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Hi JP,
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<div>That doesn't sound normal at all... 200K elements is not that large.</div>
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<div>I'm suspecting that the time is spent in factoring the XXt-based coarse grid operator..., but</div>
<div>that should really take only 20 minutes for the numbers you report (which is still too long).</div>
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<div>My guess is that a switch to AMG for the coarse-grid solve would fix your problem --- My first</div>
<div>guess about the long time is that somehow the partitioning is messed up --- XXt depends</div>
<div>crucially on having a good partition and genmap is designed to provide this.</div>
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<div>Please let me know if you have any issues switching to AMG (which we typically only do</div>
<div>at around a million elements or so...)</div>
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<div>Best,</div>
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<div>Paul</div>
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<div id="divRpF57338" style="direction: ltr;"><font face="Tahoma" size="2" color="#000000"><b>From:</b> nek5000-users-bounces@lists.mcs.anl.gov [nek5000-users-bounces@lists.mcs.anl.gov] on behalf of nek5000-users@lists.mcs.anl.gov [nek5000-users@lists.mcs.anl.gov]<br>
<b>Sent:</b> Tuesday, July 07, 2015 9:52 AM<br>
<b>To:</b> nek5000-users<br>
<b>Subject:</b> [Nek5000-users] Large simulations<br>
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<div dir="ltr">Dear All,
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<div>Is it normal for a nek simulation (220 000 elements with lx1=12) to have long initial setup times (basically gs_setup) such as 5 hours when running on 32768 cores, even when restarting?</div>
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<div>As expected, more elements and/or more cores used results in longer setup times. My problem is that I wish to carry out simulations with a higher number of elements but I am limited to 24 hour runs and must carry out restarts.</div>
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<div>Is there a way to carry out faster restarts?</div>
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<div>Thank you,</div>
<div>jp</div>
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