[2360] | 1 | /* -*- C++ -*- |
---|
| 2 | * |
---|
| 3 | * This file is a part of LEMON, a generic C++ optimization library |
---|
| 4 | * |
---|
| 5 | * Copyright (C) 2003-2006 |
---|
| 6 | * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
---|
| 7 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
---|
| 8 | * |
---|
| 9 | * Permission to use, modify and distribute this software is granted |
---|
| 10 | * provided that this copyright notice appears in all copies. For |
---|
| 11 | * precise terms see the accompanying LICENSE file. |
---|
| 12 | * |
---|
| 13 | * This software is provided "AS IS" with no warranty of any kind, |
---|
| 14 | * express or implied, and with no claim as to its suitability for any |
---|
| 15 | * purpose. |
---|
| 16 | * |
---|
| 17 | */ |
---|
| 18 | |
---|
| 19 | #ifndef LEMON_CSP_H |
---|
| 20 | #define LEMON_CSP_H |
---|
| 21 | |
---|
| 22 | ///\ingroup flowalgs |
---|
| 23 | ///\file |
---|
| 24 | ///\brief Algorithm for the Resource Constrained Shortest Path problem. |
---|
| 25 | /// |
---|
| 26 | /// |
---|
| 27 | ///\todo dijkstraZero() solution should be revised. |
---|
| 28 | |
---|
| 29 | #include <lemon/list_graph.h> |
---|
| 30 | #include <lemon/graph_utils.h> |
---|
| 31 | #include <lemon/error.h> |
---|
| 32 | #include <lemon/maps.h> |
---|
| 33 | #include <lemon/tolerance.h> |
---|
| 34 | #include <lemon/dijkstra.h> |
---|
| 35 | #include <lemon/path.h> |
---|
| 36 | #include <lemon/counter.h> |
---|
| 37 | namespace lemon { |
---|
| 38 | |
---|
| 39 | ///Algorithms for the Resource Constrained Shortest Path Problem |
---|
| 40 | |
---|
| 41 | ///\e |
---|
| 42 | /// |
---|
| 43 | template<class Graph, |
---|
| 44 | class CM=typename Graph:: template EdgeMap<double>, |
---|
| 45 | class DM=CM> |
---|
| 46 | class ConstrainedShortestPath |
---|
| 47 | { |
---|
| 48 | public: |
---|
| 49 | |
---|
| 50 | GRAPH_TYPEDEFS(typename Graph); |
---|
| 51 | |
---|
| 52 | typedef SimplePath<Graph> Path; |
---|
| 53 | |
---|
| 54 | Graph &_g; |
---|
| 55 | Tolerance<double> tol; |
---|
| 56 | |
---|
| 57 | CM &_cost; |
---|
| 58 | DM &_delay; |
---|
| 59 | |
---|
| 60 | class CoMap |
---|
| 61 | { |
---|
| 62 | CM &_cost; |
---|
| 63 | DM &_delay; |
---|
| 64 | double _lambda; |
---|
| 65 | public: |
---|
| 66 | typedef typename CM::Key Key; |
---|
| 67 | typedef double Value; |
---|
| 68 | CoMap(CM &c,DM &d) :_cost(c), _delay(d), _lambda(0) {} |
---|
| 69 | double lambda() const { return _lambda; } |
---|
| 70 | void lambda(double l) { _lambda=l; } |
---|
| 71 | Value operator[](Key &e) const |
---|
| 72 | { |
---|
| 73 | return _cost[e]+_lambda*_delay[e]; |
---|
| 74 | } |
---|
| 75 | } _co_map; |
---|
| 76 | |
---|
| 77 | |
---|
| 78 | Dijkstra<Graph, CoMap> _dij; |
---|
| 79 | ///\e |
---|
| 80 | |
---|
| 81 | ///\e |
---|
| 82 | /// |
---|
| 83 | ConstrainedShortestPath(Graph &g, CM &cost, DM &delay) |
---|
| 84 | : _g(g), _cost(cost), _delay(delay), |
---|
| 85 | _co_map(cost,delay), _dij(_g,_co_map) {} |
---|
| 86 | |
---|
| 87 | |
---|
| 88 | ///Compute the cost of a path |
---|
| 89 | double cost(const Path &p) |
---|
| 90 | { |
---|
| 91 | double s=0; |
---|
| 92 | // Path r; |
---|
| 93 | for(typename Path::EdgeIt e(p);e!=INVALID;++e) s+=_cost[e]; |
---|
| 94 | return s; |
---|
| 95 | } |
---|
| 96 | |
---|
| 97 | ///Compute the delay of a path |
---|
| 98 | double delay(const Path &p) |
---|
| 99 | { |
---|
| 100 | double s=0; |
---|
| 101 | for(typename Path::EdgeIt e(p);e!=INVALID;++e) s+=_delay[e]; |
---|
| 102 | return s; |
---|
| 103 | } |
---|
| 104 | |
---|
| 105 | ///Runs the LARAC algorithm |
---|
| 106 | |
---|
| 107 | ///This function runs a Lagrange relaxation based heuristic to find |
---|
| 108 | ///a delay constrained least cost path. |
---|
| 109 | ///\param s source node |
---|
| 110 | ///\param t target node |
---|
| 111 | ///\retval lo_bo a lower bound on the optimal solution |
---|
| 112 | ///\return the found path or an empty |
---|
| 113 | Path larac(Node s, Node t, double delta, double &lo_bo) |
---|
| 114 | { |
---|
| 115 | NoCounter cnt("LARAC iterations: "); |
---|
| 116 | double lambda=0; |
---|
| 117 | double cp,cq,dp,dq,cr,dr; |
---|
| 118 | Path p; |
---|
| 119 | Path q; |
---|
| 120 | Path r; |
---|
| 121 | { |
---|
| 122 | Dijkstra<Graph,CM> dij(_g,_cost); |
---|
| 123 | dij.run(s,t); |
---|
| 124 | cnt++; |
---|
| 125 | if(!dij.reached(t)) return Path(); |
---|
| 126 | p=dij.path(t); |
---|
| 127 | cp=cost(p); |
---|
| 128 | dp=delay(p); |
---|
| 129 | } |
---|
| 130 | if(delay(p)<=delta) return p; |
---|
| 131 | { |
---|
| 132 | Dijkstra<Graph,DM> dij(_g,_delay); |
---|
| 133 | dij.run(s,t); |
---|
| 134 | cnt++; |
---|
| 135 | q=dij.path(t); |
---|
| 136 | cq=cost(q); |
---|
| 137 | dq=delay(q); |
---|
| 138 | } |
---|
| 139 | if(delay(q)>delta) return Path(); |
---|
| 140 | while (true) { |
---|
| 141 | lambda=(cp-cq)/(dq-dp); |
---|
| 142 | _co_map.lambda(lambda); |
---|
| 143 | _dij.run(s,t); |
---|
| 144 | cnt++; |
---|
| 145 | r=_dij.path(t); |
---|
| 146 | cr=cost(r); |
---|
| 147 | dr=delay(r); |
---|
| 148 | if(!tol.less(cr+lambda*dr,cp+lambda*dp)) { |
---|
| 149 | lo_bo=cq+lambda*(dq-delta); |
---|
| 150 | return q; |
---|
| 151 | } |
---|
| 152 | else if(tol.less(dr,delta)) |
---|
| 153 | { |
---|
| 154 | q=r; |
---|
| 155 | cq=cr; |
---|
| 156 | dq=dr; |
---|
| 157 | } |
---|
| 158 | else if(tol.less(delta,dr)) |
---|
| 159 | { |
---|
| 160 | p=r; |
---|
| 161 | cp=cr; |
---|
| 162 | dp=dr; |
---|
| 163 | } |
---|
| 164 | else return r; |
---|
| 165 | } |
---|
| 166 | } |
---|
| 167 | }; |
---|
| 168 | |
---|
| 169 | |
---|
| 170 | } //END OF NAMESPACE LEMON |
---|
| 171 | |
---|
| 172 | #endif |
---|