Re: [xsl] help with random number generation

["Dimitre Novatchev dnovatchev@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Michael,

Reading the requirements you listed, it seems to me that you need:

      Num-TimeSlices * NumNodesPerTimeSlice

different random numbers.

Why not generate a sequence of random numbers with this length?

This will require a single seed, that you could use based on the current
time (the start of the simulation).

Thus, for every simulation there will be a different seed.

In case you need the seeds to be not too-close, you  could generate a
separate sequence of random numbers each of which to be used as the seed
for a separate simulation.

Or maybe I don't understand the requirements well?

Thanks,
Dimitre

On Thu, Nov 17, 2022 at 8:02 AM C. M. Sperberg-McQueen
cmsmcq@xxxxxxxxxxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

>
> "Martin Honnen martin.honnen@xxxxxx" <
> xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> writes:
>
> > On 11/16/2022 8:31 PM, C. M. Sperberg-McQueen cmsmcq@xxxxxxxxxxxxxxxxx
> > wrote:
> >> Some readers of this list may know enough about pseudo-random number
> >> generators and their use to advise me.  I hope so!
> >>
> >> ...
>
> >
> > In what setting do you work?
>
> At the moment, I am running the XSLT of the simulator from bash, using
> Saxon HE.  I like that environment, but if getting the simulation to
> work correctly requires moving into a different environment (running
> from within Oxygen, rewriting in XQuery, ...), then I can change to that
> environment (within reason -- rewriting in a language other than XSLT or
> XQuery is not a path I would willingly take -- well, maybe Prolog or
> Lisp).
>
> > With Saxon PE/EE (and I think SaxonJS) there is saxon:timestamp() so e.g.
> >
> >   <xsl:accumulator name="rnd" as="map(*)"
> > initial-value="random-number-generator(saxon:timestamp())">
> >     <xsl:accumulator-rule match="*" select="$value?next()"/>
> >   </xsl:accumulator>
> >
> >
> > might work better than
> >
> >
> >   <xsl:accumulator name="rnd" as="map(*)"
> > initial-value="random-number-generator(current-dateTime())">
> >     <xsl:accumulator-rule match="*" select="$value?next()"/>
> >   </xsl:accumulator>
>
> Thank you; that's worth knowing.
>
> I don't think I can usefully use accumulators in this application,
> though, since each time I process the tree describing the state of the
> simulation, the root node would get the same two random numbers.  So at
> each time slice in a particular execution of the simulation, it would
> behave in exactly the same way.  That won't work for my purposes,
> because it will not produce a random sample of the space I want to
> explore.
>
> In order for the simulation to produce a random sample of the logical
> space inhabited by the process being modeled, the random numbers
> generated for any given node in one time slice need to be independent of
> those generated in the preceding or next time slice.
>
> > The rest of your requirements were too complicated for me to follow
> > through.
>
> In a given run, any given node will be processed many times (for as many
> time slices as the node is 'alive'); for each 'live' node, I need two
> random numbers during each time slice.  The requirements, as I
> understand them, are:
>
>   - The numbers generated for a given node on one time slice need to be
>     independent of those generated for that node in other time slices.
>
>     (This is why an accumulator doesn't seem to work for me -- no way to
>     make the value of the seed differ sufficiently from time slice to
>     time slice.)
>
>   - The numbers generated for a given node on one time slice need to be
>     independent of those generated for other nodes (e.g. siblings,
>     children) in that time slice.
>
>     If siblings (for example) tend to get similar random numbers, then
>     siblings will have a marked and disproportionate tendency all to
>     behave in the same way in the simulation.
>
>   - In different executions of the simulator, it is desirable that
>     different numbers be generated -- otherwise running the simulator
>     100 times will produce 100 copies of the same result, rather than
>     100 random samples from the logical space of the process.
>
> My current methods of generating random numbers for different nodes seem
> to have trouble with the second and third of these requirements.  I
> think this is related to the phenomenon noted by Mike Kay in his
> response to my query: when seeds are 'too similar' (e.g. if they are all
> small integers), calling random-number-generator() with those seeds will
> produce results which all have the same first few digits and are not
> randomly distributed in the interval (0, 1).
>
> Michael
>
>
> --
> C. M. Sperberg-McQueen
> Black Mesa Technologies LLC
> http://blackmesatech.com