[Pw_forum] QE and mpich2, Linux

[Gabriele Sclauzero]

Il giorno 02/feb/2011, alle ore 03.54, ac.rain at inbox.com ha scritto:
> 
> I am running it now in blocks of 4 cpus to match the number-combination requirement.
> 4 cores on the same system completes in 1h47m , 16 cores on the same system completes in 2h19m.
> 
> Is this not going to get faster on a single system until we add more memory to the system? or perhaps to drop the number of cpus specified in mpiMachinefile.txt so it spreads a fewer number of jobs over a greater number of systems?

> or is the bottleneck to do with the local hard drives not being fast enough?

This should be easy to test, by changing the value in disk_io

> 
> I am not familiar with the maths equations/terminology mentioned in the document.

Also your terminology is not familiar to us and is not easy to understand what you are saying... what is the "number-combination requirement"? And what does it mean "it spreads a fewer number of jobs over a greater number of systems"? Please make an effort to adopt more clear statements (reading some reviews or following a small tutorial on parallel/high-performance computing might help), otherwise we can only continue to guess what you mean.

In order to improve the speed up you should understand (at least broadly) the different levels of parallelization implemented in the code. Another important thing is to understand the timings at the end of the output. Try to compare those numbers for the two different runs.


GS

> 
> thanks,
> 
> nick
> 
>> -----Original Message-----
>> From: giannozz at democritos.it
>> Sent: Mon, 31 Jan 2011 11:16:06 +0100
>> To: pw_forum at pwscf.org
>> Subject: Re: [Pw_forum] QE and mpich2, Linux
>> 
>> in order to take advantage of parallelization, some understanding of
>> how parallelization works in QE is needed. The user guide and this
>> document:
>> http://www.fisica.uniud.it/~giannozz/QE-Tutorial/tutorial_para.pdf
>> contain some info. Throwing in more processors will not by itself do
>> the job.
>> 
>> P.
>> ---
>> Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
>> Phone +39-0432-558216, fax +39-0432-558222
>> 
>> 
>> 
>> 
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne

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