From: MonkeeSage <MonkeeSage@...>
Date: 2007-11-29T07:40:03+09:00
Subject: Re: Ruby needs continuations...

On Nov 28, 3:22 pm, Charles Oliver Nutter <charles.nut...@sun.com>
wrote:
> MonkeeSage wrote:
> > On Nov 28, 9:41 am, Charles Oliver Nutter <charles.nut...@sun.com>
> > wrote:
> >> MonkeeSage wrote:
> >>> You actually need a generator, which can be implemented with
> >>> continuations, but doesn't have to be (in 1.9 the generators are
> >>> implemented with threads -- have a look at generator.rb in 1.8 and 1.9
> >>> to see the differences). Using generators, you can implement izip (and
> >>> all of itertools if you'd like, though most of it already has
> >>> equivalent ruby solutions). Here is a pretty close translation of the
> >>> python given in the itertools docs:
> >> Ruby 1.9 also moves continuations out of core, but provides a form of
> >> bounded continuations (coroutines) that's possible to implement in JRuby:
>
> >> require 'fiber'
> >> f = Fiber.new { a = 1; while true; Fiber.yield a; a += 1; end }
> >> 5.times { puts f.resume }
>
> >> $ jruby -J-Djruby.compat.version=ruby1_9 fiber_example.rb
> >> 1
> >> 2
> >> 3
> >> 4
> >> 5
>
> >> Under JRuby, it's using a native thread per live Fiber, so it's heavier
> >> than in Ruby 1.9 which uses green threads. However they'll actually run
> >> in parallel on JRuby, so that's a benefit. JRuby also supports a thread
> >> pool in 1.1 that helps blunt the cost of spinning up native threads.
>
> >> - Charlie
>
> > I just tried the above izip function in jruby, but it only gave me two
> > iterations...
>
> Could be a bug in generator; could you try it on a more recent release
> (like 1.0.2 or 1.1b1) and report it if it's actually a problem?
>
> http://jira.codehaus.org/browse/JRUBY
>
> - Charlie

I downloaded the precompiled versions of 1.0.2 and 1.1b1 and both
displayed the same behavior. I'll submit a bug report.

Regards,
Jordan