[Pw_forum] how does the quantum espresso scale with increasingthe number of nodes.

[Huiqun Zhou]

vicky,

If by node you mean a compute node with 4 or 8 CPU cores, I'm afraid you
used too much compute resource. I had ever successfully optimized a spin 
polarized structure with 56 atoms by vc-relax on one compute node with 8 
CPU cores within several hours. Although you didn't mention what system 
you are calculating, I strongly recommend you try to run on one or two nodes 
to see how much wall time it'll take.

Efficiency of parallel computing depends on many things, one of which is the
system size. Usually you need to do simpler calculations to determine how
many cpu cores are optimal for your job. 


huiqun zhou
@earth sciences, nanjing University, china

  ----- Original Message ----- 
  From: vicky singh 
  To: PWSCF Forum 
  Sent: Wednesday, July 21, 2010 5:50 PM
  Subject: Re: [Pw_forum] how does the quantum espresso scale with increasingthe number of nodes.


  Dear prof Giannozzi

  sorry to disturb you but i want to ask one question. the same work raran QE simulation with 40 atoms with 8 nodes and 12 nodes. the system got relaxed in 2 days 11 hrs with 8 nodes but it could nod relax even in 3 days with 12 nodes. even it got relaxed with 16 nodes in 2 days 11 hrs but not relax in 6 days with 32 nodes.

  can u help me out.

  with regards 




  vicky singh
  research student
  Bangalore




  On Tue, Jul 20, 2010 at 1:17 PM, Paolo Giannozzi <giannozz at democritos.it> wrote:

    vicky singh wrote:

    > Can anybody let me know how does the quantum espresso scale with
    > increasing the number of nodes or number of processors.


    short answer: it depends. Please read the documentation, in
    particular sec.3 of the userguide; sec.5 of J.Phys. Condens.
    Matter 21, 395502 (2009); the following slides:
    http://www.fisica.uniud.it/~giannozz/QE-Tutorial/tutorial_para.pdf

    P.
    --
    Paolo Giannozzi, Democritos and University of Udine, Italy

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