random streams

[Doug Lea]

On 12/31/12 13:41, Brian Goetz wrote:
> On the list of requested stream sources is 'stream of random numbers'.
>
> Here's a one-line addition to Random:
>
>      public IntStream ints() {
>          return PrimitiveStreams.repeatedly(this::nextInt);
>      }
>
> Certainly the implementation is straightforward enough (modulo renaming of
> PrimitiveStreams and repeatedly, which are not yet nailed down.)

This is not so straightforward under parallel operations.
This is a surprisingly deep topic with a lot of technical papers etc.
As a first pass, you'd just use ThreadLocalRandom() as sources
(to avoid horrible update contention), and make no promises
about the aggregate randomness across parallel operations.
However, people will come to expect that if you start off
computations with a common seed, then you get both replicability
and independence, which is not easy to deliver.
As a start, you'd need a better generator than the
one in Random (which is and must be the same algorithm
used in ThreadLocalRandom).

-Doug