<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body><div>Thanks for your kind reply.</div><div>I am trying to run GaN supercell with 12 parallel processors. But want to know about k points for this.</div><div>Please also guide me about RTMAX </div><div><br></div><div style="font-size:100%;color:#000000"><!-- originalMessage --><div>-------- Original message --------</div><div>From: Laurence Marks <L-marks@northwestern.edu> </div><div>Date: 3/12/19 7:34 PM (GMT+05:00) </div><div>To: A Mailing list for WIEN2k users <wien@zeus.theochem.tuwien.ac.at> </div><div>Subject: Re: [Wien] (no subject) </div><div><br></div></div><div dir="ltr"><div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">The number of k-points needed depends upon:</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">a) Whether you are doing a pre-convergence, e.g. MSR1a or a final convergence.</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">b) The size of the cell</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">c) Whether you have a metal or an insulator (partially occupied states at E_F)</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">d) The atomic number -- high Z can converge worse -- and whether you have d/f electrons.</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">I would estimate that for a metal something like a k-point density of 50 nm^3 is good for reasonable precision. Divide by 2-4 for an insulator, divide by 2-4 for pre-convergence and perhaps multiply by 2-4 for phonons or high precision.</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">So long as memory is not an issue, you should try and divide the k-points across cores/nodes in an even fashion. It will also depend upon whether mpi or threading is better on your system, this seems to vary. It is hard to make clean statements without more information.</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">For a small problem (e.g. RKM=200-500) I would tend to distribute with 1-2 cores per k-point, e.g. use</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">1:node1</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">1:node1</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">1:node1</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">1:node1</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000000">In .machines. (Add a :2 after the node1 to use mpi.) For a larger problem (e.g. RKM+12000) you probably want to just run one process. For a very large problem, e.g. RKM=30000 -- get access to a larger cluster!</div></div><div><br></div><div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)">Experiment.</div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Mar 12, 2019 at 8:34 AM umbreenrasheed <<a href="mailto:umbreenrasheed@yahoo.com">umbreenrasheed@yahoo.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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How many k points should be selected for 8 parallel processors selection in wein2k..
<div>What is general relation between the two?</div>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><span style="font-size:12.8px">Professor Laurence Marks</span><br></div><div dir="ltr"><span style="font-size:12.8px">"Research is to see what everybody else has seen, and to think what nobody else has thought", </span><span style="font-size:12.8px">Albert Szent-Gyorgi</span><br><a href="http://www.numis.northwestern.edu" target="_blank">www.numis.northwestern.edu</a> ; <span style="font-size:12.8px">Corrosion in 4D: </span><a href="http://MURI4D.numis.northwestern.edu" style="font-size:12.8px" target="_blank">MURI4D.numis.northwestern.edu</a><div><span style="font-size:12.8px">Partner of the CFW 100% program for gender equity, </span><a href="http://www.cfw.org/100-percent" style="font-size:12.8px" target="_blank">www.cfw.org/100-percent</a></div><div>Co-Editor, Acta Cryst A</div></div></div></div></div></div></div></div></div></div></div></div>
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