SyntaxHighlighter.defaults.gutter = false;I prefer to write happy posts...I really do. But tonight I'm completely defeated by the JDK's implementation of subprocess launching, and I need to tell the world why.

JRuby has always strived to mimic MRI's behavior as much as possible, which in many cases has meant we need to route around the JDK to get at true POSIX APIs and behaviors.

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I shouldn't be up this late, but I've been doing lots of thinking and exploring tonight.

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With every JRuby release, there's always at least a handful of optimizations. They range from tiny improvements in the compiler to perf-aware rewrites of core class methods, but they're almost always driven by real-world cases.

In JRuby 1.7.1 and 1.7.2, I made several improvements to the performance of Ruby constants and global variables that might be of some interest to you, dear reader.

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What does the following code do?

If you answered "it upcases two strings and adds them together, returning the result" you might be wrong because of a new Ruby feature called "refinements".

Let's start with the problem refinements are supposed to solve: monkey-patching.

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I was recently asked for a list of "hard problems" a Ruby implementation really needs to solve before reporting benchmark numbers. You know...the sort of problems that might invalidate early perf numbers because they impact how you optimize Ruby. This post is a rework of my response...I hope you find it informative!

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JRuby has, for some time now, run the same test suite as MRI (C Ruby, Matz's Ruby). Because not all tests pass, we use minitest-excludes to mask out the failures, and over time we unmask stuff as we fix it.

However, there's a number of warnings we get from the suite that are nonfatal and unmaskable. I thought I'd show them to you and tell their stories.

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While at GoGaRuCo this weekend, I finally made good on an experiment I had been thinking about for a while: a static compiler for Ruby. I thought I'd share it with you good people today.

First we have a simple Ruby script with a class in it:

We compile it with fastruby, and it produces two .java source files: Hello.java and RObject.java.

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I had an interesting realization tonight: I'm terrified of hash tables. Specifically, my work on JRuby (and even more directly, my work optimizing JRuby) has made me terrified to ever consider using a hash table in the hot path of any program or piece of code if there's any possibility of eliminating it. And what I've learned over the years is that the vast majority of execution-related (as opposed to data-related, purely dynamic-sourced lookup tables) hash tables are totally unnecessary.

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This was originally posted as a comment on @fogus's blog post "Why Clojure doesn’t need invokedynamic, but it might be nice". I figured it's worth a top-level post here.

Ok, there's some good points here and a few misguided/misinformed positions. I'll try to cover everything.

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This is the first of a set (not a series...there's no particular order) of articles I'll write on how JRuby is using invokedynamic. Hopefully they will show Rubyists how drastically invokedynamic is going to improve JRuby, and show other JVM language folks how to use invokedynamic effectively.

Hello friends!

I figured it's about time for me to start writing a bit on how JRuby is actually using invokedynamic.

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Java 7 has landed, with a modest set of new features and a few major improvements as well. What can you expect from JRuby running on Java 7?

What's In Java 7


The biggest changes in Java 7 are not related to the Java language at all. Sure, there's the "project coin" enhancements to the Java language, which add some exception-handling shortcuts, new literals for numbers, arrays, hashes, the oft-requested "strings in switch" support, and a few other things. But they're modest incremental changes; the real revolution is at the JVM and JDK level.

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So after months of not blogging anything technical, I'm going to blog something non-technical. Hopefully tech posts will pick up soon once my new baby boy Elliott is a bit older and less needy :)

When Is "This Friday"?

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Android is really an amazing little platform, but occasionally you will run into API differences. Some of these are actual bugs (like a number of reflection and enum issues in early releases), and others are just weakly-specified APIs.

Today, I worked on JRUBY-5541: Problem with java_import on Android (Ruboto)

The issue boiled down to how we turn Java's camelCased method names into Ruby's snake_cased form. We were using the following code:

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You may have seen recently that Java suffers from a similar floating-point parsing bug to the one that recently affected PHP users. The basic gist of it is that for this special 64-bit floating point value, the Java call Double.parseDouble("2.2250738585072012e-308") will get stuck in an infinite loop. Read the link above to understand what's happening.

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Amazon this week announced Elastic Beanstalk, a managed Apache Tomcat service for AWS. Naturally, I had to try JRuby on it.