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<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Hi,</span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span></p>
<span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I
changed that in the script since the assignment said to limit
the number of threads per node to one. (Or at least that is
how I interpreted the instructions.) So I can change back to
the way it was but how do I keep the thread count limited to
meet the requirements of the assignment? Or am I just reading
it wrong? Thanks.</span></blockquote>
</p>
<p>The multinode scripts I have given you have all been limited to
one process per node <b>with the flag on the mpirun command</b>.
While you are welcome to rewrite the scripts to try different
things -- the easiest thing to do is use one MPI process per node
and then allow the on-node shared-memory parallelism to be
controlled by either Pthreads or OpenMP. <br>
</p>
<p>In a naive approach you could just use more MPI processes per
node, but this tends to overload the communication channels. To
account for this drawback, the HPC code that I write which needs
to use multiple MPI processes uses one global communicator for
work between nodes and a local communicator for work on the node
with each node having a communication process, a process to break
up the work on the node, and the worker processes. <br>
</p>
<p>Keep it simple for this exercise - one MPI process per node and
OpenMP for on-node shared-memory parallelism. If you use a big
enough matrix you should see marked speedups when you go from 1 to
8 OpenMP threads per node.<br>
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<div class="moz-signature">-- <br>
<b><i>Andrew J. Pounds, Ph.D.</i></b><br>
<i>Professor of Chemistry and Computer Science</i><br>
<i>Director of the Computational Science Program</i><br>
<i>Mercer University, Macon, GA 31207 (478) 301-5627</i></div>
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