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The thread: Two counts, two rankings — page 3

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a loop over the alphabet107.9the compound walk10.0the cheapest hereone descent per step19.016 exact patterns of 12ranks per step · sigma 21 What the libraries do

The saving that is a loss

An operation that is seventy-eight times cheaper on a branching search costs twice as much on an exact one. It reports every symbol present in order to hand back the one that was asked for, and a search that knows its character needs none of the rest.

020406080255075100125one sampled position in every …of the plain index, per centsize: 84.7%67.5 steps16,384 characters · 8-character patternssize falls, the walk lengthens Structures

Bits and steps on one frame

The size falls from ninety-nine per cent to eighty-six as the sampling thins, and the walk to a sampled position rises from two and a half steps to sixty-four. Neither line is the answer; the answer is a point on the pair.

phrases examined per probethe linear scan207.0sorted, with a running maximum10.9 — 19xthe running maximum costs 2,821 bits — 21.6% of the index40 of 40 positions checked, and the two agree at all of them238 phrases · 6,144 characters19x on the scan What the libraries do

The scan the order does not touch

Two hundred and seven phrases examined per probe, against eleven. A running maximum of the source regions' right ends lets a leftward walk stop for good, and it costs twenty-two per cent more bits.

10010³10⁴10³10⁴10⁵characters of textoperations, construction includedcrosses at 256the NFAthe DFA64 DFA statescrosses at 256 characters What the libraries do

Where the table starts paying

Five thousand and sixty-five operations before the first character, then one per character. Against nothing before the first character and thirty-nine per character. They cross at two hundred and fifty-six characters, and that crossing is what an engine's compile decision actually is.

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