[Help-smalltalk] Adding the random mersenne twister to gst

[Mathieu Suen]

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:
address@hidden 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 ].
    
]
address@hidden smalltalk $ time gst BenchRand.st 

real    0m0.096s
user    0m0.072s
sys     0m0.012s
address@hidden 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 ].
    
]
address@hidden smalltalk $ time gst BenchRand.st 
"Global garbage collection... done"

real    0m0.308s
user    0m0.276s
sys     0m0.022s
address@hidden smalltalk $

Questions or comments are welcome.
Thanks

        Mth




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