Re: [Swarm-Support] Query regarding changing seed in a RNG

[Paul Johnson]

Kavita Gangal wrote:
> Hello,
> My problem is as follows:
>
> I need to generate varying series of random integers between 1 and 60 using 
> swarm Random Number Generators.
> Currently I am using the following syntax:
>
> Globals.env.uniformIntRand.getIntegerWithMin$withMax (1,60);
>
> But it turns out that, in this, the Initial seed can not vary. So each time 
> when the program is run, it generates the SAME series.
>
> And, 
Yes, the sequence is the same every time because we want to make sure 
models are replicatable.  If you want to change the seed, you can do so. 
   The command line option to set the seed for the default RNG is -S 
and in your code you can set the seed easily. the setStateFromSeed 
command tells a generator to do so:

  [myGenerator setStateFromSeed: 46464];


Here's an obj-c example where I grab a random number integer from the 
default randomGenerator and use that as a seed for a new MT19937 generator
    long initseed =  [randomGenerator getUnsignedSample];
    aGenerator = [MT19937gen create: aZone
                         setStateFromSeed: initseed];


And then that generator is used to initialize a new uniform distribution

    uniformDist1 = [UniformDoubleDist create: aZone setGenerator: 
aGenerator setDoubleMin: 0.0 setMax: 1.0];


IN your case, I think you should follow this same logic.  Either use the 
builtin randomGenerator or create a new one, then create a distribution 
object.


  myDist = [UniformIntegerDist: aZone setGenerator: myGenerator 
setIntegerMin: 1 setIntegerMax: 60];


Or, if you already have the distribution object in hand, you can just do

 [myDist setIntegerMin: 1 setMax: 60];


--
Paul E. Johnson                       email: address@hidden
Dept. of Political Science            http://pj.freefaculty.org
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University of Kansas                  Office: (785) 864-9086
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