From: Charles Oliver Nutter <headius@...>
Date: 2012-05-19T22:00:03+09:00
Subject: Re: break down of differences between interpreters?

On Sun, May 6, 2012 at 6:13 AM, ruby gem <lists@ruby-forum.com> wrote:
> All I can ever find is performance comparisons, but it must be more than
> just this or else why wouldn't everyone use Jruby? Would someone who
> knows layout the differences between the major interpreters? Why
> shouldn't I always use Jruby considering it has so much better
> performance? What are the advantages and disadvantages of each
> interpreter?

I'll give you the reasons people tell us they choose (and do not choose) JRuby.

Pro:

* JVM features
** Solid parallelism and concurrency libraries that have been tested
for many years
** Excellent performance through JIT and the new invokedynamic features
** The best GCs in the world
** Wide selection of libraries that are also 100% managed, and don't
impose restrictions like C extensions do
** Portability - JRuby works on any platform where the JVM is available
* Existing JVM infrastructure
* Android applications
* Large datasets (JVM handles much better than e.g. MRI)
* Straight-line performance (JRuby should generally be the fastest
when running on JRuby 1.7 + Java 7 JVM)

Con:

* Slow startup (partially JVM's fault and partially our fault...we
continuously improve here).
* C extension support (we have partial support, but it's not being maintained).
* Process size (we are larger, but you can often do more than MRI
without needing multiple processes).
* Many POSIX features from Ruby aren't or can't be implemented (fork,
low-level sockets, process control).
* Some people just hate Java or the JVM and anything associated with them.

We've never had anyone say they're not using JRuby because our licenses.

- Charlie