[2391] | 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) 2003-2007 |
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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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[2196] | 19 | /** |
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| 20 | \page maps2 Maps II. |
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| 21 | |
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| 22 | Here we discuss some advanced map techniques. Like writing your own maps or how to |
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| 23 | extend/modify a maps functionality with adaptors. |
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| 24 | |
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| 25 | \section custom_maps Writing Custom ReadMap |
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| 26 | \subsection custom_read_maps Readable Maps |
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| 27 | |
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| 28 | Readable maps are very frequently used as the input of an |
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| 29 | algorithm. For this purpose the most straightforward way is the use of the |
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| 30 | default maps provided by LEMON's graph structures. |
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| 31 | Very often however, it is more |
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| 32 | convenient and/or more efficient to write your own readable map. |
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| 33 | |
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| 34 | You can find some examples below. In these examples \c Graph is the |
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| 35 | type of the particular graph structure you use. |
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| 36 | |
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| 37 | |
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| 38 | This simple map assigns \f$\pi\f$ to each edge. |
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| 39 | |
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| 40 | \code |
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| 41 | struct MyMap |
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| 42 | { |
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| 43 | typedef double Value; |
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| 44 | typedef Graph::Edge Key; |
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| 45 | double operator[](Key e) const { return M_PI;} |
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| 46 | }; |
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| 47 | \endcode |
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| 48 | |
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| 49 | An alternative way to define maps is to use MapBase |
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| 50 | |
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| 51 | \code |
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| 52 | struct MyMap : public MapBase<Graph::Edge,double> |
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| 53 | { |
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| 54 | Value operator[](Key e) const { return M_PI;} |
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| 55 | }; |
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| 56 | \endcode |
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| 57 | |
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| 58 | Here is a bit more complex example. |
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| 59 | It provides a length function obtained |
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| 60 | from a base length function shifted by a potential difference. |
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| 61 | |
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| 62 | \code |
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| 63 | class ReducedLengthMap : public MapBase<Graph::Edge,double> |
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| 64 | { |
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| 65 | const Graph &g; |
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| 66 | const Graph::EdgeMap<double> &orig_len; |
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| 67 | const Graph::NodeMap<double> &pot; |
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| 68 | |
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| 69 | public: |
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| 70 | Value operator[](Key e) const { |
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| 71 | return orig_len[e]-(pot[g.target(e)]-pot[g.source(e)]); |
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| 72 | } |
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| 73 | |
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| 74 | ReducedLengthMap(const Graph &_g, |
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| 75 | const Graph::EdgeMap &_o, |
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| 76 | const Graph::NodeMap &_p) |
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| 77 | : g(_g), orig_len(_o), pot(_p) {}; |
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| 78 | }; |
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| 79 | \endcode |
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| 80 | |
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| 81 | Then, you can call e.g. Dijkstra algoritm on this map like this: |
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| 82 | \code |
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| 83 | ... |
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| 84 | ReducedLengthMap rm(g,len,pot); |
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| 85 | Dijkstra<Graph,ReducedLengthMap> dij(g,rm); |
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| 86 | dij.run(s); |
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| 87 | ... |
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| 88 | \endcode |
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| 89 | |
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| 90 | */ |
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