From: Pit Capitain <pit@...>
Date: 2001-11-04T05:42:17+09:00
Subject: [ruby-talk:24288] Re: cost of threads vs. continuations

Hi Avi,

when I developed my Iterator class (see ruby-talk:20270) which 
uses continuations, I (of course : ) had a number of unit tests. 
Running the test suite several times gave me out of memory errors, 
IIRC. When I changed the implementation to release all references 
to the continuation objects as soon as they weren't needed 
anymore the out of memory errors went away. Might be a hint that 
continuations aren't cheap...

On 2 Nov 2001, at 9:41, Avi Bryant wrote:

> How different are the costs of a continuation and a suspended thread? 
> It seems like they ought to be almost identical, but is there anything
> in the internals that makes one preferable to the other?  Is it
> reasonable to have, say, a hundred or even a few hundred active
> threads or continuations at once?
> 
> I'm playing with extending iowa to allow web apps written in something
> like a continuation-passing style (normally, passing control to
> another page is much like a goto,

One of the first implementations of the Iterator class used a module 
named Goto : ) that was intended to make the use of continuations 
easier to read.

> , and I want to allow something that
> looks like a subroutine call), and although the idea is most naturally
> expressed using call/cc it may be hackable with threads instead.  Of
> course, if continuations are cheaper, then I won't bother. ;-)
> 
> Avi

Regards,
Pit