Steve Vivian wrote:
Based on a preliminary test using multiple threads, the issue is not
resolved.
This leads me to believe that my Unit Cell is not built properly.
Below is the procedure used to build the unit cell. I have reviewed it many
times, but I would appreciate any input regarding potential improvements,
specifically on the line using trjconv in the EM/Shrink loop.
Safe up to here, (I hope)...
cat KALP_newbox.gro dppc128_whole.gro > system.gro
update minim.mdp
; Strong position restraints for InflateGRO
#ifdef STRONG_POSRES
#include "strong_posre.itp"
#endif
Create Strong Position Restraint for protein
genrestr -f KALP_newbox.gro -o strong_posre.itp -fc 100000 100000 100000
Scale Lipid positions by a factor of 4
perl inflategro.pl system.gro 4 DPPC 14 system_inflated.gro 5 area.dat
Begin loop of repeated Energy Minimizations and Shrinking
(repeat loop approximately 25 times until area is approx 71 Ang sq)
Begin LOOP (from n=1 to n = 26)
grompp -f minim.mdp -c systm_inf_n.gro -p topol.top -o em_n.tpr
mdrun -v -deffnm em_n
trjconv -s em_n.tpr -f em_n.gro -o em_n_out.gro -pbc mol -ur compact
perl inflategro.pl em_n_out.gro 0.95 DPPC 0 sys_shr_1.gro 5
One problem here: you start the loop every time with system_inf_n? What is
system_inf_n? It seems that you should start one (non-loop) shrink and then
process the subsequent shrinking steps from there. At the end of the loop, you
write to sys_shr_1.gro, which then never gets used again.
-Justin
ar_shr1.dat
End LOOP
Add water
Add ions
Re-run EM
Equilibrate (and watch it all explode)
-----Original Message-----
From: gmx-users-boun...@gromacs.org [mailto:gmx-users-boun...@gromacs.org]
On Behalf Of Justin A. Lemkul
Sent: Thursday, March 10, 2011 12:56 PM
To: Discussion list for GROMACS users
Subject: Re: [gmx-users] Fwd: KALP-15 in DPPC Tutorial Step 0 Segmentation
Fault
Steve Vivian wrote:
On 03/08/2011 10:23 PM, Justin A. Lemkul wrote:
Steve Vivian wrote:
New to Gromacs.
Worked my way through the tutorial with relatively few issues until
the Equilibration stage. My system blows up!!
Returned to the Topology stage and rebuilt my system ensuring that I
followed the procedure correctly for the InflateGro process. It
appears to be correct, reasonable lipid area, no water inside my
bilayer, vmd shows a structure which appears normal (although I am
new to this). There are voids between bilayer and water molecules,
but this is to be expected, correct?
Energy Minimization repeatedly produces results within the expected
range.
Again system blows up at equilibration, step 0 segmentation fault.
Regardless of whether I attempt the NVT or Anneal_Npt process (using
the provided mdp files, including the updates for restraints on the
protein and the lipid molecules).
I have attempted many variations of the nvt.mdp and anneal_npt.mdp
files hoping to resolve my issue, but with no success. I will post
the log information from the nvt.mdp file included in the tutorial.
Started mdrun on node 0 Tue Mar 8 15:42:35 2011
Step Time Lambda
0 0.00000 0.00000
Grid: 9 x 9 x 9 cells
Energies (kJ/mol)
G96Angle Proper Dih. Improper Dih.
LJ-14 Coulomb-14
8.52380e+01 6.88116e+01 2.23939e+01
-3.03546e+01 2.71260e+03
LJ (SR) Disper. corr. Coulomb (SR)
Coul. recip. Position Rest.
1.49883e+04 -1.42684e+03 -2.78329e+05
-1.58540e+05 2.57100e+00
Potential Kinetic En. Total
Energy Conserved En. Temperature
-4.20446e+05 *1.41436e+14 1.41436e+14
1.41436e+14 1.23343e+12*
Pres. DC (bar) Pressure (bar) Constr. rmsd
-1.56331e+02 5.05645e+12 1.18070e+01
As you can see the Potential Energy is reasonable, but the Kinetic
Energy and Temperature seem unrealistic.
I am hoping that this is enough information for a more experienced
Gromacs user to provide guidance. Note: that I have tried all of the
suggestions that I read on the mailing list and in the "blowing up"
section of the manual, specifically:
-reduced time steps in Equilibration Stages
-reduced Fmax during EM stage (down as low as 100kJ which did not help)
-modified neighbours list parameters
Any help is appreciated. I can attach and forward any further
information as required, please let me know.
Which Gromacs version are you using? It looks like you're running in
serial, is that correct? Otherwise, please provide your mdrun command
line. If you're using version 4.5.3 in serial, I have identified a
very problematic bug that seems to affect a wide variety of systems
that could be related:
Yes I am currently using Gromacs 4.5.3 in serial.
http://redmine.gromacs.org/issues/715
I have seen even the most robust tutorial systems fail as well, as
some new lab members experienced the same problem. The workaround is
to run in parallel.
If I understand you correctly, the recommended workaround is to
re-configure gromacs 4.5.3 with mpi enabled and complete the
Equilibration and Production simulation in parallel.
Strictly speaking, an external MPI library is no longer required. Gromacs
now
builds with internal threading support (as long as your hardware and
compilers
support such features). In fact, thread support builds by default if
possible,
so if your mdrun has an -nt flag, you don't need to do anything else except
use
"mdrun -nt (number of threads)" when running your command.
Do you have a recommendation for which mpi library to install (lam mpi
seems to be referenced in other articles on the mailing list)?
I've had good luck with OpenMPI in the past, but this is not strictly
necessary
in all cases.
Are there documented installation procedures for this process (upgrading
to gromacs with mpi enabled)?
http://www.gromacs.org/Downloads/Installation_Instructions#Using_MPI
-Justin
Thanks for your assistance.
Steve.
-Justin
Regards,
Steve Vivian.
sviv...@uwo.ca
--
========================================
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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