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<p>Thank you for pointing this out, and my apologies for this
technical problem. I converted them in .txt extension in the hope
that it would fit the taste of our mailers.</p>
<p>I also limited the simulation to 1 iteration as you suggested to
get a proper time report, thank you for this advice.</p>
<p>I have to report that I just noticed that the version of QE on my
computer is 6.0 while the one on the cluster is 6.3, but I would
not expect it to be the main cause of such a big discrepancy
(especially since the problem occurs on the side which has the
most updated version). I will try to update the software on my
computer to 6.3 to see if this changes anything.</p>
<p><br>
</p>
<p>Here is my initial question:</p>
<p> </p>
<p class="MsoNormal">I am starting to use a hpc cluster of my
university, but I am very green on parallel computation.</p>
<p class="MsoNormal">I have made a first test (test #1) on a very
small-scale simulation (relaxation of a GO sheet with 19 atoms,
with respect to the gamma point). The calculation took 3m20s to
run on 1 proc on my personal computer. On the cluster with 4 proc
and default parallel options, it took 1m5s, and on 8 proc it took
44s. This seems like a reasonable behavior, and at least shows
that raising the number of procs does reduce computation time in
this case (with obvious limitations if too many procs for the
job).</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">However I tried with another test, a bit bigger
(test #2). This example is a scf calculation with 120 atoms (still
with respect to the gamma point). In this case, the
parallelization brings absolutely no improvement. In fact,
although the <i>outfile</i> confirms that the code is running on
N procs, it has similar performances as if it was running on 1
proc (sometimes even worse actually, but probably not in a
significant manner, as the times are fluctuating a bit from 1 run
to another)</p>
<p class="MsoNormal">I tried to run this same input file on my
personal computer both on 1 and 2 cores. Turns out that it takes
10376s to run 10 iterations on 1 core, while it takes 6777s on two
cores, so it seems that the parallelization is doing ok on my
computer.</p>
<p class="MsoNormal">I have tried to run with different number of
cores on the hpc, and different parallelization options (like for
instance –nb 4), but nothing seems to improve the time</p>
<p class="MsoNormal"> <br>
</p>
<p class="MsoNormal">Basically, I am stuck with those 2 seemingly
conflicting facts:</p>
<ul>
<li><span
style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:Symbol"><span
style="mso-list:Ignore"><span style="font:7.0pt "Times
New Roman""></span></span></span>Parallelization
seems to have no particular problem on the hpc cluster because
test #1 gives good results</li>
<li>Parallelization seems to have no particular problem with the
particular input file #2 because it seems to scale reasonably
with proc number on my individual computer</li>
</ul>
<p> </p>
<p class="MsoNormal">However, combining both and running this file
in parallel on the hpc cluster ends up not working correctly…</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">I attached the input file and output file of
test #2. I also included as well as the slurm script that I use to
submit the calculation to the job manager, in case it helps
(test2.scf.slurm.txt)</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">Any suggestion on what is going wrong would be
very welcome.</p>
<p> Julien</p>
<p><br>
</p>
<div class="moz-cite-prefix">Le 10/04/2019 à 15:25, Paolo Giannozzi
a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:CAPMgbCsJkUoZ5dJJ5=7BatvAxMGZc02S3pQvZM-EuKsdEOUhUQ@mail.gmail.com">
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<div class="gmail-m_8225132656874819010WordSection1">On Wed, Apr
10, 2019 at 9:08 AM JULIEN, CLAUDE, PIERRE BARBAUD <<a
href="mailto:julien_barbaud@sjtu.edu.cn"
moz-do-not-send="true">julien_barbaud@sjtu.edu.cn</a>>
wrote:</div>
<div class="gmail-m_8225132656874819010WordSection1"><br>
</div>
<div class="gmail-m_8225132656874819010WordSection1">
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<p class="MsoNormal">I attached the input file and output
file of test #2 </p>
</blockquote>
<div><br>
</div>
<div>you did, but many mailers don't like that kind of
attachments and don't let them go through<br>
</div>
<div><br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<p class="MsoNormal">(this output only ran 1 iteration
because I interrupted it).<br clear="all">
</p>
</blockquote>
<div><br>
</div>
<div>it is useful to stop the code by setting the maximum
number of scf iterations to 1. In this way one can see the
final time report.<br>
</div>
</div>
<div><br>
</div>
<div>Paolo<br>
</div>
-- <br>
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<div>Paolo Giannozzi, Dip. Scienze Matematiche
Informatiche e Fisiche,<br>
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>
Phone +39-0432-558216, fax +39-0432-558222<br>
<br>
</div>
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