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base repository: python/cpython
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head repository: eendebakpt/cpython
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compare: gh-149079-find-nfc-index
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Commits on Jun 2, 2026

  1. gh-149079: Speed up find_nfc_index in unicodedata composition 

    find_nfc_index() linearly scanned the nfc_first / nfc_last reindex tables
(nfc_first has ~225 entries) for every starter character during NFC/NFKC
composition. The tables are sorted ascending by .start with disjoint
[start, start+count] ranges, so replace the scan with a galloping
(exponential + binary) search: it stays as cheap as the linear scan for
low-codepoint starters near the front of the table (e.g. Latin, the common
case) while being logarithmic for codepoints deeper in the table.

Interleaved benchmark of unicodedata.normalize('NFC', ...) on decomposed
input (geomean 1.80x faster):
  combining-mark runs   1.88x faster
  decomposed Latin      ~flat (no regression)
  decomposed Greek      2.83x faster

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
    @eendebakpt @claude
    eendebakpt and claude committed Jun 2, 2026
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