[gmx-users] Question about 'mdrun -nosum'

Da-Wei Li lidawei at gmail.com
Fri Dec 14 17:04:49 CET 2012

I think the same way as you. They do bring in errors but this is acceptable
in normal MD because we already have lots of approximations. BTW, -sum has
been dropped from 4.5, in other words, Gromacs won't calculate global
Energy every step by default now.


On Fri, Dec 14, 2012 at 9:46 AM, Thomas Schlesier <schlesi at uni-mainz.de>wrote:

> Dear all,
> i have a small question regarding the '-nosum' option of 'mdrun'.
> The manual states:
> For a global thermostat and/or barostat the temperature and/or pressure
> will also only be updated every nstlist steps. With this option the energy
> file will not contain averages and fluctuations over all integration steps.
> Second sentence is clear to me. But the first sentence give me some
> thoughts.
> I think this would introduce some errors, but what is about the magnitude
> of these?
> I would expected that the errors are in the same order of the errors in
> the forces due to the neighborlist search (error due to the fact that one
> uses 'nstlist=5' instead of 'nstlist=1') and would be more or less
> negilegible, if one doesn't use a very larger 'nstlist'-value.
> But to be on the save side i wanted to ask.
> Greetings
> Thomas
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