[gmx-users] When are .trr files essential?

[Mark Abraham]

On 12/10/2012 6:27 PM, Jianguo Li wrote:
>
> One situation is the analysis that require velocities, such as calculating velocity autocorrelation function or lateral pressure.

Or forces, for some reason. Also see 
http://www.gromacs.org/Documentation/How-tos/Reducing_Trajectory_Storage_Volume

>>> Hello Friends,
>>>
>>> I have two very specific queries regarding gromacs output files.
>>>
>>> 1) Since we can generate .xtc file during mdrun, Is is possible to
>>> stop generating .trr files, because it used to be very huge and less
>>> useful.
>>>
>> "Less useful" depends on the application, but in many cases yes.
> Hello Eric,
>
> After generating 17 GB of trajectory data, I too am questioning my need for
> .trr files.  Can you take a moment to describe those functions for which
> .trr files are essential?
>
> I can create the PDB files I need to perform visualizations, using trjconv
> and an .xtc file as input.  Macroscopic system parameters are stored in .edr
> files, and can be extracted using g_energy.  If I want to extend a completed
> run, the .cpt file that was written when the run finished allows me to do
> that.
>
> The only reason that I can see for creating a .trr file is if one might need
> to start from an EXACT point somewhere in the MIDDLE of a trajectory.

Yes, but even then you'd generally need .edr file information too.

Mark