[gmx-users] double and single precision

Mark Abraham Mark.Abraham at anu.edu.au
Mon Feb 20 09:26:30 CET 2012

On 20/02/2012 7:19 PM, Edvin Erdtman wrote:
> Hi
> I have been running GMX in double precision and by mistake an extension
> of a run in single precision was written to the same files.
> When I run for example gmxcheck or g_energy I get the following error
> after the program has scanned through the double part:
> Fatal error:
> Energy header magic number mismatch, this is not a GROMACS edr file
> If you want to use the correct frames before the corrupted frame and
> avoid this fatal error set the env.var. GMX_ENX_NO_FATAL
> For more information and tips for troubleshooting, please check the
> website at http://www.gromacs.org/Documentation/Errors
> Can I do something to divide the file into a double and a single part?

We should probably put in a check to prevent this occurring (and an 
environment variable to override it?).

I expect you can get the first part back through using eneconv -e and 
the above environment variable.

I can't think of a way to access the second (and subsequent) parts 
without writing new code - but perhaps that code should exist anyway, 
emitting a warning that a change of precision was detected.


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