On 11/03/11, Anna Marabotti  <[email protected]> wrote:
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> Dear 
> all,
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> a very quick 
> question: I 
> would like to know if a checkpoint file produced with a simulation with 
> Gromacs 
> contains really ALL information needed to restart a simulation; or better, if 
> I 
> keep only the .cpt file and the .xtc file of a simulation, which 
> information I lost (apart from the precision of the result)? At present I'm 
> keeping he .trr files (which contains all information) only to be sure I can 
> restart a simulation, but I need DESPERATELY free disk 
> space...
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> 




There is no longer any need to keep a .trr unless you can identify a reason 
(e.g. keeping velocities, or you need full precision for some analytical 
purpose). The .cpt has a full-precision trajectory frame + state variables in 
it. You should be able to see that the .cpt file size is around 2/N of the size 
of a positions-only N-frame .trr file, because it has full-precision arrays of 
positions and velocities, plus a little bit more.

You can easily satisfy yourself that the .cpt restarts are exact - get a small 
water box and do both a split run and two part runs from the same initial 
conditions on a single processor using mdrun -reprod.

Mark
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