From: Charles Oliver Nutter <headius@...>
Date: 2010-01-18T07:04:34+09:00
Subject: Re: Float Points error

On Sat, Jan 16, 2010 at 6:37 AM, Colin Bartlett <colinb2r@googlemail.com> wrote:
> I think it's worth reminding people that it's possible to use Java with JRuby.
> On an admittedly low-spec laptop I've found that for heavy numeric calculations
> (for example calculating CRCs of large files, and for large floating
> point calcs)
> using JRuby to call Java gives similar performance to compiled FreePascal.
> The MRI Zlib.crc32 is written in C (that is correct?) and albeit that is
> integer arithmetic, again I've found that a JRuby/Java equivalent
> has a similar speed.
> I'd be interested in any speed tests comparing heavy floating point calculations
> with MRI + C extensions and JRuby with Java.

You may as well remove MRI and JRuby from that and look at the many
benchmarks comparing Java and C numeric algorithm performance. In most
cases, you can get close to or equivalent performance from
appropriately-written Java numeric algorithm code (which may or may
not be *idiomatic* Java code). If you start doing things more OO, then
a better comparison would be equivalent OO-like code in C++, and Java
is still about equivalent.

The cost of calling from (J)Ruby out to Java is probably a bit higher
than calling from Ruby to C extensions, but if you keep the number of
call-outs under control, it's not going to impact application
performance.

And it's worth pointing out that writing portable Java code is a hell
of a lot easier than writing portable C (especially for backend code
that doesn't have user-facing UI components); you don't even need a
compiler on most target systems, and the same code will run anywhere
there's a Java VM (which is basically anywhere).

If you'd rather not futz with compilers and you're running on Java 6,
there's a few useful projects:

* My java-inline project (based on RubyInline), which allows embedding
the Java code directly into your Ruby script:
http://github.com/jruby/java-inline
* My "Duby" language, which attempts to use Ruby syntax to produce
Java code and bytecode without writing in Java:
http://github.com/headius/duby
* My BiteScript project, which is a DSL for generating JVM bytecode
directly: http://github.com/headius/bitescript
* There's also a scala-inline which I will (if I haven't already)
merge into java_inline, allowing you to embed Scala directly into a
Ruby script.

All of which can run on any system with a JVM, with or without a
compiler present.

- Charlie