[gmx-developers] Re: nstenergy and nstcalcenergy?

[Berk Hess]

Not exactly.

nstcalcenergy controls the calculation frequency of energies, which also
affects the statistics in the "exact" averages and fluctuations in the
energy files.
If this would not be the case we would not need a parameter at all and
we would
just need a conditional with many components in the md loop.

I had thought of adding nstcouple, but that is yet another parameter
which the user
can set and also has to be checked against several other nst...
parameters for reasonable
performance. Currently there would not be an advantage to having the
freedom to
set nstcouple different from nstenergy, except for the NVT ensemble
where you only
need to determine ekin and no other energies or pressures.

On the other hand, having an nstcouple might be easier to understand for
the user,
since then is it much clearer what the function of nstcouple and
nstcalcenergy is.

Berk

Shirts, Michael (mrs5pt) wrote:
> Following up on the last one, currently nstcalcenergy controls the frequency
> at which coupling occurs. Perhaps there should be a nstcoupling, and then
> nstcalcenergy is determined as a function of nstcoupling, nstenergy, nstlist
> and any other variables that are affected, instead of controlling it
> directly? 
>
> Best,
> ~~~~~~~~~~~~
> Michael Shirts
> Assistant Professor
> Department of Chemical Engineering
> University of Virginia
> michael.shirts at virginia.edu
> (434)-243-1821
>
>
>   
>> From: "Shirts, Michael (mrs5pt)" <mrs5pt at eservices.virginia.edu>
>> Reply-To: "michael.shirts at virginia.edu" <michael.shirts at virginia.edu>
>> Date: Thu, 10 Jun 2010 17:41:06 -0400
>> To: "gmx-developers at gromacs.org" <gmx-developers at gromacs.org>
>> Subject: nstenergy and nstcalcenergy?
>>
>> I'm wondering about the relationship between nstenergy and nstcalcenergy.
>> Is there a need for two variables?   This seems to lead to confusion.  For
>> example, one issue that's appearing is that when nstenergy = 1, gromacs now
>> only computes the energy every nstcalcenergy steps.  It seems that there
>> should be either one variable, or they should be synchronized in some way.
>> Or perhaps change the variable names if they are actually controlling
>> something else.
>>
>> Best,
>> ~~~~~~~~~~~~
>> Michael Shirts
>> Assistant Professor
>> Department of Chemical Engineering
>> University of Virginia
>> michael.shirts at virginia.edu
>> (434)-243-1821
>>
>>     
>
>