Invisible <voi### [at] devnull> wrote:
> As far as computer programming is concerned, writing programs which 
> aren't single-threaded is a "hard problem". Oh, it depends on the task 
> of course. But many programs are just really awkward to write in a way 
> that utilises multiple cores.

  The problems with concurrent and parallel programming are quite fundamental
(and not all that dependent eg. on the programming language used). There are
many severe problems, mutual exclusion, deadlocks and livelocks being
just a few examples of them (and even with them, they often become a problem
in programs which are supposedly thread-aware and use all kinds of locking
and mutual exclusion mechanisms). Curiously the majority of these problems
appear even in single-core systems which run multiple threads (even though
no two threads are ever physically run at the same time in parallel). The
problems are only aggravated in situations where separate processes need to
communicate with each other through an unreliable channel (which is the
case in distributed and client/server type systems). The problems that may
arise are sometimes quite surprising and not at all evident from the program
itself, even if it's competently implemented. These problems have been known
for a really long time and there are tons and tons of entire books dedicated
to them. Also lots of theory and software has been developed in order to
try to model such parallel systems and try to find flaws in them, and to
verify that a proposed implementation works.

  I don't think that switching from current serial design CPUs to something
that is more parallel is going to solve any of those problems (if anything,
they could only aggravate them). AFAIK the problems are more fundamental
than the precise CPU design used.

-- 
                                                          - Warp

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