[CPMD-list] problem with path integrals restart

[Axel Kohlmeyer]

marek,

i had a closer look at the PI code (while debugging something related)
and found that those "spurious" NaNs and Infinities can come from
when you are not using a thermostat and thus the target temperature
is not defined. if just you put a TEMPERATURE statement into
the &CPMD section, even though it will be ignored when restarting
with velocities, those denormalized (information only) numbers go away.

now as a result this brings up the question: does it make sense at all
to run an NVE path-integrals run and if yes, how to handle this case?
should one compute the instantenous temperature? or just skip that output?

cheers,
    axel.
2008/4/2 Marek Naryniecki <marek at elrond.chem.uni.wroc.pl>:
>
>  Dear  Axel and Serge
>
>  I know DIPOLE shouldn't apeare in PI calculation. My mistake.
>  Calculation without DIPOLE produce the same problem.
>  I put 2 replicas for fast check of the problem on varius machines and
>  pseudos. This problem also occure with 8 replicas in 120K. I know it is
>  small number but more replicas is to expensive for me. I'll try some short
>  calculation with 32 replicas.
>
>
>   > On Wed, 2 Apr 2008, Marek Naryniecki wrote:
>  >
>  > MN> Dear All
>  >
>  > dear marek,
>
> >
>  > MN> ***************************************************************
>  > MN>  *                    CHARACTERISTIC RADII                     *
>  > MN>  ***************************************************************
>
> > MN>    SPECIES  R OF GYRATION  FREE PARTICLE  (IN ANGSTROM)
>  > MN>    1   P    0.06799       Infinity
>  > MN>    2   O    0.05446       Infinity
>  > MN>    3   K    0.08015       Infinity
>  > MN>    4   H    0.12800       Infinity
>  >
>
> > looks like a division by zero somewhere.
>  >
>  > [...]
>  >
>
> > MN> what is the reason of that? After that calculations go on and average
>  > MN> values for bonds seems to be good.
>  > MN> I looked into cpmd code but without  succes.
>  >
>
> > you're neither giving enough information to reproduce
>
> > that run somewhere else (full input!) nor enough details
>
> I'm sorry, I thought it will be easier to read. Now I know it was stupid.
>
> I attached inputs for replicas generation and dynamic. if I stop dynamic
>
> and then restart it this problem occures.
>
> > to narrow it down. what machine are you running on?
>
> > does the error happen in serial or in parallel?
>
> it happen in serial and in parallel. I chacked on several machines i was
>
> able and the problem happen.
>  >
>
> > looking at the code itself may not be enough.
>
> > compile cpmd with debug info, find the code
>
> > where the properties from above are computed,
>
> > set a breakpoint and try to figure out where the
>
> > denormalized numbers are coming from...
>
> I'm not familar with fortran, but I will try
>  >
>
> > MN>     100.0
>  > MN>  &END
>  > MN> ..
>  > MN> &PIMD
>  > MN>    TROTTER DIMENSION
>  >
>
> > it has become a very bad habit on this list lately to
>
> > exclude vital information from inputs posted. if you
>
> > don't make it easy to reproduce your problem, you'll
>
> > have to solve it by yourself.
>
> ok, You're right.
>  >
>  > [...]
>  > MN>
>  > MN> Please help me.
>
> >
>  > quid pro quo. you have to help us to help you.
>  >
>
> Thank You very much for reply. I'm still trying to figure out what
>
> is wrong. I thought someone tell me what can this mean physically.
>
>
> Many Thanks
>   marek
>  > cheers,
>  >    axel.
>  >
>
> > MN>
>  > MN> Best Regards,
>  > MN>
>  > MN>
>
> > MN> Marek Naryniecki
>  > MN> Wydzial Chemii
>
> > MN> Uniwersytet Wroclawski
>  > MN>
>  > MN>
>  > MN>
>  > MN> _______________________________________________
>
> > MN> CPMD-list mailing list
>  > MN> CPMD-list at cpmd.org
>  > MN> http://cpmd.org/mailman/listinfo/cpmd-list
>  > MN>
>  >
>  > --
>
>
> > =======================================================================
>  > 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.
>  >
>
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>
>



-- 
=======================================================================
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.