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FM-index による全文検索
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Sho Iizuka
February 02, 2015
Programming
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FM-index による全文検索
https://kujira16.hateblo.jp/entry/2015/02/06/210630
Sho Iizuka
February 02, 2015
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Transcript
FM-IndexʹΑΔશจݕࡧ ܭࢉػ࣮शE ࣗ༝՝
• จॻ͔ΒจࣈྻΛݕࡧ͢Δํ๏2௨ΓʹྨͰ͖Δ A. લॲཧ͕ෆཁͳํ๏ (ྗͤͳํ๏, KMP๏, BM๏) B. લॲཧ͕ඞཁͳํ๏ (సஔΠϯσοΫε,
ඌࣙྻ) • Bલॲཧͷ͕࣌ؒඞཁͳ͔ΘΓʹ, ಉ͡จॻ͔ΒԿճݕࡧ͢Δ߹AΑΓߴ • FM-IndexBʹྨ͞ΕΔํ๏Ͱ, จॻͷ͞ʹґଘ͠ͳ͍࣌ؒͰݕࡧͰ͖Δ
લॲཧ̍ɿඌࣙྻͷߏங จॻ mississippi mississippi$ ΤϯυϚʔΧ$ΛՃ mississippi$ ississippi$ ssissippi$ sissippi$ issippi$
ssippi$ sippi$ ippi$ ppi$ pi$ i$ $ ඌࣙͷྻڍ
લॲཧ̍ɿඌࣙྻͷߏங 0 mississippi$ 1 ississippi$ 2 ssissippi$ 3 sissippi$ 4
issippi$ 5 ssippi$ 6 sippi$ 7 ippi$ 8 ppi$ 9 pi$ 10 i$ 11 $ 11 $ 10 i$ 7 ippi$ 4 issippi$ 1 ississippi$ 0 mississippi$ 9 pi$ 8 ppi$ 6 sippi$ 3 sissippi$ 5 ssippi$ 2 ssissippi$ ࣙॻॱͰιʔτ͢Δ ※$ҙͷΞϧϑΝϕοτΑΓ ॱҐ͕খ͍͞ͱ͢Δ ඌࣙྻSA
લॲཧ̎ɿBWT (Burrows-Wheeler Transform) 11 $ 10 i$ 7 ippi$ 4
issippi$ 1 ississippi$ 0 mississippi$ 9 pi$ 8 ppi$ 6 sippi$ 3 sissippi$ 5 ssippi$ 2 ssissippi$ ݩͷจࣈྻʹ͓͚Δ ͻͱͭલͷจࣈʹ͢Δ i p s s m $ p i s s i i BWTจࣈྻT
ݕࡧॲཧ • BWTจࣈྻT = ipssm$pissii ʹ͍ͭͯ, ࣍ͷؔΛఆٛ͢Δ • Rank(c,p) :
T[0,p)ͷൣғͰ, ΞϧϑΝϕοτcͷग़ݱΛฦ͢ • RankLT(c) : TશମͰ, cΑΓॱҐ͕খ͍͞ ΞϧϑΝϕοτͷग़ݱΛฦ͢
ݕࡧॲཧ $ i$ ippi$ issippi$ ississippi$ mississippi$ pi$ ppi$ sippi$
sissippi$ ssippi$ ssissippi$ i p s s m $ p i s s i i BWTจࣈྻT ඌࣙྻSA
ݕࡧॲཧ $ i$ ippi$ issippi$ ississippi$ mississippi$ pi$ ppi$ sippi$
sissippi$ ssippi$ ssissippi$ i p s s m $ p i s s i i BWTจࣈྻT ඌࣙྻSA 'i'+"ppi$"ͷ ඌࣙྻ্Ͱͷ ग़ݱҐஔʁ
ݕࡧॲཧ $ i$ ippi$ issippi$ ississippi$ mississippi$ pi$ ppi$ sippi$
sissippi$ ssippi$ ssissippi$ i p s s m $ p i s s i i BWTจࣈྻT ඌࣙྻSA 'i'+"ppi$"ͷ ඌࣙྻ্Ͱͷ ग़ݱҐஔʁ
ݕࡧॲཧ $ i$ ippi$ issippi$ ississippi$ mississippi$ pi$ ppi$ sippi$
sissippi$ ssippi$ ssissippi$ i p s s m $ p i s s i i BWTจࣈྻT ඌࣙྻSA 'i'+"ppi$"ͷ ඌࣙྻ্Ͱͷ ग़ݱҐஔʁ LF-mapping c=T[p] ʹଓ͘จࣈྻͷ SA্Ͱͷग़ݱҐஔ RankLT(c)+Rank(c,p)
ݕࡧॲཧ $ i$ ippi$ issippi$ ississippi$ mississippi$ pi$ ppi$ sippi$
sissippi$ ssippi$ ssissippi$ i p s s m $ p i s s i i BWTจࣈྻT ඌࣙྻSA "ssi"ͷݕࡧ [RankLT('i')+Rank('i', 0), RankLT('i')+Rank('i', 12)) 'i'Ͱ࢝·Δ จࣈྻ
ݕࡧॲཧ $ i$ ippi$ issippi$ ississippi$ mississippi$ pi$ ppi$ sippi$
sissippi$ ssippi$ ssissippi$ i p s s m $ p i s s i i BWTจࣈྻT ඌࣙྻSA "ssi"ͷݕࡧ [RankLT('s')+Rank('s', 1), RankLT('s')+Rank('s', 5)) 's'+"i"Ͱ࢝·Δ จࣈྻ
ݕࡧॲཧ $ i$ ippi$ issippi$ ississippi$ mississippi$ pi$ ppi$ sippi$
sissippi$ ssippi$ ssissippi$ i p s s m $ p i s s i i BWTจࣈྻT ඌࣙྻSA "ssi"ͷݕࡧ [RankLT('s')+Rank('s', 8), RankLT('s')+Rank('s', 10)) 's'+"si"Ͱ࢝·Δ จࣈྻ
ݕࡧॲཧ • FM-index, ݕࡧจࣈྻʹରԠ͢ΔҐஔͷߜΓࠐΈΛ LF-mappingͷ܁Γฦ͠ʹΑͬͯߦ͏ • LF-mapping Rank ͱ RankLT
Ͱߦ͑Δ • ͜ͷ2ͭͷॲཧ, ΣʔϒϨοτΣʔϒϨοτߦྻΛ͑ O(log σ) ࣌ؒͰՄೳ (σ ΞϧϑΝϕοτͷछྨ) • LF-mappingΛݕࡧจࣈྻQͷ͚ͩ͞܁Γฦ͢ͷͰ, Ұճͷݕࡧ͕O(m log σ) ࣌ؒͰՄೳ (m Q ͷจࣈ) • ݕࡧ͕࣌ؒจॻͷ͞ʹґଘ͠ͳ͍
੍࡞ • ੨ۭจݿͰਓؾ͕͋Δਤॻ500Λରͱͨ͠ Σϒϒϥβ͔Β͑ΔΠϯΫϦϝϯλϧݕࡧΛ੍࡞ • ඌࣙྻͷߏஙsais.hxx (ߴͳϥΠϒϥϦ) Λ༻ • ΣʔϒϨοτߦྻͱFM-IndexࣗͰ࣮
(C++), boost-pythonʹΑΓPython༻ͷ֦ுϞδϡʔϧʹม • Flask (Web App Framework@Python) ͔Βݺͼग़͢
͏·͍͔͘ͳ͔ͬͨͱ͜Ζ • ͍͋·͍ݕࡧΛ࣮͠Α͏ͱͯ͠จݙΛ୳ͯ͠Έͨ → ฤूڑʹରͯ͠ࢦ͔͔࣌ؒΔΒ͍͠… • ࡞ͨ͠ࡧҾΛϑΝΠϧ͔ΒಡΈࠐΉॲཧͰ, طଘͷϥΠϒϥϦΛͬͨΒ༻ϝϞϦͷྔ͕രൃ (ݪҼෆ໌)
·ͱΊ • ߴͳจࣈྻݕࡧͷΞϧΰϦζϜΛ࣮ͯ͠Έͨ • ϒϥβ͔Β͑ΔΑ͏ʹͯ͠Έͨ ! • ࢀߟจݙ • Ԭݪ
େี. ߴจࣈྻղੳͷੈք. ؠॻళ. 2012.
(ิ) ΣʔϒϨοτ 3101212213 1000101101 10111 32223 10111 10001 ԼҐ2Ϗοτ →
ԼҐ1Ϗοτ → 0 1111 222 33 0 1 0 1 0 1