Archive for April, 2008

Currently, there are at least FIVE actively developed Ruby implementations out there in the wild. For an excellent overview of the current state of affairs take a look at the Charles’ article: “Promise and Peril for Alternative Ruby Impls”. Having that many implementations, despite all the good things, also brings a new set of challenges. One of the biggest challenges is the compatibility. Some are even starting to say “balkanization” word. (You know who you are!)

That’s where RubySpecs come in. The great promise of the RubySpecs is to provide a unified compatibility and conformance test suite, universally used by all Ruby implementations. The Ruby implementers are not only going to use the tests, but also contribute back the new specs, increasing the value and the quality of the test suite over time. At the moment, we know that Rubinius folks (who started the whole RubySpec thing) actively use them on a daily basis, with a couple of continuous integration bots, and using the RubySpecs as a driver to implement new features in a test-driven approach. Brian Ford is doing an outstanding job supporting the mspec (the engine behind the specs) and accommodating users requests for new features and enhancements. JRuby uses the RubySpecs equally actively, running them on MacOS, Linux and partially on Windows. All the new tests that are of compatibility/conformance nature typically go directly to the RubySpec repository. IronRuby uses the RubySpecs too. Hopefully, we’ll see some contributions from them too, that would be really sweet! And last, but not least, during the first “Design Meeting” with ruby-core folks (including Matz), the RubySpec question was raised, and it seems that even Matz Ruby folks would start looking into it, and eventually using it.

So, if all goes well, most of the current active Ruby implementers would be using the common set of conformance tests. The RubySpecs are going to be forked off from the Rubinius repository and would live in the proper place as a main project on its own, with a bug tracker, a web site, etc. Also, some more folks would start working on the specs via Google’s Summer of Code program. Very exciting!

As an example, take a look at the BigDecimal support. At the beginning of April, there were no specs for BigDecimal. JRuby had a skeleton implementation, missing some methods or just having stubs for some other methods. Rubinius had no BigDecimal support altogether. Three weeks and 43 commits later (by the way, five different folks contributed to the tests), there are 1772 test cases for BigDecimal in the RubySpecs, JRuby has already fixed hundreds of failures, now passing most of them (with 6 remaining tests to be fixed soon) and Rubinius has a actively improving BigDecimal support too.

I guess, the main thing I’m trying to say here is that now it’s the perfect time to look into the RubySpecs and to start contributing. That way, you’ll affect ALL the Ruby implementation, making ALL of them better! For more info, take a look here and here.

This was always confusing me, since Ruby has many ways to perform the division. So, here’s a fresh quote by Matz himself:

We have /, div, fdiv, and quo:
  /     – normal division, according to the class of operands
div    – integer division
fdiv   – float division
quo   – most accurate division (float if either operand is float, otherwise rational)
rdiv   – (which always results in rational) is obsolete.

So, you have that new and shiny JRuby 1.1 and would like to try it out with rails. Here’s a quickest guide to do so! The guide assumes that you want to use MySQL as the database, and it has already been installed.

First, install the following gems:

• mongrel – simple but powerful web server.
• activerecord-jdbcmysql-adapter – all you need for activerecord on JRuby to talk to MySQL.
• rails – well, the Ruby on Rails proper.

The command line:

   1: jruby -S gem install mongrel activerecord-jdbcmysql-adapter rails

Create a sample rails application with MySQL backend:

   1: jruby -S rails myapp -d mysql

Enter the newly-created “myapp” directory, then modify the config/database.yml. First and foremost, you need to adjust the adapter name, and instead of ‘mysql’ you should specify ‘jdbcmysql’. You might also want to delete the lines starting with “socket:”.

Here’s a simple example for the development environment:

   1: development:

   2:   adapter: jdbcmysql

   3:   encoding: utf8

   4:   database: myapp_development

   5:   username: root

   6:   password:

Now, it’s time to create our database:

   1: jruby -S rake db:create:all

The next step is to create some minimal scaffolding so that you could actually play with some dynamic functionality and database access:

   1: jruby script/generate scaffold post title:string body:text published:boolean

We need to update the database after that:

   1: jruby -S rake db:migrate

And we’re basically done here, just start rails via:

   1: jruby script/server

and point your browser to the:

   1: http://localhost:3000/posts

Enjoy!

This is a quick guide for those, who’d like to run the Rubyspecs with minimal effort. For those who have JRuby repository checked out, the steps are even easier: ‘ant spec’ – and you’ll run all the unexcluded specs against the freshly built JRuby.

1. Pull the Rubinius repository (and you have to have git for that):

      1: git clone git://git.rubini.us/code rbx

2. Alternatively, you could just download the snapshot of the repository in a compressed file. (Look for “snapshot” links at the page).
3. Basically, that’s it for the setup. Now, just run the tests:

      1: cd rbx  # Step into the directory you've created when pulled

      2: bin/mspec -t ruby spec/ruby/1.8 # Run all Ruby 1.8 specs

      3: bin/mspec -t ruby spec/ruby/1.8/core/kernel # Run Kernel specs

      4: bin/mspec -f s -t ruby spec/ruby/1.8 # More verbose output

4. During the execution, the dots will be printed out, and the final summary, but with “-f s” option, the output is much more interesting:

      1: Kernel.proc

      2: - returns a Proc

      3: - raises an ArgumentError when no block given

      4: - raises an ArgumentError when given too many arguments

      5: - returns from block into caller block

So, that’s about it. The rubyspec format is compatible with Rspec, so there should be no major surprises there. More info *is* available at the official page. I’d suggest to start with “Specs – Overview” and explore from there.

The long awaited JRuby 1.1 is finally out. Working on it was fun, much more fun than I expected — so much to do, so many interesting things, so little time! It is a perfect mixture of Java and Ruby, actually improving my skills in both areas.

For me, it all started last Fall, after a couple of very convincing blog posts by Charlie: How Easy Is It To Contribute To JRuby? and Easy JRuby 1.0.2 Bugs. So I started playing with JRuby, looking for things I could fix, and it turned out that the easiest way to get involved is to look at the Rubyspecs and try to pass as many of them on JRuby as possible. I’ve started filing bugs and submitting patches, and eventually become a JRuby core comitter.

And since then, my main focus is on the compatibility with Ruby, on tests and especially the Rubyspecs. Having spent about 10 years in Java SE and Java ME compatibility, it was rather natural choice for me. We now have the rubyspecs nicely integrated into JRuby build, we maintain an exclude list for those specs that currently fail (and for every new failure we have the bug filed), we sync-up with the main rubyspecs repository frequently and contribute new specs back.

Some major things to do in the future: set up the continuous integration runs for rubyspecs, make the rubyspec runs on Windows and fix the specs to work properly on Windows. It is expected that much more effort will be put into Java Integration infrastructure, and we’ll need an extensive set of tests/specs for the area. The barriers to entry are very low now, and it’s very easy to contribute, so consider doing so!

Some random stats: So far, I’ve filed 232 bug reports, fixed 112 bugs and made 195 commits.

On to JRuby 1.1.1!

It was a “JVM performance week” in JRuby-land. It all started when some recent code changes is JRuby caused an interesting performance degradation with JDK6 on multi-core CPUs. See the original post to the [jvm-l] list and extended coverage of what happened on Charlie’s blog. So, while following the discussion and participating, I learned a few new things and got some interesting additional info and links that I’d like to share:

1. Let’s start with basics. John Rose posted a good starting guide for those who’d like to micro-benchmark things on JVM: So You Want to Write a Micro-Benchmark.
2. Performance techniques used in the Hotspot JVM wiki entry with the list of optimizations JVM does, sweet and to the point.
3. Fundamental work by Ulrich Drepper: What Every Programmer Should Know About Memory, a MUST read, but painful
4. Deep dive into assembly code from Java blog post by Kohsuke Kawaguchi, on how to print out the assembly code that JIT is producing.
5. Examining generated code with OpenJDK 7, exciting stuff!
6. Polymorphism Performance Mysteries Explained, the Issue #158 of The Java Specialists’ Newsletter.
7. How fast is Java Volatile? or Atomic? or Synchronized?, with nice charts and comparisons.
8. Escape analysis can help optimize synchronization by Brian Goetz.

Enjoy!

The Rubyspecs, an extensive set of conformance tests for Ruby platform, is a great tool to enforce the compatibility of JRuby (and Rubinius, and IronRuby). But the specs are currently being mostly run on Linux/BSD/MacOS (against Ruby, JRuby, Rubinius), and are rarely (if ever) executed in Windows environment. Until now, that is.

I tried to run them on Windows some time ago and the mspec, the testing framework that powers Rubyspecs, had some issues with Windows paths. Since then, the issues have been resolved and the Rubyspecs are functional on Windows.

I’ve run them against JRuby, found 4-5 bugs right away (crashes in calls that are not supported on Windows even in Matz Ruby), fixed those, and was able to run the specs to the completion! There are couple of hang-ups here and there, and lots of failures due to fact that rubyspecs were never used on Windows and don’t expect Windows-specific behavior.

I guess, that’s the next big thing, to go over all the specs and adjust them to take Windows specifics into account when needed.