Re: [AMBER] rounding issue

From: Ross Walker <ross.rosswalker.co.uk>
Date: Tue, 3 Jan 2012 10:50:48 -0800

Hi Dmitry,

> NSTEP =167945000 TIME(PS) = 335990*.000* TEMP(K) = 301.78 PRESS
> NSTEP =167945500 TIME(PS) = 335990*.999* TEMP(K) = 298.40 PRESS
> NSTEP =167946000 TIME(PS) = 335991*.999* TEMP(K) = 296.82 PRESS
> NSTEP =167946500 TIME(PS) = 335992*.999* TEMP(K) = 300.10 PRESS

I assume the issue you are referring to here is that suddenly the time is
being printed as X.999 instead of X+1.000 - I have seen this happen before
although I have never been able to track it down. It is definitely a
rounding issue and is almost certainly compiler dependent. I guess one
solution would be to calculate the time in the code from the integer NSTEP +
the initial time from the restart file rather than just incrementing the
time each time. It could also be easily fixed by tweaking the time printing
format in the mdout file. I'll list it as a bug and see if there might be an
easy way to address it. In the meantime you'll probably just have to tweak
your post processing scripts a little to round it up. If you are plotting
the results vs time though it should make any difference to what the plot
looks like etc.

If the issue seems to be more major than this - I.e. the time actually
'jumped' several ps then let me know.

All the best
Ross

/\
\/
|\oss Walker

---------------------------------------------------------
| Assistant Research Professor |
| San Diego Supercomputer Center |
| Adjunct Assistant Professor |
| Dept. of Chemistry and Biochemistry |
| University of California San Diego |
| NVIDIA Fellow |
| http://www.rosswalker.co.uk | http://www.wmd-lab.org/ |
| Tel: +1 858 822 0854 | EMail:- ross.rosswalker.co.uk |
---------------------------------------------------------

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Received on Tue Jan 03 2012 - 11:00:03 PST
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