
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| 674 | if (d > 1) { |
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| 675 | while ((e = _pred[u]) != INVALID) { |
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| 676 | Capacity rc; |
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| 677 | if (u == _graph.target(e)) { |
---|
| 678 | rc = _res_cap[e]; |
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| 679 | u = _graph.source(e); |
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| 680 | } else { |
---|
| 681 | rc = (*_flow)[e]; |
---|
| 682 | u = _graph.target(e); |
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| 683 | } |
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| 684 | if (rc < d) d = rc; |
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| 685 | } |
---|
| 686 | } |
---|
| 687 | u = t; |
---|
| 688 | while ((e = _pred[u]) != INVALID) { |
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| 689 | if (u == _graph.target(e)) { |
---|
| 690 | (*_flow)[e] += d; |
---|
| 691 | _res_cap[e] -= d; |
---|
| 692 | u = _graph.source(e); |
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| 693 | } else { |
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| 694 | (*_flow)[e] -= d; |
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| 695 | _res_cap[e] += d; |
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| 696 | u = _graph.target(e); |
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| 697 | } |
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| 698 | } |
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| 699 | _excess[s] -= d; |
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| 700 | _excess[t] += d; |
---|
| 701 | } |
---|
| 702 | |
---|
| 703 | // Handling non-zero lower bounds |
---|
| 704 | if (_lower) { |
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| 705 | for (ArcIt e(_graph); e != INVALID; ++e) |
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| 706 | (*_flow)[e] += (*_lower)[e]; |
---|
| 707 | } |
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| 708 | return true; |
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| 709 | } |
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| 710 | |
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| 711 | }; //class CapacityScaling |
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| 712 | |
---|
| 713 | ///@} |
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| 714 | |
---|
| 715 | } //namespace lemon |
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| 716 | |
---|
| 717 | #endif //LEMON_CAPACITY_SCALING_H |
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