[CPMD-list] error in BO-PIMD

[Axel Kohlmeyer]

On Sat, 9 Jun 2007, qfzhang wrote:

QZ> Hi,
QZ>   So sorry for that. It is very strange that when running BO-PIMD job,nothing is
QZ>  written to the output file since "force initialization", and nothing to the fil
QZ> e TRAJECTORY and ENERGY. But the job will not stop until the walltime limit, and

hi,
this is not strange, you just discovered a 'deadlock' bug due to 
a so-called race condition. this can happen with PI-MD, when the
individual replica take significantly different time to do some
work yet the code is written in a way that expects about the same
time spent.

you don't see any output to the files, since you compiler defaults
to buffered output (inded something is written, but the first MD
step stalls, at least when trying to reproduce it on my machine).

QZ>  no error message.But when specify PORCESSOR GROUP=1,no problem.when I use CP-PI

with no processor groups there is no parallelization over replica,
and it seems that exactly that is causing the problems. with CP-MD
all operations take about the same time per replica, but with BO-MD
this is not always the case (different number of WF-opt steps for
different replica).

QZ> MD for calculations, no such problem. So I really don't know what's wrong with i
QZ> t.the output file is as below.

the cause can probably be found or narrowed down by tracing 
the parallelization in pi_diag.F. 

please note, that even though your job appears to be working, all
it does, is checking for the other parts to communicate which are
waiting for the first nodes in return (=> deadlock).

cheers,
   axel.

[...]

QZ> > -- 
QZ> > =======================================================================
QZ> > Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
QZ> >  Center for Molecular Modeling   --   University of Pennsylvania
QZ> > Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
QZ> > tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
QZ> > =======================================================================
QZ> > If you make something idiot-proof, the universe creates a better idiot.
QZ> 
QZ> 
QZ> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.