Re: Is there solution to numerical inaccuracy

From: Himanshu Khandelia (hkhandel_at_memphys.sdu.dk)
Date: Thu Nov 22 2007 - 02:19:55 CST

> Hi,

> For different parallel runs, NAMD will perform non-deterministically, in the
> sense that the order of completion of different processors (and even the work
> that is assigned to them) will likely change, altering the order of summed
> energies. Due to the non-associativity of floating point addition, you should
> eventually see slightly different energy values from two parallel runs of an
> identical trajectory.

I thought the non-reproducibility of simulations in NAMD was mainly
because of the Berendsen pressure controller employed, which gives random
kicks to particles every few steps. Whether or not the run is parallel, I
do not think the trajectories will be reproducible, although I have not
tested this myself.

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