How heavy are threads compared to procedure calls?

[Lars Ivar Igesund]

Charles D Hixson wrote:

> I realize that they aren't exactly identical, but I have a project in
> mind that should, logically, be done via forked processes...thousands of
> forked processes.  This is obviously impractical.  I could do two
> different redesigns:  one, based around threads, would still involve the
> creation of immense numbers of threads.  The other, based around
> procedure calls, would be theoretically a much poorer model.  (Well, a
> neural net *IS* a bunch of processes that execute relatively
> independently...)
> 
> Typically people decompose a neural net into collections of arrays, but
> I would prefer to model each "cell" as an object.  This is obviously a
> poor match of the design of the algorithm to the structure of the
> processor, but I suspect that there will be details revealed in the
> operation that will only be detected if each cell is an object.  So
> that's what I need.
> 
> The question is, just how inefficient would it be to model each "firing"
> of a neuron as the spawning of a thread.  If I can do it this way then
> the "cells" can operate pseudo-simultaneously.  If I can't, I'll need to
>  add a separate buffer and a bunch of code to emulate synchronous
> operation.  Messy.  Necessary?

When you get into thousands, I think you should avoid at least normal
threads. Light weight stack threads / fibers / co-routines might be a
better solution, especially if you'd like cooperative switching (very nice
for simulations). There has been floating a few suggestions around lately,
search the news groups for the terms above. I don't think Mikola has
released his updated version yet, though. I think it looked very good.

-- 
Lars Ivar Igesund
blog at http://larsivi.net
DSource & #D: larsivi