On Wed, Sep 15, 2010 at 1:46 AM, Simon Peyton-Jones
| > (Oh now I see Ivan mentions existing PRNGs that don't (can't?) support | > split... that may be a reasonable argument; I'll have to think about it; is | > this the main motivation? or just one observation among many?) | | I think it's the main one; that things like the Mersenne twister can't be | made instances of Random has stuck in people's craws for a while.
In GHC's unique-supply generator we use a trick due to Lennart Augustsson to turn a linear generator (such as the Mersenne twister) into a splittable one.
Code is here: http://darcs.haskell.org/ghc/compiler/basicTypes/UniqSupply.lhs
Maybe the same would work for Mersenne.
(Yes it uses unsafeInterleaveIO under the hood.)
Simon
Here's a go at it: http://hpaste.org/30094/any_randomgen_can_be_splitable I haven't done any benchmarking to see how much overhead there is to wrapping a random generator with this. I could probably switch to using atomicModifyIORef, but I don't have much experience with it. Feedback is welcome. Antoine