Issue #20512 has been reported by giner (Stanislav German-Evtushenko). ---------------------------------------- Bug #20512: Order of magnitude performance differenfce in single character slicing UTF-8 strings before and after length method is executed https://bugs.ruby-lang.org/issues/20512 * Author: giner (Stanislav German-Evtushenko) * Status: Open * ruby -v: ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- Slicing of a single character of UTF-8 string becomes ~15 times faster after method "length" is executed on the string. ```ruby # Single byte symbols letters = ("a".."z").to_a length = 100000 str = length.times.map{letters[rand(26)]}.join # Slow start = Time.now length.times{|i| str[i]} puts Time.now - start # 0.169156201 str.length # performance hack # Fast start = Time.now length.times{|i| str[i]} puts Time.now - start # 0.009883919 # UTF-8 Symbols letters = ("а".."я").to_a length = 10000 str = length.times.map{letters[rand(26)]}.join # Slow start = Time.now length.times{|i| str[i]} puts Time.now - start # 0.326204007 str.length # performance hack # Fast start = Time.now length.times{|i| str[i]} puts Time.now - start # 0.016943093 ``` -- https://bugs.ruby-lang.org/