[gecode-users] How to set an arbitrary RandomGenerator for randomized branching?!?

[Mikael Zayenz Lagerkvist]

Hi,

Currently it is not possible to exchange the random number generator.
Furthermore, the implementation uses properties of the random number
generator that would most probably compromise efficiency if they were
abstracted away (for example, the state is limited to a single
unsigned int as seed). If you want to use your own random number
generator, I would suggest writing your own subclasses of ViewSelBase
and ValSelbase similar to ViewSelRnd and ValRnd.

For curiosity, what is the reason that you want to change the random
number generator used?

Cheers,
Mikael

On Sat, May 16, 2009 at 12:37 AM, Martin Mann
<mmann at informatik.uni-freiburg.de> wrote:
>
> Hi everybody,
>
> I digged a bit into the Gecode source about the randomized branching
> supported since version 3.
>
> In line 124 in gecode/support/random.hpp I found the definition of
> RandomGenerator internally used in the view selection:
>
> http://www.gecode.org/doc-latest/reference/group__FuncSupport.html#g02fe942f90a57a25639f09960dab4459
>
> As given there, it is just a typedef onto the
> LinearCongruentialGenerator provided by Gecode but I would like to set
> up my own random number generator...
>
> Is there a possibility to support user defined generators? e.g. in
> coming versions?
>
> If not available right now, maybe you like the following suggestion:
>
> A possibility would be a super class 'RNG' that has to be implemented by
> every generator plus a kind of factory class 'RNF' with static members only.
> The RNF would be a wrapper around the current RNG instance to use
> (stored in a static internal member). Thus, all Gecode internals that
> need a random number use a static interface of RNF instead of some RNG
> instance members. So the library gets independent of the concrete RNG
> used and you get the possibility to register a user defined RNG within
> the RNF. Per default the RNF can use the linear congruential generator
> provided. The static interface and data member would avoid annoying
> copies of RNGs all around and won't complicate your Gecode internals/source.
>
>
> Just a suggestion... if it is already possible just ignore and please
> let me know how to do with the current Gecode version. :)
>
>
> Have a nice weekend,
>
> Martin
>
>
> _______________________________________________
> Gecode users mailing list
> users at gecode.org
> https://www.gecode.org/mailman/listinfo/gecode-users
>



-- 
Mikael Zayenz Lagerkvist, http://www.ict.kth.se/~zayenz/