Hello,
I have been using GROMACS for some very long (in wall clock terms)
simulations, and am curious as to how other users on this list solve the
problem of checkpointing long MD runs. It's a problem because of the
tendency of computational nodes in large HPC facilities (the more
processors, the more prevalent the problem, it seems) to keel over near
the end of a very time consuming run. Intermittent disk and scheduler
faults can also trigger such conditions.
Checkpointing at the operating system level is very system-specific, and
occasionally compilers can produce executable 'dump' files that continue
from where your program left off, but I'm thinking that someone must
have automated this process directly using conventionally-compiled
GROMACS executables.
Of course, it is possible to do an exact continuation from a crashed run
using .edr and trajectory (.trr) files by generating a new .tpr from the
last trajectory frame that had both position and velocity data. This
seems to be, by necessity, an entirely interactive process (unless
someone out there has a cool auto-restart script ..).
I am thinking more in terms of 'proactive' checkpointing for long jobs,
by the following process:
A script parses the desired .mdp file describing the user's MD run of T
timesteps, then asks the user how many sections (N) to split the run
into. The script will then auto-generate a shell script containing all
the necessary GROMACS commands to:
* Generate a new .mdp file almost identical to the original, but with
the number of timesteps set to T/N.
* Run N successive mdrun commands, where the output .trr and .edr files
from each short run using the modified .mdp file are used, to generate
an 'exact restart' .tpr file for the next 'mdrun' command, with the
appropriate continuation flag set.
* Log (to a file) how many of the N partial runs have been completed, in
such a way that if the shell script containing the commands is
restarted, it will jump to the correct point in the sequence, restarting
from the most recently completed partial run.
Has anyone else already solved this problem, or have a method
implementing some of the desirable properties above that I can then
extend to do exactly the things described above?
--
Dr. Steven R. Kirk <[EMAIL PROTECTED], [EMAIL PROTECTED]>
Dept. of Technology, Mathematics & Computer Science (P)+46 520 223215
University West (F)+46 520 223299
P.O. Box 957 Trollhattan 461 29 SWEDEN http://beacon.webhop.org
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