Hi Oliver,
You are not specifying tempi. Thus it defaults to 0.0. Hence there are no
initial velocities and therefore the random number generator is not used
(with ntt=1). Hence the value of ig will have no effect and your simulations
will therefore be totally deterministic as you observe. Any differences you
see with the CPU version are just the result of divergence caused by
rounding differences during summation which the GPU code is not affected by.
All the best
Ross
> -----Original Message-----
> From: Oliver Kuhn [mailto:oak.amber.googlemail.com]
> Sent: Friday, February 24, 2012 8:37 AM
> To: AMBER Mailing List
> Subject: [AMBER] same simulation using different random seeds on GPU
>
> Hi.
>
> I want to use differing initial random velocities for simulations
> running
> on GPU.
> That has always been working on CPU, but on the GPU I get exactly the
> same
> simulation.
>
> For example, input 1 is:
>
> production simulation (NPT) - 2 ns
> &cntrl
> ig=1,
> irest=0,ntx=1,
> nstlim=1000000,dt=0.002,
> temp0=300.0,ntt=1,tautp=1.0,
> ntc=2,ntf=2,
> cut=9,
> ntpr=500,ntwx=500,ntwv=0,ntwe=500,iwrap=1,
> ntb=2,ntp=1,pres0=1.0,taup=1.0,
> ntr=0
> /
>
> and another input has ig=41
> giving me same simulations!?
>
> As I googled, I found a comment from Ross that GPU uses different
> random
> number generators.
> I'm quite sure he does not mean also different syntax in using it.
> Has anyone experienced similar problem and can help me?
>
> Greets,
> Oliver
>
> --
> Oliver Kuhn, Department of Bioinformatics,
> Center for Medical Biotechnology, University of Duisburg-Essen,
> Universitätsstr. 1-5, 45141 Essen, Germany
> phone +49 201 183-3121, oliver.kuhn.uni-due.de
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Received on Fri Feb 24 2012 - 09:30:02 PST
