Re: [AMBER] regarding random number generator

From: Ross Walker <ross.rosswalker.co.uk>
Date: Sat, 14 Aug 2010 11:28:22 -0700

Hi Sangita

> So if I use ntt=1,tempi=0 and tempo=300 then should I set ig value or I
> can do
> without it.
> Is it necessary to set ig value during MD simulation or will it
> consider default
> value
> 71277.

No, with the Berendsen thermostat the random number stream is used only to
seed the initial velocities when the initial temperature is non-zero. If you
are restarting the velocities are read from the restart file so no seeding
of velocities is done and the random number stream is not used.

You can try this out for yourself. Try setting up a 100 step run, with
ntpr=1. Then run it 3 or 4 times from the same restart files just changing
the value of ig each time and you should see that the results are the same
if you use ntt=1 but different if you use ntt=3.

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 |
| 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 Sat Aug 14 2010 - 11:30:03 PDT
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