You can implement a reasonable split if you can fast-forward the generator. There's no known method to fast-forward the MT, but other generators like MRG32k3a can handle it.
-- Lennart On Thu, Feb 26, 2009 at 12:08 PM, Bertram Felgenhauer <bertram.felgenha...@googlemail.com> wrote: > hask...@kudling.de wrote: >> Do you think it would be feasable to replace the GHC implementation >> of System.Random with something like System.Random.Mersenne? > > There's a problem with using the Mersenne Twister: System.Random's > interface has a split method: > > class RandomGen g where > split :: g -> (g, g) > > The Mersenne Twister is good at producing a single stream of random > numbers - in fact it works by generating a whole block of random > numbers in one go, then consuming the block, and only then generating > the next block. > > I have no idea how to implement a split method that produces > independent streams. Even if I did, using split a lot would likely > spoil the performance benefit of the generator. > > (System.Random.Mersenne.Pure64 provides a RandomGen instance for > PureMT, but it cheats:) > > split = error "System.Random.Mersenne.Pure: unable to split the mersenne > twister" > > Bertram > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
