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<span id="Function-netcellfun"></span><h3 class="section">3.8 Function netcellfun</h3>
<span id="index-netcellfun-1"></span>
<span id="XREFnetcellfun"></span><dl>
<dt id="index-netcellfun">Function File: <em></em> <strong>netcellfun</strong> <em>(<var>connections</var>, <var>fun</var>, …)</em></dt>
<dd><p>Evaluates function <var>fun</var> in a parallel cluster and collects results.
</p>
<p>This function handles arguments and options equivalently to
<code>parcellfun</code> and returnes equivalent output. Differently, the
first argument specifies server machines for parallel remote
execution, see <code>pconnect</code> for a description of the
<var>connections</var> variable. A further difference is that the option
"ChunksPerProc" is ignored and instead the chunk size can be
specified directly with an option "ChunkSize".
</p>
<p>This function can only be successfully called at the client machine
of the parallel cluster. <var>connections</var> can contain all
connections of the network, a subset of them, or a single connection.
The local machine (client), if contained in <var>connections</var>, is
ignored. However, one of the servers can run at the local machine
under certain conditions (see <code>pconnect</code>) and will not be
ignored in this case, so that the local machine can take part in
parallel execution with <code>netcellfun</code>.
</p>
<p>As a second level of parallelism, <var>fun</var> is executed at each
server machine (using <code>parcellfun or pararrayfun</code>) by default in
as many local processes in parallel as the server has processor cores
available. The number of local parallel processes can be configured
for each server with the "nlocaljobs" option (see
<code>network_set</code>), a value of <code>0</code> means that the default value
will be used, a value of <code>1</code> means that execution is not
parallel within the server (but still parallel over the cluster).
</p>
<p>See <code>parallel_doc ("limitations")</code> for possible limitations
e.g. on how <var>fun</var> can be defined.
</p>
<p>Cluster execution incurs a considerable overhead. A speedup is
likely if the computation time of <var>fun</var> is long. To speed up
execution of a large set of arguments with short computation times
of <var>fun</var>, increase "ChunkSize", possibly use "Vectorize" (see
<code>pararrayfun</code>), and possibly experiment with increasing
"nlocaljobs" from the default.
</p>
<p><strong>See also:</strong> <a href="netarrayfun.html#XREFnetarrayfun">netarrayfun</a>, <a href="pconnect.html#XREFpconnect">pconnect</a>, <a href="pserver.html#XREFpserver">pserver</a>, <a href="sclose.html#XREFsclose">sclose</a>, <a href="rfeval.html#XREFrfeval">rfeval</a>, <a href="install_005fvars.html#XREFinstall_005fvars">install_vars</a>.
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