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<div> Thanks Bill, but let me pursue this just a bit to be sure I’m not missing something. I understand how the coarse and fine nests are processed. I am asking how the two equal, but separate, 0.333 km fine nests are handled when their “time” comes. Are
you saying that there is no (significant) difference whether wrf runs each of the fine nests sequentially (each getting all the allotted processors) or simultaneously (sharing the total number of processors)? </div>
<div> Consider a simplistic example. For a sequential run of the two fine nests, if I make the x and y dimensions of each fine nest divisible by 10 and 5 respectively, then I know wrf can create 50 subgrids for an efficient run on 50 processors. I would
want each of the fine grids to have this same structure. </div>
<div> But if they will be running simultaneously, then wouldn’t I want the total number of subgrids for the two nests
<i>combined</i> to be 50? (My two fine nests are <i>not</i> the same size.) Of course, I am assuming that wrf makes some reasonable choice for the sub grids – maybe I need to better understand how it does that as well.</div>
<div> Thanks!</div>
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<div>Dave</div>
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<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">Dr. David J Smith</font></font></div>
<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">College of Science and Mathematics</font></font></div>
<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">University of the Virgin Islands</font></font></div>
<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">St. Thomas, VI 00802</font></font></div>
<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">340 693-1257</font></font></div>
<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">dsmith@uvi.edu</font></font></div>
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<span style="font-weight:bold">From: </span>"Gustafson, William I" <<a href="mailto:William.Gustafson@pnnl.gov">William.Gustafson@pnnl.gov</a>><br>
<span style="font-weight:bold">Date: </span>Wed, 8 Jun 2016 20:25:35 +0000<br>
<span style="font-weight:bold">To: </span>Dave Smith <<a href="mailto:dsmith@uvi.edu">dsmith@uvi.edu</a>>, wrf-users <<a href="mailto:wrf-users@ucar.edu">wrf-users@ucar.edu</a>><br>
<span style="font-weight:bold">Subject: </span>Re: [Wrf-users] How wrf processes nests<br>
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<div>Dave,</div>
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<div>The grids all share the same processors and are kept in sync at the end of each coarse-domain timestep. So, the outer nest runs on the processors first, then that nest waits while the finer nest is calculated. Then, the fine nest waits while the coarse
nest calculates, and on-and-on it goes. So, within a timestep, each nest is run sequentially. However, if one sees thinks of this in terms of the processor usage, they are simultaneous.</div>
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<div>-Bill</div>
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<div style="font-size: 12px;"><font class="Apple-style-span" face="Helvetica"><font style="font-size: 14px;"><font size="2"><span style="font-size: 10pt;"><b><font class="Apple-style-span" color="#dc871b">___________________________________________________________________</font></b></span></font></font></font></div>
<div style="font-size: 12px;"><font class="Apple-style-span" face="Helvetica"><font color="#dc871b" size="1" style="font-family: Helvetica, sans-serif;"><b><br>
</b></font></font></div>
<div style="font-size: 12px;"><font class="Apple-style-span" face="Helvetica"><font style="font-family: Helvetica, sans-serif;"><b>William I. Gustafson Jr., Ph.D.<br>
</b></font><font style="font-family: Helvetica, sans-serif;"><font style="font-size: 11px;">Scientist<br>
ATMOSPHERIC SCIENCES AND GLOBAL CHANGE DIVISION<br>
<br>
Pacific Northwest National Laboratory<br>
P.O. 999, MSIN K9-30<br>
Richland, WA 99352<br>
Tel: 509-372-6110<br>
</font></font></font><span class="Apple-style-span" style="font-size: 11px;"><u><a href="mailto:William.Gustafson@pnnl.gov"><font color="#df8800">William.Gustafson@pnnl.gov</font></a></u></span></div>
<div style="font-size: 12px;"><font class="Apple-style-span" face="Helvetica"><font style="font-family: Helvetica, sans-serif;"><font style="font-size: 11px;"><a href="http://www.pnnl.gov/atmospheric/staff/staff_info.asp?staff_num=5716" style="color: blue;"><font class="Apple-style-span" color="#dc871b">http://www.pnnl.gov/atmospheric/staff/staff_info.asp?staff_num=5716</font></a></font></font></font></div>
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<span class="Apple-style-span" style="font-size: 12px; font-family: Helvetica, sans-serif;"><font class="Apple-style-span" style="font-size: 11px;" color="#df8800"><a href="http://www.researcherid.com/rid/A-7732-2008">http://www.researcherid.com/rid/A-7732-2008</a></font></span></div>
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<span style="font-weight:bold">From: </span><<a href="mailto:wrf-users-bounces@ucar.edu">wrf-users-bounces@ucar.edu</a>> on behalf of David Smith <<a href="mailto:dsmith@uvi.edu">dsmith@uvi.edu</a>><br>
<span style="font-weight:bold">Date: </span>Wednesday, June 8, 2016 at 12:55 PM<br>
<span style="font-weight:bold">To: </span>wrf-users <<a href="mailto:wrf-users@ucar.edu">wrf-users@ucar.edu</a>><br>
<span style="font-weight:bold">Subject: </span>[Wrf-users] How wrf processes nests<br>
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<div>Hi,</div>
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<div> I am running wrf using mpirun on a 10 node cluster with 12 processors each – 120 total. I have two fine nests (0.333 km) within a 1.0 km coarser nest. I am trying to make a judicious choice for the dimensions of the fine nests, to minimize runtime.
(Making one fine nest would double the area.) Will wrf run the two fine grids sequentially or simultaneously? I would think this info would be in the users guide, but I’m not finding it. Thanks!</div>
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<div>Dave Smith</div>
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<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">Dr. David J Smith</font></font></div>
<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">College of Science and Mathematics</font></font></div>
<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">University of the Virgin Islands</font></font></div>
<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">St. Thomas, VI 00802</font></font></div>
<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri">340 693-1257</font></font></div>
<div><font class="Apple-style-span" color="rgb(0, 0, 0)"><font class="Apple-style-span" face="Calibri"><a href="mailto:dsmith@uvi.edu">dsmith@uvi.edu</a></font></font></div>
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