Re: tlug: Karl-Max has cool dreams [was: dual-pentium processors]

["Manuel M. T. Chakravarty" <chak@example.com>]

"Stephen J. Turnbull" <turnbull@example.com> wrote,

> Well, we've got Karl-Max using whitespace to make his text readable
> ...
> 
> >>>>> "Karl-Max" == Karl-Max Wagner <karlmax@example.com> writes:
> 
>     >> of work.  And then there are more problems where we don't know
>                                     ^^^^
>     >> any useful parallel algorithm than problems where such
> 
>     Karl-Max> Right. But they are in the minority.
>               ~~~~~                      ^^^^^^^^
> ... now maybe we can get him to read what he's responding
> to?

:-)

> I am not a specialist, but I do read about this for philosophical
> interest (and because as soon as we have a good technical analysis of
> abstract distributed processing	I plan to apply it to microeconomic
> theory), and it seems to me that I've read Manuel's statement
> (relatively few problems are parallelizable) many times, and I've
> never seen it denied---until Karl-Max just did so.
> 
> It seems to me that our choice of problems may be biased by our much
> better understanding of sequential algorithms.  It is clear from my
> (best characterized as "abortive", if not "abortions") attempts to
> apply automata theory to economics that societies and economies choose 
> problems that can be solved in parallel (that's why the market economy 
> works better than any other) and end up with "efficient" solutions (no 
> single processor can achieve a better processor-local solution without 
> lowering some other processor's solution) rather than "global maxima" 
> (inasmuch as the latter requires lots of expensive communication).

I should maybe clarify that my comments where purely aimed
at the use of parallelism in programs written by humans.  A
parallel system that is self-organizing -- economics should
qualify for that -- is something completely different.  The
problem with writing parallel programs is that humans are
awfully bad at *designing* a highly parallel process and we
didn't manage to invent the (software) tools yet that
support us to do it -- except for some rather simple cases
like regular parallelism etc.[1]

But, Steve, I don't follow you completely.  What is your
definition of a ``global maximum'' in that context?  I would
think, it is the best possible solution that the system as a
whole can achieve.  It seems that you define it a bit
differently; maybe one processor is better (according to
whatever cost function you choose) than all others?

I am not sure, but you might be interested in the work on
parallel solutions (in the sense of algorithms) to
optimization problems -- a relatively new, but it seems
rather hot topic (in the sense of, it is easy to get
funding) in the parallel computing community.

Cheers,

Manuel

[1] Nevertheless, I think, inventing such tools is an
    exciting challenge.
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