Thanks for the reply Chris :).

It is not possible to get the data with -b option, since trjconv crashes when 
it meets the corrupted frame.

I never had corruption issues in the past and thereby didn't use gmxcheck early 
enough to avoid the second corruption. The problems should have occurred in 
runtime and I strongly suspect they took place at continuation points. I used 
Gromacs 4.5.6.

If .trr formatted frames start with a specific number, I would be grateful if 
anyone of the developers of Gromacs could share it. Otherwise, I will contact 
the developers of gmx_rescue.

Best,
Yiannis


If the corrupted frame is at 1000 ps, and you can not get at the data after the 
corrupted frame by using:
trjconv -b 1100 , then I suspect that you don't have any good solution here, 
unless the developers put in
some type of magic number at the start of each frame that you could search for 
with a c program (perhaps
contact the developers of gmx_rescue for advice?)

A related question is how you ended up with a long .trr file that has 
corruption in the middle.
Did that corruption happen at runtime or later due to a filesystem problem? If 
it was a later filesystem
problem, then you might look into backup solutions. If it happened at runtime, 
then it would be
useful to figure out what happened because ideally gromacs would not forever 
append to corrupted files
since many of us don't look at information in the .trr files until very late in 
the analysis and an optional
0.1% loss in efficiency might be reasonable to ensure that this doesn't happen 
(at least our system admins
would tell us so). For that, you'll probably need to provide details, including 
what version of gromacs you
used.

Chris.

-- original message --

I have some corrupted frames in different trajectories. gmxcheck with .trr 
trajectories gives extraordinary positions or velocities and with .xtc 
trajectories gives rise to the magic number error. I am aware of the program 
gmx_rescue kindly offered to us by its developers. However, this program can 
only work with .xtc files. It is possible to rescue .trr files when there is a 
maximum of one corrupted frame by checking the size of healthy frames, chopping 
the parts of the trajectory before and after, using e.g. programs head and tail 
with the corresponding integer multiples of one healthy frame in bytes and 
stitching them together. However, when there is two or more corrupted frames in 
different locations, although it is not hard to spot the exact locations, it is 
no longer possible to remove the problematic frames size-wise (or at least it 
is less likely to succeed than winning the lottery) , since the size of each 
corrupted frame is non-standard. Is there any corresponding s
 oftware to gmx_rescue that can be used with .trr files? Is there any other 
recent program or any other way of coping with the problem? I did not post any 
details of my systems or the specific error messages I get because I believe my 
question is clear.

Thank you in advance!

Best,
Yiannis
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