Re: Sufficiently large values for 'firsttimestep' can lead to immediate simulation abort.

From: Axel Kohlmeyer (akohlmey_at_gmail.com)
Date: Sun Apr 08 2012 - 12:38:10 CDT

On Sun, Apr 8, 2012 at 1:25 PM, Nikolaos Glykos <glykos_at_mbg.duth.gr> wrote:
>
> Dear Developers,
>
> This is just to mention again an unexpected NAMD behavior when large initial
> values of 'firsttimestep' are used. Excerpts from a log file illustrating
> the
> issue follow :

the symptoms you describe are that of a signed 32bit integer
overflow. it is a little bit premature, since the maximum representable
signed 32-bit integer would be 2,147,483,647. did you ask for
500,000,000 steps or more of additional MD?

cheers,
     axel.

> __________________________________________________________________________________
>
> ...
> Info: NAMD 2.9b2 for Linux-x86_64-multicore-CUDA
> ...
> Info: DCD FIRST STEP         1666100400
> Info: FIRST TIMESTEP         1666100000
> ...
> ETITLE:      TS           BOND          ANGLE          DIHED ...
> ENERGY: 1666100000       134.8295       332.0096       441.0666 ...
>
> OPENING EXTENDED SYSTEM TRAJECTORY FILE
> WRITING EXTENDED SYSTEM TO OUTPUT FILE AT STEP -2128867296
> CLOSING EXTENDED SYSTEM TRAJECTORY FILE
> WRITING COORDINATES TO OUTPUT FILE AT STEP -2128867296
> COORDINATE DCD FILE WAS NOT CREATED
> The last position output (seq=-2) takes 0.036 seconds, 59.082 MB of memory
> in use
> WRITING VELOCITIES TO OUTPUT FILE AT STEP -2128867296
> The last velocity output (seq=-2) takes 0.033 seconds, 59.215 MB of memory
> in use
> ====================================================
>
> WallClock: 0.884799  CPUTime: 0.884800  Memory: 59.214844 MB
> Program finished.
>
> __________________________________________________________________________________
>
>
> --
>            Nicholas M. Glykos, Department of Molecular Biology
>     and Genetics, Democritus University of Thrace, University Campus,
>  Dragana, 68100 Alexandroupolis, Greece, Tel/Fax (office) +302551030620,
>    Ext.77620, Tel (lab) +302551030615, http://utopia.duth.gr/~glykos/
>

-- 
Dr. Axel Kohlmeyer
akohlmey_at_gmail.com  http://goo.gl/1wk0
College of Science and Technology
Temple University, Philadelphia PA, USA.

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