2 docs tagged with "determinism"

Almost every mechanism that makes a computer fast makes it less predictable, and the trade is usually invisible in source code. Caches, prefetchers, branch speculation, bus arbitration and dynamic memory allocation are all bets on history repeating: they are fast when the recent past resembles the present and slow when it does not. In a throughput-oriented system that is an unambiguously good bargain. In a system with deadlines it means the number you have to defend — the worst case — is set by the unlucky path through every one of them, while every measurement you take is dominated by the lucky one.

Same code, same data, different result. This should be alarming, and it usually traces to one of a small, well-understood set of non-determinism sources — reproducibility is layered, and the right response is deciding which layer actually matters before paying for the strictest possible guarantee.