<div dir="ltr"><div class="gmail_extra">Dear <span style="font-family:arial,sans-serif;font-size:13px">Marcella,</span></div><div class="gmail_extra"><font face="arial, sans-serif"><br></font></div><div class="gmail_extra">
<font face="arial, sans-serif">Thank you for your reply. I know what your mean that the increasing number of SCF cycles leads to the longer time to converge the wave function. </font></div><div class="gmail_extra"><font face="arial, sans-serif"><br>
</font></div><div class="gmail_extra"><font face="arial, sans-serif">But it does not make sense, because I also checked the BLYP results. For the same benzene-water cluster with the same input settings, when I used <b>32-CUP</b>, the CPU-time increased from about 40 second per step to about 150 second per step after 1200 steps and <b>the SCF cycles also increased from 8 to 37</b>. </font></div>
<div class="gmail_extra"><font face="arial, sans-serif"><br></font></div><div class="gmail_extra"><font face="arial, sans-serif">However, when I stopped this calculation and restarted it with<font color="#0000ff"> </font><b><font color="#0000ff">8-CPU</font></b>, it only takes about 40 second per step, <b><font color="#0000ff">the SCF cycles was about 7</font></b>. And most importantly, </font><span style="font-family:arial,sans-serif">the speed and SCF cycles were very stable until finished the whole 10000 steps.</span><span style="font-family:arial,sans-serif"> </span></div>
<div class="gmail_extra"><span style="font-family:arial,sans-serif"><br></span></div><div class="gmail_extra"><span style="font-family:arial,sans-serif">When I restarted this calculation again with 32-CPU, the CPU-time was around 150 second per step and SCF cycles was about 41. <font color="#ff0000"><b>These tests were performed in the same node.</b></font></span></div>
<div class="gmail_extra"><font face="arial, sans-serif"><br></font></div><div class="gmail_extra"><font face="arial, sans-serif">It so strange. Why the same calculation takes different number of iterations when using different number of CPU?</font></div>
<div class="gmail_extra"><font face="arial, sans-serif"><br></font></div><div class="gmail_extra"><font face="arial, sans-serif">And back to the PBE functional, since I tried 8-CPU, 16-CPU, 24-CPU and 32-CPU for PBE funcitional, the calculation speed always slowed down after several steps. Why PBE functional do not have an "optimized performance" as BLYP functional with 8-CPU? Is it common that the speed of calculation with PBE functional slower than that with BLYP functional?</font></div>
<div class="gmail_extra"><font face="arial, sans-serif"><br></font></div><div class="gmail_extra"><font face="arial, sans-serif">Best regards,</font></div><div class="gmail_extra"><font face="arial, sans-serif">Huan</font></div>
<div class="gmail_extra"><font face="arial, sans-serif"><br></font><br><div class="gmail_quote">On Sun, Oct 27, 2013 at 9:04 PM, Marcella Iannuzzi <span dir="ltr"><<a href="mailto:marc...@pci.uzh.ch" target="_blank">marc...@pci.uzh.ch</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div style="word-wrap:break-word">Dear Huan,<div><br></div>
<div>the reason for the slowing down of the MD simulation is </div>
<div> the increasing number of iterations needed to converge the wave function.</div><div><br></div><div>regards</div><div>marcella</div><div><br></div><div><div>
<span style="text-indent:0px;letter-spacing:normal;font-variant:normal;text-align:-webkit-auto;font-style:normal;font-weight:normal;line-height:normal;border-collapse:separate;text-transform:none;font-size:medium;white-space:normal;font-family:Helvetica;word-spacing:0px"><span style="border-collapse:separate;font-variant:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><div style="word-wrap:break-word">
<div>--------------------------------------------------------------<br>Marcella Iannuzzi Phone : <a href="tel:%2B%2B41%2044%20635%204479" value="+41446354479" target="_blank">++41 44 635 4479</a><br>Physical Chemistry Institute FAX : <a href="tel:%2B%2B41%2044%20635%206838" value="+41446356838" target="_blank">++41 44 635 6838</a><br>
University of Zurich E-mail: <font color="#103ffb"><u>marcella<a href="mailto:hut...@pci.uzh.ch" target="_blank">@pci.uzh.ch</a></u></font><br>Winterthurerstrasse 190<br>CH-8057 Zurich, Switzerland<br>---------------------------------------------------------------</div>
<div style="font-style:normal;font-size:medium;font-family:Helvetica;font-weight:normal"><br></div></div></span><br></span><br>
</div>
<br><div><div><div>On Oct 27, 2013, at 4:42 PM, <a href="mailto:huan...@mail.huji.ac.il" target="_blank">huan...@mail.huji.ac.il</a> wrote:</div><br></div><blockquote type="cite"><div><div dir="ltr">
Dear All,<br><br>I am a newbie on CP2K and I have some questions on running CP2K with PBE functional.<br><br>Last week I did some tests on my benzene-water cluster project using both BLYP and PBE functional. I found that for BLYP functional, 8 CPU was the best choice for my research system, while using more CPUs for MD simulation, such as 16, 24, 32, the speed for every step slowed down. It can be explained that the more CPUs I used, the more time spent on communication.<br>
<br>But when it comes to PBE functional, no matter how many CPUs I used, the calculation speed always slowed down after about 40 steps. (The first 40 steps, the calculation just take about 50 seconds per step, but after 44 steps, it takes about 300 second for each step). Please see my <b>nve_PBE_50steps.ener</b> file in attachment. Actually, the structure of the benzene-water cluster is the same for both BLYP and PBE input files. And I just changed the functional into PBE, choosing the potential as GTH-PBE type, and using the same basis set as BLYP functional used. The rest of setting are the same with the input file of BLYP functional. I also attached the output file for detail information. (<b>nve_PBE_50steps.out</b>)<br>
<br>These decreasing of speed phenomena also happened when I used more than 8
CPU with BLYP functional. But if I use 8 CPU for calculation with BLYP
functional, the speed was very stable, which was about 40 seconds per
step.<br><br>My question is why the calculation speed slow down after 40 steps when I use PBE functional? Why the speed could not stable as using BLYP functioanl?<br><br>Best regards,<br>Huan<br><br></div><div><br></div>
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