Removing a layer of synchronization on Math.random

[Martin Buchholz]

Thanks to all the reviewers who were too polite to say:

"""What was Martin thinking?"""

For some reason I had imagined that Math.random()
was itself synchronized.

After editing, I have a very small change that is hardly worth doing
except that I already have a webrev.

http://cr.openjdk.java.net/~martin/webrevs/openjdk7/Math.random/

Martin

On Sat, Jun 5, 2010 at 07:00, Eamonn McManus <Eamonn.McManus at sun.com> wrote:
> It seems to me that if two threads call this Math.random() at the same time
> then two instances of Random() can be constructed. That contradicts the
> specification of the method, and is theoretically observable because the two
> values from Math.random() will typically not be a pair of values that could
> have been returned from consecutive calls to nextDouble() on a single Random
> instance. Granted, the chances of this actually mattering are infinitesimal,
> but I think the performance gain of avoiding a synchronized method only on
> the very first call to Math.random() is infinitesimal too. So I'd be
> inclined to leave well enough alone here.
> Eamonn
>
> Martin Buchholz wrote:
>>
>> Here's an optimization for Math.random() that appears to be safe,
>> despite the double-check access:
>>
>> http://cr.openjdk.java.net/~martin/webrevs/openjdk7/Math.random/
>>
>> David, if you agree, could you file a bug?
>>
>> Thanks,
>>
>> Martin
>>
>