<span>On 11/03/11, <b class="name">Anna Marabotti </b> <anna.marabotti@isa.cnr.it> wrote:</span><blockquote cite="mid:96175CEE60A44F59AC4EAC141CA18019@AnnaNetbook" class="iwcQuote" style="border-left: 1px solid rgb(0, 0, 255); padding-left: 13px; margin-left: 0pt;" type="cite"><div class="mimepart text html">
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</p><div><font face="Arial" size="2"><span class="437005708-11032011">Dear
all,</span></font></div>
<div><font face="Arial" size="2"><span class="437005708-11032011">a very quick
question: </span></font><font face="Arial" size="2"><span class="437005708-11032011">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...</span></font></div></td></tr></tbody></table></p></span></div></blockquote><table><tbody><tr><td><br /></td></tr></tbody></table>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.<br /><br />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.<br /><br />Mark