[gmx-users] Regarding extending simulations

Dilip H N cy16f01.dilip at nitk.edu.in
Tue Mar 21 05:39:33 CET 2017

I ran a md run of 20ns [10000000*.002] and i got the files as md.edr,
md.log, md.tpr, md.gro, md.xtc, md.cpt etc.,
Now i want to extend/continue my simulation from 20 ns to again 20 ns
(total 40 ns).
So i gave the command as -
gmx convert-tpr -s md.tpr - extend 20000 -o md1.tpr
gmx mdrun -v -s md1.tpr -cpi md.cpt -append

But i am getting the following errors..

Output file appending has been requested,
but some output files listed in the checkpoint file md.cpt
are not present or not named as the output files by the current program:
Expect output files present:

Expected output files not present or named differently:

Program:     gmx mdrun, version 2016.2
Source file: src/gromacs/mdrunutility/handlerestart.cpp (line 177)

Fatal error:
File appending requested, but 3 of the 4 output files are not present or are
named differently. For safety reasons, GROMACS-2016 and later only allows
appending to be used when all files have the same names as they had in the
original run. Checkpointing is merely intended for plain continuation of
For safety reasons you must specify all file names (e.g. with -deffnm), and
all these files must match the names used in the run prior to checkpointing
since we will append to them by default. If the files are not available, you
can add the -noappend flag to mdrun and write separate new parts. For mere
concatenation of files, you should use the gmx trjcat tool instead.

why is this error coming in spite i have all the above files in my workin
directory and i have not changed any names neither have edited any of

With Best Regards,

Research Scholar,
Department of Chemistry, NITK.

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