I stopped reading it after it said concurrency in Ruby was "N/A". That's a silly statement for a language that has threads and coroutines built in, as well as a number of event loop and actor libraries.

When run on JRuby, threads also offer parallelism.

http://ruby-doc.org/core-2.2.0/Thread.html

http://ruby-doc.org/core-2.2.0/Fiber.html

Hello, post author here. What I mean by "N/A" here is "Not Applicable" as in Ruby was not designed for concurrency. I didn't mean to say that it is "Not Available" or not possible. I also was only describing language features without considering libraries.

Even JRuby's first recommendation for concurrency is "don't do it": https://github.com/jruby/jruby/wiki/Concurrency-in-jruby

So, you're saying threads and coroutines aren't concurrency?

I'm pretty sure Matz is still working at re-architecting the Ruby global interpreter lock (GIL) for genuine concurrency. JRuby and Rubinius are alternative Implementations of ruby that do support Concurrency, but they are just that, alternative Implementations.