[infinispan-dev] deadlock detection - coin toss

[Jason T. Greene]

Random is definitely thread-safe in the Sun derived JVMs, and probably 
thread-safe in other JVMs. I would just use that.

Otherwise you could implement MT:
http://en.wikipedia.org/wiki/Mersenne_twister

Mircea Markus wrote:
> this is regarding: http://tinyurl.com/nunmyu
> In order to be able to determine which tx should commit and which will 
> rollback, I need to generate a coin toss for each node - a random number.
> In order to do that I'm thinking to use on of the following:
> 
> 1) use java.util.Random . The issue with this class is that it has an 
> undocumented behavior when it comes to concurrent access, so I cannot 
> rely on it behaving correctly if  I don't  enforce proper 
> synchronization. I'm afraid this might become a bottleneck as all the 
> prepapares requests might want to synchronize on it.
> 2) Another approach would be to build an Random instance for each call. 
> I made a test an the performance cost of new Random() + Random.nextLong 
> is about 4 times bigger than call of random.nextLong only (on my laptop 
> only), still about 15 mils for 1k creations
> 3) use System.nanos. Even though the conflicting tx are created at the 
> same time, the chance for it to happen in the same nanosecond is very 
> small, I would say. Don't know how this works for all architectures, 
> though...
> 
> Any feedback much welcomed!
> 
> Cheers,
> Mircea
> 
> _______________________________________________
> infinispan-dev mailing list
> infinispan-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/infinispan-dev


-- 
Jason T. Greene
JBoss, a division of Red Hat