[gmx-developers] stuff in double precision

[hessb at mpip-mainz.mpg.de]

>> A very simple workaround would be to always use the free energy loops,
>> also for "reference no-free energy simulations", then you are running
>> the same code twice.
>
> I agree that that works in this particular case, and that's what we're
> doing. But obviously this hasn't been checked. What if this happens in
> other cases? i.e., do soft core parameters affect energies at
> lambda=0? In general one would like to know that if one evaluates the
> potential energy of a particular snapshot in a particular Hamiltonian,
> one will get the same energies to accuracies well below a kJ/mol
> (preferably a lot better -- we can get statistical uncertainties in
> free energy calculations down to 0.1 kJ/mol or less in some cases;
> you'd like to be sure your potential energy evaluations are reliable
> to better than this).

I have checked all these things and they work.
Also your system gives perfectly identical energies
with and without free-energy stuff in double precision.

Berk.