Compilation statistics

Inspect cached scalar diagnostics with getStats(), available since v3.2.0.

Read statistics

import AhoCorasick from 'modern-ahocorasick'

const matcher = new AhoCorasick(['he', 'she', 'he'])
const stats = matcher.getStats()
stats.patternCount // 3
stats.backend // 'compact'
Object.isFrozen(stats) // true
stats === matcher.getStats() // true

Fields and storage accounting

Field	Meaning
backend	compact or double-array
patternCount	Input entries, including duplicates
stateCount	States including root, excluding unused DAT slots
transitionCount	Trie edges
alphabetSize	Distinct compiled symbols
maxPatternUnits	Longest pattern in the units below
unit	grapheme or folded-codepoint
typedArrayBytes	Retained typed scan and auxiliary arrays

Folded units are codepoints after Unicode folding, so ß occupies two units in a folded profile. Statistics are computed at compilation; reads do not traverse the automaton. /text is a mapping adapter and has no getStats() method.

typedArrayBytes includes allocated but unused slots. It excludes strings, Maps, JS objects, temporary build allocations and native ICU, and is not total heap usage.

Statistics after persistence

Compact deserialization recreates the same statistics. /fast saves the portable compact format, so the restored backend and storage statistics describe compact storage.

Measure application memory

Use these fields to inspect compiled structure, not to estimate total process memory. Measure build time, scan time, retained JavaScript heap and ArrayBuffer storage separately.

See Backend tradeoffs and measurements.