[Haskell-cafe] Performance problem with random numbers

Don Stewart dons at galois.com
Sat Oct 13 17:37:39 EDT 2007

> ntupel wrote:
> >Thanks for your reply Stefan. Unfortunately I could measure only a
> >relatively small improvement by changing to concrete types
> >the sample code was about one second faster when compiled with -O2.
> >Profiling again indicated that most time was spend in random and randomR
> GHC StdGen's random and randomR are somewhat slow.  I found that 
> changing to a custom ((x*a + b) `mod` c) random-generator (instance of 
> RandomGen) much sped things up (since nothing depended on the random 
> numbers being good quality).  (Then I switched to a small C function to 
> do the randomization and make all the OpenGL calls, and it sped up by 
> another factor of 4.)

I've seen similar results switching to the SIMD mersenne twister C
implementation for randoms:

If there's interest, I can package up the bindings for hackage.

-- Don

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