[Shootout-list] Re: Improvements to ocaml Random entry

[Yaron Minsky]

Actually, on my poor-old 700Mhz machine, it's almost twice as fast for
large n.  Here are the timings.

dragonfly: yminsky $ time ./foo1 10000000
41.548068

real	0m1.305s
user	0m1.287s
sys	0m0.003s
dragonfly: yminsky $ time ./foo 10000000
41.548068

real	0m0.713s
user	0m0.696s
sys	0m0.005s
dragonfly: yminsky $ 

On Thu, 17 Jun 2004 22:07:02 -0400, Yaron Minsky <yminsky@gmail.com> wrote:
> 
> I've got a somewhat improved version of the ocaml random number
> generator.  it's a bit longer in lines, but only because it's in more
> idiomatic ocaml form.  For some reason, the ocaml entries all seem
> artificially low on carriage returns.
> 
> Anyway, this is more straightforward and about 15-20% faster (at
> least, when the RNG function is run in a tight loop.  I'd think
> everything would get dwarfed by the printf in the shootout.)
> 
> let im = 139968
> and ia = 3877
> and ic = 29573
> and first_last = 42
> let n = try int_of_string Sys.argv.(1) with _ -> 1
> 
> let rec gen_random max last i =
>   let new_last = (last * ia + ic) mod im in
>   if i > 1 then gen_random max new_last (i - 1)
>   else max *. float_of_int new_last /. float im
> 
> let () = Printf.printf "%9f\n" (gen_random 100.0 first_last n)
>