Ah, you also need the sign conversion applied to the uses of seed in right
shifts, but that's still a simplification.
Eliot (phone)
On Apr 3, 2015, at 7:15 AM, Stefan Marr <smallt...@stefan-marr.de> wrote:
> Hi:
>
> I am porting some benchmarks to Pharo, which rely on a deterministic random
> number generator that uses 32 bit values.
>
> In order to have properly comparable results across platforms, it needs to
> generated the same sequence of numbers.
>
> So, I am looking for efficient ways to implement it, any ideas?
> I am a little at a loss, with SmallInts and Long Ints, how to get the proper
> 32-bit values, and how to apply the correct shifts, especially the right
> shift can be problematic.
>
> Code examples below.
>
> Thanks
> Stefan
>
> In Java it looks like this:
>
> private static int seed;
>
> // Robert Jenkins' 32 bit integer hash function.
> public static int random() {
> seed = ((seed + 0x7ed55d16) + (seed << 12)) & 0xffffffff;
> seed = ((seed ^ 0xc761c23c) ^ (seed >>> 19)) & 0xffffffff;
> seed = ((seed + 0x165667b1) + (seed << 5)) & 0xffffffff;
> seed = ((seed + 0xd3a2646c) ^ (seed << 9)) & 0xffffffff;
> seed = ((seed + 0xfd7046c5) + (seed << 3)) & 0xffffffff;
> seed = ((seed ^ 0xb55a4f09) ^ (seed >>> 16)) & 0xffffffff;
> return seed;
> }
>
>
> In SOM Smalltalk, it looks like this:
>
>
> JenkinsRandom = (
> ----
> | seed |
>
> seed: val = ( seed := val )
>
> "Robert Jenkins' 32 bit integer hash function."
> random = (
> seed := ((seed + 2127912214 "0x7ed55d16") + (seed
> as32BitUnsignedValue << 12) as32BitSignedValue) as32BitSignedValue.
> seed := ((seed bitXor: 3345072700 "0xc761c23c") bitXor: (seed
> as32BitUnsignedValue >>> 19)) as32BitSignedValue.
> seed := ((seed + 374761393 "0x165667B1") + (seed
> as32BitUnsignedValue << 5) as32BitSignedValue) as32BitSignedValue.
> seed := ((seed + 3550635116 "0xd3a2646c") bitXor: (seed
> as32BitUnsignedValue << 9) as32BitSignedValue) as32BitSignedValue.
> seed := ((seed + 4251993797 "0xfd7046c5") + (seed
> as32BitUnsignedValue << 3) as32BitSignedValue) as32BitSignedValue.
> seed := ((seed bitXor: 3042594569 "0xb55a4f09") bitXor: (seed
> as32BitUnsignedValue >>> 16)) as32BitSignedValue.
> ^ seed
> )
> )
>
> --
> Stefan Marr
> INRIA Lille - Nord Europe
> http://stefan-marr.de/research/
>
>
>
>
