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<p>Hi,</p>
<p>This question is not so easy to answer, since it is not so clear
what kind of HPC you would "rent" (But even 2000 hours is "very
little/nearly nothing").<br>
</p>
<p>A 60 atom cell (with "complicated atoms, LDA+U, ...") can still
be run on a modern PC with 8 cores and 64 (better 128) GB RAM. A
single scf calculation may take 1-10 h on this PC.</p>
<p>Of course such calculations run faster, when you couple a few PCs
(or nodes on a HPC) together and let them work in parallel. <br>
</p>
<p>Much more difficult is to estimate how many such scf cycles you
will have to run. This depends a lot on your skills and what you
actually want to calculate. Certainly, phase transitions, entropy,
... require MANY such calculations (100 to a few 1000 ?). There is
no "input switch: "Phase transition" or "entropy", you have to set
up models, calculate them and derive from the results (total
energies) your information. It requires quite some expertise !</p>
<p>I don't know what they would charge you for 2000 h on a HPC
cluster, but this is just the cpu time you get from a single PC
(costs 2000 US$) in 3 month. Unless you get "very good prices"
(nearly for free), renting CPU hours is usually quite expensive as
compared to buying your own small cluster, in particular when you
go with standard PCs and not with a rack solution based on Xeon
processors. <br>
</p>
<p>The drawback is, that you need to be able to administer the Linux
installation (including network and NFS setup, ...)</p>
<p>For this project, I'd probably buy 4 - 8 PCs (or more, I don't
know how much money you have) (latest Intel I7 or I9 processors
(or whatever the numbers are now) with 8 cores, 128 GB RAM) and a
good Gbit switch (unless your University provides a good network
anyway). Such a cluster can then run for a couple of years (at
least the life of a PhD student) providing you with more than
100000 cpu-h.<br>
</p>
<p>HPC systems really are needed only if you go to systems with more
than 100-500 atoms/cell, where one MUST use highly parallel mpi
jobs, which need several nodes and a Infiniband network. It is a
waist of HPC ressources, when you use just one node of such a
cluster. A single node on a HPC system is NOT faster than a modern
PC !!!<br>
</p>
<p>Hope this helps.</p>
<p>Peter Blaha<br>
</p>
<div class="moz-cite-prefix">Am 10.02.2022 um 10:22 schrieb Mohammed
S. Mohammed:<br>
</div>
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<pre><span><span><span style="font-size:14.0pt;line-height:107%;font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";color:black;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA"><sub><span><span style="font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:Arial;mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA"><span><span style="font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:Arial;mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA"></span></span></span></span></sub></span></span><span class="ydpaae3e8dbMsoCommentReference"><span style="font-size:8.0pt;line-height:107%;font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:Arial;mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA"><a class="ydpaae3e8dbmsocomanchor" id="ydpaae3e8db_anchor_1" href="#_msocom_1" name="_msoanchor_1" rel="nofollow" target="_blank" moz-do-not-send="true"></a></span></span></span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi">Dear Wien2k</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"> Mailing list users</span><div>
<span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi">In Egypt we are about to invest some money from a project fund to <b>Buy or Rent </b>a high performance computer to calculate the magnetic, electronic, elastic, and magnetocaloric<span> </span>properties of selected rare-earth transition metal compounds to include R<sub>2</sub>Fe<sub>14</sub>B, Nd<sub>3</sub>Co<sub>11</sub>B<sub>4</sub>.</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"></span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi">The problem is we have to state in our request for this fund how much computer</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"> CPU usage will be required for say a 60-atom model to run. Therefore, we want</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"> CPU requirements versus the number of atoms for Wein2k. Also need to estimate</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"> how many times these models will need to be executed to perform the field,</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"> temperature ranges, first and second order phase transitions, magnetization, specific</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"> heat, entropy, and MCE properties i.e. the isothermal change in entropy and the</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"> adiabatic change in temperature in a wide range of magnetic fields and in a</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"> temperature range up to the Curie temperature of the studied systems.</span>
<p class="ydp83908200MsoNormal" style="text-align:justify"><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi">I am not sure that we can estimate the number of flops; so far, I have not seen this type of information on the internet for wien2k. There are tools, but not clear, if there has been a paper on the subject. The issue I see is that we need to estimate how much computer time to ask for, so if we can get an estimate that
would be a good idea. If they give us, 200 or 2000 hours will that, be enough to do what we want? How much computer time/gflops do we ask for?</span></p>
<span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi">Thank you for</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"> your patience.</span>
<p class="ydp83908200MsoNormal" style="text-align:justify"><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi">Dr / Mohammed Said M. Abu-Elmagd</span></p><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi">Ph.D. in Theoretical</span><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi"> Physics</span>
<i><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Department of</span></i><i><span style="font-size:12.0pt;line-height:107%;font-family:"Times New Roman",serif;mso-ascii-theme-font:major-bidi;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA"> Physics, Higher Institute of Engineering,
Shourok Academy, Cairo, Egypt.</span></i></div>
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Peter Blaha, Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
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