Adwait Mevada wrote:

On 01/20/11, Adwait Mevada  <adw...@imsc.res.in> wrote:

 Dear gmx-users,
I am simulating a dppc + chol system, the force field is martini with gromacs 3.3.3 the system was initially run for 150 ns, but i had to later extend the simulation, so using the confout.gro and with mdp options:
gen_vel = no
unconstrained_start = yes
I gave a re-run for another 850 ns, now due to some interaction the box explodes after 460ns of run.I found that the cause was due to some unwanted bad contact. It is important that the system continue from the previous state, but the extension is leading to this bad contact.


Actually, you didn't preserve your ensemble if you used the .gro file for the coordinates. See http://www.gromacs.org/Documentation/How-tos/Doing_Restarts Actually providing us with copies of the commands you're using is always a good idea when asking for help.

150ns.gro was the output of the previous simulation run i.e. confout.gro
mdp file for the previous simulation is taken as is except for change of
simulation steps and making unconstrained_start = yes
grompp -np 8 -f 850ns.mdp -p dppc_chol.top -c 150ns.gro -o 512lip_256chol_850ns.tpr

As Mark suspected, you have failed to preserve your ensemble, due to the fact that you're using a reduced precision (.gro) format for coordinates, and you are not supplying the .trr and .edr file from the previous run, so you're losing velocities, temperature and pressure coupling information, etc.

-Justin

mpiexe.openmpi -np 8 mdrun_mpi.openmpi -np 8 -s 512lip_256chol_850ns.tpr -o 512lip_256chol_850ns -e 512lip_256chol_850ns -g 512lip_256chol_850ns &

Mark


My question is, is there a way to avoid this while retaining the continuation of the previous simulation? Is using lower precision file a solution to this problem? if yes how do i go about it.
-Adwait

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-Adwait

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--
========================================

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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