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<div class="title">CAStarAlgorithm.h</div> </div>
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<a href="_c_a_star_algorithm_8h.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/* +---------------------------------------------------------------------------+</span>
<a name="l00002"></a>00002 <span class="comment"> | The Mobile Robot Programming Toolkit (MRPT) C++ library |</span>
<a name="l00003"></a>00003 <span class="comment"> | |</span>
<a name="l00004"></a>00004 <span class="comment"> | http://www.mrpt.org/ |</span>
<a name="l00005"></a>00005 <span class="comment"> | |</span>
<a name="l00006"></a>00006 <span class="comment"> | Copyright (C) 2005-2011 University of Malaga |</span>
<a name="l00007"></a>00007 <span class="comment"> | |</span>
<a name="l00008"></a>00008 <span class="comment"> | This software was written by the Machine Perception and Intelligent |</span>
<a name="l00009"></a>00009 <span class="comment"> | Robotics Lab, University of Malaga (Spain). |</span>
<a name="l00010"></a>00010 <span class="comment"> | Contact: Jose-Luis Blanco <jlblanco@ctima.uma.es> |</span>
<a name="l00011"></a>00011 <span class="comment"> | |</span>
<a name="l00012"></a>00012 <span class="comment"> | This file is part of the MRPT project. |</span>
<a name="l00013"></a>00013 <span class="comment"> | |</span>
<a name="l00014"></a>00014 <span class="comment"> | MRPT is free software: you can redistribute it and/or modify |</span>
<a name="l00015"></a>00015 <span class="comment"> | it under the terms of the GNU General Public License as published by |</span>
<a name="l00016"></a>00016 <span class="comment"> | the Free Software Foundation, either version 3 of the License, or |</span>
<a name="l00017"></a>00017 <span class="comment"> | (at your option) any later version. |</span>
<a name="l00018"></a>00018 <span class="comment"> | |</span>
<a name="l00019"></a>00019 <span class="comment"> | MRPT is distributed in the hope that it will be useful, |</span>
<a name="l00020"></a>00020 <span class="comment"> | but WITHOUT ANY WARRANTY; without even the implied warranty of |</span>
<a name="l00021"></a>00021 <span class="comment"> | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |</span>
<a name="l00022"></a>00022 <span class="comment"> | GNU General Public License for more details. |</span>
<a name="l00023"></a>00023 <span class="comment"> | |</span>
<a name="l00024"></a>00024 <span class="comment"> | You should have received a copy of the GNU General Public License |</span>
<a name="l00025"></a>00025 <span class="comment"> | along with MRPT. If not, see <http://www.gnu.org/licenses/>. |</span>
<a name="l00026"></a>00026 <span class="comment"> | |</span>
<a name="l00027"></a>00027 <span class="comment"> +---------------------------------------------------------------------------+ */</span>
<a name="l00028"></a>00028 <span class="preprocessor">#ifndef CASTARALGORITHM_H</span>
<a name="l00029"></a>00029 <span class="preprocessor"></span><span class="preprocessor">#define CASTARALGORITHM_H</span>
<a name="l00030"></a>00030 <span class="preprocessor"></span><span class="preprocessor">#include <map></span>
<a name="l00031"></a>00031 <span class="preprocessor">#include <vector></span>
<a name="l00032"></a>00032 <span class="preprocessor">#include <cmath></span>
<a name="l00033"></a>00033 <span class="preprocessor">#include <<a class="code" href="_c_tic_tac_8h.html">mrpt/utils/CTicTac.h</a>></span>
<a name="l00034"></a>00034
<a name="l00035"></a>00035 <span class="keyword">namespace </span>mrpt
<a name="l00036"></a>00036 {
<a name="l00037"></a><a class="code" href="namespacemrpt_1_1graphs.html">00037</a> <span class="keyword">namespace </span>graphs
<a name="l00038"></a>00038 {<span class="comment"></span>
<a name="l00039"></a>00039 <span class="comment"> /** This class is intended to efficiently solve graph-search problems using heuristics to determine the best path. To use it, a solution class must be defined</span>
<a name="l00040"></a>00040 <span class="comment"> * so that it contains all the information about any partial or complete solution. Then, a class inheriting from CAStarAlgorithm<Solution class> must also be</span>
<a name="l00041"></a>00041 <span class="comment"> * implemented, overriding five virtual methods which define the behaviour of the solutions. These methods are isSolutionEnded, isSolutionValid,</span>
<a name="l00042"></a>00042 <span class="comment"> * generateChildren, getHeuristic and getCost.</span>
<a name="l00043"></a>00043 <span class="comment"> * Once both classes are generated, each object of the class inheriting from CAStarAlgorithm represents a problem who can be solved by calling</span>
<a name="l00044"></a>00044 <span class="comment"> * getOptimalSolution. See http://en.wikipedia.org/wiki/A*_search_algorithm for details about how this algorithm works.</span>
<a name="l00045"></a>00045 <span class="comment"> * \sa CAStarAlgorithm::isSolutionEnded</span>
<a name="l00046"></a>00046 <span class="comment"> * \sa CAStarAlgorithm::isSolutionValid</span>
<a name="l00047"></a>00047 <span class="comment"> * \sa CAStarAlgorithm::generateChildren</span>
<a name="l00048"></a>00048 <span class="comment"> * \sa CAStarAlgorithm::getHeuristic</span>
<a name="l00049"></a>00049 <span class="comment"> * \sa CAStarAlgorithm::getCost</span>
<a name="l00050"></a>00050 <span class="comment"> * \ingroup mrpt_graphs_grp</span>
<a name="l00051"></a>00051 <span class="comment"> */</span>
<a name="l00052"></a>00052 <span class="keyword">template</span><<span class="keyword">typename</span> T> <span class="keyword">class </span><a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html" title="This class is intended to efficiently solve graph-search problems using heuristics to determine the b...">CAStarAlgorithm</a> {
<a name="l00053"></a>00053 <span class="keyword">public</span>:<span class="comment"></span>
<a name="l00054"></a>00054 <span class="comment"> /**</span>
<a name="l00055"></a>00055 <span class="comment"> * Client code must implement this method.</span>
<a name="l00056"></a>00056 <span class="comment"> * Returns true if the given solution is complete.</span>
<a name="l00057"></a>00057 <span class="comment"> */</span>
<a name="l00058"></a>00058 <span class="keyword">virtual</span> <span class="keywordtype">bool</span> <a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#a3cacbb941191dc5cbaf0effb443b91f4" title="Client code must implement this method.">isSolutionEnded</a>(<span class="keyword">const</span> T &sol)=0;<span class="comment"></span>
<a name="l00059"></a>00059 <span class="comment"> /**</span>
<a name="l00060"></a>00060 <span class="comment"> * Client code must implement this method.</span>
<a name="l00061"></a>00061 <span class="comment"> * Returns true if the given solution is acceptable, that is, doesn't violate the problem logic.</span>
<a name="l00062"></a>00062 <span class="comment"> */</span>
<a name="l00063"></a>00063 <span class="keyword">virtual</span> <span class="keywordtype">bool</span> <a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#ab6067bc6a713333fb507b18ce67ba81a" title="Client code must implement this method.">isSolutionValid</a>(<span class="keyword">const</span> T &sol)=0;<span class="comment"></span>
<a name="l00064"></a>00064 <span class="comment"> /**</span>
<a name="l00065"></a>00065 <span class="comment"> * Client code must implement this method.</span>
<a name="l00066"></a>00066 <span class="comment"> * Given a partial solution, returns all its children solution, regardless of their validity or completeness.</span>
<a name="l00067"></a>00067 <span class="comment"> */</span>
<a name="l00068"></a>00068 <span class="keyword">virtual</span> <span class="keywordtype">void</span> <a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#a31eba07eb05f33881575c5839a506dcf" title="Client code must implement this method.">generateChildren</a>(<span class="keyword">const</span> T &sol,<a class="code" href="classstd_1_1vector.html">std::vector<T></a> &sols)=0;<span class="comment"></span>
<a name="l00069"></a>00069 <span class="comment"> /**</span>
<a name="l00070"></a>00070 <span class="comment"> * Client code must implement this method.</span>
<a name="l00071"></a>00071 <span class="comment"> * Given a partial solution, estimates the cost of the remaining (unknown) part.</span>
<a name="l00072"></a>00072 <span class="comment"> * This cost must always be greater or equal to zero, and not greater than the actual cost. Thus, must be 0 if the solution is complete.</span>
<a name="l00073"></a>00073 <span class="comment"> */</span>
<a name="l00074"></a>00074 <span class="keyword">virtual</span> <span class="keywordtype">double</span> <a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#a8958d2e9de1aa8f944edaafb662ab940" title="Client code must implement this method.">getHeuristic</a>(<span class="keyword">const</span> T &sol)=0;<span class="comment"></span>
<a name="l00075"></a>00075 <span class="comment"> /**</span>
<a name="l00076"></a>00076 <span class="comment"> * Client code must implement this method.</span>
<a name="l00077"></a>00077 <span class="comment"> * Given a (possibly partial) solution, calculates its cost so far.</span>
<a name="l00078"></a>00078 <span class="comment"> * This cost must not decrease with each step. That is, a solution cannot have a smaller cost than the previous one from which it was generated.</span>
<a name="l00079"></a>00079 <span class="comment"> */</span>
<a name="l00080"></a>00080 <span class="keyword">virtual</span> <span class="keywordtype">double</span> <a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#a86474ca549124ada5fbe44884697952c" title="Client code must implement this method.">getCost</a>(<span class="keyword">const</span> T &sol)=0;
<a name="l00081"></a>00081 <span class="keyword">private</span>:<span class="comment"></span>
<a name="l00082"></a>00082 <span class="comment"> /**</span>
<a name="l00083"></a>00083 <span class="comment"> * Calculates the total cost (known+estimated) of a solution.</span>
<a name="l00084"></a>00084 <span class="comment"> */</span>
<a name="l00085"></a><a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#aec123ec3e5afc6cad29736385c4c7c7a">00085</a> <span class="keyword">inline</span> <span class="keywordtype">double</span> <a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#aec123ec3e5afc6cad29736385c4c7c7a" title="Calculates the total cost (known+estimated) of a solution.">getTotalCost</a>(<span class="keyword">const</span> T &sol) {
<a name="l00086"></a>00086 <span class="keywordflow">return</span> <a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#a8958d2e9de1aa8f944edaafb662ab940" title="Client code must implement this method.">getHeuristic</a>(sol)+<a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#a86474ca549124ada5fbe44884697952c" title="Client code must implement this method.">getCost</a>(sol);
<a name="l00087"></a>00087 }
<a name="l00088"></a>00088 <span class="keyword">public</span>:<span class="comment"></span>
<a name="l00089"></a>00089 <span class="comment"> /**</span>
<a name="l00090"></a>00090 <span class="comment"> * Finds the optimal solution for a problem, using the A* algorithm. Returns whether an optimal solution was actually found.</span>
<a name="l00091"></a>00091 <span class="comment"> * Returns 0 if no solution was found, 1 if an optimal solution was found and 2 if a (possibly suboptimal) solution was found but the time lapse ended.</span>
<a name="l00092"></a>00092 <span class="comment"> */</span>
<a name="l00093"></a><a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#a490443150b04e71cb1466b92b6c16d24">00093</a> <span class="keywordtype">int</span> <a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#a490443150b04e71cb1466b92b6c16d24" title="Finds the optimal solution for a problem, using the A* algorithm.">getOptimalSolution</a>(<span class="keyword">const</span> T &initialSol,T &finalSol,<span class="keywordtype">double</span> upperLevel=HUGE_VAL,<span class="keywordtype">double</span> maxComputationTime=HUGE_VAL) {
<a name="l00094"></a>00094 <span class="comment">//Time measuring object is defined.</span>
<a name="l00095"></a>00095 mrpt<a class="code" href="classmrpt_1_1utils_1_1_c_tic_tac.html" title="This class implements a high-performance stopwatch.">::utils::CTicTac</a> time;
<a name="l00096"></a>00096 time.<a class="code" href="classmrpt_1_1utils_1_1_c_tic_tac.html#aae7e29d8fc37e441960004c6ffe31e81" title="Starts the stopwatch.">Tic</a>();
<a name="l00097"></a>00097 <span class="comment">//The partial solution set is initialized with a single element (the starting solution).</span>
<a name="l00098"></a>00098 std<a class="code" href="classstd_1_1multimap.html" title="STL class.">::multimap<double,T></a> partialSols;
<a name="l00099"></a>00099 partialSols.insert(std::pair<double,T>(<a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#aec123ec3e5afc6cad29736385c4c7c7a" title="Calculates the total cost (known+estimated) of a solution.">getTotalCost</a>(initialSol),initialSol));
<a name="l00100"></a>00100 <span class="comment">//The best known solution is set to the upper bound (positive infinite, if there is no given parameter).</span>
<a name="l00101"></a>00101 <span class="keywordtype">double</span> currentOptimal=upperLevel;
<a name="l00102"></a>00102 <span class="keywordtype">bool</span> found=<span class="keyword">false</span>;
<a name="l00103"></a>00103 std<a class="code" href="classstd_1_1vector.html">::vector<T></a> children;
<a name="l00104"></a>00104 <span class="comment">//Main loop. Each iteration checks an element of the set, with minimum estimated cost.</span>
<a name="l00105"></a>00105 <span class="keywordflow">while</span> (!partialSols.empty()) {
<a name="l00106"></a>00106 <span class="comment">//Return if elapsed time has been reached.</span>
<a name="l00107"></a>00107 <span class="keywordflow">if</span> (time.<a class="code" href="classmrpt_1_1utils_1_1_c_tic_tac.html#a7eef1a30d6fa540ef116cb978db7aed8" title="Stops the stopwatch.">Tac</a>()>=maxComputationTime) <span class="keywordflow">return</span> found?2:0;
<a name="l00108"></a>00108 <span class="keyword">typename</span> std<a class="code" href="classstd_1_1multimap_1_1iterator.html" title="STL iterator class.">::multimap<double,T>::iterator</a> it=partialSols.begin();
<a name="l00109"></a>00109 <span class="keywordtype">double</span> tempCost=it->first;
<a name="l00110"></a>00110 <span class="comment">//If the minimum estimated cost is higher than the upper bound, then also is every solution in the set. So the algorithm returns immediately.</span>
<a name="l00111"></a>00111 <span class="keywordflow">if</span> (tempCost>=currentOptimal) <span class="keywordflow">return</span> found?1:0;
<a name="l00112"></a>00112 T tempSol=it->second;
<a name="l00113"></a>00113 partialSols.erase(it);
<a name="l00114"></a>00114 <span class="comment">//At this point, the solution cost is lesser than the upper bound. So, if the solution is complete, the optimal solution and the upper bound are updated.</span>
<a name="l00115"></a>00115 <span class="keywordflow">if</span> (<a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#a3cacbb941191dc5cbaf0effb443b91f4" title="Client code must implement this method.">isSolutionEnded</a>(tempSol)) {
<a name="l00116"></a>00116 currentOptimal=tempCost;
<a name="l00117"></a>00117 finalSol=tempSol;
<a name="l00118"></a>00118 found=<span class="keyword">true</span>;
<a name="l00119"></a>00119 <span class="keywordflow">continue</span>;
<a name="l00120"></a>00120 }
<a name="l00121"></a>00121 <span class="comment">//If the solution is not complete, check for its children. Each one is included in the set only if it's valid and it's not yet present in the set.</span>
<a name="l00122"></a>00122 <a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#a31eba07eb05f33881575c5839a506dcf" title="Client code must implement this method.">generateChildren</a>(tempSol,children);
<a name="l00123"></a>00123 <span class="keywordflow">for</span> (<span class="keyword">typename</span> <a class="code" href="classstd_1_1vector_1_1const__iterator.html" title="STL iterator class.">std::vector<T>::const_iterator</a> it2=children.begin();it2!=children.end();it2++) <span class="keywordflow">if</span> (<a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#ab6067bc6a713333fb507b18ce67ba81a" title="Client code must implement this method.">isSolutionValid</a>(*it2)) {
<a name="l00124"></a>00124 <span class="keywordtype">bool</span> alreadyPresent=<span class="keyword">false</span>;
<a name="l00125"></a>00125 <span class="keywordtype">double</span> cost=<a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#aec123ec3e5afc6cad29736385c4c7c7a" title="Calculates the total cost (known+estimated) of a solution.">getTotalCost</a>(*it2);
<a name="l00126"></a>00126 <span class="keyword">typename</span> std<a class="code" href="eigen__plugins_8h.html#a8dbda719917732693c56cee228465ed9">::pair<typename std::multimap<double,T>::const_iterator</a>,<span class="keyword">typename</span> std<a class="code" href="classstd_1_1multimap_1_1const__iterator.html" title="STL iterator class.">::multimap<double,T>::const_iterator</a>> range = partialSols.equal_range(cost);
<a name="l00127"></a>00127 <span class="keywordflow">for</span> (<span class="keyword">typename</span> <a class="code" href="classstd_1_1multimap_1_1const__iterator.html" title="STL iterator class.">std::multimap<double,T>::const_iterator</a> it3=range.first;it3!=range.second;it3++) <span class="keywordflow">if</span> (it3->second==*it2) {
<a name="l00128"></a>00128 alreadyPresent=<span class="keyword">true</span>;
<a name="l00129"></a>00129 <span class="keywordflow">break</span>;
<a name="l00130"></a>00130 }
<a name="l00131"></a>00131 <span class="keywordflow">if</span> (!alreadyPresent) partialSols.insert(std::pair<double,T>(<a class="code" href="classmrpt_1_1graphs_1_1_c_a_star_algorithm.html#aec123ec3e5afc6cad29736385c4c7c7a" title="Calculates the total cost (known+estimated) of a solution.">getTotalCost</a>(*it2),*it2));
<a name="l00132"></a>00132 }
<a name="l00133"></a>00133 }
<a name="l00134"></a>00134 <span class="comment">//No more solutions to explore...</span>
<a name="l00135"></a>00135 <span class="keywordflow">return</span> found?1:0;
<a name="l00136"></a>00136 }
<a name="l00137"></a>00137 };
<a name="l00138"></a>00138 }
<a name="l00139"></a>00139 } <span class="comment">//End of namespaces</span>
<a name="l00140"></a>00140 <span class="preprocessor">#endif</span>
</pre></div></div>
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