[Pw_forum] phonon parallel calculations

[Carlo Nervi]

Dear QE developers,
I would like to have your opinion on the procedure I followed in doing
phonon calculations.
I found that the use of nimages on my machine (8 numa zones) greatly
improves the speed of some calculations, but the first (initialization?)
part of the calculation (epsil=.true., i.e. the Electric Fields
Calculation) is much faster when performed without the use of "-ni 8"
switch in ph.x

So, I tested the following procedure and apparently worked for a small test
crystal:

1) pw.x (vc-relax optimization) without using "-ni"
2) scf on the optimized structure containing "wf_collect=.true." and using
"-ni 8"
3) ph.x containing "only_init = .true." and without using "-ni"
 This calculate the electric fields
4) duplicate the directory _ph0 and copied to _ph1 ... _ph7 (in output
directory)
5) ph.x containing "recover = .true." and using "-ni 8"
  This is the part where I get most of the speedup
6) ph.x of the input used in 5), but now without using "-ni"
  This is to collect the partial data and produce the final .out

I would greatly appreciate any comments in understanding if this procedure
is correct.
On a small crystal was working, but on a bigger crystal gave error.
Either the procedure is not completely correct or I have to start to look
for a problem in the RAM...

Thank you,

 Carlo

-- 

------------------------------------------------------------
Prof. Carlo Nervi carlo.nervi at unito.it  Tel:+39 0116707507/8
Fax: +39 0116707855      -      Dipartimento di Chimica, via
P. Giuria 7, 10125 Torino, Italy.    http://lem.ch.unito.it/
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