[gmx-users] number of frames in trajectory

Berk Hess gmx3 at hotmail.com
Mon Jul 5 17:27:17 CEST 2004

>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
This is not implemented in Gromacs.


>Hi David,
>There's no way of doing that without reading to the end - when we write  
>the first frame we don't know if the simulation will be stopped with a  
>signal or crash for some reason. The user might also have concatenated  
>trajectories from several runs, so don't trust the tpr file either...
>Theoretically you could imagine back and setting the number of frames  in a 
>header when the simulation is finished, but that type of random  file 
>access wouldn't work on a lot of filesystems.
>On Jun 29, 2004, at 5:36 PM, David L. Bostick wrote:
>>Dear all,
>>I am writing an analysis code, and I want to know the best way to get  the
>>number of frames contained in a trajectory file ... preferably w/o  
>>all the frames.  I saw in statutil.h the nframes_read() function, but  I'm
>>not sure if this is what I need.

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