193 lines
4.8 KiB
HTML
193 lines
4.8 KiB
HTML
<HTML>
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<!--
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Copyright (c) Jeremy Siek, Lie-Quan Lee, and Andrew Lumsdaine 2000
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt)
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-->
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<Head>
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<Title>Boost Graph Library: predecessor_recorder</Title>
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<BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b"
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ALINK="#ff0000">
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<IMG SRC="../../../boost.png"
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ALT="C++ Boost" width="277" height="86">
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<BR Clear>
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<H1>
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<pre>
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predecessor_recorder<PredecessorMap, EventTag>
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</pre>
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</H1>
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This is an <a href="./EventVisitor.html">EventVisitor</a> that records
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the predecessor (or parent) of a vertex in a predecessor property
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map. This is particularly useful in graph search algorithms where
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recording the predecessors is an efficient way to encode the search
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tree that was traversed during the search. The predecessor recorder is
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typically used with the <tt>on_tree_edge</tt> or
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<tt>on_relax_edge</tt> events and cannot be used with vertex events.
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<p>
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<tt>predecessor_recorder</tt> can be used with graph algorithms by
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wrapping it with an algorithm-specific adaptor, such as <a
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href="./bfs_visitor.html"><tt>bfs_visitor</tt></a> and <a
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href="./dfs_visitor.html"><tt>dfs_visitor</tt></a>. Also, this event
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visitor can be combined with other event visitors using
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<tt>std::pair</tt> to form an EventVisitorList.
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<p>
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Algorithms such as Dijkstra's and breadth-first search will not assign
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a predecessor to the source vertex (which is the root of the search
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tree). It is often useful to initialize the source vertex's
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predecessor to itself, thereby identifying the root vertex as the only
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vertex which is its own parent. When using an algorithm like
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depth-first search that creates a forest (multiple search trees) it
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is useful to initialize the predecessor of every vertex to itself. This
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way all the root nodes can be distinguished.
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<h3>Example</h3>
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See the example for <a href="./bfs_visitor.html"><tt>bfs_visitor</tt></a>.
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<h3>Model of</h3>
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<a href="./EventVisitor.html">EventVisitor</a>
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<H3>Where Defined</H3>
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<P>
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<a href="../../../boost/graph/visitors.hpp">
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<TT>boost/graph/visitors.hpp</TT></a>
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<H3>Template Parameters</H3>
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<P>
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<TABLE border>
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<TR>
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<th>Parameter</th><th>Description</th><th>Default</th>
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</tr>
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<TR><TD><TT>PredecessorMap</TT></TD>
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<TD>
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A <a
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href="../../property_map/doc/WritablePropertyMap.html">WritablePropertyMap</a>
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where the key type and the value type are the vertex descriptor type
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of the graph.
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</TD>
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<TD> </TD>
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</TR>
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<TR><TD><TT>EventTag</TT></TD>
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<TD>
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The tag to specify when the <tt>predecessor_recorder</tt> should be
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applied during the graph algorithm. <tt>EventTag</tt> must be an
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edge event.
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</TD>
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<TD> </TD>
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</TR>
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</table>
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<H2>Associated Types</H2>
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<table border>
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<tr>
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<th>Type</th><th>Description</th>
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</tr>
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<tr>
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<td><tt>predecessor_recorder::event_filter</tt></td>
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<td>
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This will be the same type as the template parameter <tt>EventTag</tt>.
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</td>
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</tr>
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</table>
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<h3>Member Functions</h3>
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<p>
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<table border>
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<tr>
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<th>Member</th><th>Description</th>
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</tr>
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<tr>
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<td><tt>
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predecessor_recorder(PredecessorMap pa);
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</tt></td>
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<td>
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Construct a predecessor recorder object with predecessor property map
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<tt>pa</tt>.
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</td>
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</tr>
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<tr>
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<td><tt>
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template <class Edge, class Graph><br>
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void operator()(Edge e, const Graph& g);
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</tt></td>
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<td>
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Given edge <i>e = (u,v)</i>, this records <i>u</i> as the
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predecessor (or parent) of <i>v</i>.
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</td>
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</tr>
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</table>
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<h3>Non-Member Functions</h3>
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<table border>
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<tr>
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<th>Function</th><th>Description</th>
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</tr>
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<tr><td><tt>
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template <class PredecessorMap, class Tag><br>
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predecessor_recorder<PredecessorMap, Tag> <br>
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record_predecessors(PredecessorMap pa, Tag);
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</tt></td><td>
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A convenient way to create a <tt>predecessor_recorder</tt>.
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</td></tr>
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</table>
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<h3>See Also</h3>
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<a href="./visitor_concepts.html">Visitor concepts</a>
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<p>
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The following are other event visitors: <a
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<a href="./distance_recorder.html"><tt>distance_recorder</tt></a>,
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<a href="./time_stamper.html"><tt>time_stamper</tt></a>,
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and <a href="./property_writer.html"><tt>property_writer</tt></a>.
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<br>
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<HR>
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<TABLE>
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<TR valign=top>
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<TD nowrap>Copyright © 2000-2001</TD><TD>
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<A HREF="http://www.boost.org/people/jeremy_siek.htm">Jeremy Siek</A>,
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Indiana University (<A
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HREF="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</A>)<br>
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<A HREF="http://www.boost.org/people/liequan_lee.htm">Lie-Quan Lee</A>, Indiana University (<A HREF="mailto:llee@cs.indiana.edu">llee@cs.indiana.edu</A>)<br>
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<A HREF="https://homes.cs.washington.edu/~al75">Andrew Lumsdaine</A>,
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Indiana University (<A
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HREF="mailto:lums@osl.iu.edu">lums@osl.iu.edu</A>)
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</TD></TR></TABLE>
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</BODY>
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</HTML>
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<!-- LocalWords: PredecessorMap EventTag EventVisitor map bfs dfs const
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-->
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<!-- LocalWords: EventVisitorList WritablePropertyMap Siek Univ Quan
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-->
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<!-- LocalWords: Lumsdaine
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-->
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