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<title>Parallel BGL MPI BSP Process Group</title>
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<h1 class="title"><a class="reference external" href="http://www.osl.iu.edu/research/pbgl"><img align="middle" alt="Parallel BGL" class="align-middle" src="pbgl-logo.png" /></a> MPI BSP Process Group</h1>

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<div class="contents topic" id="contents">
<p class="topic-title first">Contents</p>
<ul class="simple">
<li><a class="reference internal" href="#introduction" id="id1">Introduction</a></li>
<li><a class="reference internal" href="#where-defined" id="id2">Where Defined</a></li>
<li><a class="reference internal" href="#reference" id="id3">Reference</a></li>
</ul>
</div>
<div class="section" id="introduction">
<h1><a class="toc-backref" href="#id1">Introduction</a></h1>
<p>The MPI <tt class="docutils literal"><span class="pre">mpi_process_group</span></tt> is an implementation of the <a class="reference external" href="process_group.html">process
group</a> interface using the Message Passing Interface (MPI). It is the
primary process group used in the Parallel BGL at this time.</p>
</div>
<div class="section" id="where-defined">
<h1><a class="toc-backref" href="#id2">Where Defined</a></h1>
<p>Header <tt class="docutils literal"><span class="pre">&lt;boost/graph/distributed/mpi_process_group.hpp&gt;</span></tt></p>
</div>
<div class="section" id="reference">
<h1><a class="toc-backref" href="#id3">Reference</a></h1>
<pre class="literal-block">
namespace boost { namespace graph { namespace distributed {

class mpi_process_group
{
public:
  typedef boost::mpi::communicator communicator_type;

  // Process group constructors
  mpi_process_group(communicator_type comm = communicator_type());
  mpi_process_group(std::size_t num_headers, std::size_t buffer_size,
                    communicator_type comm = communicator_type());

  mpi_process_group();
  mpi_process_group(const mpi_process_group&amp;, boost::parallel::attach_distributed_object);

  // Triggers
  template&lt;typename Type, typename Handler&gt;
    void trigger(int tag, const Handler&amp; handler);

  template&lt;typename Type, typename Handler&gt;
    void trigger_with_reply(int tag, const Handler&amp; handler);

  trigger_receive_context trigger_context() const;

  // Helper operations
  void poll();
  mpi_process_group base() const;
};

// Process query
int process_id(const mpi_process_group&amp;);
int num_processes(const mpi_process_group&amp;);

// Message transmission
template&lt;typename T&gt;
  void send(const mpi_process_group&amp; pg, int dest, int tag, const T&amp; value);

template&lt;typename T&gt;
  void receive(const mpi_process_group&amp; pg, int source, int tag, T&amp; value);

optional&lt;std::pair&lt;int, int&gt; &gt; probe(const mpi_process_group&amp; pg);

// Synchronization
void synchronize(const mpi_process_group&amp; pg);

// Out-of-band communication
template&lt;typename T&gt;
  void send_oob(const mpi_process_group&amp; pg, int dest, int tag, const T&amp; value);

template&lt;typename T, typename U&gt;
  void
  send_oob_with_reply(const mpi_process_group&amp; pg, int dest, int
                      tag, const T&amp; send_value, U&amp; receive_value);

template&lt;typename T&gt;
  void receive_oob(const mpi_process_group&amp; pg, int source, int tag, T&amp; value);

} } }
</pre>
<p>Since the <tt class="docutils literal"><span class="pre">mpi_process_group</span></tt> is an implementation of the <a class="reference external" href="process_group.html">process
group</a> interface, we omit the description of most of the functions in
the prototype. Two constructors need special mentioning:</p>
<pre class="literal-block">
mpi_process_group(communicator_type comm = communicator_type());
</pre>
<p>The constructor can take an optional MPI communicator. As default a communicator
constructed from MPI_COMM_WORLD is used.</p>
<pre class="literal-block">
mpi_process_group(std::size_t num_headers, std::size_t buffer_size,
                  communicator_type comm = communicator_type());
</pre>
<p>For performance fine tuning the maximum number of headers in a message batch
(num_headers) and the maximum combined size of batched messages (buffer_size)
can be specified. The maximum message size of a batch is
16*num_headers+buffer_size. Sensible default values have been found by optimizing
a typical application on a cluster with Ethernet network, and are num_header=64k
and buffer_size=1MB, for a total maximum batches message size of 2MB.</p>
<hr class="docutils" />
<p>Copyright (C) 2007 Douglas Gregor</p>
<p>Copyright (C) 2007 Matthias Troyer</p>
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