[CPMD-list] NaNQ on P690 & on P630

[Dr. Balasubramanian Sundaram]

Dear Everyone,
     This is for the records. The problem that I faced while running 
MD on P690/630 using USPPs has gotten solved with CPMD v.3.7.2.
Thanks to all those (particularly, Dr. Curioni) who replied. 

Regards,
Bala
http://www.jncasr.ac.in/bala

Alessandro Curioni wrote:
> 
> Hello.
> 
> First of all,  a due answer for all the hard work of the ESSL developers:
> all this has nothing to do with ESSL FFT and
> ESSL has to be always used on IBM platform to obtain  the best
> performances, especially if running in MIXED mode
> ( the best way to obtain outstanding performances on clustered p690).
> As I already pointed out, since CPMD is a very complex program, only the
> fact that changing  a configure option seems to solve a problem doesn't
> mean that  the problem is really solved and that was the reason, i.e. we
> have recently corrected some memory allocation problems that shown up only
> in MD + USPP, but  were indeed very general.
> 
> Coming back to your problem:
> 
>  Apart  from the  *strange* choice of the nose parameters,  your problems
> are the TIMESTEP and EMASS
> you have chosen.
> 
> The integration of the equation of motion is not stable  for your system
> with TIMESTEP 5 and EMASS 400; the same
> run with the more reasonable choice  of TIMESTEP 4 and EMASS 500 or
> TIMESTEP 3 and EMASS 400  run smoothly
> on the p690 with xlf7  or xlf8  (by the way, the full suite of cpmd tests
> doesn't show any problem with xlf 8) as well on  intel-based linux cluster
> with intel or portland compilers.
> 
> Your example with  EMASS 400 and TIMESTEP 5 show instabilities in the
> integrations after 20 steps  (check the value
> of EHAM that should be exactly conserved), these become evident  in the
> p690 run, where you get the NaNQs.
> On intel based architectures, with  the ifc compiled code you get an
> exception in the iterative orthognalization  and a subsequent stop,
> whereas a pgf compiled code doesn't stop but goes on with numbers that have
> no meaning.
> This is simply do to a different way to treat exceptions by different
> compilers.
> 
> Could you please re-run your dynamics using  the TIMESTEP and EMASS I have
> suggested ?
> And also for completenes, could you send me the output of the run you were
> saying to work for thousands of step on IFC/Intel, since  my tests confirms
> that the program stops with your input with ifc/intel after 26 steps.......
> 
> I hope that this helps.
> 
> PS
> If you want to make a dynamics that make sense, heat up the system
> gradually and choose NOSE parameters
> that allow some coupling.
> 
> Alessandro CURIONI, PhD
> Research Staff Member
> Computational Biochemistry and Material Science group
> IBM Research Division - Zurich Research Laboratory
> Saumerstrasse 4
> 8003 Rueschlikon - Switzerland
> e-mail: cur at zurich.ibm.com
> www:    www.zurich.ibm.com
> Tel: +41-1-7248633
> Fax: +41-1-7248958