Why Use Rubinius

Why should I use Rubinius? We have been asked that question many, many times over the past four years. It is a great question. It is an important question. It’s a hard question. I’m not holding out on you. I want to give you an answer that sates your curiosity, helps you make informed decisions, and empowers you to speak eloquently when you are inevitably asked, “Why do you use Rubinius?”

The trouble is, there are many different situations in which people use Ruby and there is simply no answer, however comprehensive, that really speaks to everyone’s concerns. So rather that boring you at length, I thought a Choose your own adventure style would be a better approach.

From the list below, select the persona that best describes you. Don’t worry, if the one you select doesn’t sound right, you can easily backtrack here. Read as many as interest you. After all, none of us fit easily into any one box. When you are done exploring all the fascinating reasons to use Rubinius, let’s meet up at the Conclusion for some parting words.


Choose Your Persona

Rails or Ruby Newby

You are pretty new to programming and after hearing about Ruby on Rails you watched a screencast and made a website. You are curious and enthusiastic.

You are the empty teacup of the Zen proverb. You are a fresh-faced flower glistening with the morning dew. The sun smiles on you and you smile back. You seem to like this Ruby language that makes programmers happy and you’ve come to lend your cheery spirit…


So, you have heard of this thing called Rubinius or rbx or whatever and some folks you respect or admire seem to like it and naturally you want to know what the big deal is and you’re like, “Yo, why would I use Rubinius?”.


Well, you should use Rubinius because I said so. Try your code on it. Tell us what worked for you. Tell us if something didn’t work by opening an issue. Set your imagination loose and tell us what tool you would use if you could.

Spend some time reading the Rubinius source code. Start at the kernel/ directory. It’s full of Ruby code! As you read through how Ruby is implemented, how it actually works, it will give you a level of understanding of your code that many programmers don’t have in any language.

Most of all, hang on to your curiosity and enthusiasm. Those were vital to the creation of the Rubinius project in the beginning and have sustained us through many challenges. We can make our Ruby experience better, freeing us from the shackles of other languages and foreign libraries. We can have fast and reliable web servers, games, editors, websites and applications written in Ruby. We can have first class tools written for and with Ruby. The world can be rosy red without our glasses.

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The Creative

Ruby is groovy. No, not that Groovy, eww, no. I mean:

groovy |ˈgroōvē| adj.

  • fashionable and exciting : sporting a groovy new haircut
  • enjoyable and excellent : he played all the remarkably groovy guitar parts himself

(Apple's dashboard dictionary widget.)

Ruby respects creativity. It has an aesthetic. You don’t just write Ruby code, you write beautiful Ruby code. It would be unthinkable to do otherwise. Sure, there is more than one way to do many things. This is not some sterile laboratory. We are not automatons; we are people. Of course, being utilitarian is not bad. But other languages have that angle pretty well covered. There is probably only one right way to implement Python.

Rubinius has an aesthetic, too: excellence, utility, simplicity, beauty, joy. Mostly in that order. Useful code that isn’t of very good quality is a drag. It slows you down. It gives you a headache. It drives you away. We strive to keep it out of Rubinius. On the other hand, we are not just writing sonnets here. This is Serious Business™. We have some hard-core problems to solve. So we strive for excellent, useful, beautiful code that is a joy to work with.

Of course, this is an ongoing process. It is a journey, not a destination. There are areas of Rubinius that could use a thorough cleaning or a new perspective on making the implementation of this beautiful object-oriented language more beautiful and object-oriented.

We welcome your artistic perspective. Help us improve the dialog between Rubinius and the person using it. The command line doesn’t have to be a desolate place of obscure, condescending error messages. Web interfaces to the diagnostic tools deserve a good dose of user-experience and interaction design. You know that feeling you get when looking at an Enterprise web application? That weird plastic-masquerading-as-quality-material feeling? The too much 1996-Enterprise-faux-rounded-corner-wanabe-2006-hip gloss? Gives me the willies whenever I have to use an app like that. Yeah, we don’t want that.

We want to create tools that are powerful, graceful, easy to use, and beautiful to look at. Beautiful tools are easier to use. (Yehuda Katz provided a couple links related to this: The Impact of Design and Aesthetics on Usability, Credibility, and Learning in an Online Environment and In Defense of Eye Candy. If you know of other research, leave us a comment.) So if you have a creative bent but enjoy writing code also, try out Rubinius and let us know where it could use some polish.

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Experienced programmer

That saying, Time is Money, you live by it. You have applications to deliver and you choose the best tool for the job. You are professional, conscientious, duly cautious, and not inclined to episodes of emotional exuberance about the latest fad. You accept compromises. There are always trade-offs. The correct approach is cost-benefit analysis. The numbers tell the story and level-headed decision making follows the numbers.

You have heard about Rubinius and you are curious whether it may be appropriate for your current project. As usual, rather than speculating or paying too much heed to the buzz, you look into it yourself. After some investigation, you discover that:

  1. Much of Rubinius is implemented in Ruby itself. This may be a big help when tracking down troublesome bugs.
  2. Rubinius has a very fast bytecode virtual machine, as well as a modern generational garbage collector so memory profiles should be more predictable and consistent in deployed applications.
  3. It has a profile-driven JIT compiler that uses type-feedback to aggressively inline methods resulting in significant performance improvements.
  4. It has a built-in debugger and precise method profiler, both of which are fast due to being well integrated.
  5. It has a built-in API for monitoring a VM out-of-process, even on a remote machine. We are building a variety of diagnostic tools atop this API.

Of course, even if the technology in Rubinius sounds terrific in theory, how suitable is Rubinius for your application? How does it perform under your specific constraints? Again, you do some investigating. You have a solid test suite for your application, so you start by running that. If you hit any problems, please open an issue to let us know.

If everything goes well with the tests, you start running some of the benchmarks that you have accumulated while doing performance tuning. Of course, no sensible person asks for benchmark results from other people’s code. That defies logic. It’s like asking if your program will run because your Aunt Mabeline likes decaf coffee. It’s contrary to the very point of benchmarking, where you are trying to correlate two values that are connected.

Again, if you note an significant issues, please let us know. Sometimes Rubinius exposes issues in existing code. Performance characteristics of real applications are vital to making Rubinius faster. Also, if you have suggestions for tools you would like to use, tell us. If you just want to chat about the technology, that’s fine, too. We’re hanging out in the #rubinius channel on freenode.net.

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Seasoned programmer

Well, I am being kind by saying seasoned. You know when you look in the mirror that jaded and cynical are much more apt. You’ve seen it all and it has worn you down. You’ve been fighting the good fight, carefully guarding that last flicker of optimism that burns in the secret place deep in your heart. You’ve programmed Java/.NET/C++ professionally. You’ve even sucked it up and written some PHP and Python when asked; you are a professional, they ask and you deliver. You’ve seen attacked servers on fire off the shoulder of Rackspace…

Rubinius has a lot to offer you. Remember that little flicker of optimism? It is only the idealists that get ground down by the complete indifference to pursuit of an ideal in so much of the world. Deep down, you are an idealist and you will find plenty to refresh you here.

Rubinius aims to be the best possible implementation of Ruby by putting Ruby itself front and center. We are using modern technology and always improving. We change when there is a better way to do things. We judiciously rewrite and are not too attached to any code or algorithm. The legacy Enterprise isn’t on the steering committee. Our work will be done when you can use Ruby, just Ruby, to solve your thorny problems.

Sure, that sounds idealistic. But never mind the pessimists that tell you that you have to compromise. If you are not idealistic, you will not be unsatisfied with things that are not as good as they could be; you will not try to change the world. So give Rubinius a try, you may be surprised. And if you are, put all that hard-earned wisdom you have gained to use for the betterment of Ruby.

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Academic Researcher

Forgive me for staring, I know it is impolite. I’m just… intrigued. Of course, you know Ruby is a late bound language, every message sent could conceivably fail to find a target, potentially resulting in an uncaught exception and program termination. There’s shared state, wild orgies of mutation that disallow any reasonable attempt at automated parallelization. Program proof is as oxymoronic a concept as military intelligence. It’s a very messy affair of programming and meta-programming and meta-meta-programming, which, for the love of Lisp, could be done so simply with macros. There’s all this eager evaluation and complete disregard for purity. Despite vast odds, somehow programs are written that actually run. You have noted all this with great objectivity but you are nonetheless interested.

Excellent, we are pleased. We have much to learn and welcome the opportunity for lively discussions about bringing formal methods to bear on the problems of making Ruby as fast as possible.

Java benefited tremendously from the amount of attention it received by academic researchers. Ruby can benefit from some of this research as well, not to mention the research into Smalltalk and Self that preceded it. But Ruby has its own set of problems to solve and deserves specific attention. The problems are hard but not insurmountable. Rubinius is already demonstrating that. The suggestion that we need to add more keywords, restrict Ruby dynamism, or write public static final int all over are simply nonsense.

Rubinius already leverages research for fast virtual machines, garbage collection (e.g. the generational approach and the Immix mark-region algorithm), and JIT compilers (based on pioneering research done in Self and used in the JVM Hotspot VM). Rubinius uses the exceptional LLVM project for optimization and code generation in the JIT compiler. We are also working on better infrastructure for the JIT to address Ruby complexities head-on.

Rubinius would be excellent to use in teaching. A compiler construction class could study the architecture of the bytecode compiler written in Ruby and experiment with exploratory changes to the compiler using IRB without having to recompile anything! A 30-minute introduction to Rubinius could proceed immediately to simple AST generation and have students experimenting with their own syntax immediately. While it is easy to get started, there is plenty of depth for exploring complex topics in virtual-machine construction and garbage collection.

Whether you are interested in language research or language pedagogy, Rubinius is an great project to consider. We look forward to hearing from you.

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Über programmer

You learned the untyped lambda calculus sitting on your mother’s knee while she worked on her doctorate in computer science. You were substituting terms before you even uttered the word, “dada”. You wrote three different Lisp implementations in Commodore Basic before you were seven. You can write multi-threaded web servers in one pass with no tests and never hit a deadlock or critical data race. You write parsers and compilers for odd languages on a Friday night for the heck of it while waiting for the pizza to arrive before a night out at the karaoke bar where you give an inspiring performance of Laga Gaga’s Poker Face.

(Loooong pause. You’re not reading this. You’ve already written one or a few languages on Rubinius and posted them to our Projects page. But anyway, I’ll continue…)

You are the Luke Skywalker of Ruby; Yoda has nothing more to teach you. Only your fate confronts you now. Use the Source Luke and save the Federation of Ruby loyalists from the Evil Oracle and its Java the Hurt.

There are a number of domains in which Ruby could benefit tremendously from excellent libraries:

  1. Servers and web servers: the web is here to stay but the argument that all applications are going to be in Javascript on the client is not valid. A variety of hybrid client-server architectures will continue to be the norm. We need software that enables application authors to build a suitable solution to their particular problems rather than trying to stuff their apps into someone else’s solution with layers of wrapping.
  2. Concurrency: multi-core is here to stay but it is not only functional programming that is suitable for high-concurrency applications.
  3. Graphical user interface: the web browser is also here to stay but it is not the last word in applications. There are many cases where GUI apps are the best option and Ruby needs a mature library or set of libraries to build these apps on any major platform. I know some of these libraries exist, but they seem to be collecting dust lately.
  4. Big data and data analysis libraries: our industry repeatedly witnesses the same pattern: domain X starts with huge applications running on huge horsepower servers for huge businesses and then it starts appearing in small applications on small computers for small businesses. Accounting and geographic information systems (GIS) are two examples. Data analysis is coming to a laptop near you.

These are general areas in which Ruby can be an excellent solution. So how does Rubinius fit in? Rubinius is dedicatedly pushing more and more into Ruby itself. Each of these domain is typically handled in Ruby right now by going to find a library in a foreign language to wrap in a fuzzy Ruby embrace. Rubinius is calling on the über-programmers of the world to implement solutions in Ruby to help us identify performance challenges and address them.

Rubinius is also being used in some fascinating language experiments. Two of these are Atomo (http://atomo-lang.org which is implemented in Haskell, with a Rubinius implementation code-named quanto) and Fancy (http://fancy-lang.org). So, if language design is your cup of tea, Rubinius offers an excellent platform for experimentation.

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Philosophy Student Seeking the Meaning of Ruby

Like your persona description, you tend to be long winded. You find most descriptions too brief, almost dismissive. There are words and words should be used to delve into the minutiae of minutiae. You, more than anyone, want to know “Why?” with every fiber of your being. You will continue asking long after the supply of hallucinogens has been exhausted and everyone else is drooling in their sleep.

For you, Rubinius is an existential dilemma crying out for justification. If we already have MRI, why build Rubinius?

It would be accurate to say that Rubinius has a philosophy. That philosophy is simply this: Ruby should be a first class language. What does that mean? Simply that it should be possible to solve problems writing Ruby code.

Let’s consider libraries: Being first class means not having to wrap a Java library or build a C extension. If wrapping the library were the end of the story, it wouldn’t be so bad. But that is never the case. Libraries have bugs, weird APIs, incompatibility with other libraries, threading issues, and disappearing maintainers. They may even be incompatible with newer versions of the language in which they are written.

This list goes on. To address any one of these issues requires delving into a different language with weird and incompatible semantics. If the library is your core competency, that’s not such a big deal. But I will wager that it is not, which is why you are using the library in the first place. Also, the language in which you are wrapping the library (Ruby here) is not likely the core competency of the library author, or you probably wouldn’t need to be wrapping it. So Ruby wrapping one of these libraries will always be a second-class citizen. Decisions will be made about the library’s API that do not give one thought to the Ruby programs using it. Furthermore, the code written in that foreign language does nothing to support the ecosystem of Ruby. The knowledge gained in writing the library and the improved skills of the library author do not benefit Ruby. Ruby deserves better.

Ruby has gotten a big boost recently with the production release of MRI 1.9.2. There are significant speed improvements and welcomed additions to the core libraries, like powerful handling of String encodings. At the same time, the Complex and Rational libraries were added to the core library and rewritten from Ruby to C code. This is disappointing. We should be able to solve these problems more effectively in Ruby itself.

The philosophy of Rubinius is to make Ruby a first-class citizen. Ruby plays second fiddle to no one. There is no other language whose history, semantics, or vested interests compete with Ruby’s. It is true that there are difficult problems to solve in making Ruby fast. But much of the technology already exists and we will build what does not. Evan often quips that if we can get Rubinius caught up to the dynamic language technology of ten years ago, Ruby will be light-years ahead. That may be overstating how far behind Ruby is, but it illustrates the focus of Rubinius.

There’s the saying, In theory, there is no difference between theory and practice. In practice, there is. In Rubinius, theory and practice are merging. We are motivated by the desire for Ruby to be a first-class language. But we are also showing real progress in making that a reality. The Rubinius VM executes Ruby code blazingly fast. The JIT compiler, while still being quite young, is showing great promise. Compatibility with MRI is quite good and speed is constantly improving.

Is the Rubinius philosophy valid? We think the proof is in the pudding.

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No, it did not cross my mind to describe this persona as Pointy-haired Boss. Not only would that be unfair to Dilbert, but that persona would be reading an article on Web Scale. No, you are someone who has fought hard battles in the trenches and learned valuable lessons: it’s about execution and execution depends on good technology.

Rubinius is building solid technology. We started the RubySpec project and have contributed tens of thousands of lines of code to it. With the support of Rubyspec, in just over four years as a public project, we have basically caught up with MRI 1.8.7 in compatibility and performance. For some code, our performance is much better, for other code, it is not as good. However, Rubinius is built on solid, modern technology and the project’s trajectory and velocity are outstanding.

Rubinius is a completely new implementation of core Ruby. Rubinius did not start as a port of existing code. Furthermore, Rubinius implements its own virtual machine and garbage collector in C++. The bytecode compiler that targets the virtual machine is pure Ruby. The core Ruby library is mostly Ruby with some primitive operations in C++. The JIT compiler uses the LLVM project. Given the amount of work being done in the project, Rubinius is pacing extremely well relative to other implementations.

Currently, we are working on support for Ruby 1.9 features, Windows support, and full concurrency with no global interpreter lock (GIL).

If you are looking at Ruby to implement your next project, rest assured that Ruby will have the support of excellent technology. If you are already using Ruby, consider investigating how your application runs on Rubinius. We welcome the feedback and look forward to solving challenging engineering problems.

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Knowledge Seeker

You thirst for Knowledge. You follow it wherever it leads you. You’ll happily walk Haskell’s hallowed halls of pure laziness or sit at the feet of the meta-program gazing raptly at class transmorgrification. You don’t judge. You have more than enough knowledge to be dangerous, enough to know that the universe is amoral and knowledge is the only Truth there is. Nor does any mere mortal language bind you. All languages are finite. You’ll be here today and gone tomorrow; there is no permanence for the knowledge seeker.

Rubinius is merely a step along the path you journey. Take what you want, it is all free. As a Ruby implementation, it has much to offer your quest for knowledge. The Ruby code in the core library is accessible and easy to follow. The interface between Ruby and the C++ primitives is consistent. The C++ code itself is restrained. You won’t need a PhD in Turing-complete template languages to understand it.

Rubinius offers extensive opportunities to learn about programming languages in general and Ruby in particular. When I first started working with Rubinius, I knew a little bit about garbage collection and virtual machines. I would call what I knew, toy knowledge. As I struggled to learn more, it seemed helpful to consider layers of understanding:

  1. General programming language semantics: the procedure abstraction, looping and iteration, recursion, references and values, etc.
  2. Ruby semantics: modules and classes, access restrictions, blocks and lambdas, etc. Even with fundamental programming knowledge, a particular language can be confusing. When I was learning C, a friend was also studying it. One day he walked over and threw The C Programming Language book down on my desk and said, “This for loop makes no sense!” He was quite upset. “Look,” he said, “in this example for (i=0; i < n; i++) how can i < n get executed after the code in the body?!” It’s easy to laugh at that confusion, but coming from BASIC, that really threw him. Deepening our understanding to this second level requires confronting some “counter-intuitive” notions.
  3. Hypothetical implementation: knowing how Ruby works, how might one implement it. I think this is an important layer of understanding and it is easy to miss or gloss over it. By pausing at this layer and thinking how you might implement something, you test whether or not you are really understanding it.
  4. The MRI implementation: Reading the MRI source code is an excellent way to investigate Ruby. For one thing, it will inform you how Ruby actually works, and you may be surprised.
  5. The Rubinius implementation: here you are exposed to the philosophy of Rubinius and the challenges to implementing Ruby. We are attempting to bring the beauty of Ruby as an object-oriented language deep into the core of Ruby itself.

While the Rubinius code itself offers many opportunities for learning, don’t hesitate to drop by the #rubinius channel on freenode.net and ask us questions. Perhaps you already know a lot about another language and are interested in how Rubinius implements some feature. Or you may be relatively new to programming languages and have some basic questions. We enjoy talking about these concepts. If you are quite new to Rubinius, you may find these posts informative:

Finally, consider helping other knowledge seekers by writing blog posts on what you learn about Rubinius. Or, help us write documentation!

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Language Enthusiast

You like languages for their intrinsic value. Of course the world comes in many shapes and sizes. You wouldn’t have it any other way. That’s the fun and spice, joie de vivre, raison d’etre, supermarché… Sometimes you get carried away writing a program in another language just because you like how the letters arrange down the screen. Ruby is definitely one of the impressive languages and sometimes you almost notice a tiny bit of favoritism in your normally egalitarian attitude.

As with any enthusiast, you like to experiment. Your interest is not mere curiosity or sterile investigation. You want to get your feet wet and your hands dirty. Rubinius is an excellent opportunity to delve into a number of fascinating subjects. We can merely suggest a path; your experiences along the way will tell you whether or not Rubinius has value to you.

If you are most interested in languages themselves, the syntax and arrangement of features, Rubinius offers you immediate gratification. Look for Evan’s upcoming post on his Language Toolkit or check out the code to prattle, a Smalltalk dialect used to illustrate the ease of building a language on Rubinius. Also look at some of the existing languages projects targeting Rubinius.

If it is the machinery under the covers that is more interesting, start reading some code. The bytecode compiler lives in lib/compiler/. The virtual machine is in vm/, and the garbage collector is in vm/gc. As you are reading through, consider helping us write better documentation. There are already sections for the virtual machine, garbage-collector, JIT compiler and bytecode compiler in the documentation, so adding content is easy.

You may also be interested in these previous posts about Rubinius:

Most of all, experiment. Rubinius is easy to hack on. Are you curious about a particular feature needed in your language? Try adding it to Rubinius. Think Lua is all the rage because it uses a register VM? You could probably write a register-based bytecode interpreter for Rubinius in an afternoon. That’s just an example, of course. The point is to play around with your ideas and have fun doing it. I think you’ll find Rubinius to be an adventuresome companion.

Be sure to let us know what you’re working on. We like to be inspired, too! Consider writing a blog post about things that you find interesing, like this recent post by Yehuda Katz.

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So there you have it. Just like there are many different viewpoints, there are many different reasons to use Rubinius. Not all those reasons make sense to everyone. We believe, however, that Rubinius has something to offer to just about everyone interested in Ruby. Most importantly, try it!

If we didn’t answer your question here, leave us a comment. If you have a reason for using Rubinius that we didn’t mention, let us know. As always, we appreciate your feedback. Chat with us in the #rubinius channel on freenode.net, watch our Github project, and follow us on Twitter.

P.S. Thanks to David Waite for suggesting the Academic Researcher and Language Enthusiast personas, I always forget those!

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