random number generator of Math.random() ?

[Bart Vandewoestyne]

Simple question: does the Java standard specify what random
number generator algorithm should be used for Math.random() ? If
'no', then can anybody tell me what PRNG is behind Sun's version
of Math.random()?

Thanks,
Bart

--
"Share what you know. Learn what you don't."

[Oliver Wong]

"Bart Vandewoestyne" <My************ ********@telene t.be> wrote in message
news:11******** *******@seven.k ulnet.kuleuven. ac.be...

Simple question: does the Java standard specify what random
number generator algorithm should be used for Math.random() ?
Yes it does.
If
'no', then can anybody tell me what PRNG is behind Sun's version
of Math.random()?

See http://java.sun.com/j2se/1.5.0/docs/...il/Random.html

- Oliver

[Bart Vandewoestyne]

On 2006-05-30, Oliver Wong <ow***@castorte ch.com> wrote:

'no', then can anybody tell me what PRNG is behind Sun's version
of Math.random()?

See http://java.sun.com/j2se/1.5.0/docs/...il/Random.html

Hmm... so if I understand things correctly, the pseudo-random
numbers produced by Random.nextDoub le() are the same as the ones
produced by Math.random() and the underlying algorithm is the one
as specified in

http://java.sun.com/j2se/1.5.0/docs/...ml#nextDouble()

namely

public double nextDouble() {
return (((long)next(26 ) << 27) + next(27))
/ (double)(1L << 53);
}

Looking at Random.next() then tells me that the PRNG used here is a linear
congruential pseudorandom number generator, as defined by D. H. Lehmer and
described by Donald E. Knuth in The Art of Computer Programming, Volume 2:
Seminumerical Algorithms, section 3.2.1

So am I correct if I say that the Java standard specifies the above PRNG as the PRNG to use when implementing Math.random() ?

Bart

--
"Share what you know. Learn what you don't."

[Oliver Wong]

"Bart Vandewoestyne" <My************ ********@telene t.be> wrote in message
news:11******** *******@seven.k ulnet.kuleuven. ac.be...
[...]

public double nextDouble() {
return (((long)next(26 ) << 27) + next(27))
/ (double)(1L << 53);
}
[...] So am I correct if I say that the Java standard specifies the above PRNG
as the PRNG to use when implementing Math.random() ?

Yes, I think so, or at least one which returns the exact same set of
numbers given the same initial seed.

- Oliver