Dump command with temper


A simple question: when running replica exchange with temper, if you invoke the dump command, which replica does it dump? I have searched the forum and the documentation and have not found a definitive answer. Apologies in advance if I just missed it.

Kind regards,

all of them.

I have run temper simulations before (such as the one whose trajectory is linked below on my protondrive), and if I do a regular dump command, such as:

dump dump1 all custom 1000 AAPoly322bdump.*.dump id x y z ix iy iz

then it looks like it is dumping discontinuous trajectories from all replicas, but only one replica is shown per timestep, hence my initial question. This is also a bit confusing because in the log file it does not show that replicas are being swapped, but in the dump files it looks like replicas are being swapped.

So I guess my question is twofold:

  1. Since there is only one replica being dumped for each timestep, which replica is dumped at any given timestep? I understand that all of them are being swapped back and forth, and so all of them are dumped, but is there a rationale behind which one is dumped at a given time?
  2. Do the apparent swapping of replicas that appear like discontinuous trajectories actually correspond to a swapping of replicas (one replica getting another replica’s conformation)?

Hopefully that’s not too vague. The input files and all the output files for a sample run are here.

Kind regards,

You are drawing the wrong conclusion here because you are dumping to the same filename from all replica. This means there is some randomness involved in what is output. If you define a “world” style variable and assign a suitable string for each “world” and use that as part of the filename, then you will get one dump file per replica.

This is shown in the documentation for the temper command — LAMMPS documentation

What is swapped it the thermostat target temperature. That is much simpler than swapping systems and keeping the temperature.

There is a python program in the tools/replica folder that can swap the trajectories around so that each trajectory represents a specific temperature.

Makes sense. Thanks :slight_smile: