Concept

Optimisation — where it appears

The act of choosing the best member of a set under a stated objective, where the objective is a choice rather than a fact. Changing it changes which member wins, so dividing an optimum by something afterwards answers a different question from optimising the quotient.

Named by 2 essays across 2 fields — each of them below, with the objects they name alongside it.

A distance divided by a length is not a rate

Two substitutions turn "ab" into "ba", a distance of two over an alignment of two columns — a rate of 1.00. Deleting, matching and inserting also costs two, over three columns, for 0.67. Both are alignments of the same pair, the second has the better rate, and the optimal alignment is not the one that achieves it. Over every pair of strings up to three characters on three letters, 21% disagree.

tables · Cost

The flat bottom of a shallow curve

The low width is chosen as the floor of log of the universe over the count. Rounding it up instead costs one bit on five thousand, because the total is m·w plus n over two to the w and the minimum is where those two are equal.

bounds · Space

Named alongside it

The objects these essays reach for when they reach for this one.

Alignment Bit vector Cost model Denominator Dynamic programming Edit distance Elias fano Honest limit Index size Measured count Metric Normalisation

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