Re: [Caml-list] Thread behaviour

[Chet Murthy <murthy.chet@gmail.com>]

> This is my situation. I don't care if the code runs on a single core
> (in fact, I hope it does), but I do want to use threads which are
> scheduled reasonably independently and reasonably fairly. My first
> example shows that one thread is effectively starved by the other
> thread.

Ah.  ok.  In this case, it's easier.  You just need to ensure that in
every loop,in every recursive function, there's a call to something
that yield()s, on every path.  It's that simple, and that icky.  But
then, if you have code that literally doesn't do anything that yields,
in a loop, it's compute-intensive, and -that- means you're not really
asking for concurrency, are you?

BTW, to your original question "why should the while loop affect
scheduling of f's thread": because there is a global operation
(scheduling) that needs cooperation from all threads in order to
execute.  And that requires explicit coding by the programmer.  Now,
the compiler -could- have inserted code to do the yield() (in some old
LISPms, it was done at every backward jump and return, I think).

I can't speculate as to why it wasn't done, but given that the goal of
ocaml's threads is concurrency, and not parallelism, it isn't common
(at least, in my experience) to write code that doesn't naturally
reach yield points frequently.

--chet--