Hi, all- This not a problem with W-L, but is instead something that is wrong with a particular combination of mdp options that are not working for expanded ensemble simulations. W-L can equilibrate to incorrect distributions because it decreases the weights too fast (more on that later), but that is not the problem here. The option wl-oneovert allows switching to a slower scaling that is more likely to converge.
The reason that it is not a W-L problem is that after the WL weights are equilibrated, it is equilibrium sampling in the expanded ensemble. If the W-L equilibration was a problem, then the distribution of states would not be flat. They are flat, so therefore the expanded ensemble dynamics are wrong. I have example expanded ensemble setups. http://www.alchemistry.org/wiki/GROMACS_4.6_example:_Ethanol_solvation_with_expanded_ensemble These mdp files should work. Note that you should be able to swap out any top, and it will still work. If you get CORRECT results (and it should take just a few ns to see) with these tops, then I will go through and try to figure out which differences are causing the problems. Thanks for the patience while we test this new functionality. Frequently when one puts new code in the hands of others it breaks in ways that were not foreseen! On Tue, Jul 16, 2013 at 12:53 PM, Dejun Lin <dejun....@gmail.com> wrote: > I have a similar question here. Can anyone tell if the Wang-Landau algorithm > in lambda space is robust in that it doesn't depend on the choice of the > convergence factor (weight-equil-wl-delta), the flatness of the histogram > (wl-ratio) and/or the frequency of trial move (nstexpanded), especially in > the case of barely overlapping energy distribution corresponding to > different lambdas? I can imagine in the extreme case, with only 2 lambdas ( > l = 1 or 0), the gap between the 2 energy distributions might be so large > such that for most of the time, trial moves from the "center" of > distribution 1 would frequently end up in the "tail" of distribution 0. In > this case, the Wang-Landau weights would be biased if there's not enough > time for the system to relax back to equilibrium. > > Thanks, > Dejun > > > > -- > View this message in context: > http://gromacs.5086.x6.nabble.com/gmx-4-6-1-Expanded-ensemble-weird-balancing-factors-tp5007681p5009892.html > Sent from the GROMACS Users Forum mailing list archive at Nabble.com. > -- > gmx-users mailing list gmx-users@gromacs.org > http://lists.gromacs.org/mailman/listinfo/gmx-users > * Please search the archive at > http://www.gromacs.org/Support/Mailing_Lists/Search before posting! > * Please don't post (un)subscribe requests to the list. Use the > www interface or send it to gmx-users-requ...@gromacs.org. > * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists -- gmx-users mailing list gmx-users@gromacs.org http://lists.gromacs.org/mailman/listinfo/gmx-users * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/Search before posting! * Please don't post (un)subscribe requests to the list. Use the www interface or send it to gmx-users-requ...@gromacs.org. * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists
