Thread Pooling

[kris]

Sean Kelly wrote:
> Craig Black wrote:
> 
>>
>> I realize that you haven't had time to think this through completely, 
>> so perhaps I can help to stimulate your thinking.  And as always,  I 
>> could be missing something here so correct me if I'm way off base.
>>
>> What benefit does this approach have over a thread pool?  It seems to 
>> be basically the idea that I had originally presented, except that I 
>> had not presented a solution for methods with return values.
> 
> 
> Compared to working directly with a thread pool, it allows for the 
> scheduling policy to be separated from the task queue.  So actives could 
> be run sequentially in the main thread, spread across multiple threads, 
> etc.  However, a more general task processor could really do the same 
> thing.  For the rest, I think it mostly provides a decent framework to 
> use for asynchronous task completion.  For example, I think it's 
> potentially useful to be able to wait on combinations of futures using 
> or/and logic.
> 
>> The approach that you outline does not allow for active classes and so 
>> misses a large part of what the Concur pseudocode syntax provides.  
>> For example,
>>
>> active class C {
>>   void f() { ... }
>>   void g() { ... }
>> }
>> ...
>> active C c;
>> c.f();
>> c.g();
> 
> 
> I'll admit I skipped that part for the sake of brevity, but it should be 
> possible to create active objects via subclassing or perhaps with a 
> combination of mixins and interfaces.  However, I think the ad hoc 
> approach may prove to be much more useful in practice.
> 
>> Even still, this approach lacks the OO elegance of the active class 
>> pseudocode.  But it's perhaps better than using locks.
> 
> 
> Depends on the problem, I think.  I think the non-OO active syntax 
> better illustrates just how easy it is to break sequential code into 
> parallel chunks.
> 
> I'll probably have more to say once I've read the links Kris posted.
> 
> 
> Sean


Sean ~ you might find these interesting:

A Java library of CSP primitives. This was built with the cooperation of 
  the CSP and occam communities, and was used by Doug Lea for the CSP 
examples in his book "Concurrent Programming in Java" 2nd Ed.

Intro: http://www.cs.kent.ac.uk/projects/ofa/jcsp/explain.html

JDocs: http://www.cs.kent.ac.uk/projects/ofa/jcsp/jcsp1-0-rc4/jcsp-docs/

Presentation & commentary on CSP-style concurrency versus thread/monitor 
style: http://www.cs.kent.ac.uk/projects/ofa/jcsp/jcsp.pdf

Presentation on distributed JCSP:
http://www.cs.kent.ac.uk/projects/ofa/jcsp/jcsp-net-slides.pdf