[gmx-users] NVE of water

Berk Hess gmx3 at hotmail.com
Mon Mar 1 16:53:36 CET 2010

> Date: Mon, 1 Mar 2010 15:44:28 +0100
> From: r.friedman at bioc.uzh.ch
> To: gmx-users at gromacs.org
> Subject: Re: [gmx-users] NVE of water
> Mark Abraham wrote:
> > On 2/03/2010 12:39 AM, Ran Friedman wrote:
> >> Hi,
> >>
> >> I would still argue that double precision is important.
> >
> > Oh? The discussion of Table 4 of
> > http://pubs.acs.org/doi/abs/10.1021/ct700301q (2008 GROMACS 4 JCTC
> > paper) suggested to me that single-precision NVE could be done well in
> > GROMACS. Am I missing something?
> >
> > Mark
> "The presented benchmarks were performed in the NVT ensemble" (section IX).
> Or am I missing something?

No, but everything that affects energy conservation in NVE also affects it in NVT,
in addition the thermostat affect the integration accuracy in NVT (and in NVT
you do not measure energy conservation from the total energy, but from the
conserved energy quantity).

Double precision can be important for energy conservation, but often other
factors deteriorate the energy conservation orders of magnitude from what
can be reached in single precision already. Double precision is only required
for testing or when you really need to generate an NVE ensemble.


> Ran
> -- 
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