Re: [boost] Updated version of futures library

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-06-02 21:58:14

I wrote that

> If the scheduler performance is insufficient, it will not be able to
> maintain a low M. If it does manage to maintain a low M, then its
> performance is sufficient.

Now that I think about it, this isn't true for the typical fork-join 
parallelism.

http://gee.cs.oswego.edu/dl/papers/fj.pdf

If we have for example an active function fib(n) that returns 
fib(n-1)+fib(n-2), it will quickly generate a large N. In this case however, 
if the task queue is actually a stack, it can be reduced in a single 
execution as the older tasks will become ready as soon as the newer tasks 
are done. (But it will take logN to fill it. On second thought, with a FIFO 
policy it will be generated in a single pass and then reduced in logN 
passes. So it's basically the same.)

Not that fork-join parallelism makes much sense for a single-threaded active 
object. :-)