<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div><div><font face="times new roman, new york, times, serif">Dear Users ,</font></div><div><font face="times new roman, new york, times, serif"><br></font></div><div><font face="times new roman, new york, times, serif"> I am trying to use PLUMED with gromacs4.5.4 to perform umbrella sampling simulation using replica exchange as implemented within gromacs. I am using radius of gyration as the collective variable along which umbrella sampling is being performed. However, I find that whenever I try to run replica exchange with umbrella sampling using the plumed compiled gromacs, it always crashes saying that </font></div><div><font face="times new roman, new york, times, serif"><br></font></div><div><font face="times new roman, new york, times, serif"> "The properties of the 23 systems are all the same, there is
nothing to exchange</font></div><div><font face="times new roman, new york, times, serif">For more information and tips for troubleshooting, please check the GROMACS</font></div><div><font face="times new roman, new york, times, serif">website at http://www.gromacs.org/Documentation/Errors"</font></div><div><font face="times new roman, new york, times, serif"><br></font></div><div><font face="times new roman, new york, times, serif">I had generated 23 replica each corresponding to a particular temperature and then used grompp (compiled using plumed ) to generate 23 .tpr file. Now, I use only one plumed.dat file . But, running the simulation using command</font></div><div><font face="times new roman, new york, times, serif"><br></font></div><div><font face="times new roman, new york, times, serif">~/UTIL/OPENMPI/bin/mpirun -np 46 mdrun_plumed_s -multi 23 -replex 500 -s hremd -plumed plumed_umb.dat >& log_replica</font></div><div><font
face="times new roman, new york, times, serif"><br></font></div><div><font face="times new roman, new york, times, serif">But, it ctashes..</font></div><div><font face="times new roman, new york, times, serif"><br></font></div><div><font face="times new roman, new york, times, serif">I have also tried running regular replica exchange simulation without this plumed.dat file and then again it crashes saying the same error that it finds all replica identical.</font></div><div><font face="times new roman, new york, times, serif"><br></font></div><div><font face="times new roman, new york, times, serif">However, same simulation with official gromacs 4.5.4 executable ( i.e without the plumed plugin) runs without any problem. </font></div><div><font face="times new roman, new york, times, serif">Also, the plumed plugin works great for a single temperature simulation.</font></div><div><font face="times new roman, new york, times,
serif"><br></font></div><div><font face="times new roman, new york, times, serif">So, I wonder whether the plumed plugin is causing any trouble in running replica exchange simulation or I am missing something.</font></div><div><font face="times new roman, new york, times, serif">Thanks in advance for help</font></div><div><font face="times new roman, new york, times, serif">Sanku </font></div></div></div></body></html>