[gmx-users] Using mdrun -rerun to get energy values

[Krzysztof Mlynarczyk]

Hi,

You need to use md integrator for -rerun to work.

Good luck,
Chris

2010/11/6 Martin Kamp Jensen <martin.kamp.jensen at gmail.com>

> Hello,
>
> Hopefully someone can help me understand how to use the mdrun -rerun
> functionality, because currently I am confused. I would like to be able to
> look up potential energy values for a number of conformations by calling
> mdrun -rerun once.
>
> The idea to use mdrun -rerun is from advice given to me by Mark Abraham on
> the gmx-developers list (
> http://lists.gromacs.org/pipermail/gmx-developers/2010-September/004731.html
>  and
> http://lists.gromacs.org/pipermail/gmx-developers/2010-October/004770.html
> ):
>
> You want GROMACS to find the energy of a potentially infinite set of
>> coordinates that appear magically, and that is what mdrun -rerun does.
>
>
>> The elegant way to do that is to write your series of conformations to a
>> pseudo-trajectory (in whichever of GROMACS many trajectory formats is
>> convenient to you), and then invoke mdrun -rerun on that trajectory with a
>> suitable .tpr. Then you either parse the .log file or the output .edr file
>> for the energies.
>
>
> I wanted to find out how this works so I have been experimenting. I started
> out by looking at the Peptide tutorial at
> http://manual.gromacs.org/current/online/speptide.html. I used three
> different mdp files (integrator = steep, nsteps = 0, 1, 2). This gave me
> three conformations and their energy values. For testing purposes I then
> wanted to get the energy values for those three conformations using mdrun
> -rerun (and since I already have the correct energy values it is easy to
> verify the results).
>
> First, I created a trajectory by concatenating the three conformations (gro
> files) into one gro file (which is okay according to
> http://manual.gromacs.org/current/online/gro.html: "gro files can be used
> as trajectory by simply concatenating files"). I then used an mdp file with
> integrator = steep and nsteps = 0 indicating that I just want the energy
> value (listed in the output, in the log file or by using g_energy). Now, by
> using mdrun -s <tpr file> -rerun <gro trajectory file> I only get the energy
> value for the first conformation listed in the gro file used to create the
> tpr file. The -rerun option does not seem to have any effect at all.
>
> I used the following commands three times to create three different
> conformations (one conf_mdrun.gro file for each time) with different energy
> values. I am just setting nsteps to 0, 1, or 2 (integrator = steep) in
> em.mdp.
>
> pdb2gmx -f speptide -o conf_pdb2gmx -p top_pdb2gmx -i top_pdb2gmx << EOF
>
> 1
>
> 1
>
> EOF
>
>
>> editconf -f conf_pdb2gmx -o conf_editconf -d 0.5
>
>
>> genbox -cp conf_editconf -cs -p top_pdb2gmx -o conf_genbox
>
> mv top_pdb2gmx.top top_genbox.top
>
> mv "#top_pdb2gmx.top.1#" top_pdb2gmx.top
>
>
>> grompp -f em -po em_grompp -c conf_genbox -p top_genbox -o em_grompp
>
>
>> mdrun -s em_grompp -o mdrun -c conf_mdrun -e mdrun -g mdrun
>
>
> I was hoping the following would give me the three energy values for the
> three conformations in 2+1+0.gro, which is the concatenation of the three
> conf_mdrun.gro files from before. However, I just get the energy value from
> the first conformation in the file. Using the -rerun option does not make a
> difference (I can put whatever after -rerun, even files that do not exist,
> without any effect).
>
> grompp -f em -po em_grompp -c gro/2+1+0 -p top_genbox -o em_grompp
>
>
>> mdrun -s em_grompp.tpr -rerun gro/2+1+0.gro
>
>
> Regards,
> Martin.
>
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