Determinism [LWN.net]

Determinism

Posted Aug 22, 2005 6:07 UTC (Mon) by xoddam (subscriber, #2322)
Parent article: Looking at Real Time for Linux, PowerPC, and Cell (developerWorks)

Paul seems to be using the word "deterministic" in the sense of
having a guaranteed maximum latency; so Linux is "not yet
deterministic" because certain subsystems can't be guaranteed
to respond (or alternatively, to yield a required resource) in
a given time.

I always thought a "deterministic" system was one that, given
the same inputs on any number of occasions, would produce the
same outputs each time. As soon as you introduce randomness
(from the real world or, in thought-experiments like Schrödinger's
cat-box, from nuclear decay), you don't have a deterministic system
any more.

The concepts are related, but I was confused for a while.

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Determinism

Posted Aug 22, 2005 12:00 UTC (Mon) by ncm (subscriber, #165) [Link]

He's talking about deterministic timing, not output. I.e., does it always take the same amount of time to do the same operation? If you can't get that, you settle for maximum latency instead. With sufficiently blurred vision, the response patterns match, providing you have someplace to wait if the result comes back too quickly.