JRuby Roundup: 1.4 Features, JRubyConf Schedule, MLVM

Posted by Werner Schuster on Sep 29, 2009

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A first release candidate of JRuby 1.4 is expected soon, so it's time to have a look at what's coming up.

JRuby team member Nick Sieger gave a quick overview of what's to come in JRuby 1.4. Next to new YAML support and further improvements in the 1.9 support, work on the JRuby's 1.8.7 support continues.

JRuby 1.4 will default to Ruby version 1.8.7. While most of the 1.8.7 support is done, Charles Nutter explains why external iterators, added in 1.9.x and 1.8.7, are currently slow and hard to optimize:

Ruby 1.8.7 added the ability to "next" your way through an Enumerator. At a glance, this seems fine; it's just external enumeration. The problem, however, is that enumeration can be arbitrarily complex. [..]
In Ruby 1.8.7 and Ruby 1.9, [external iterators are] implemented using continuations (delimited continuations, i.e. Fibers or coroutines), making it dreadfully slow to "next" your way through a collection. On JRuby, because there's an in-progress #each we have to pause for every element, Enumerator#next has to spin up a *new native thread*. Each #next call then pings the thread to produce a new result.

It remains to be seen whether a fast solution can be found.

JRuby 1.4 will probably also bring improvements in the Java integration, making it easier (or in some cases, at all possible) to access overloaded methods in Java classes from Ruby code. Possible changes will include improvements in type coercion and new methods such as java_send (GitHub commit for java_send) which takes the method signature of the method to invoke.
The specific feature set in 1.4 is still in flux, and it remains to be seen what parts of the Java integration overhaul make it in.

Future versions of the JVM are supposed to include support for improving the speed of dynamic languages. First bundles of JRuby and the MLVM with the new dynamic features are available.

Finally, very soon after the announcement of the first JRubyConf, it was booked out. EngineYard now announced the final program of JRubyConf
as well as the availability of further tickets:

Last, but certainly not least exciting: with the addition of our new sponsors, and some magic logistical mojo at the Embassy Suites, we've managed to move the event to a larger space, doubling the attendee headcount.

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