[gmx-users] Lambda Weights from Expanded Ensemble Code

[Daniel Kozuch]

Hello,

I am interested in using simulated tempering in GROMACS (2019.5) under the
expanded ensemble options. Is there a way to monitor the ensemble weights
as the simulation progresses? I think in theory they are supposed to be
printed out in the log file, but it is only printing 0, -nan, and inf:

            MC-lambda information
  N  Temp.(K)    Count   G(in kT)  dG(in kT)
...
 36  359.105      118       -nan       -nan <<
 37  366.880       96       -nan       -nan
 38  374.852      107       -nan       -nan
 39  383.026      129       -nan       -nan
 40  391.407      166       -nan       -nan
 41  400.000      199       -nan    0.00000

Here are my relevant mdp settings:
simulated-tempering             = yes
nstexpanded                     = 500
simulated-tempering-scaling     = exponential
lmc-stats                       = metropolis-transition
lmc-move                        = metropolis

Any suggestions?

Best,
Dan Kozuch