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| <Head> |
| <Title>Boost Graph Library: AStarVisitor</Title> |
| <BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" |
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| <BR Clear> |
| |
| <H1>AStar Visitor Concept</H1> |
| |
| This concept defines the visitor interface for <a |
| href="./astar_search.html"><tt>astar_search()</tt></a>. Users can |
| define a class with the AStar Visitor interface and pass an object of |
| the class to <tt>astar_search()</tt>, thereby augmenting the actions |
| taken during the graph search. |
| |
| <h3>Refinement of</h3> |
| |
| <a href="../../utility/CopyConstructible.html">Copy Constructible</a> |
| (copying a visitor should be a lightweight operation). |
| |
| |
| <h3>Notation</h3> |
| |
| <Table> |
| <TR> |
| <TD><tt>V</tt></TD> |
| <TD>A type that is a model of AStar Visitor.</TD> |
| </TR> |
| |
| <TR> |
| <TD><tt>vis</tt></TD> |
| <TD>An object of type <tt>V</tt>.</TD> |
| </TR> |
| |
| <TR> |
| <TD><tt>G</tt></TD> |
| <TD>A type that is a model of Graph.</TD> |
| </TR> |
| |
| <TR> |
| <TD><tt>g</tt></TD> |
| <TD>An object of type <tt>const G&</tt>.</TD> |
| </TR> |
| |
| <TR> |
| <TD><tt>e</tt></TD> |
| <TD>An object of type <tt>boost::graph_traits<G>::edge_descriptor</tt>.</TD> |
| </TR> |
| |
| <TR> |
| <TD><tt>s,u,v</tt></TD> |
| <TD>An object of type <tt>boost::graph_traits<G>::vertex_descriptor</tt>.</TD> |
| </TR> |
| |
| <TR> |
| <TD><tt>d</tt></TD> |
| <TD>An object of type <tt>DistanceMap</tt>.</TD> |
| </TR> |
| |
| <TR> |
| <TD><tt>WeightMap</tt></TD> |
| <TD>A type that is a model of <a |
| href="../../property_map/doc/ReadablePropertyMap.html">Readable Property |
| Map</a>.</TD> |
| </TR> |
| |
| <TR> |
| <TD><tt>w</tt></TD> |
| <TD>An object of type <tt>WeightMap</tt>.</TD> |
| </TR> |
| |
| </table> |
| |
| <h3>Associated Types</h3> |
| |
| none |
| <p> |
| |
| <h3>Valid Expressions</h3> |
| |
| <table border> |
| <tr> |
| <th>Name</th><th>Expression</th><th>Return Type</th><th>Description</th> |
| </tr> |
| |
| <tr> |
| <td>Initialize Vertex</td> |
| <td><tt>vis.initialize_vertex(u, g)</tt></td> |
| <td><tt>void</tt></td> |
| <td> |
| This is invoked on each vertex of the graph when it is first |
| initialized (i.e., when its property maps are initialized). |
| </td> |
| </tr> |
| |
| <tr> |
| <td>Discover Vertex</td> |
| <td><tt>vis.discover_vertex(u, g)</tt></td> |
| <td><tt>void</tt></td> |
| <td> |
| This is invoked when a vertex is first discovered and is added to the |
| OPEN list. |
| </td> |
| </tr> |
| |
| <tr> |
| <td>Examine Vertex</td> |
| <td><tt>vis.examine_vertex(u, g)</tt></td> |
| <td><tt>void</tt></td> |
| <td> |
| This is invoked on a vertex as it is popped from the queue (i.e., it |
| has the lowest cost on the OPEN list). This happens immediately before |
| <tt>examine_edge()</tt> is invoked on each of the out-edges of vertex |
| <tt>u</tt>. |
| </td> |
| </tr> |
| |
| <tr> |
| <td>Examine Edge</td> |
| <td><tt>vis.examine_edge(e, g)</tt></td> |
| <td><tt>void</tt></td> |
| <td> |
| This is invoked on every out-edge of each vertex after it is |
| examined. |
| </td> |
| </tr> |
| |
| |
| <tr> |
| <td>Edge Relaxed</td> |
| <td><tt>vis.edge_relaxed(e, g)</tt></td> |
| <td><tt>void</tt></td> |
| <td> |
| Upon examination, if the following condition holds then the edge is |
| relaxed (the distance of its target vertex is reduced) and this method |
| is invoked: |
| <blockquote> |
| <pre> |
| tie(u, s) = incident(e, g); |
| D d_u = get(d, u), d_v = get(d, s); |
| W w_e = get(w, e); |
| assert(compare(combine(d_u, w_e), d_s)); |
| </pre> |
| </blockquote> |
| </td> |
| </tr> |
| |
| <tr> |
| <td>Edge Not Relaxed</td> |
| <td><tt>vis.edge_not_relaxed(e, g)</tt></td> |
| <td><tt>void</tt></td> |
| <td> |
| Upon examination, if an edge is not relaxed (see above) then this |
| method is invoked. |
| </td> |
| </tr> |
| |
| <tr> |
| <td>Black Target</td> |
| <td><tt>vis.black_target(e, g)</tt></td> |
| <td><tt>void</tt></td> |
| <td> |
| This is invoked when a vertex that is on the CLOSED list is |
| ``rediscovered'' via a more efficient path and is re-added to the |
| OPEN list. |
| </td> |
| </tr> |
| |
| <tr> |
| <td>Finish Vertex</td> |
| <td><tt>vis.finish_vertex(u, g)</tt></td> |
| <td><tt>void</tt></td> |
| <td> |
| This is invoked on a vertex when it is added to the CLOSED list. This |
| happens after all of its out-edges have been examined. |
| </td> |
| </tr> |
| |
| </table> |
| |
| <h3>Models</h3> |
| |
| <ul> |
| <li><a href="./astar_visitor.html"><tt>astar_visitor</tt></a> |
| </ul> |
| |
| |
| <h3>See also</h3> |
| |
| <a href="./visitor_concepts.html">Visitor concepts</a> |
| |
| <br> |
| <HR> |
| <TABLE> |
| <TR valign=top> |
| <TD nowrap>Copyright © 2004</TD><TD> |
| <A HREF="http://www.cs.rpi.edu/~beevek/">Kristopher Beevers</A>, |
| Rensselaer Polytechnic Institute (<A |
| HREF="mailto:beevek@cs.rpi.edu">beevek@cs.rpi.edu</A>) |
| </TD></TR></TABLE> |
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