AMBER Archive (2008)

Subject: AMBER: Initial velocities based on date and time are NOT changing ?

From: Markus Kaukonen (markus.kaukonen_at_iki.fi)
Date: Mon Dec 15 2008 - 07:14:38 CST

Dear Amber,

I was trying to get random initial velocities for atoms (using AMBER
9) based on date and time:

Manual amber10 page 30
> If ig=-1, the random seed will be based on the current date and time, and hence will be different for every run.

My input:

50 ps MD equilibration NVT
 &cntrl
  irest=0,ntx=1,
  nstlim=50000,dt=0.001,
  temp0=300.0,ntt=1,tautp=1.0,ig=-1,tempi=300.0,
  ntc=2,ntf=2,
  cut=9,
  ntpr=10000,ntwx=0,ntwv=0,ntwe=0,iwrap=1
 &end

Problem:
to me it seems that the initial velocities are identical when
comparing different runs when having ig=-1
since the temperature at step 0 remains exactly the same.
If I manually change ig=SOME POSITIVE NUMBER
the velocity at step 0 is changing (as it should).

Could somebody check this? The program was compiled using ifort .

Terveisin Markus 

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