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Wenzel Jakob
83 lines
3.4 KiB
HTML
83 lines
3.4 KiB
HTML
<HTML>
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<BODY>
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<H2>Overview</H2>
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This directory contains a simple example that solves the single source
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shortest path problem. It is parameterized by N, a number of nodes,
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and a start and end node in [0..N). A graph is generated with N nodes
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and some random number of connections between those nodes. A parallel
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algorithm based on A* is used to find the shortest path. This
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algorithm varies from serial A* in that it needs to add nodes back to
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the open set when the g estimate (shortest path from start to the
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node) is improved, even if the node has already been "visited". This
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is because nodes are added and removed from the open-set in parallel,
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resulting in some less optimal paths being explored. The open-set is
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implemented with the concurrent_priority_queue. Note that since we
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re-visit nodes, the f estimate (on which the priority queue is sorted)
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is not technically needed, so we could use this same parallel
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algorithm with just a concurrent_queue. However, keeping the f
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estimate and using concurrent_priority_queue results in much better
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performance. Silent mode prints run time only, regular mode prints
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shortest path length, and verbose mode prints out the shortest path.
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The generated graph follows a pattern in which the closer two pairs of
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node ids are together, the fewer hops there are in a typical path
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between those nodes. So, for example, the path between 5 and 7 likely
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has few hops whereas 14 to 78 has more and 0 to 9999 has even more,
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etc.
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<H2>Files</H2>
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<DL>
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<DT><A HREF="shortpath.cpp">shortpath.cpp</A>
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<DD>Driver.
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<DT><A HREF="Makefile">Makefile</A>
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<DD>Makefile for building example.
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</DL>
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<H2>Directories</H2>
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<DL>
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<DT><A HREF="msvs">msvs</A>
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<DD>Contains Microsoft* Visual Studio* 2010 workspace for building and running the example with the Intel® C++ compiler (Windows* systems only).
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<DT><A HREF="xcode">xcode</A>
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<DD>Contains OS X* Xcode* workspace for building and running the example (OS X* systems only).
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</DL>
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<H2>To Build</H2>
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General build directions can be found <A HREF=../../index.html#build>here</A>.
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<P></P>
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<H2>Usage</H2>
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<DL>
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<DT><TT>shortpath <I>-h</I></TT>
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<DD>Prints the help for command line options
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<DT><TT>shortpath [<I>#threads</I>=value] [<I>verbose</I>] [<I>silent</I>] [<I>N</I>=value] [<I>start</I>=value] [<I>end</I>=value] [<I>#threads</I>]</TT>
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<DD><I>#threads</I> is the number of threads to use; a range of the form <I>low</I>[:<I>high</I>] where low and optional high are non-negative integers, or 'auto' for the TBB default.<BR>
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<I>verbose</I> print full path to screen<BR>
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<I>silent</I> limits output to timing info; overrides verbose<BR>
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<I>N</I> number of nodes in graph<BR>
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<I>start</I> node to start path at<BR>
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<I>end</I> node to end path at<BR>
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<DT>To run a short version of this example, e.g., for use with Intel® Parallel Inspector:
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<DD>Build a <I>debug</I> version of the example
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(see the <A HREF=../../index.html#build>build directions</A>).
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<BR>Run it with a small problem size and the desired number of threads, e.g., <TT>shortpath 4 N=20 start=0 end=19</TT>.
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</DL>
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<HR>
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<A HREF="../index.html">Up to parent directory</A>
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<p></p>
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Copyright © 2005-2014 Intel Corporation. All Rights Reserved.
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<P></P>
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Intel is a registered trademark or trademark of Intel Corporation
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or its subsidiaries in the United States and other countries.
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<p></p>
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* Other names and brands may be claimed as the property of others.
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</HTML>
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