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Date: Tue, 13 Sep 2011 06:57:05 -0400
From: "Peter C. Chapin" <PChapin@vtc.vsc.edu>
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Subject: Re: Does GNAT support a thread-free RTS?
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Date: 2011-09-13T06:57:05-04:00
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On 2011-09-13 04:30, Simon Wright wrote:

> Simon Wright<simon@pushface.org>  writes:
>
> My prompt for asking this was a colleague who was used to Erlang and was
> complaining that GNAT's use of OS threads meant he would have to change
> his design mindset to not use thousands of tasks (Erlang processes).

If one is in control of the run time library and if the underlying OS 
supports asynchronous I/O, then I believe it is possible to write a user 
mode thread library that works "nicely" even in the face of I/O 
operations. When calling an I/O operation that might block the library 
uses asynchronous I/O so that the single kernel thread can be scheduled 
onto a different user thread while the I/O completes.

> I believe Scala is similar.

In Scala you can create "thread based" actors that consume a single 
thread each or "event based" actors that can all share a single thread. 
I haven't experimented with this but my guess is that if you do a 
blocking operation while handling an event you may well tie up all event 
based actors. I imagine the thread based actors would continue to work, 
however.

Peter