Swift and Timsort - Speaker Deck

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Takanori Hirobe SwiftͷιʔτΞϧΰϦζϜͷಛ௃Λ 5෼Ͱ͖ͪΜͱ஌Δ iOSDC 2021

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ͲΜͳΞϧΰϦζϜΛ࢖͍ͬͯΔͷ͔

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ͲΜͳΞϧΰϦζϜΛ࢖͍ͬͯΔͷ͔ 🤔

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Timsort ͱݺ͹ΕΔΞϧΰϦζϜ Λ࢖͍ͬͯΔ

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Timsortͱ͸ ؆୯ͳ֓ཁ

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Timsortͱ͸ ؆୯ͳ֓ཁ • 2002೥ʹTim PetersʹΑͬͯPythonͷιʔτΞϧΰϦζϜͱ࣮ͯ͠૷͞Εͨ

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Timsortͱ͸ ؆୯ͳ֓ཁ • 2002೥ʹTim PetersʹΑͬͯPythonͷιʔτΞϧΰϦζϜͱ࣮ͯ͠૷͞Εͨ • SwiftͰ͸Swift 5.0(ABI҆ఆԽͷλΠϛϯά)͔Β࠾༻͞Ε͍ͯΔ

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Timsortͱ͸ ؆୯ͳ֓ཁ • 2002೥ʹTim PetersʹΑͬͯPythonͷιʔτΞϧΰϦζϜͱ࣮ͯ͠૷͞Εͨ • SwiftͰ͸Swift 5.0(ABI҆ఆԽͷλΠϛϯά)͔Β࠾༻͞Ε͍ͯΔ • Swift 5.0ະຬͰ͸ҟͳΔΞϧΰϦζϜ͕࢖ΘΕ͍ͯͨ

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Timsortͱ͸ ؆୯ͳ֓ཁ • 2002೥ʹTim PetersʹΑͬͯPythonͷιʔτΞϧΰϦζϜͱ࣮ͯ͠૷͞Εͨ • SwiftͰ͸Swift 5.0(ABI҆ఆԽͷλΠϛϯά)͔Β࠾༻͞Ε͍ͯΔ • Swift 5.0ະຬͰ͸ҟͳΔΞϧΰϦζϜ͕࢖ΘΕ͍ͯͨ • ༏ΕͨੑೳΛ͍࣋ͬͯͯɺRust΍JavaͳͲͰ΋࠾༻͞Ε͍ͯΔ

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ΞϧΰϦζϜͷੑೳ

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ΞϧΰϦζϜͷੑೳ • ଎͞ • ҆ఆੑ • ϝϞϦ࢖༻ྔ

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ΞϧΰϦζϜͷੑೳ • ଎͞ • ҆ఆੑ • ϝϞϦ࢖༻ྔ

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଎͞

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଎͞ • ଎͍ʂ

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଎͞ • ଎͍ʂ • Ҏ্ɻ

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଎͞ • ଎͍ʂ • Ҏ্ɻ • ଎͞ʹ͍ͭͯ࿩͍ͯͨ͠Β5෼Ͱ͸શ͘଍Γͳ͍

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ΞϧΰϦζϜͷੑೳ • ଎͞ • ҆ఆੑ • ϝϞϦ࢖༻ྔ

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ιʔτΞϧΰϦζϜͱ҆ఆੑ

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҆ఆੑ ྫΛ࢖ͬͯߟ͑Δ

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҆ఆੑ ྫΛ࢖ͬͯߟ͑Δ

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҆ఆੑ ྫΛ࢖ͬͯߟ͑Δ

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҆ఆੑ ྫΛ࢖ͬͯߟ͑Δ

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ਤʹ͢Δͱ

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value

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ιʔτͰ͖ͨʂʂ

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҆ఆੑʁ

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҆ఆͳιʔτͱෆ҆ఆͳιʔτ

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҆ఆͳιʔτ

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҆ఆͳιʔτ ιʔτલ ιʔτޙ

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҆ఆͳιʔτ ιʔτલ ιʔτޙ

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҆ఆͳιʔτ value͕ಉ͡ ιʔτલ ιʔτޙ

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҆ఆͳιʔτ value͕ಉ͡ value͕ಉ͡Ͱ΋લޙͷҐஔؔ܎͕อଘ͞ΕΔ ੨ ԫ ੺ ੨ ԫ ੺

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҆ఆͳιʔτ value͕ಉ͡ value͕ಉ͡Ͱ΋લޙͷҐஔؔ܎͕อଘ͞ΕΔ ੨ ԫ ੺ ੨ ԫ ੺

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ෆ҆ఆͳιʔτ ιʔτલ ιʔτޙ

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ෆ҆ఆͳιʔτ value͕ಉ͡ ԫ ੺ ੨ ੨ ԫ ੺ ιʔτલ ιʔτޙ

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ෆ҆ఆͳιʔτ value͕ಉ͡ ԫ ੺ ੨ ੨ ԫ ੺ ಉ͡valueಉ࢜ͷલޙͷҐஔؔ܎͕อଘ͞Εͳ͍

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ෆ҆ఆͳιʔτ value͕ಉ͡ ԫ ੺ ੨ ੨ ԫ ੺ ಉ͡valueಉ࢜ͷલޙͷҐஔؔ܎͕อଘ͞Εͳ͍

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ͳͥ҆ఆੑ͕ॏཁͳͷ͔

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Swiftͷྺ࢙తͳࣄ৘

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Swiftͷྺ࢙తͳࣄ৘ • Timsort͸҆ఆͳιʔτ

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Swiftͷྺ࢙తͳࣄ৘ • Timsort͸҆ఆͳιʔτ • Swift 5.0Ҏ߱

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Swiftͷྺ࢙తͳࣄ৘ • Timsort͸҆ఆͳιʔτ • Swift 5.0Ҏ߱ • Swift 5.0ະຬͰ͸Introsort͕࢖ΘΕ͍ͯͨ

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Swiftͷྺ࢙తͳࣄ৘ • Timsort͸҆ఆͳιʔτ • Swift 5.0Ҏ߱ • Swift 5.0ະຬͰ͸Introsort͕࢖ΘΕ͍ͯͨ • Introsort͸ෆ҆ఆͳιʔτ

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Swiftͷྺ࢙తͳࣄ৘ • Timsort͸҆ఆͳιʔτ • Swift 5.0Ҏ߱ • Swift 5.0ະຬͰ͸Introsort͕࢖ΘΕ͍ͯͨ • Introsort͸ෆ҆ఆͳιʔτ • SwiftͷόʔδϣϯʹΑͬͯιʔτͷ҆ఆੑ͕ҟͳΔ

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Swiftͷྺ࢙తͳࣄ৘ • Timsort͸҆ఆͳιʔτ • Swift 5.0Ҏ߱ • Swift 5.0ະຬͰ͸Introsort͕࢖ΘΕ͍ͯͨ • Introsort͸ෆ҆ఆͳιʔτ • SwiftͷόʔδϣϯʹΑͬͯιʔτͷ҆ఆੑ͕ҟͳΔ • ιʔτ݁Ռ͕ҟͳΔՄೳੑ͕͋Δ

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࠷ޙʹ஫ҙ఺

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࠷ޙʹ஫ҙ఺ • υΩϡϝϯτͰ͸҆ఆੑʹ͍ͭͯ͸อো͍ͯ͠ͳ͍ͷͰ஫ҙ • ҆ఆੑʹ͍ͭͯ͸ Implementation Detail (࣮૷ʹґଘ)ͱ͍͏ѻ͍ "The sorting algorithm is not guaranteed to be stable." https://developer.apple.com/documentation/swift/array/1688499-sort

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ΞϧΰϦζϜͷੑೳ • ଎͞ • ҆ఆੑ • ϝϞϦ࢖༻ྔ

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ϝϞϦ࢖༻ྔ

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TimsortͷϝϞϦ࢖༻ྔ • ιʔτΞϧΰϦζϜ͝ͱʹϝϞϦ࢖༻ྔ͸ҟͳΔ

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TimsortͷϝϞϦ࢖༻ྔ • ιʔτΞϧΰϦζϜ͝ͱʹϝϞϦ࢖༻ྔ͸ҟͳΔ • Timsort͸ɺιʔτ͞ΕΔ഑ྻͷ൒෼ͷେ͖͞ͷϝϞϦΛ֬อ͢Δ • ͋͘·Ͱཧ࿦্ͷ࠷େͷ஋ͳͷͰɺ࣮ࡍ͸΋ͬͱগͳ͍ • ͨͩ͠ɺ׬શϥϯμϜͳ഑ྻ͸ϝϞϦ࢖༻ྔ͕େ͖͘ͳΔ܏޲͕͋Δ

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TimsortͷϝϞϦ࢖༻ྔ

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TimsortͷϝϞϦ࢖༻ྔ Ұॠ͚ͩϝϞϦ࢖༻ྔ͕૿͑Δ

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TimsortͷϝϞϦ࢖༻ྔ Ұॠ͚ͩϝϞϦ࢖༻ྔ͕૿͑Δ ී௨ͷΞϓϦͰ໰୊ʹͳΔ͜ͱ͸ͳ͍͸ͣ

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·ͱΊ • ݱࡏͷSwiftͰ࢖ΘΕ͍ͯΔTimsort͸҆ఆੑ΍࣌ؒܭࢉྔͷ؍఺Ͱɺ༏Εͨੑ ೳΛ͍࣋ͬͯΔ • ྺ࢙తࣄ৘ʹΑΓɺSwift 5.0ͷલޙͰιʔτ݁Ռ͕มΘΔՄೳੑ͕͋Δ • Timsort͸ɺ࠷େͰݩͷ഑ྻͷ൒෼ͷϝϞϦΛ֬อ͢ΔՄೳੑ͕͋Δ

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ࣗݾ঺հ • Takanori Hirobe / ኍ෦وಙ • 4ࡀ͝Ζ͔Βͣͬͱؔ੢ʹࡏॅ • @taka1068 • Twitter, GitHub, Qiita

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Further Reading • ೔ຊޠࢿྉ • https://tech.preferred.jp/ja/blog/tim-sort/ • ӳޠࢿྉ • https://swiftrocks.com/introsort-timsort-swifts-sorting-algorithm • ΞϧΰϦζϜมߋͷPull request • https://github.com/apple/swift/pull/19717

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͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠