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<p><font face="serif">So chapter 11 of your text is all about hybrid
MPI-OpenMP programming. Some of you are reporting that you are
seeing little to no speedup. <br>
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<p><font face="serif">I am seeing something like the following...</font></p>
<p><font face="serif">Nodes Threads/Node Megaflops</font></p>
<font face="serif">1 1 627.363474<br>
1 2 1420.332565</font><br>
<font face="serif">2 2 2610.730625</font><br>
<font face="serif">2 4 4881.539916</font><br>
<font face="serif">4 2 4363.807638</font><br>
<font face="serif">4 4 7121.024514</font><br>
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<div class="moz-signature">Clearly, in this small sample you can see
that for the same number of nodes, increasing the number of
threads enhances the performance. You can also see that the same
number of total processes (like 2 nodes and 4 ppn or 4 nodes and 2
ppn) does not necessarily result in the same performance. That is
exactly what you are trying to show (and that this also changes
based on the dimension of the problem). You will find the "sweet
spot" of nodes and processors for each problem size on the final.<br>
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<div class="moz-signature">I think what most of you are missing is
that you have to do some minimal reading -- and note that you will
most likely have to change your MPI_Init function to the
MPI_Init_thread function call (p 268-269 of your text). Since I
have requested that you use only one MPI call per node, I
recommend that you use the MPI_THREAD_FUNNELED level of support.</div>
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<div class="moz-signature">Keep me posted. I have a day full of
ZOOM calls tomorrow, so I am going be working from the house.
Please let me know if you need anythin or if the cluster is giving
your problems.</div>
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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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