Adding the random mersenne twister to gst

> Hi All,
>
> Some time ago Paolo did post a message to see if we could
> change the rng because will fast it was making garbage.
>
> Thus Paolo did suggest to implement the Mersenne Twister.
> So here you can find an implementation of it:
> rev:
> c0a83d2 https://github.com/mathk/smalltalk/commit/c0a83d2
> a1f137b https://github.com/mathk/smalltalk/commit/a1f137b
> ab8cc96 https://github.com/mathk/smalltalk/commit/ab8cc96
> ed9360a https://github.com/mathk/smalltalk/commit/ed9360a
>
> For the time being I did a separate class namely RandomMT19937.
> only the #next differ from the original Random class.
> Now #next return a positive SmallInteger (30bit wise)
> so no object are allocated on 32bit and 64bit arch.
>
> I have made a tiny bench:
> mathk@Nani smalltalk $ cat BenchRand.st
> Eval [
>    | n k r o |
>    r := RandomMT19937 source.
>    n := 100000.
>    k := 500.
>    o := OrderedCollection new.
>    1 to: n do: [:x |
>        ((r between: 0 and: (n := n - 1)) < k
>            ifTrue: [o add: x. k := k - 1]) notNil ].
>
> ]
> mathk@Nani smalltalk $ time gst BenchRand.st
>
> real    0m0.096s
> user    0m0.072s
> sys     0m0.012s
> mathk@Nani smalltalk $ cat BenchRand.st
> Eval [
>    | n k r o |
>    r := Random source.
>    n := 100000.
>    k := 500.
>    o := OrderedCollection new.
>    1 to: n do: [:x |
>        ((r between: 0 and: (n := n - 1)) < k
>            ifTrue: [o add: x. k := k - 1]) notNil ].
>
> ]
> mathk@Nani smalltalk $ time gst BenchRand.st
> "Global garbage collection... done"
>
> real    0m0.308s
> user    0m0.276s
> sys     0m0.022s
> mathk@Nani smalltalk $
>
> Questions or comments are welcome.
> Thanks
>
>        Mth
>
>
>
>
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