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[EnergyPlus_Support] Re: How to properly set the random seed for stochastic processes in EMS?

Hi Edwin,

Thanks for your input. My issue is not with the implementation, but rather with choosing the proper range of integers. As I noted in my post, sometimes energyplus crashes when the integer is too large. Specifically, 2^31 or larger numbers cause it to crash on the machine I'm using. So the solution is to never use a seed larger than (2^31-1). Thanks to Brent for providing that answer.

Ryan

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Edwin Lee <leeed2001@...> wrote:
>
> Without having the documentation at hand, I can only offer my thoughts on
> an option.  You could generate those 1000 seeds separately, and set them
> for each of the 1000 runs.  I am assuming you are running this as a script,
> so you could use a command line tool such as `sed` to search and replace a
> string in each case, pulling from a pre-calculated base of 1000 random
> numbers.
> 
> 
> On Tue, Jun 4, 2013 at 7:11 PM, Ryan_Element <ryan_element@...> wrote:
> 
> > **
> >
> >
> > Greetings,
> >
> > I have a working energyplus model that uses the @SeedRandom object
> > (function) in the EnergyManagementSystem.
> >
> > I understand that to ensure a repeatable sequence of numbers, the argument
> > to the @SeedRandom field must be the same each time.
> >
> > My question is, what is the proper range of numbers that I can use to
> > specify the random seed? 0-100? 1-1,000,000? And given the proper range,
> > will every unique integer result in a unique sequence of random numbers? I
> > ask for two reasons
> >
> > 1. large numbers (e.g. 3867681373) cause something deep in energyplus to
> > break (Energyplus Version 8.0.0), resulting in a fortran runtime language
> > error:
> > --error snip--
> > forrtl: error (140): floating inexact
> > Image PC Routine Line Source
> >
> > Stack trace terminated abnormally.
> > /Applications/EnergyPlus-8-0-0/runenergyplus: line 493: 78098 Abort trap:
> > 6 "$ENERGYPLUS_DIR/bin/$PRG_N"
> > --error snip--
> >
> > 2. In the past (Energyplus Version 7.0.0), I noticed that very large
> > numbers that are close to one another (e.g. 3867681373 and 3867681374)
> > result in the same sequence of random numbers in spite of being unique
> > integers.
> >
> > The I/O reference provides this detail on the argument to @SeedRandom:
> > The argument is rounded to the nearest whole number and then used to set
> > the size and values of the seed for the number generator.
> >
> > Can anyone provide more information? I want to ensure that 1000
> > simulations get 1000 unique sequences of random numbers. And then I want to
> > be able to repeat those 1000 simulations, and get the same results, so I
> > need to explicitly set 1000 unique random seeds.
> >
> > Cheers,
> > Ryan
> >
> >  
> >
> 
> 
> 
> -- 
> Edwin Lee, PhD
> Oklahoma State University
>




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