[gmx-users] number of frames in trajectory

[Erik Lindahl]

Hi,

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.


Cheers,

Erik