Hi OpenMM!
I am wondering what is the right way to reweight observables calculated from simulated tempering trajectories with the default weighting algorithm? Is reweighting even necessary? I am new to this technique so I apologize if the question is naive.
Thank you!
Dan
simulated tempering (re)weighting
- Daniel Konstantinovsky
- Posts: 77
- Joined: Tue Jun 11, 2019 12:21 pm
- Peter Eastman
- Posts: 2573
- Joined: Thu Aug 09, 2007 1:25 pm
Re: simulated tempering (re)weighting
On every output, it reports the current temperature. Every conformation visited by the simulation reflects a Boltzmann distribution at the current temperature, so the probability is proportional to exp(-E/kT) where E is the total energy (potential+kinetic). The most common use of simulated tempering is that you want to collect a distribution at one temperature (say 300K) but use higher temperatures to let it cross barriers more easily. In that case you either could ignore all the samples from higher temperatures, or you could reweight them by the ratio of temperature factors, exp(-E/kT1)/exp(-E/kT2).
- Daniel Konstantinovsky
- Posts: 77
- Joined: Tue Jun 11, 2019 12:21 pm
Re: simulated tempering (re)weighting
So the E in the numerator and denominator is the same (it's the current total energy at whatever temperature?), just the temperatures are different?
- Peter Eastman
- Posts: 2573
- Joined: Thu Aug 09, 2007 1:25 pm
Re: simulated tempering (re)weighting
Exactly. Different samples are drawn from different temperature ensembles. At higher temperatures, most samples will have energies that would be very improbable at the lower temperature, so the weighting factor will be very small.
- Daniel Konstantinovsky
- Posts: 77
- Joined: Tue Jun 11, 2019 12:21 pm
Re: simulated tempering (re)weighting
Got it, thank you Peter!