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| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="mpi.performance"></a>Performance Evaluation</h2></div></div></div> |
| <p> |
| Message-passing performance is crucial in high-performance distributed computing. |
| To evaluate the performance of Boost.MPI, we modified the standard <a href="http://www.scl.ameslab.gov/netpipe/" target="_top">NetPIPE</a> |
| benchmark (version 3.6.2) to use Boost.MPI and compared its performance against |
| raw MPI. We ran five different variants of the NetPIPE benchmark: |
| </p> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| MPI: The unmodified NetPIPE benchmark. |
| </li> |
| <li class="listitem"> |
| Boost.MPI: NetPIPE modified to use Boost.MPI calls for communication. |
| </li> |
| <li class="listitem"> |
| MPI (Datatypes): NetPIPE modified to use a derived datatype (which itself |
| contains a single <code class="computeroutput"><span class="identifier">MPI_BYTE</span></code>) |
| rathan than a fundamental datatype. |
| </li> |
| <li class="listitem"> |
| Boost.MPI (Datatypes): NetPIPE modified to use a user-defined type <code class="computeroutput"><span class="identifier">Char</span></code> in place of the fundamental <code class="computeroutput"><span class="keyword">char</span></code> type. The <code class="computeroutput"><span class="identifier">Char</span></code> |
| type contains a single <code class="computeroutput"><span class="keyword">char</span></code>, |
| a <code class="computeroutput"><span class="identifier">serialize</span><span class="special">()</span></code> |
| method to make it serializable, and specializes <code class="computeroutput"><a class="link" href="../boost/mpi/is_mpi_datatype.html" title="Struct template is_mpi_datatype">is_mpi_datatype</a></code> |
| to force Boost.MPI to build a derived MPI data type for it. |
| </li> |
| <li class="listitem"> |
| Boost.MPI (Serialized): NetPIPE modified to use a user-defined type <code class="computeroutput"><span class="identifier">Char</span></code> in place of the fundamental <code class="computeroutput"><span class="keyword">char</span></code> type. This <code class="computeroutput"><span class="identifier">Char</span></code> |
| type contains a single <code class="computeroutput"><span class="keyword">char</span></code> |
| and is serializable. Unlike the Datatypes case, <code class="computeroutput"><a class="link" href="../boost/mpi/is_mpi_datatype.html" title="Struct template is_mpi_datatype">is_mpi_datatype</a></code> |
| is <span class="bold"><strong>not</strong></span> specialized, forcing Boost.MPI |
| to perform many, many serialization calls. |
| </li> |
| </ol></div> |
| <p> |
| The actual tests were performed on the Odin cluster in the <a href="http://www.cs.indiana.edu/" target="_top">Department |
| of Computer Science</a> at <a href="http://www.iub.edu" target="_top">Indiana University</a>, |
| which contains 128 nodes connected via Infiniband. Each node contains 4GB memory |
| and two AMD Opteron processors. The NetPIPE benchmarks were compiled with Intel's |
| C++ Compiler, version 9.0, Boost 1.35.0 (prerelease), and <a href="http://www.open-mpi.org/" target="_top">Open |
| MPI</a> version 1.1. The NetPIPE results follow: |
| </p> |
| <p> |
| <span class="inlinemediaobject"><img src="../../../libs/mpi/doc/netpipe.png" alt="netpipe"></span> |
| </p> |
| <p> |
| There are a some observations we can make about these NetPIPE results. First |
| of all, the top two plots show that Boost.MPI performs on par with MPI for |
| fundamental types. The next two plots show that Boost.MPI performs on par with |
| MPI for derived data types, even though Boost.MPI provides a much more abstract, |
| completely transparent approach to building derived data types than raw MPI. |
| Overall performance for derived data types is significantly worse than for |
| fundamental data types, but the bottleneck is in the underlying MPI implementation |
| itself. Finally, when forcing Boost.MPI to serialize characters individually, |
| performance suffers greatly. This particular instance is the worst possible |
| case for Boost.MPI, because we are serializing millions of individual characters. |
| Overall, the additional abstraction provided by Boost.MPI does not impair its |
| performance. |
| </p> |
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| <td align="right"><div class="copyright-footer">Copyright © 2005-2007 Douglas Gregor, |
| Matthias Troyer, Trustees of Indiana University<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top"> |
| http://www.boost.org/LICENSE_1_0.txt </a>) |
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