[PRL] "Threads Considered Harmful" in the news

[Joe Marshall]

On 1/24/07, Matthias Felleisen <matthias at ccs.neu.edu> wrote:
>
> Do you care about predictability? I find Will's reaction is over the
> top.
> I really do like predicting the outcome of a computation as a
> programmer.
> It helps me reason (test/debug/etc). -- Matthias

Predictability and determinism aren't the same thing.  There are deterministic,
but unpredictable programs (assuming that by `predict' you wish to make
statements about the outcome without running the program).  There are
non-deterministic, but predictable programs:  any reliable Scheme program
that does not depend on order of argument evaluation.

My initial reaction was that Will was over the top, but when I gave it
a second or
third thought, I realized that determinism is really about imposing a temporal
order above and beyond the necessary causality.  Certainly physics doesn't
require this (there is no temporal order between two events separated in a
space-like manner), so it isn't a fundamental property of the universe.



-- 
~jrm