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<p>Sometimes it can be better to have a cheap computer if you can
remote connect to a high performance computing (hpc) [1] cluster.</p>
<p>There can be quite a bit of difference in the computing resources
that a thousand dollar desktop computer provides compared at a
million dollar hpc [2].<br>
</p>
<p>If your in academia, there are usually more options available for
getting access to a hpc such as use your own university's or
department's one if available, use a research center if there is
one nearby, collaborate with a professor at another university
that has one, get a research grant to pay to use a commercial one
(e.g., Amazon Cloud [3]), and so on. If in industry, it might be
harder to get access to one unless you work at a large corporation
that has one.</p>
<p>Desktop computers used to ship with 100 Mbps cards. However, in
new computers nowadays, you will likely find them to have 1 Gbps
cards. A Gigabit switch used to be expensive, but they have
probably come down in price now.</p>
<p>If you can find some buddies (aka fellow researchers) at your
local site and can connect them up to a Gigabit switch, while not
as good as a hpc with InfiniBand [4], you may be able to Beowulf
cluster [5] them to be better than a single desktop computer.<br>
</p>
<p>You might recall reading, since it has been in the archive and
has been re-posted a few times, the post at [6] about how a
Gigabit network of computers with i7 processors worked relatively
well.<br>
</p>
[1] <a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/High-performance_computing">https://en.wikipedia.org/wiki/High-performance_computing</a><br>
[2]
<a class="moz-txt-link-freetext" href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg22676.html">https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg22676.html</a><br>
[3] <a class="moz-txt-link-freetext" href="https://aws.amazon.com/education/">https://aws.amazon.com/education/</a><br>
[4] <a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/InfiniBand">https://en.wikipedia.org/wiki/InfiniBand</a><br>
[5] <a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Beowulf_cluster">https://en.wikipedia.org/wiki/Beowulf_cluster</a><br>
[6]
<a class="moz-txt-link-freetext" href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09334.html">https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09334.html</a><br>
<p>Kind Regards,</p>
Gavin<br>
WIEN2k user<br>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">On 8/22/2023 11:48 PM, Victor Zenou
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAOFFwJ6WUHLGc4naT_pM4jrJj-ygdOURTU-61zwPSU25CJEGkQ@mail.gmail.com">
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<div dir="rtl">
<div dir="ltr">Dear Laurie and Pavel,</div>
<div dir="ltr">Thanks for your answer </div>
<div dir="ltr">1. In fact I'm using RKMAX 5.4 and 125 kpts</div>
<div dir="ltr">0.01 cc and 0.001 ec </div>
<div dir="ltr">
<p class="MsoNormal" dir="RTL"
style="background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial;margin:0cm 0cm 8pt;line-height:107%;direction:rtl;unicode-bidi:embed;font-size:11pt;font-family:Calibri,sans-serif"><br>
</p>
</div>
<div dir="ltr"><span
style="font-size:11pt;line-height:107%;font-family:"Times New Roman",serif">2.
About my boss, it took me more than one year to get a new
computer. </span><span
style="font-family:"Times New Roman",serif;font-size:11pt">Please
define "fast"!</span></div>
<div dir="ltr"><span
style="font-size:11pt;line-height:107%;font-family:"Times New Roman",serif">Victor</span><br>
</div>
<div dir="ltr"><span
style="font-size:11pt;line-height:107%;font-family:"Times New Roman",serif"><br>
</span></div>
</div>
<br>
<div class="gmail_quote">
<div dir="rtl" class="gmail_attr">בתאריך יום ג׳, 22 באוג׳ 2023
ב-14:35 מאת Laurence Marks <<a
href="mailto:laurence.marks@gmail.com"
moz-do-not-send="true" class="moz-txt-link-freetext">laurence.marks@gmail.com</a>>:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="auto">
<div>Beyond what Pavel said, you are still talking weeks for
a calculation. A critical issue is whether you are using
sensible parameters. Many people have used RKMAX 7 and
1000 kpts assuming that those are "right" -- they are not.
If your H and He have small RMTs then RKMAX should also be
smaller. Also, what is needed is a k-point density, so the
number of k-points is less for a supercell.
<div dir="auto"><br>
</div>
<div dir="auto">I suggest that you copy your case.struct
file to a new directory then do init_lapw in that
directory. 23.2 will pick appropriate values for you,
and you can then copy them over.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Beyond that, get your boss to buy you a
faster computer.<br>
<br>
<div dir="auto">--<br>
Professor Laurence Marks (Laurie)<br>
Walter P Murphy Professor Emeritus<br>
Department of Materials Science and Engineering,
Northwestern University<br>
<a href="http://www.numis.northwestern.edu"
rel="noreferrer" target="_blank"
moz-do-not-send="true">www.numis.northwestern.edu</a><br>
"Research is to see what everybody else has seen, and
to think what nobody else has thought" Albert
Szent-Györgyi</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Aug 22, 2023,
04:32 Victor Zenou <<a
href="mailto:zanov@post.bgu.ac.il" rel="noreferrer"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">zanov@post.bgu.ac.il</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">
<div dir="rtl">
<div style="text-align:left"><font
face="Times New Roman, serif"><font
style="font-size:12pt" size="3">Dear Wien2k
users!</font></font>
<pre
style="margin-bottom:0.5cm;background:rgb(255,255,255);break-before:page;font-family:"Times New Roman",serif;font-size:12pt;color:rgb(0,0,0);direction:ltr"><font
face="Times New Roman, serif"><font
style="font-size:12pt" size="3">I’m investigating a 54 tungsten atoms supercell , with 1 helium atom and 1 hydrogen atom (primitive cell) at different interstitial sites. It takes ~ 46 hr per calculation cycle, and half of it (~23 hr) in parallel mode. The Wien2k version 23.2 was installed <span
style="font-weight:normal">on </span><span
lang="en-US"><span style="font-weight:normal">Ubuntu 22.04.2 LTS. using gfortran and I set OMP_NUM_THREADS to 1, and used 2 parallel_jobs in the current work. The computer is build from </span></span> <span
lang="en-US"><span style="font-weight:normal">i7-10700 processor @ 2.90GHz (8 cores; 16 Threads), 32 GB memory and 500 GB SSD. </span></span></font></font>
<font face="Times New Roman, serif"><font style="font-size:12pt"
size="3"><span lang="en-US">In the past using the same computer , it took me ~ 14 hr per cycle for the same calculations, meaning 2-4 times faster than today. The wien2k version was 21.1, bur I can’t remember if the calculations were done in parallel, probably yes (I think the number of parallel jobs was chosen automatically), and I think I set OMP_NUM_THREADS to 4, but again I’m not sure.</span></font></font>
<font face="Times New Roman, serif"><font style="font-size:12pt"
size="3"><span lang="en-US">How can I speed up my calculations using the same computer?</span></font></font>
<font face="Times New Roman, serif"><font style="font-size:12pt"
size="3">Best regards, Victor</font></font>
</pre>
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