I'm trying to use the REPDSTR module for running multiple replicas in
slightly different potentials (and the same temp) The system is the four
residue peptide tuftsin with 1000 waters provided in the c36test directory.

As far as I figured out, we need to call the subroutine REPEXCHGL in the repdstr.src and this is done with the following command line: repd nrep <int> exlm freq <int>

The problem is that the probability of exchange is always zero even if the
replicas have the same potential... I checked that the correct formula in line 746 in repdstr.src is indeed used.

Do I use the right command line, or is there a bug somewhere?

Best wishes