On Thu, Jun 4, 2009 at 10:31 AM, Robert Duke<rduke.email.unc.edu> wrote:
> Well, I would not recommend doing that. It looks to me like there is
> nothing to stop one from doing this in the code, but the random number
> initialization code clearly states the seed should be > 0. I would have to
> dink with it to see what really happens when you do this.
> [...]
Bob, please correct me if I'm wrong here but, looking at the
random.fpp file in pmemd/src dir, it lloks like the seed provided by
the amber input is used to generate two internal seeds, is1 and is2:
=======================================================
data is1max, is2max /31328, 30081/
! Construct two internal seeds from single unbound Amber seed:
!
! is1 and is2 are quotient and remainder of iseed/IS2MAX. We add
! one to keep zero and one results from both mapping to one.
! max and min functions keep is1 and is2 in required bounds.
is1 = max((iseed / is2max) + 1, 1)
is1 = min(is1, is1max)
is2 = max(1, mod(iseed, is2max) + 1)
is2 = min(is2, is2max)
========================================================
So, if you enter a seed of "-1", both is1 and is2 will end up being 1.
There's nothing "illegal" about that, but then you are again always
running your calculation with the same seeds.
Gustavo.
_______________________________________________
AMBER mailing list
AMBER.ambermd.org
http://lists.ambermd.org/mailman/listinfo/amber
Received on Sat Jun 06 2009 - 01:07:55 PDT
