[Pw_forum] Graphene phonon calculations too slow

Lorenzo Paulatto lorenzo.paulatto at impmc.upmc.fr
Wed May 25 19:13:34 CEST 2016

On Wednesday, 25 May 2016 15:13:28 CEST Abualnaja, Faris wrote:
> Any suggestions on how to speed up the process and if I am missing
> something?! Thank you in advance for all your kind help and time.

Dear faris,
1. try using the last version of QE, 4.3 is quite an old one.
2. did you check the scaling of the phonon run with the number of CPUs? 
Sometimes adding more CPUs does not make the calculation faster, and could 
actually make it slower, this is especially true for phonon
3. are you using pools to improve scalability? you can use as many pools as 
there are k-point in the pw calculation (-npool option)
4. you can do several phonon calculations at the same time, using the startq 
and lastq options, it is better to run them with different values of outdir


Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
+33 (0)1 44 275 084 / skype: paulatz
23-24/4é16 Boîte courrier 115, 
4 place Jussieu 75252 Paris Cédex 05

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