Oh, by the way, Ryan,
If you really want to randomize the set of random seeds, use jEPlus. You can specify the EMS random seed as a parameter, and then generate a random sample with
a jEPlus random seed. This will ensure you get the same set of E+ random seeds every time. A few experiments with “random random seeds” may be able to tell you (and us) if 1, 2, 3… is good enough.
Cheers,
Yi
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
On Behalf Of Yi Zhang
Sent: 06 June 2013 11:49
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: RE: [EnergyPlus_Support] Re: How to properly set the random seed for stochastic processes in EMS?
Ryan,
I guess you can assume that the intrinsic Fortran random number generator is as good as any standard RNGs. So using 1, 2, 3 …, 1000
‘should’ give you what you want, without showing any obvious patterns. On the other hand, if there are problems with the RNG, you are unlikely to improve your chance by ‘randomizing’ the random seeds; just think about buying lottery tickets…
Brent,
I think the exception comes from the “FuncRandSeed” function (in RuntimeLanguageProcessor.f90) taking @SEEDRANDOM operand as a float,
and then converting it into integer… The simple solution will be put the acceptable range for random seed in the user’s manual
J The random seed handling in v8.0 is a big improvement over v7.x, by the way.
Cheers,
Yi
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
On Behalf Of Griffith, Brent
Sent: 05 June 2013 23:18
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: RE: [EnergyPlus_Support] Re: How to properly set the random seed for stochastic processes in EMS?
Ah that is difficult to answer definitively, but I would not make that assumption. EMS is using Fortran intrinsics here and the implementation
is actually in the CPU hardware. So different computer chips will behave differently. I agree with your reasoning but if you were getting sufficiently random sequences in V7.2, then it may be that integers 1,2,3,… will suffice in V8.0.
If I can ask another question, would I be limiting the random number generator if I just used the integers 1,2,3,...,1000 as seeds? would this lead to somehow similar, or ordered sequences of random numbers? My assumption is yes, which is why i want to use
seeds distributed across the entire range of possi ble integers.
Thanks again,
Ryan
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