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< H2 > Overview< / H2 >
This directory contains a simple example that solves the single source
shortest path problem. It is parameterized by N, a number of nodes,
and a start and end node in [0..N). A graph is generated with N nodes
and some random number of connections between those nodes. A parallel
algorithm based on A* is used to find the shortest path. This
algorithm varies from serial A* in that it needs to add nodes back to
the open set when the g estimate (shortest path from start to the
node) is improved, even if the node has already been "visited". This
is because nodes are added and removed from the open-set in parallel,
resulting in some less optimal paths being explored. The open-set is
implemented with the concurrent_priority_queue. Note that since we
re-visit nodes, the f estimate (on which the priority queue is sorted)
is not technically needed, so we could use this same parallel
algorithm with just a concurrent_queue. However, keeping the f
estimate and using concurrent_priority_queue results in much better
performance. Silent mode prints run time only, regular mode prints
shortest path length, and verbose mode prints out the shortest path.
The generated graph follows a pattern in which the closer two pairs of
node ids are together, the fewer hops there are in a typical path
between those nodes. So, for example, the path between 5 and 7 likely
has few hops whereas 14 to 78 has more and 0 to 9999 has even more,
etc.
< H2 > Files< / H2 >
< DL >
< DT > < A HREF = "shortpath.cpp" > shortpath.cpp< / A >
< DD > Driver.
< DT > < A HREF = "Makefile" > Makefile< / A >
< DD > Makefile for building example.
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< H2 > Directories< / H2 >
< DL >
< DT > < A HREF = "msvs" > msvs< / A >
< DD > Contains Microsoft* Visual Studio* 2010 workspace for building and running the example with the Intel® C++ compiler (Windows* systems only).
< DT > < A HREF = "xcode" > xcode< / A >
< DD > Contains OS X* Xcode* workspace for building and running the example (OS X* systems only).
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< H2 > To Build< / H2 >
General build directions can be found < A HREF = ../../index.html#build > here< / A > .
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< H2 > Usage< / H2 >
< DL >
< DT > < TT > shortpath < I > -h< / I > < / TT >
< DD > Prints the help for command line options
< 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 >
< 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 >
< I > verbose< / I > print full path to screen< BR >
< I > silent< / I > limits output to timing info; overrides verbose< BR >
< I > N< / I > number of nodes in graph< BR >
< I > start< / I > node to start path at< BR >
< I > end< / I > node to end path at< BR >
< DT > To run a short version of this example, e.g., for use with Intel® Parallel Inspector:
< DD > Build a < I > debug< / I > version of the example
(see the < A HREF = ../../index.html#build > build directions< / A > ).
< 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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< HR >
2016-05-12 12:28:09 +01:00
< A HREF = "../../index.html" > Up to parent directory< / A >
2015-02-02 16:34:24 +01:00
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2016-05-12 12:28:09 +01:00
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