Fifty seconds for half a megabyte: the optimisation that fixed the constant, not the order

A cryptography library had a bottleneck no test could see: encrypting half a The cause is a trap that keeps recurring: a correct, well-documented — and whose comment, Quipu renders encrypted data as a sequence of symbols. To do The code did not divide one digit at a time. It carried a sensible optimisation: opened by saying , and then described the All true. And the result was still quadratic: extracting nine digits per pass That sentence — "doing it this way would be quadratic" — reads in the past tense, Size Time Factor per doubling 64 KiB 0.79 s — 128 KiB 3.16 s ×4.0 256 KiB 12.6 s ×4.0 512