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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hello all,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I am running WRF on a new AMD Opteron-based Linux cluster
(using PGI compilers, DM Parallel, RSL_LITE). I have used similarly configured
clusters with great success, but on this particular system I am seeing very
poor scalability when exceeding more than two nodes (I actually see 0 and even
some negative scalability for a problem that should be scaling well across the
cluster). The two main differences between this new cluster and previous
clusters I have used are:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<ol style='margin-top:0in' start=1 type=1>
<li class=MsoNormal style='mso-list:l0 level1 lfo1'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>The compute nodes on this new
cluster have two dual-core Opteron processors, whereas in the past I have
only had access to dual single-core Opterons.<o:p></o:p></span></font></li>
<li class=MsoNormal style='mso-list:l0 level1 lfo1'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>This compute node only has
Gigabit Ethernet for MPICH, whereas in the past I have always had
Myrinet. The “conventional wisdom” is that for a small
cluster (8 nodes or less), there is not a huge advantage in using Myrinet
vs. Gig-E. However, I wonder if that is still true now that we can run 4
processes/node instead of 2? <o:p></o:p></span></font></li>
</ol>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Do any of you out there in WRF-land have a similar cluster
for which you would be willing to share some benchmark results? I am in the
process of running the standard WRF CONUS 12-km benchmark on a range of 1-16
processors.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Thanks in advance to anyone willing to discuss this with me!<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Brent<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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