[Wrf-users] HyperThreading

[HEDDE Thierry 137147]

Hi,
My computer server is based on :
model name	: Intel(R) Xeon(R) CPU E7- 4807  @ 1.87GHz
with 24 physical processors

it used to have hyperthreading (HT) to double the processor number but it was not working at all with WRF : as soon as I was using more than 24 proc the server performances were collapsing. We've just reboot the server without HT.

best regards
T HEDDE

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Envoyé : lundi 28 mars 2016 20:00
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Objet : Wrf-users Digest, Vol 139, Issue 32

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Today's Topics:

   1. Re: Use or not use HyperThreading (?????? ?????????)


----------------------------------------------------------------------

Message: 1
Date: Mon, 28 Mar 2016 10:30:29 +0300
From: ?????? ????????? 	<kmironakis at gmail.com>
Subject: Re: [Wrf-users] Use or not use HyperThreading
To: Julio Castro <jcastro at gac.cl>
Cc: wrf-users at ucar.edu
Message-ID:
	<CAJtVLmNWqOmDwWhjRKS6HvqVytmwztHMoGZxZs1aRtXfa9XEDw at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Hello,
of course, but this job make the operating system of your PC (Linux, Unix).
We need it because the HyperThreading used one arithmetic unit and two logical units in each core of the processor.
When running the WRF most of the calculations of the program is not the numerical but the logical.
In practice the HyperThreading has double performance.

In Centos OS (Linux)
if i used the top command i see something like this

...

  PID USER      PR  NI  VIRT  RES  SHR S   %CPU %MEM    TIME+
COMMAND
11828 user1       20   0  8860 1192  844 R       786     50.0      10:00.02
wrf

...

which mean that the WRF in a 4 core machine with HyperThreading used the ~786% (800% max) of the power and not 400%.
Again, this job make automatic the linux or Unix and of course we enable the -omp option in the makefiles of WRF.


Efstathios Konstantinos Mironakis
http://www.forecastmaps.eu



2016-03-21 21:49 GMT+02:00 Julio Castro <jcastro at gac.cl>:

> Dear Users,
>
>
>
> Question, use or not use HyperThreading when running WRF on a single 
> machine?
>
>
>
> Many thanks
>
>
>
> *Julio Castro M.*
>
> Ingeniero Civil, MSc., PhD.
>
> Jefe del ?rea de Modelaci?n y Calidad del Aire
>
> [image: cid:83969B68-5B60-49B4-AE8A-CFDE16B1D669]
>
> Padre Mariano 103, Of. 307
> Providencia, Santiago
> Fono: +56 2 27195 610
> Fax: +56 2 22351 100
> www.gac.cl
>
>
>
>
>
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