Scalable Nonblocking Data Structures

An anonymous reader writes "InfoQ has an interesting writeup of Dr. Cliff Click's work on developing highly concurrent data structures for use on the Azul hardware (which is in production with 768 cores), supporting 700+ hardware threads in Java. The basic idea is to use a new coding style that involves a large array to hold the data (allowing scalable parallel access), atomic update on those array words, and a finite-state machine built from the atomic update and logically replicated per array word. The end result is a coding style that has allowed Click to build 2.5 lock-free data structures that also scale remarkably well."

Comments

Re:Java????

[JMZero]

Java is perfectly fast for real world applications, and I'd agree that the "Java is Slow" idea is outdated.

But it's not conclusively faster than C++, at least not in a general sense. In terms of a small task involving lots of simple operations, you'll still often see a significant speed increase using C++. This is a good example. Now I'm sure there's more optimizations available on both sides - and plenty of stuff to tweak - but C++ is going to come out ahead by a significant margin on a lot of these tasks.

A good example where the participants on both sides have some motivation is on TopCoder (where I spend a fair bit of time). Performance isn't usually the driving factor in language choice there - but sometimes it is, and when it is the answer is pretty much always C++ (unless it's a comparison between Java BigInteger and a naive implementation of the same in C++).

Reasonably often you'll see people write an initial solution in Java, find it runs a bit too slow, and quickly port it to C++ (or pre-emptively switch to C++ if they think they'll be near the time limit). It's not uncommon to see a factor of two difference in performance.

To be clear - these are not usually "real world" tasks. As more memory and objects come into play, Java is going to do better and better. But these kinds of tasks still exist - there's still plenty of places where C++ is going to be the choice because of performance.

In any case, your contention that Java is so much faster that nobody does benchmarks anymore is unsupported and wrong.