[Pw_forum] Speeding up the calculations

[Huiqun Zhou]

Mehmet,

Hope you are the same person who posted a very good tutorial on phonon calculation via
small displacement method (SDM) and DFPT at Siesta forum.

Interestingly, I noticed that in your tutorial DFPT (PW+PH: 328 sec at 8CPU) was much faster 
than SDM (Siesta+PHON: 520 sec at 8CPU, VASP+PHON: 1674 sec at 16CPU) for the case 
of graphene, at least by the criteria of getting identical phonon dispersion relation. So, your 
current recommendation means that was just a individual case for you, right? 

My feel (no concret numbers) with qe shows that for the previous version of qe (before 4.0 
or earllier?) PW+PH was somewhat slower than PW+PHON, but the situation is reversed 
with recent versions of qe.   

If you have further examples, please share with us.

Thank you in advance!

huiqun zhou
@earth sciences, nanjing university, china
 
  ----- Original Message ----- 
  From: Mehmet Topsakal 
  To: PWSCF Forum 
  Sent: Sunday, August 15, 2010 3:52 PM
  Subject: Re: [Pw_forum] Speeding up the calculations


  Dear  Bipul,


  You can try Small Displacement Method ( see http://www.homepages.ucl.ac.uk/~ucfbdxa/ ) which has different idea than DFPT.
  It requires you to make 2 displacement in a supercell and calculate the forces with single scf. You can run scf's at the same time.  
  For example, you need to calculate the forces in 5x5x1 graphene supercell having 50 carbon atoms for 2 displacemet.


  BUT you cannot observe LO-TO splitting in polar materials (such as honeycomb monolayer ZnO) by using SDM.


  Regards.                    


  On Sat, Aug 14, 2010 at 9:44 PM, Bipul Rakshit <bipulrr at gmail.com> wrote:

    Hi PWSCF user,
    I am mainly doing Phonon calculation, which generally is time consuming ( even in parallel). I just want to know if there is any possible way to speed up the calculations. i.e. by installing certain libraries or so. Or using some appropirate methods

    The machine had many nodes, and each nodes have 8/16 processors. Some of the other details of the machines are as follows:

     Intel(R) Xeon(R) CPU  E5345  @ 2.33GHz, 64 bit
    4GB RAM

    compiler: mpif90 and icc

    Thanks
    -- 
    Bipul Rakshit
    Research Fellow
    S N Bose Centre for Basic Sciences,
    Salt Lake,
    Kolkata 700 098
    India

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  -- 

  Mehmet Topsakal  (Ph.D. Student)
  UNAM-Institute of Materials Science and Nanotechnology. 
  Bilkent University. 06800 Bilkent, Ankara/Türkiye
  Tel: 0090 312 290 3527 ; Fax: 0090 312 266 4365
  UNAM-web  : www.nano.org.tr




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