[gmx-users] number of frames in trajectory

Erik Lindahl lindahl at csb.stanford.edu
Mon Jul 5 17:37:35 CEST 2004


On Jul 5, 2004, at 5:27 PM, Berk Hess wrote:

>> From the frame header you can calculate the frame size and
> then you can immediately set the framepointer to the next frame.
> I think g_openmol does this. This is much faster than reading
> everything.
> This is not implemented in Gromacs.
Right, that works for xtc files to if you peek inside the format.

The reason it isn't implemented by default in Gromacs is that file 
positioning for large offset (64-bit) streams isn't part of the XDR 
standard. It probably would work on many architectures, at least for 
relative offsets, but we can't count on it.



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