原著論文
ゲーム理論に基づいた複雑ネットワーク形成のモデル化
今
井
哲
郎
*・田
中
敦
**・吉
澤
康
介
***・三
宅
修
平
*** 情報通信や社会学,生物学など多様な分野において,要素とその要素間の関係で構成されるネッ トワーク構造(トポロジ)が複雑ネットワークと呼ばれる特性を持っていることが明らかになって きている.多数の主体が自己組織的に複雑ネットワークを形成する原理を,構成主体の個人合理性 に落とし込むことで明らかにするために,我々はこれまでにゲーム理論に基づいた複雑ネットワー ク形成のモデル化を行い,その特性について分析してきた.本稿では,これまでの研究成果を概観 し,今後の展望について述べる. キーワード:複雑ネットワーク,ネットワーク形成ゲーム,戦略的ネットワーク形成,ネットワー クダイナミクス,コンピュータシミュレーションModeling of Complex Network Formation Based on Game Theory
Tetsuo IMAI
*, Atsushi TANAKA
**,
Kousuke YOSHIZAWA
***and Shuhei MIYAKE
***In various fields such as communication technology, sociology, and biology, it has been revealed that network structure (topology) composed of elements and relationships of the elements has property of the complex networks. By the concept of individual rationality, in order to reveal why numerous individuals tend to self-organize complex networks, we have modeled complex networks formation based on game theory and analyzed their properties. In this paper, an overview of the research results and prospects are described.
Keywords: Complex network, Network formation game, Strategic network formation, Network dynamics, Computer simulation
*東京情報大学 看護学部 遠隔看護実践研究センター 2017年5月15日受付
Telenursing Research Center, Faculty of Nursing, Tokyo University of Information Sciences 2017年8月18日受理
**山形大学大学院 理工学研究科
Graduate School of the Science and Engineering, Yamagata University
***東京情報大学 総合情報学部
Faculty of Informatics, Tokyo University of Information Sciences
1
͡Ίʹ
ใ௨৴ࣾձֶɼੜֶͳͲଟ༷ͳʹ͓͍ ͯɼཁૉͱͦͷཁૉؒͷؔͰߏ͞ΕΔωοτ ϫʔΫ(ҎԼɼNW)ͷߏ(τϙϩδ)͕ෳࡶNW ͱݺΕΔಛੑΛ͍࣋ͬͯΔ͜ͱ͕໌Β͔ʹͳͬͯ ͖͍ͯΔɽෳࡶNWɼεέʔϧϑϦʔੑ 1 εϞʔϧϫʔϧυੑ 2 ͱ͍ͬͨಛΛ࣋ͭ NWͰ͋ΔɽεέʔϧϑϦʔੑʹ͍ͭͯɼϊʔ υϦϯΫͷϥϯμϜͳোʹରͯ͠ؤ݈Ͱ͋ΔҰ ํɼϋϒΠϯϑϧΤϯαʔͱ͍ͬͨNWͷதͰ ॏཁੑͷߴ͍ཁૉͷোʹରͯ͠ɼඇৗʹ੬ऑͰ ͋Δͱ͍͏ಛΛ࣋ͭ͜ͱ͕ΒΕ͍ͯΔɽͦͷͨ Ίɼྫ͑௨৴NWͷτϙϩδͱͯ͠ɼඞͣ͠ ·͍͠ಛੑͰͳ͍ɽෳࡶNWͷதʹɼߴ ʹࣗతͳஅೳྗΛ࣋ͬͨଟͷओମʹΑͬͯࣗ ݾ৫తʹߏங͞Εͨͷ͕ଟ͋Δɽོۙͷ FacebookInstagramͳͲʹද͞ΕΔSNSʹ ͓͚Δ༑ਓؒNWͷτϙϩδɼͦͷΑ͏ͳNW ͷҰͭͱݟΒΕ͍ͯΔɽ ෳࡶ NW Λੜ͢ΔϞσϧɼෳࡶ NW ݚ ڀͷՐ͚ͱͳͬͨBarab´asi-Albert Ϟσϧ Watts-StrogatzϞσϧͳͲɼ͜Ε·ͰʹଟఏҊ ͞Ε͍ͯΔɽ͔ͦ͠͠ͷଟ͘ɼଟͷओମ͕རݾ తͳબΛ࣋ͪɼ͓ޓ͍ͷ૬ޓঝೝʹΑͬͯϦϯΫ ͕ܗ͞Ε͍ͯΔͱ͍͏໘Λेʹදݱ͖͠Ε͍ͯ ͳ͔ͬͨɽݴ͍͑Εɼଟͷओମ͕ʮͲͷΑ͏ ʹʯৼΔ͑ෳࡶNW͕ܗ͞ΕΔ͔Λ໌Β͔ ʹͨ͠Ϟσϧଟ͋͘ΔҰํͰɼଟͷओମ͕ʮͳ ͥʯෳࡶNWΛܗ͢Δͷ͔Λेʹ໌Β͔ʹ͠ ͨϞσϧɼචऀΒͷΔݶΓଟ͘ͳ͍ɽ ͜ͷ͍Λղܾ͢ΔͨΊͷ༗ͳΞϓϩʔνͱ͠ ͯɼήʔϜཧͷʹ͓͚ΔNWܗήʔϜ͕ ͋ΔɽήʔϜཧɼෳͷߦಈओମͷҙࢥܾఆ͕ ૬ޓʹӨڹΛ༩͑߹͏ঢ়گΛੳ͢ΔͨΊͷཧత ΈͰ͋ΔɽNWܗήʔϜɼ͜ͷήʔϜཧ ͷΈΛ༻͍ͯɼརݾతͳଟओମʹΑΔήʔϜ తͳঢ়گԼͰߏங͞ΕΔτϙϩδΛ໌Β͔ʹ͢Δऔ ΓΈͷதͰఏҊ͞ΕͨͷͰ͋ΔɽήʔϜཧʹ ج͍ͮͯෳࡶNWܗΛϞσϧԽ͢Δ͜ͱɼଟ ͷओମ͕ʮͳͥʯࣗݾ৫తʹෳࡶNWΛܗ ͢Δͷ͔ͱ͍͏͍ΛɼNWΛߏ͢Δओମͷݸ ਓ߹ཧੑʹམͱ͠ࠐΉ͜ͱͰ໌Β͔ʹ͢Δ͜ͱΛҙ ຯ͍ͯ͠Δɽ͜ͷΑ͏ͳཱ͔Βকདྷతʹɼݸਓ ߹ཧੑΛߟྀͨ͠NWΛઃܭ͢ΔͨΊͷख๏ͷ֬ ཱʹܨ͕ΓɼͦΕڧྗͰݱ࣮తʹ࣮ߦՄೳͳख๏ ͱͳΔ͜ͱ͕ظ͞ΕΔɽ චऀΒ͜Ε·ͰʹɼήʔϜཧʹج͍ͮͯෳࡶ NWͷܗΛϞσϧԽ͠ɼͦͷಛੑʹ͍ͭͯੳ ͖ͯͨ͠ɽຊߘͰͦΕΒͷݚڀՌΛ֓؍͠ɼࠓ ޙͷలʹ͍ͭͯٞ͢Δɽ2
ωοτϫʔΫܗήʔϜ
2.1 ੩ֶతϞσϧNWܗήʔϜ(network formation game)ɼ
MyersonʹΑͬͯఏҊ(Myerson 1976)[13]͞Εɼ ޙʹJacksonͱWolinskyʹΑͬͯઓུܗήʔϜ ͷܗͰఆࣜԽ(Jackson and Wolinsky 1996)[10]
͞Εͨ 3 ɽຊߘͰɼචऀΒ͕ఏҊ͍ͯ͠ΔϞ σϧͱͷରൺͷͨΊʹɼJacksonΒͷϞσϧΛʮ੩ ֶతʯNWܗήʔϜͱݺͿɽ ੩ֶతNWܗήʔϜҎԼͷΑ͏ʹఆࣜԽ͞ ΕΔɽͳ͓ຊߘͰ؆୯ͷͨΊɼϊʔυiͱjΛ݁ ͿϦϯΫΛij ͱه͠ɼ͋ΔNWͷτϙϩδ(άϥ ϑཧʹ͓͚Δάϥϑͱಉٛ)g ∈ GΛϦϯΫͷू ߹Ͱද͢ɽຊߘͰѻ͏NWτϙϩδશͯϦϯΫ ʹ͖Λ࣋ͨͤͳ͍ແάϥϑͰ͋Δɽ ϓϨΠϠʔ ͦΕͧΕͷϊʔυ͕ϓϨΠϠʔΛද ͢ɽ ઓུ ϊʔυiͷઓུɼϒʔϧมͷn− 1࣍ ݩϕΫτϧsi = (si1, si2, . . . , si(i−1), si(i+1), . . . sin) ∈ {0, 1}n−1 Ͱ ද ͞ Ε Δ ɽ͜ ͜ Ͱ sij = 0 ͷͱ͖ɼϊʔυ i ͕ϊʔυ j ͱϦ ϯΫΛுΔ͜ͱΛر͠ͳ͍͜ͱΛҙຯ͠ɼ sij = 1Ͱ͋Εر͢Δ͜ͱΛҙຯ͢Δɽ ؼ݁ ઓུͷs = (s1, s2, . . . , sn)ʹରͯ͠ؼ݁ ͱͯ͠ಘΒΕΔNWτϙϩδg(s)ɼg(s) = {ij|sij = sji = 1}ͱͳΔɽ͢ͳΘͪɼͯ͢ ͷϊʔυϖΞͰɼϖΞͷํ͕ڞʹرͨ͠ͱ ͖ʹϦϯΫ͕ܗ͞ΕΔɽ རಘ NWτϙϩδg(s)ʹ͓͚Δϊʔυiͷརಘ ui(g(s)) : G → Rͱͯ͠ɼຊߘͰҎԼͷؔ Λ༻͍Δ 4 ɽ ui(g(s)) = j�=i δdij − j∈{j|ij∈g(s)} cij (1) [ [ [ [ ] ] ] ]
͜͜Ͱ0 < δ < 1ݮਰύϥϝʔλΛɼdij ϊʔυi, jؒͷ࠷ܦ࿏(ͨͩ͠iͱj͕ ౸ୡՄೳͰͳ͍ͱ͖ʹdij =∞)Λɼcij ϊʔυi, jؒͷίετύϥϝʔλΛද͢ɽ ੩ֶత NWܗήʔϜʹ͓͚Δ҆ఆੑʹ͍ͭ ͯɼ௨ৗͷઓུܗήʔϜʹ͓͚Δφογϡۉ ߧʹΘͬͯɼҎԼʹΑͬͯఆٛ͞ΕΔʮର҆ ఆ 5 (pairwise stability)ʯͷ֓೦͕ఏҊ͞Ε ͍ͯΔɽ ର҆ఆੑͷఆٛͷલʹ·ͣɼදهΛཧ͢Δɽ ij /∈ gͰ͋Δgʹର͠ϦϯΫij ΛՃͨ͠NW τϙϩδΛg + ijɼಉ༷ʹij ∈ gͰ͋Δgʹର͠ ϦϯΫij Λআͨ͠NWτϙϩδΛg− ijͱද ه͢Δͱɼ͋ΔNWτϙϩδg͔ΒϦϯΫij ͷ ༗ແΛมԽͤͨ͞ͱ͖ͷϊʔυiͷརಘͷมԽྔ Δugi(ij) Δugi(ij) = ui(g− ij) − ui(g), if ij∈ g ui(g + ij)− ui(g), if ij /∈ g. (2) ͱද͞ΕΔɽ͋ΔNWτϙϩδg͕ର҆ఆͰ͋Δ ͱɼ
∀ij ∈ gʹର͠Δugi(ij)≤ 0, Δugj(ij)≤ 0 (3)
͔ͭ
∀ij /∈ gʹର͠Δugi(ij) > 0⇒ Δugj(ij) < 0
(4) ͕Γཱͭ͜ͱΛ͍͏ɽ͜ͷର҆ఆੑɼطʹଘࡏ ͢ΔϦϯΫʹରͯ͠ɼ྆ͷϊʔυͷͲͪΒͦ ͷϦϯΫΛஅ͢ΔΠϯηϯςΟϒ(༠Ҽ)͕ͳ͍ ͜ͱ(ࣜ(3))ɼ·ͨϦϯΫ͕ଘࡏ͠ͳ͍ϊʔυϖΞ ʹରͯ͠ɼগͳ͘ͱҰํͷϊʔυʹϦϯΫΛ ܗ͢ΔΠϯηϯςΟϒ͕ͳ͍͜ͱΛද͍ͯ͠Δ (ࣜ(4))ɽ ͜͜ͰޙͷٞͷͨΊʹɼՄೳͳϦϯΫมಈ
(possible link change)ʹ͍ͭͯड़ΔɽҎ Լͷ͕݅Γཱͭͱ͖ɼϦϯΫij ՄೳͳϦϯ
ΫมಈͰ͋Δͱ͍͏ɽ
ij ∈ gͰ͋Ε
Δugi(ij) > 0 ·ͨ Δugj(ij) > 0 (5)
ij /∈ gͰ͋Ε
Δugi(ij)≥ 0 ͔ͭ Δugj(ij)≥ 0,
ͨͩ͠Δugi(ij) = Δugj(ij) = 0Λআ͘ɽ (6)
͢ͳΘͪɼՄೳͳϦϯΫมಈͱɼ྆ͷϓϨΠ Ϡʔͷগͳ͘ͱҰํͷརಘΛ૿Ճͤ͞ΔϦϯΫ আڈɼ͋Δ͍྆ͷϓϨΠϠʔͷརಘΛڞʹ૿ Ճͤ͞Δ(·ͨҰํͷརಘΛ૿Ճͤ͞ɼ͏Ұํ ͷརಘΛมԽͤ͞ͳ͍)Α͏ͳϦϯΫՃͷ͜ͱΛ ͍͏ɽ͋Δτϙϩδ͕ର҆ఆͰ͋Δ͜ͱɼશͯͷ ϊʔυϖΞͷؒʹՄೳͳϦϯΫมಈ͕Ұͭଘࡏ͠ ͳ͍͜ͱͰ͋Δͱݴ͍͑Δ͜ͱ͕Ͱ͖Δɽ ઓུܗήʔϜͷղ֓೦ʹφογϡۉߧ͕༻͍Β ΕΔ͜ͱ͕ଟ͍ɽ͔͠͠੩ֶతNWܗήʔϜʹ φογϡۉߧ(ͱͦͷਫ਼៛Խ) ͷ֓೦Λ༻͍ͯੳ Λ͢ΔͱɼϦϯΫͷܗʹϦϯΫͷ྆ͷϓϨΠ Ϡʔͷ߹ҙ͕ͳ͚ΕͳΒͳ͍ͱ͍͏੩ֶతNW ܗήʔϜͷಛघੑʹΑͬͯɼແҙຯͳۉߧ͕ଟ ͘ͳͬͯ͠·͏ͱ͍͏͕͋Δ 6 ɽର҆ఆੑ ɼ͜ͷಛघੑΛөͯ͠ఏҊ͞Εͨ֓೦Ͱ͋Δ ͕ɼҎԼͷ2ʹ͍ͭͯҙ͕ඞཁͰ͋ΔɽҰͭ ɼφογϡۉߧ͕ઓུͷมߋʹؔ͢Δۉߧ֓೦Ͱ ͋ͬͨͷʹରͯ͠ɼର҆ఆੑϦϯΫͷ༗ແͷมߋ ʹؔ͢Δ҆ఆੑͷ֓೦Ͱ͋Δͱ͍͏ɼ͏Ұͭ ɼϓϨΠϠʔͷઓུʹ֬తͳࠞ߹ઓུΛڐͤ ɼඞͣφογϡۉߧ͕ଘࡏ͢Δ͜ͱ͕อূ͞Εͯ ͍Δͷʹର͠ɼର҆ఆղଘࡏ͠ͳ͍߹͕͋Δͱ ͍͏Ͱ͋Δɽ ͜͜Ͱɼ੩ֶతNWܗήʔϜʹؔ͢Δطଘͷ ղੳత݁Ռʹ͍ͭͯ2հ͢ΔɽҰͭɼϦϯ Ϋίετ͕શ͍ͯ͠߹(cij = c)ͷɼର҆ఆղ ͱޮղͷؔʹؔ͢Δ2ͭͷఆཧͰ͋Δɽ ఆཧ 2.1. ϦϯΫίετ͕શ͍ͯ͠߹ͷଓϞ σϧʹ͓͍ͯɼޮղʹؔͯ͠ҎԼ͕Γཱͭɽ (1) c < δ− δ2ͷͱ͖ɼͯ͢ͷϊʔυϖΞͷؒʹ ϦϯΫ͕ଘࡏ͢ΔશNW͕།ҰͷޮղͰ ͋Δɽ (2) δ− δ2 < c < δ + n−2 2 δ 2ͷͱ͖ɼશϊʔυʹ ΑΔελʔܕNW͕།ҰͷޮղͰ͋Δɽ [ [ ] ]
(3) δ +n−22 δ2< cͷͱ͖ɼ1ͭϦϯΫΛ࣋ͨͳ ͍ۭͷNW͕།ҰͷޮղͰ͋Δɽ ఆཧ 2.2. རಘؔΛࣜ(1)ͱ͠ɼϦϯΫίετ͕ શ͍ͯ͠߹ͷଓϞσϧʹ͓͍ͯɼର҆ఆղʹ ؔͯ͠ҎԼ͕Γཱͭɽ (1) ର҆ఆͳ NW ͕࣋ͭඇۭͷ࿈݁ͷ ߴʑ1ͭͰ͋Δɽ (2) c < δ− δ2ͷͱ͖ɼ།Ұͷର҆ఆNWશ NWͰ͋Δɽ (3) δ− δ2< c < δͷͱ͖ɼશϊʔυʹΑΔελʔ ܕNWର҆ఆͰ͋Δ͕ɼඞͣ͠།Ұͷର ҆ఆNWͱݶΒͳ͍ɽ (4) δ < cͷͱ͖ɼର҆ఆͳNWۭͷNW͔ɼ ͯ͘͢͠ͷϊʔυ͕2ຊͷϦϯΫΛ࣋ͭɽ ֤ఆཧͷূ໌ɼࡾ্(2006)[18]͋Δ͍૿ࢁ (2013)[19] Λࢀর͞Ε͍ͨɽҎ্ͷ݁ՌΛ·ͱΊ ͨͷΛਤ1ʹࣔ͢ɽ࠷͖͢ྖҬ�(3 ͢ ͳΘͪδ < c < δ +n−22 δ2ͷͱ͖)Ͱɼ͜ͷͱ͖ ର҆ఆղͱޮղৗʹҟͳΔɽ ͜ͷ݁Ռɼର҆ఆղͱޮղ͕ͲͷΑ͏ͳNW τϙϩδΛऔΔ͔ΛɼϦϯΫίετͱݮਰύϥϝʔ λͷେ͖͞ͷؔʹؔ͢Δ֤έʔεʹ͍ͭͯղੳత ʹࣔͨ͠ͷͰɼॏཁͳ݁ՌͰ͋ΔɽҰํͰɼ͜ͷ ݁ՌϦϯΫίετ͕શ͍ͯ͠߹ʹݶఆͨ͠ ͷͰ͋Δ͜ͱʹҙ͕ඞཁͰ͋ΔɽͦͷͨΊɼఆཧ ʹݱΕΔNWτϙϩδɼରশ͔ͦΕʹ͍ۙͷ ʹͳ͍ͬͯΔɽݴ͏·Ͱͳ͘ɼݱ࣮ͷNWͰ ֤ϊʔυͷؒͷϦϯΫίετ͕͘͠ͳΔͱ͍͏อ ূͳ͍Ͱ͋Ζ͏ɽ طଘͷղੳత݁Ռͱͯ͠ೋͭʹڍ͛Δͷɼ
Jackson and Rogers (2005)[8]ʹΑͬͯ͞Εͨɼ ੩ֶతNWܗήʔϜͱෳࡶ NWͱͷؔ࿈ੑʹ ؔ͢Δ݁ՌͰ͋Δ 7 ɽ൴ΒϦϯΫίετʹؔ ͯ͠ౡϞσϧͱݺΕΔϞσϧΛѻͬͨɽౡϞσϧ Ͱɼશͯͷϊʔυ͕KݸͷౡʹJ ϊʔυׂͣͭ ΓͯΒΕɼࣗͱಉ͡ౡͷϊʔυͱͷଓʹখ ͞ͳϦϯΫίετc͕ɼࣗͱҟͳΔౡͷϊʔυ ͱͷଓʹେ͖ͳϦϯΫίετC͕ඞཁͱͳΔɽ ·ͨརಘؔΓࣺͯ͋ΓͷଓϞσϧͰɼΓ ࣺͯΒΕͳ͍ڑͷ্ݶΛDͱ͢Δɽ൴Β͜ͷ ౡϞσϧʹ͓͍ͯɼc < δ− δ2, C < δ + (J− 1)δ2 Λຬͨ͢ϦϯΫίετͰɼର҆ఆͳτϙϩδ͕Ҏ Լͷ3ͭͷੑ࣭Λ࣋ͭ͜ͱΛղੳతʹࣔͨ͠ɽ(1) ౡͰͯ͢ͷϊʔυ͕શʹଓ͞ΕΔ෦ શNWͱͳΔ͜ͱɽ(2)ܘ(ͯ͢ͷϊʔυ ϖΞͷ࠷ܦ࿏ͷ࠷େ)͓Αͼฏۉ࠷ܦ࿏ ɼD + 1ΑΓখ͘͞ͳΔ͜ͱɽ(3)·ͨಛʹ δ− δ3 < CΛຬͨ͢ͱ͖ʹɼ֤ϊʔυͷΫϥε λϦϯά(J−1)(J−2) (JK)2 ΑΓେ͖͘ͳΔ͜ͱɽ ౡϞσϧʹ͓͚Δର҆ఆͳτϙϩδͷҰྫΛਤ2ʹ ࣔ͢ɽ ͜ͷ݁ՌʹΑΓɼΓࣺͯ͋Γͷ࿈݁Ϟσϧʹ͓ ͍ͯɼϦϯΫίετʹؔ͢Δগ͠ͷόϦΤʔγϣ ϯΛڐ͢͜ͱʹΑͬͯɼ͋Δύϥϝʔληοτʹ͓ ͍͍ͯฏۉ࠷ܦ࿏ͱߴ͍ΫϥελϦϯά ΛͭεϞʔϧϫʔϧυNW͕ର҆ఆͳτϙϩδ ͱͯ͠ݱΕΔ͜ͱ͕ࣔ͞Εͨɽ͜Εɼݱ࣮ͷ༷ʑ ͳ໘ͰݱΕΔෳࡶNWͷܗͷΈ͕ɼNW ܗήʔϜͷΈͰදݱ͞ΕΔՄೳੑ͕͋Δ͜ͱ Λࣔࠦͨ͠ͷͰ͋ΔɽҰํͰɼౡϞσϧͷϦϯΫ ίετͷઃఆዞҙతͰɼݱ࣮ͷϦϯΫίετ ͬͱෳࡶͳΛ͍ͯ͠ΔͰ͋Ζ͏ͱ͍͏ɼ ෳࡶNWͷ͏Ұํͷੑ࣭Ͱ͋ΔεέʔϧϑϦʔ ੑʹؔͯ͠ݴٴ͍ͯ͠ͳ͍Λࢦఠ͓ͯ͘͠ɽ Ҏ্ɼ੩ֶతNWܗήʔϜͷ݁Ռʹ͍ͭͯ ཧΛͨ͠ɽͰɼେنͳϊʔυΛ࣋ͪɼෆۉҰ ͳΛ࣋ͭίετύϥϝʔλʹରͯ͠ɼ͜ͷϞσ ϧͰ༧ଌ͞ΕΔؼ݁Ͳ͏͍ͬͨͷʹͳΔͩΖ͏ ͔ʁݱ࣮ʹ؍ଌ͞ΕΔɼεέʔϧϑϦʔੑεϞʔ ϧϫʔϧυੑΛඋ͑ͨNWɼ͜ͷϞσϧ͔Βੜ ͞ΕΔͷͩΖ͏͔ʁ͜ͷ͍ʹ͑Δʹɼ੩ֶ తNWܗήʔϜͷΈͰेͰͳ͍ɽ۩ ମతʹɼҎԼͷ3ͭͷ͕ڍ͛ΒΕΔɽ 1ɽର҆ఆղͷ୳ࡧ͕ࠔ ର҆ఆੑͷఆٛʮͲͷϊʔυϖΞͦͷτϙ ϩδΛมಈͤ͞ΔΠϯηϯςΟϒΛ࣋ͨͳ͍ʯ ͱ͍͏͜ͱͰ͋Δ͕ɼର҆ఆͱͳΔτϙϩδΛ ޮΑ͘ٻΊΔΞϧΰϦζϜະͩΒΕ͍ͯ ͳ͍ɽ·ͨϊʔυ͕nݸͷͱ͖ɼͦͷϊʔ υ͕औΓಘΔτϙϩδͷ૯2(n2) Ͱ͋Δɽ n͕େ͖͍ͱ͖ʹɼ୳ࡧ͖ۭؒ͢ඇৗʹ େ͖͘ͳΓɼղͷ୳ࡧҰൠʹ͍͠ɽ [ ]
ਤ1: ޮղͱର҆ఆղͷؔɽࡾ্(2006)[18]ͱ૿ࢁ(2013)[19]ͷهड़ΛجʹචऀΒ͕࡞ɽ ϦϯΫίετcͱݮਰύϥϝʔλδ ͷؔʹΑͬͯྖҬ�∼1 �4ʹྨ͞ΕɼͦΕͧΕͷྖҬʹ͓͚Δޮ ղͱର҆ఆղΛਤࣔͨ͠ɽ 14 12 18 11 15 13 3 19 20 17 2 5 4 16 1 24 9 6 7 10 25 22 8 23 21 ਤ 2: ౡϞσϧʹ͓͚Δର҆ఆͳτϙϩδͷྫɽ
JacksonʹΑΔஶॻ (Jackson 2008)[7]ͷFigure 6.2ΛجʹචऀΒ͕࡞ɽ ౡϦϯΫͷίετc < 0.04ɼౡ֎ϦϯΫͷίε τ1 < C < 4.5ɼݮਰύϥϝʔλδ = 0.95ͷ߹ Ͱ͋Δɽౡશ෦Ͱ5ͭ͋Γɼ֤ౡͷϊʔυ શʹଓ͞Εɼౡؒগͳ͍ͷϦϯΫͰଓ ͞Ε͍ͯΔɽ25ݸͷϊʔυʹରͯ͠ฏۉܦ࿏ 2.833ɼΫϥελϦϯά0.905Ͱ͋Δɽ 2ɽήʔϜͷϓϨΠϠʔʹաେͳೳྗΛԾఆ͍ͯ͠Δ ֤ϓϨΠϠʔ͕߹ཧతͳߦಈΛऔΓɼର҆ఆղ Λಋͨ͘ΊʹɼଞͷϓϨΠϠʔ͕ͲͷΑ͏ͳ ઓུΛͱΔ͔Λਖ਼֬ʹஅ͢ΔͨΊͷใΛ ؍ଌ͢Δඞཁ͕͋Δ(؍ଌೳྗͷ)ɽ͞Β ʹɼऔಘͨ͠ใͷԼͰɼࣗʹͱͬͯ࠷దͳ ઓུΛબͼऔΔೳྗ͕ඞཁͰ͋Δ(࠷దԽೳྗ ͷ)ɽ੩ֶతϞσϧͷΈͰɼϓϨΠ Ϡʔ͕͜ΕΒͷೳྗΛ͍࣋ͬͯΔ͜ͱΛ҉ ʹԾఆ͍ͯ͠Δ͜ͱʹͳΔɽϊʔυ͕େ͖ ͍NWͰɼ͜ΕΒͷԾఆͷෆࣗવ͞ಛʹ ݦஶͱͳΔɽෳࡶNWͷੳର͋Δఔ نͷେ͖ͳ NW Ͱɼ͜ͷΑ͏ͳෳࡶNW ͷܗΛ੩ֶతϞσϧͷΈ͚ͩͰϞσϧ Խ͢Δ͜ͱɼඇݱ࣮తͱݴΘ͟ΔΛಘͳ͍ɽ 3ɽର҆ఆղಉ࢜ͷൺֱ͕Ͱ͖ͳ͍ ੩ֶతNWܗήʔϜʹҰൠʹෳͷର҆ ఆղ͕ଘࡏ͢ΔɽࠓҪɾాத6ϊʔυͷNW ʹ͍ͭͯɼ͋Δύϥϝʔλʹ͓͍ͯର҆ఆղͷ ͕Ͳͷ͘Β͍ݱΕΔ͔ʹ͍ͭͯશௐࠪΛ ߦ͓ͬͯΓɼͦͷ݁ՌͷҰྫͰऔΓಘΔτϙ ϩδͷ૯32,768(= 2(62))ݸ͋Γɼͦͷத ͷର҆ఆղ100ʙ1,000ݸఔଘࡏͨ͠(ࠓ Ҫɾాத 2010)[16]ɽର҆ఆੑͷఆ͔ٛΒ ͔ΔΑ͏ʹɼର҆ఆੑͱ͍͏Έ͚ͩͰɼ ֤ର҆ఆղͷؒͷ༏ྼΛଌΔ͜ͱͰ͖ͳ͍ɽ ͜ΕɼҰൠʹઓུܗήʔϜʹφογϡۉߧ͕ ଟଘࡏ͠ɼͦͷ༏ྼΛൺֱ͢Δ͜ͱ͕͍͠ ͱ͍͏ͱಉ͡Ͱ͋Δɽ ࣍খઅͰɼ͜ΕΒͷΛ౿·͑ͨಈֶతϞ σϧʹ͍ͭͯड़Δɽ
2.2 ಈֶతϞσϧ
ಈֶతNWܗήʔϜϞσϧɼ্هͷΛ ؇͠ɼ·ͨଟ͘ͷ NW͕খنͳ NW͔Βେ نͳNWʹ͍ͯͬͨ͠ͱ͍͏ʹͯ͠ɼ
Jackson and Wattsͷಈֶੑͷݚڀ(Jackson and Watts 2002)[9]ΛجʹImai and TanakaʹΑͬͯ ఏҊ͞Εͨ (Imai and Tanaka 2010)[4]ɽಈֶత
NWܗήʔϜϞσϧͷجຊతͳΞΠσΞɼҎ Լͷ௨ΓͰ͋Δɽ • ֤ࢄ࣌ؒͰ੩ֶతNWܗήʔϜΛ࣮ࢪ͠ɼ ֤ϊʔυͷઓུΛܾఆ͢Δɽ • ֤ࢄ࣌ؒtͰɼՄೳͳϦϯΫมಈͷ͏ͪ1 ຊͷΈ͕࣮ࡍʹมಈ͠ɼ࣍࣌ࠁt + 1ͷ NW τϙϩδ͕ܾఆ͢ΔɽՄೳͳϦϯΫมಈ͕ଘࡏ ͠ͳ͍߹ɼϦϯΫมಈ͠ͳ͍ɽ • มಈ͢ΔϦϯΫɼͦͷϦϯΫΛมಈͤ͞Δ͜ ͱʹΑͬͯϦϯΫ྆ͷϊʔυͷརಘΛ࠷վ ળ͢ΔϦϯΫ͕બ͞ΕΔɽΑΓܗࣜతʹɼ ՄೳͳϦϯΫมಈͷू߹ΛLPLCͱ͢Δͱɼม ಈ͢ΔϦϯΫij ij ∈ argmax ij∈LPLC
maxΔugi(ij), Δugj(ij)
Λຬͨ͢ɽ͜ͷΑ͏ͳϦϯΫ͕ෳଘࡏ͢Δ ߹ɼԿΒ͔ͷܾఆతͳํ๏(ϊʔυID͕ ए͍ํΛ༏ઌ͢ΔɼͳͲ)ʹΑܾͬͯఆ͢Δɽ • ֤ϓϨΠϠʔ(=ϊʔυ)ɼ֤࣌ࠁʹ͓͍ͯϦ ϯΫ͕1ຊ͔͠มಈ͠ͳ͍͜ͱΛ͓ͬͯΓɼ ·ͨۙࢹ؟తʹઓུΛܾఆ͢Δͷͱ͢Δɽ͢ ͳΘͪɼ࣍࣌ࠁͷࣗͷརಘͷΈΛߟ͑ɼ࠷ऴ తͳNWτϙϩδʹ͓͚Δརಘ͕࠷ద͔Ͳ͏ ͔Λߟ͑ͳ͍ɽ ಈֶతNWܗήʔϜϞσϧͰɼঢ়ଶભҠաఔ ͕ҙͷॳظঢ়ଶ͔Β։࢝͢Δͱɼຖ࣌ࠁʹ1ຊͣ ͭϦϯΫ͕มಈ͍ͯ͘͠ɽॳظঢ়ଶ͕ՄೳͳϦϯΫ มಈ͕ଘࡏ͠ͳ͍NWτϙϩδʹ౸ୡ͢Δͱɼͦ ͷޙͦͷঢ়ଶʹͣͬͱཹ·Γଓ͚Δɽ͜Εྗֶܥ ʹ͓͚Δෆಈʹ૬͢Δঢ়ଶͰɼఆٛΑΓ͜ͷঢ় ଶର҆ఆͳNWτϙϩδͰ͋Δ͔Βɼ͜ΕΛର ҆ఆղͱݺͿɽҙͷॳظঢ়ଶ͕͍ͭͰର҆ఆ ͳNWτϙϩδʹ૬͢Δঢ়ଶʹ౸ୡ͢ΔΘ͚Ͱ ͳ͘ɼྗֶܥʹ͓͚Δपظղʹ౸ୡ͢Δ͜ͱ͋ ΔɽϦϯΫͷมಈͦͷ྆ͷϊʔυͷҙࢥܾఆʹ ΑͬͯͷΈ͞ΕΔͨΊɼͦͷϦϯΫมಈʹΑͬͯ ଞͷϊʔυϖΞ͕·ͨผͷϦϯΫมಈΛͨΒ͠ɼ ͦͷΑ͏ͳ࿈͕࿈ଓͯ͠ݩͷঢ়ଶʹΔ͜ͱ͕͋ ΔɽपظղͦͷΑ͏ͳ߹ʹݱΕΔɽपظͷ͞ ࠷Ͱ4Ҏ্Ͱ͋Δɽҙͷॳظঢ়ଶ͕࠷ऴ తʹ౸ୡ͢Δঢ়ଶɼର҆ఆղͱपظղͷ2छྨʹ ͔ΕΔɽঢ়ଶۭؒͷαΠζ༗ݶͰ͋Γɼपظͷ ͞༗ݶͱͳΔͨΊɼແݶͷपظΛ࣋ͭΧΦε ղଘࡏ͠ͳ͍ɽ ҎԼͰɼ੩ֶతNWܗήʔϜͷͱ͠ ͯڍ͛ͨ3ͭͷʹରͯ͠ৄ͘͠ݕ౼͢Δɽ 1ɽର҆ఆղͷ୳ࡧ͕ࠔ ಈֶతNWܗήʔϜϞσϧɼ(શͯͰͳ ͍ͷͷ)͋Δ1ͭͷର҆ఆղΛٻΊΔͨΊͷ ํ๏ͱͳ͍ͬͯΔɽͨͩ͠ɼٻΊͨղ͕पظղ Ͱ͋Δ߹͋Δɽ 2ɽήʔϜͷϓϨΠϠʔʹաେͳೳྗΛԾఆ͍ͯ͠Δ ֤ϓϨΠϠʔݱࡏͷNWτϙϩδͱϦϯΫ ͕1ຊ͚ͩҟͳΔNWτϙϩδ͚ͩΛߟྀ͢ Εྑ͘ɼ·͕ͨࣗ࣍࣌ࠁͷ݁Ռʹد༩Ͱ͖ ΔͷࣗͱଞͷϓϨΠϠʔͱͷϦϯΫมಈ ͚ͩͳͷͰɼߟྀ͖͢n− 1ݸͷϦϯΫม ಈ͚ͩͰ͋Δɽ֤ϓϨΠϠʔ͜ΕΒͷͦΕ ͧΕʹ͍ͭͯɼࣗͷརಘΛ૿େͤ͞Δ͔Ͳ͏ ͔Λݕ౼͢Εྑ͍ɽ੩ֶతNWܗήʔϜ ͰɼࣗͷઓུΛܾఆ͢ΔͨΊʹશͯͷଞ ϓϨΠϠʔͷઓུͷ(2n(n−1)ݸͷύλʔϯ ͕͋Δ)Λݕ౼͠ͳ͚ΕͳΒͳ͔ͬͨͷͰɼ ٻΊΒΕΔೳྗେ෯ʹݮ͍ͬͯΔɽ 3ɽର҆ఆղಉ࢜ͷൺֱ͕Ͱ͖ͳ͍ ಈֶతNWܗήʔϜϞσϧʹ͓͍ͯɼ֤ ର҆ఆղʹରͯ͠Ҿ͖ࠐΈྖҬ(࠷ऴతʹͦͷ ର҆ఆղʹ౸ୡ͢Δঢ়ଶͷू߹)͕ఆ·Δ͜ͱ ͔Βɼ͜ͷେ͖͞ܗঢ়ʹΑͬͯɼ֤ର҆ఆղ ಉ࢜Λൺֱ͢Δ͜ͱ͕Ͱ͖Δɽৄ͘͠4અ Ͱड़Δɽ
3
ܭࢉػγϛϡϨʔγϣϯ
ಈֶతNWܗήʔϜϞσϧʹΑͬͯੜ͞Ε ΔNWτϙϩδͷΛௐࠪ͠ɼݱ࣮ʹ؍ଌ͞Ε ΔNWͷಛɼಛʹෳࡶ NWͷಛ͕ݱΕΔ͔ Ͳ͏͔Λݕূ͢Δ͜ͱͰɼෳࡶNWܗͷઆ໌Ϟσϧͱͯ͠ͷଥੑΛධՁ͢ΔͨΊʹɼܭࢉػγ ϛϡϨʔγϣϯΛߦͬͨɽNWͷ౷ܭతಛྔʹ ɼҟͳΔنͷNWΛਖ਼͘͠ൺֱ͢ΔͨΊͷਖ਼ نԽ͕͍͠ͷ͕ଟ͋͘ΔɽͦͷͨΊখنͷܭ ࢉػγϛϡϨʔγϣϯ͚ͩͰͳ͘ɼΑΓେنͳγ ϛϡϨʔγϣϯΛߦ͍ɼܗ͞ΕΔNWτϙϩδ ͷಛྔΛධՁ͢Δ͜ͱ͕ඞཁͰ͋ΔɽຊઅͰɼ ͦͷܭࢉػγϛϡϨʔγϣϯͷ֓ཁͱ݁Ռʹ͍ͭͯ ड़Δɽ 3.1 γϛϡϨʔγϣϯͷ࣮ߦ ຊϞσϧɼ֤ϓϨΠϠʔ͕֤࣌ࠁͰརݾతʹઓ ུΛܾఆ͢Δ͜ͱ͔ΒɼଟͷϓϨΠϠʔʹΑΔେ نγϛϡϨʔγϣϯΛߦ͏ͨΊʹɼେྔͷܭࢉ ೳྗ͕ඞཁʹͳΔɽ۩ମతʹɼ1࣌ࠁઌͷNW τϙϩδͷঢ়ଶΛܭࢉ͢ΔͨΊʹඞཁͳܭࢉྔͷ Φʔμʔ(ૈ͍ݟੵΓͰ͋Δ͕)O(n5)ͱͳ Δɽ·ͨɼຊϞσϧ͍͔ͭ͘ͷύϥϝʔλΛ࣋ ͪɼҟͳΔύϥϝʔλʹΑΔγϛϡϨʔγϣϯҟ ͳΔNWΛͨΒ͢ɽͦͷͨΊʹɼຊϞσϧ͕ੜ ͢ΔNWͷಛΛධՁ͢ΔͨΊʹɼ༷ʑͳύ ϥϝʔληοτʹΑΔཏతͳγϛϡϨʔγϣϯͷ ࣮ߦ͕ඞཁͰ͋Δ͕ɼେͳͷγϛϡϨʔγϣϯ ͷ࣮ߦɼγϛϡϨʔγϣϯͷ࣮ߦͱ݁ՌͷཧΛ ࡶʹ͢Δͱ͍͏՝ΛͨΒ͢ɽ චऀΒຊϞσϧͷ2000 ϊʔυͷγϛϡϨʔ γϣϯΛ࣮ߦ͢ΔʹͨΓɼ͜ΕΒͷ՝ʹରԠ͢ ΔͨΊʹɼҎԼͷ3ͭͷରࡦΛߦͬͨɽ·ͣୈҰ ʹɼγϛϡϨʔγϣϯϓϩάϥϜͷฒྻԽΛߦ͍ɼ େنฒྻܭࢉػͰ࣮ߦ͢Δ͜ͱͰɼܭࢉ࣌ؒͷ ॖΛਤͬͨɽຊϞσϧͰɼݸʑͷϓϨΠϠʔͷઓ ུܾఆࢄతʹߦ͏͜ͱ͕Ͱ͖Δɽཧతͳ࠷େ ฒྻO(n3)Ͱ͋ΔͨΊɼฒྻԽٕज़͕ޮՌతͰ ͋ΔɽࠓճͷγϛϡϨʔγϣϯʹɼւಓେֶ ใج൫ηϯλʔͷεʔύʔίϯϐϡʔλHITACHI SR16000/M1Λ༻͍ͨɽ·ͨୈೋʹɼάϥϑ୳ࡧ ͷܭࢉΛ࠷దԽ͠ɼγϛϡϨʔγϣϯͷܭࢉྔͷ ݮΛਤͬͨɽࣄલͷௐࠪʹΑΓɼຊϞσϧͷγ ϛϡϨʔγϣϯϓϩάϥϜʹ͓͍ͯඅ͞ΕΔܭ ࢉ࣌ؒͷ΄ͱΜͲɼརಘؔͷࢉग़ͷͨΊͷ࠷ ࿏୳ࡧʹΑͬͯΊΒΕΔ͜ͱ͕֬ೝ͞Εͨ(ࠓ Ҫɾాத 2013)[17]ɽͦ͜ͰɼγϛϡϨʔγϣϯϓ ϩάϥϜͷ࠷࿏୳ࡧͷ෦ʹάϥϑ୳ࡧϥΠϒϥ ϦʮLEMONʯ(Dezs˝o et al. 2011)[3]Λ࠾༻ͯ͠ɼ
ޮతͳάϥϑ୳ࡧʹΑΓརಘؔࢉग़ͷͨΊͷ ܭࢉྔͷݮΛਤͬͨɽୈࡾʹɼେنγϛϡϨʔ γϣϯ܈ཧιϑτΣΞOACIS(Murase et al. 2014)[12]Λ࠾༻͠ɼγϛϡϨʔγϣϯ࣮ߦͱ݁Ռ ͷཧͷޮԽΛਤͬͨɽOACISɼཧԽֶݚڀ ॴܭࢉՊֶݚڀػߏͰ։ൃ͞Ε͍ͯΔιϑτΣΞ ͰɼࣾձγϛϡϨʔγϣϯͷΑ͏ʹଟ͘ͷύϥϝʔ λΛ࣋ͭϞσϧʹ͓͍ͯڊେͳύϥϝʔλۭؒͷ୳ ࡧΛߦ͏ͨΊʹɼେنͳγϛϡϨʔγϣϯͷ࣮ߦ ͱ݁ՌͷཧΛߦ͏ͨΊͷͷͰ͋Δɽ ҎԼͷখઅͰɼ͜ΕΒͷରࡦΛ࠾༻ͯ͠ߦͬͨ γϛϡϨʔγϣϯͷ݁ՌͷҰ෦Λհ͢Δɽ 3.2 ݁Ռͱߟ 2000 ϊʔυγϛϡϨʔγϣϯͷ݁ՌͷҰ෦Λɼ ਤ3ʹࣔ͢ɽ(a)͓Αͼ(c)ͷࠨଆ͕ɼޙड़͢Δτ ϥϯεϑΝʔΛಋೖ͠ͳ͍جຊϞσϧʹ͍ͭͯͷ ݁ՌͰ͋Δɽ(a)ͷ͔࣍Β͔ΔΑ͏ʹɼε έʔϧϑϦʔੑͷಛͰ͋ΔϕΩΑΓɼϥ ϯμϜάϥϑͷ࣍ͷಛͰ͋ΔϙΞιϯ ʹ͍ۙɽ͜͜ͰC=140ͷྫͷΈΛ͍ࣔͯ͠Δ ͕ɼCͷΛมԽͤͯ͞Έͯɼ͜ͷมΘ Βͳ͔ͬͨɽ͜ͷݪҼͱͯ͠ɼ(c)ͷ࠷େ࣍ͷ (11.86)ʹࣔ͞Ε͍ͯΔΑ͏ʹɼେ͖ͳنͷϋϒ ͕ܗ͞Εʹ͘͘ͳ͍ͬͯΔ͜ͱ͕ڍ͛ΒΕΔɽ͜ ͷݪҼΛɼϕΩଇʹै͏࣍Λ࣋ͭBAϞσ ϧͱରൺ͢Δ͜ͱͰड़ΔɽBAϞσϧͰɼ৽ن ࢀೖϊʔυ͕طଘͷϊʔυʹϦϯΫΛுΔ֬ɼ ͦͷϊʔυͷ࣍ʹൺྫ͢Δɽ͕ͨͬͯ͠ɼҰେ ͖͘ͳͬͨϋϒϊʔυɼଞͷϊʔυʹൺͯ৽ن ϦϯΫΛ֫ಘ͢Δͷʹ༗རͳঢ়گͱͳΓɼ݁Ռͱ͠ ͯϋϒϊʔυ·͢·͢େنͳϋϒͱͳͬͯ ͍͖ͯ͠ɼ࣍ϕΩଇʹ͕ͨ͠͏Α͏ʹͳ ΔɽຊϞσϧͰɼଞͷϊʔυ͕Ұେ͖͘ͳͬͨ ϋϒϊʔυʹରͯ͠ϦϯΫΛுΔϝϦοτɼϋϒ ϊʔυʹଓ͢Δ͜ͱͰଟͷϊʔυʹগͳ͍ڑ ͰଓͰ͖ΔΑ͏ʹͳΔͨΊɼϋϒϊʔυͷنʹ Ԡͯ͡େ͖͘ͳΔɽ͜ͷͰBAϞσϧͱಉ͡ Ͱ͋Δɽ͔͠͠ຊϞσϧͰɼϦϯΫͷܗʹࡍ͠ ͯ྆ͷϊʔυͷ߹ҙ͕ඞཁͰ͋ͬͨɽͭ·Γɼ ํʹͱͬͯརಘΛͨΒ͢Α͏ͳજࡏϦϯΫʹର͠ ͯͷΈɼ࣮ࡍͷϦϯΫܗཱ͕͢Δɽଞͷϊʔυ ͔ΒݟΔͱɼϋϒ͕͢ΔʹͭΕͯɼϋϒϊʔυ ʹϦϯΫΛுΔϝϦοτͲΜͲΜ૿Ճ͍ͯ͘͠Ұ
f(x)̬ ̬αxγ α̬ ̬ γ̬ ̬ 5̬ ̬ ฟ⌧㢖ᗘ ḟᩘ (a) ࣍(τϥϯεϑΝʔͳ͠) f(x)̬ ̬αxγ α̬ ̬ γ̬ ̬ 5̬ ̬ ฟ⌧㢖ᗘ ḟᩘ (b)࣍(τϥϯεϑΝʔ͋Γ) NWಛྔ τϥϯεϑΝʔͳ͠ τϥϯεϑΝʔ͋Γ ࠷େ࿈݁ͷαΠζ 1979.86 1940.15 ฏۉ࣍ 2.72 1.99 ࠷େ࣍ 11.86 38.04 ΫϥελϦϯά 0.00 2.26× 10−7 ฏۉ࠷ܦ࿏ 7.49 5.38 (c) ֤NWಛྔ ਤ3: ಈֶతNWܗήʔϜϞσϧ͕ͨΒ͢NWτϙϩδͷಛɽ ϊʔυΛ2000ɼ֤ϦϯΫίετcij Λ(0, C]ͷൣғͷҰ༷ʹ͕ͨ͠͏ཚͱ͠ɼ100ͷϦϯΫ ίετηοτʹ͍ͭͯγϛϡϨʔγϣϯΛߦ͍ɼݱΕΔNWಛྔͷฏۉΛࣔͨ͠ɽ(a)͓Αͼ(b) ࣍Ͱɼԣ࣠Λ࣍ɼॎ࣠Λग़ݱසͱ͢Δ྆ରάϥϑͰ͋ΔɽઢͰࣔ͞Ε͍ͯΔϑΟοςΟ ϯάؔɼf (x) = αxγ ͷαͱγ Λਪఆ͢Δ͜ͱʹΑͬͯٻΊΒΕͨͷɽ(a) τϥϯεϑΝʔͳ͠ (δ = 0.99, C = 140)ͷ߹ɽϑΟοςΟϯάؔα = 11.669, γ = −4.384ɼܾఆR2 = 0.766. (b) τϥϯεϑΝʔ͋Γ(δ = 0.99, C = 240)ͷ߹ɽϑΟοςΟϯάؔα = 3.687, γ =−3.206ɼ ܾఆR2= 0.948. (c)ͦΕͧΕͷ߹ͷ֤NWಛྔͷฏۉɽ ํͰɼϋϒϊʔυʹͱͬͯɼ࣍ͷগͳ͍ϊʔυ ʹΘ͟Θ͟ϦϯΫΛுΔϝϦοτมΘΒͳ͍ͨΊ ʹɼϦϯΫܗͷ߹ҙཱ͕ͤͣɼ݁Ռͱͯ͠ϋϒ ϊʔυͷ࣍ۃʹେ͖͘ͳΒͳ͍ɽ͜Ε͕ɼ ಈֶతNWܗήʔϜϞσϧͷجຊϞσϧʹ͓͍ ͯɼڊେͳϋϒ͕ܗ͞Εͳ͍ཧ༝Ͱ͋Δɽ ͰɼήʔϜཧΛجʹͨ͠ಈֶతNWܗήʔ ϜϞσϧͰɼεέʔϧϑϦʔNWܗ͞Εͳ ͍ͷͩΖ͏͔ɽ͜ͷ͍ʹ͑ΔͨΊʹɼ͜͜Ͱ ຊϞσϧʹτϥϯεϑΝʔͷ֓೦Λಋೖͨ͠ͷΛ ߟ͑ΔɽτϥϯεϑΝʔͱήʔϜͷϓϨΠϠʔؒ ͰߦΘΕΔࡒͷަͷ͜ͱͰ͋Δɽࡒͷτϥϯε ϑΝʔͷಋೖʹΑͬͯɼऔҾʹࢀՃ͢ΔશͯͷϓϨ ΠϠʔͷརಘΛ૿Ճͤ͞ΔΑ͏ͳ߹ҙΛऔΓ͚Δ ͜ͱ͕Ͱ͖ΔΑ͏ʹͳΔ߹͕͋ΔɽຊϞσϧʹ͓ ͚ΔτϥϯεϑΝʔͱɼϦϯΫͷมԽʹࡍ͠ɼར ಘΛ૿Ճͤ͞ΔϓϨΠϠʔ͔ΒརಘΛݮগͤ͞Δϓ ϨΠϠʔʹͦͷݮগΛิరͤ͞Δ͜ͱͱ͢Δɽ͜ ͷΈΛಋೖ͢Δ͜ͱʹΑͬͯɼଞͷϊʔυ͕ϋ ϒͱͷϦϯΫΛܗ͢Δ͜ͱʹΑͬͯेͳ(ϋϒ ʹର͢ΔิరΛࠩ͠Ҿ͍ͯ·ͩརಘͷ૿ՃΛ ͨΒ͢Α͏ͳ)རಘͷ૿ՃΛͨΒ͢Α͏ͳ߹ɼ ϋϒʹରͯͦ͠ͷརಘͷݮগΛิర͢Δ͜ͱ͕Ͱ ͖ɼ݁Ռͱͯ͠৽ͨͳ(ಛʹϋϒʹؔ͢Δ)Ϧϯ ΫܗΛଅਐͤ͞Δ͜ͱ͕Ͱ͖Δɽ τϥϯεϑΝʔ͖ͭϞσϧͷγϛϡϨʔγϣϯ݁
ՌΛɼਤ3ͷ(b)͓Αͼ(c)ͷӈଆʹࣔ͢ɽ(b)Λ ݟΔͱɼτϥϯεϑΝʔͳ͠ͷͱ͖ͷ࣍ͱൺ ͯɼϕΩʹۙ͘ͳ͍ͬͯΔ͜ͱ͕͔ΔɽC ͷΛมԽͤͯ͞ΈΔͱɼશͯͷ CͷͰϕΩ ͱͳΔΘ͚Ͱͳ͍Α͏͕ͩɼͦΕͰτϥϯε ϑΝʔͳ͠ͷ߹ͱൺֱ͢Δͱɼେ͖ͳنͷϋϒ ͕ܗ͞Ε͍ͯΔ͜ͱ͕֬ೝͰ͖ͨɽ͢ͳΘͪɼτ ϥϯεϑΝʔ͖ͭϞσϧ͕ੜ͢ΔNWτϙϩδ ɼύϥϝʔλͷʹΑͬͯεέʔϧϑϦʔੑΛ ࣋ͭNWΛੜ͠͏Δ͜ͱ͕֬ೝͰ͖ͨɽͦͷଞ ͷNWಛྔʹ͍ͭͯݟͯΈΔͱɼΫϥελϦϯ άτϥϯεϑΝʔ͋Γͳ͠ʹؔΘΒ͔ͣͳΓ খ͘͞ɼ΄΅0Ͱ͋Δɽ·ͨฏۉ࠷ܦ࿏ɼτ ϥϯεϑΝʔ͋Γͳ͠ʹؔΘΒͣɼ2000ϊʔυͱ ͍͏NWنʹର͔͠ͳΓখ͞ͳͱͳ͍ͬͯΔɽ ͢ͳΘͪɼຊϞσϧ͕ੜ͢Δ NWτϙϩδɼ τϥϯεϑΝʔ͋Γɾͳ͠ڞʹɼεϞʔϧϫʔϧυ ੑ࣋ͨͳ͍͜ͱ͕֬ೝͰ͖ͨɽ
4
μΠφϛΫεղੳ
ຊઅͰɼಈֶతNWܗήʔϜϞσϧͷಈֶ తಛੑͱɼͦͷԠ༻ʹ͍ͭͯड़Δɽ 4.1 ಈֶతNWܗήʔϜϞσϧͷμΠφϛΫ εͷಛ ಈֶతNWܗήʔϜϞσϧͷաఔɼࢄۭ ্ؒͷࢄ࣌ؒͷܾఆతͳঢ়ଶભҠͰ͋Δɽਤ 4ʹɼಈֶతNWܗήʔϜϞσϧͷঢ়ଶભҠͷ ༷ࢠΛࣔ͢ɽ͜ͷྫͰɼϊʔυ3ɼݮਰύϥ ϝʔλδ = 0.9ɼίετύϥϝʔλcab = cba = 0.3, cbc = ccb = 0.1, cca = cac = 0.6Ͱ͋Δɽਤ 4(a)ɼಈֶతNWܗήʔϜϞσϧͰঢ়ଶ͕ભ Ҡ͢Δঢ়ଶۭؒͷશମͰ͋Δɽ3ϊʔυͰߏͰ͖ Δτϙϩδ(=ঢ়ଶ)શ෦Ͱ8(= 2(32))ͭ͋Γɼ֤ ঢ়ଶg0, . . . , g7ɼͦͷঢ়ଶͱϦϯΫͷ༗ແ͕1ຊ ͚ͩҟͳΔঢ়ଶͱྡؔʹ͋ΓɼഁઢͰ݁Εͯ ͍Δɽঢ়ଶͷ෦ʹϊʔυa, b, c ͷଓ͕ؔ ਤࣔ͞Ε͍ͯͯɼ֤ϊʔυͷ෦ʹͦͷརಘͷ ͕ه͞Ε͍ͯΔɽྫ͑ɼঢ়ଶg6Ͱɼϊʔυa ͱbɼaͱcͷؒʹϦϯΫ͕ଘࡏ͠ɼϊʔυa, b, c ͷརಘͦΕͧΕ0.9ɼ1.41ɼ1.11Ͱ͋Δɽ ͋Δঢ়ଶ֤࣌ࠁʹɼྡঢ়ଶͷ͏ͪͷ1ͭʹભ Ҡ͢Δɽਤ4(b)ʹঢ়ଶભҠͷྫΛࣔ͢ɽطʹड़ ͨΑ͏ʹɼಈֶతNWܗήʔϜϞσϧʹ͓͚Δ ఆৗঢ়ଶʹɼྗֶܥʹ͓͚ΔΞτϥΫλʹରԠ ͢Δର҆ఆղ͚ͩͰͳ͘ɼ1ΑΓେ͖͍पظΛ ࣋ͭΞτϥΫλʹରԠ͢Δपظղ͕͋Δɽ͜ͷྫͰ ɼଠ͍ҹʹԊͬͯঢ়ଶભҠ͕ߦΘΕɼҙͷঢ় ଶ࠷ऴతʹg3ɼg5ɼg6ͷ͍ͣΕ͔ʹ౸ୡ͠ɼप ظղଘࡏ͠ͳ͍ɽ ͦΕͧΕͷղɼ࠷ऴతʹͦͷղ౸ୡ͢Δঢ় ଶͷू߹Λ࣋ͪɼͦΕΛҾ͖ࠐΈྖҬͱݺͿɽঢ় ଶۭؒશମɼ֤ղʹରԠ͢ΔҾ͖ࠐΈྖҬʹ ׂ͞ΕΔɽਤ4(c) ʹɼঢ়ଶۭؒͷҾ͖ࠐΈྖҬ ʹΑΔׂͷྫΛࣔ͢ɽ͜ͷྫͰɼର҆ఆղg3 ͷҾ͖ࠐΈྖҬ{g2, g3}ɼg5ͷҾ͖ࠐΈྖҬ {g0, g1, g4, g5, g7}ɼg6 ͷҾ͖ࠐΈྖҬ{g6} Ͱ ͋Δɽ ਤ5ɼಈֶతNWܗήʔϜϞσϧʹ͓͚Δ ঢ়ଶׂۭؒͷ༷ࢠΛɼผͷϊʔυ4ͷྫͰࣔ͠ ͨͷͰ͋Δɽ͜ͷਤʹࣔ͢Α͏ʹɼಈֶతNW ܗήʔϜϞσϧ͕ܗ࡞Δঢ়ଶۭؒɼύϥϝʔλ ʹΑͬͯෳࡶͰଟ༷ͳׂͷ͞ΕํΛࣔ͢ɽ 4.2 μΠφϛΫεղੳͷԠ༻ɿղͷඇޮੑͷ ධՁ ࣍ʹɼಈֶతNWܗήʔϜϞσϧͷಈֶతಛ ੑͷԠ༻ͱͯ͠ɼର҆ఆղͷඇޮੑΛҾ͖ࠐΈྖ ҬͷαΠζͰධՁͨ݁͠ՌΛհ͢Δɽ·ͣ࠷ॳʹ ήʔϜʹΑΔղͷඇޮੑͷධՁͷͨΊͷطଘͷํ ๏Λհ͠ɼ࣍ʹͦΕΛجʹͨ͠ຊϞσϧͷͨΊͷ ධՁࢦඪʹ͍ͭͯड़ɼ࠷ޙʹ࣮ྫʹΑͬͯධՁ ͢Δɽ Ұൠʹɼଟͷҙࢥܾఆओମ͕རݾతɾࢄతʹ ৼΔ͏͜ͱʹΑͬͯͨΒ͞ΕΔঢ়ଶɼ୯ಠͷ σβΠφʔ͕தԝूݖతʹޮΛ࠷దԽͨ݁͠Ռʹ ൺͯɼඇޮͳͷͱͳΔ(Տɾ2015)[15]ɽ ͜ͷඇޮੑΛఆྔతʹධՁ͢ΔͨΊʹɼແடংͷ ঈ(Price of AnarchyɼҎԼPoA)ɼ҆ఆੑ ͷঈ(Price of StatiblityɼҎԼPoS)ͷ2ͭ ͷࢦඪ͕ΒΕ͍ͯΔ 8 ɽPoAͱɼγες Ϝ͕ͨΒ͢ղͷࣾձతޮੑͷ࠷ѱͱɼࣾձత ޮੑΛ࠷େԽ͢ΔޮղͷࣾձతޮੑͷΛൺ ͨͷͰɼҎԼͷࣜͰ༩͑ΒΕΔɽ (PoA) = f (ˆs) min i f (si) (7) [ ]ਤ4: ಈֶతNWܗήʔϜϞσϧʹ͓͚Δঢ় ଶભҠͷ༷ࢠɽஶऀΒͷҰ෦ʹΑΔจݙ(Imai and Tanaka 2013)[6]ͷFig.2Λमਖ਼ͯ͠࡞ɽ
(a) 3ϊʔυͷͱ͖ঢ়ଶۭؒͷαΠζ 8ɽϦ ϯΫͷ༗ແ͕1 ຊ͚ͩҟͳΔྡঢ়ଶಉ͕࢜ ഁઢͰ݁Ε͍ͯΔɽ(b) ֤ঢ়ଶຖ࣌ࠁʹɼ ϊʔυͷརಘΛ࠷େʹ૿Ճͤ͞Δྡঢ়ଶܾ ఆతʹભҠ͢Δɽ(c) ঢ়ଶۭؒશମɼ֤ର ҆ఆղʹରԠ͢ΔҾ͖ࠐΈྖҬʹׂ͞ΕΔɽ ͜͜Ͱɼsi ∈ sγεςϜ͕ͨΒ͢ղΛɼؔ f (s)ղͷࣾձతޮੑ 9 ΛɼsˆޮղΛ ද͢ɽಉ༷ʹPoSɼγεςϜ͕ͨΒ͢ղͷࣾ ձతޮੑͷ࠷ྑͱɼࣾձతޮੑΛ࠷େԽ͢Δ ޮղͷࣾձతޮੑͷΛൺͨͷͰɼҎԼͷ ࣜͰ༩͑ΒΕΔɽ (PoS) = f (ˆs) max i f (si) (8) ఆ͔ٛΒ໌Β͔ͳΑ͏ʹɼPoAPoS1Ҏ্ͷ ΛऔΔɽPoA͕1Ͱ͋Δ͜ͱɼγεςϜ͕ඞ ͣޮղΛͨΒ͢͜ͱΛද͠ɼPoS͕1Ͱ͋Δ ͜ͱɼγεςϜ͕ͨΒ͢ղͷ͍ͣΕ͔͕ޮղ ͱͳΔ͜ͱΛද͢ɽ PoAPoSɼγεςϜ͕ͨΒ͢ղ͕࠷దޮ ղʹରͯ͠ͲΕ͘Β͍ඇޮͰ͋Δ͔ͷධՁΛɼ ଟͷղͷதͷ࠷ѱɾ࠷ྑΛͬͯධՁ͢Δ ͷͰ͋ͬͨɽγεςϜͱͯ͠ͷඇޮੑΛධՁ͢Δ ͨΊʹɼ͜ͷΓํۃͳͷͰ͋Γɼʮฏ ۉతͳʯ͋Δ͍ʮయܕతͳʯඇޮੑΛଌΓ͍ͨ ߹͋Δ͕ɼ͜ΕҰൠʹ͍͠ɽͳͥͳΒɼ ඇڠྗήʔϜʹ͓͚Δදతͳղ֓೦Ͱ͋Δφο γϡۉߧղҰൠʹෳଘࡏ͠ɼ·ͨͦΕΒͷؒ ແࠩผతͰɼղ͕ଟ͋ͬͨ߹ʹͦΕΒͷղͷؒ ʹ༏ྼΛ͚Δ͜ͱ͕Ͱ͖ͳ͍ɽͦͷͨΊʹʮى͜ Γ͍͢ʯφογϡۉߧͰ͋Δͱ͔ɼʮయܕతͳʯ φογϡۉߧΛݟ͍ͩ͢͜ͱ͍͠ɽήʔϜͷϓ ϨΠϠʔͷࢄతɾརݾతͳৼΔ͍͕ͨΒ͢γ εςϜͷࣾձతඇޮੑΛධՁ͢ΔͨΊͷํ๏ͱ͠ ͯɼଟͷղͷதͷ࠷ѱͱ࠷ྑΛ༻͍ͨͷ͕ ΘΕ͖ͯͨͷͦͷͨΊͰ͋Γɼ͜Εղ֓೦ͷ ຊ࣭తͳಛੑʹىҼ͢ΔͷͰ͋Δɽ ಈֶతNWܗήʔϜϞσϧʹ͓͚Δղͷޮ ੑΛධՁ͢Δʹͨͬͯɼجຊతʹ͜ΕΒͷߟ͑ ํΛ౿ऻ͢Δɽͨͩ͠طʹड़ͨΑ͏ʹɼຊϞσϧ Ͱ֤ղͦͷղʹରԠ͢ΔҾ͖ࠐΈྖҬΛ࣋ͬͯ ͓ΓɼͦͷαΠζܗঢ়ʹΑ֤ͬͯղͷॏཁੑΛ ධՁ͢Δ͜ͱ͕Ͱ͖Δɽͦ͜ͰImai and Tanaka
ɼ֤ղͷPoAΛҾ͖ࠐΈྖҬͷେ͖͞ʹΑͬ ͯॏΈ͚ͨ͠ॏΈ͖ฏۉΛऔΔ͜ͱʹΑͬ
(a) (b)
(c)
ਤ5: ಈֶతNWܗήʔϜϞσϧʹΑΔঢ়ଶۭ ؒͷׂͷ༷ࢠɽ ϊʔυn = 4, δ = 0.9ɼR = 2.0ɽશ෦Ͱ64ঢ় ଶ͋Γɼঢ়ଶ൪߸20ɼ22ɼ50ͷͦΕͧΕͷର҆ఆ ղʹ౸ୡ͢Δ3ͭͷҾ͖ࠐΈྖҬʹׂ͞ΕΔɽ ͯɼγεςϜͷࣾձతඇޮੑͷࢦඪͱͨ͠(Imai and Tanaka 2011, 2013)[5][6]ɽຊϞσϧܾఆ తͳঢ়ଶભҠաఔͰ͋Δ͔Βɼॳظঢ়ଶ͕ܾ·Ε ɼ࠷ऴతͳղ͕ఆ·Δɽͦͯ͠ղ͕ఆ·Εɼͦ ͷղʹର͢Δ PoAͷΛࢉग़͢Δ͜ͱ͕Ͱ͖Δɽ ·֤ͨղͷੜى֬ɼॳظτϙϩδ͕Ұ༷ʹ ͕ͨͬͯ͠ϥϯμϜʹ༩͑ΒΕͨ߹ʹɼղͷҾ ͖ࠐΈྖҬͷେ͖͞ʹൺྫͨ͠ͱͳΔɽͦͷͨ ΊɼҾ͖ࠐΈྖҬͷαΠζʹΑΔॏΈ͖PoAɼ PoAͷظͱͯ͠ଊ͑Δ͜ͱ͕Ͱ͖ɼظPoA ͱݺΕΔɽܗࣜతʹɼঢ়ଶۭؒશମͷαΠζ Λ|S|ɼղsiͷҾ͖ࠐΈྖҬͷαΠζΛ|Ai|ͱ͢ Δͱɼ (ظPoA) = f (ˆs) i |Ai| |S|f (si) (9) ͱͳΔɽ͜ͷظPoAɼ࠷ѱ/࠷ྑͷέʔεͷ ղੳͰ͋ͬͨPoA/PoSʹൺͯɼʮฏۉతͳʯڍ ಈΛධՁ͢Δ͜ͱʹͳΔɽ·ͨఆٛΑΓ໌Β͔ͳ
Α͏ʹɼPoS≤ظPoA≤ PoAͰ͋Γɼ߸
PoS =ظPoA = PoAͷͱ͖ʹͷΈཱ͢Δɽ ද1ɼظPoAͱطଘͷ2ࢦඪͷҧ͍Λ࣮ྫ ʹΑͬͯࣔͨ͠ͷͰ͋Δɽ͜ͷྫͰɼ8ϊʔυ ͷখنNWʹ͍ͭͯશͯͷର҆ఆղͱͦͷҾ͖
ࠐΈྖҬΛٻΊɼࣾձతޮੑΛϊʔυͷརಘͷ૯ ͱͨ͠ͱ͖ͷPoAɼPoSɼظPoAͷΛٻΊ ͨɽ֤ղͷҾ͖ࠐΈྖҬͷେ͖͞ʹ͔ͳΓେ͖ͳ ͕ࠩݟΒΕΔ͜ͱ͕͔Δɽ
5
ࠓޙʹ͚ͯ
͜͜·ͰɼήʔϜཧʹج͍ͮͨෳࡶNWܗ ͷϞσϧԽʹ͍ͭͯɼචऀΒͷݚڀՌΛத৺ʹड़ ͨɽຊઅͰɼࠓޙऔΓΉ͖՝ʹ͍ͭͯड़ Δɽ ·ͣୈҰʹɼ༷ʑͳ݅ʹ͓͚ΔൃNWͷௐ ͕ࠪڍ͛ΒΕΔɽ3અͰࣔͨ͠Α͏ʹɼಈֶతNW ܗήʔϜϞσϧͰɼ͋ΔύϥϝʔλઃఆͰε έʔϧϑϦʔੑΛඋ͑ͨNWτϙϩδ͕ൃੜ͢Δ ͜ͱ͕ࣔ͞Εͨɽ͔͠͠ɼ͜ͷΑ͏ͳੑ࣭͕ͲΕͩ ͚ීวతͰ͋Δ͔ɼෳࡶNW͕ੜ͡ͳ͍ύϥϝʔ λઃఆͰͲͷΑ͏ͳNWτϙϩδ͕ੜ͡Δͷ͔ ʹ͍ͭͯɼະͩेʹ໌Β͔ʹͳ͍ͬͯͳ͍ɽ ͜ͷΑ͏ͳ͜ͱΛ໌Β͔ʹ͍ͯ͘͜͠ͱͰɼಈֶ తNWܗήʔϜϞσϧ͕࣋ͭಛੑ͕ΑΓ໌֬ʹ ͳ͍ͬͯͩ͘Ζ͏ɽ ୈೋʹɼ࣮ࡍͷࣾձతɾٕज़తNWͷৄࡉͳಛ ੑͷൺֱͱϞσϧͷਫ਼៛Խ͕ڍ͛ΒΕΔɽطʹड़ ͨΑ͏ʹɼήʔϜཧʹج͍ͮͨϞσϧԽ͕༗ͳ ٕज़తɾࣾձతNWଟ͘ଘࡏ͢Δɽྫ͑ɼΠϯ λʔωοτʹ͓͚ΔAS(Autonomous-System)ؒ NWɼϑΝΠϧަͷͨΊͷඇߏܕP2P(Peer to Peer)NWɼ͋Δ͍Facebookͷ༑ਓؒNWͳ ͲͰ͋Δɽ͜ΕΒͷNWͷτϙϩδͱಈֶతNW ܗήʔϜϞσϧ͕ͨΒ͢NWτϙϩδͷৄࡉ ͳಛੑͷൺֱΛߦ͍ɼϞσϧ͕ͲͷఔݱΛදݱ Ͱ͖͍ͯΔͷ͔Λ໌Β͔ʹ͠ɼඞཁͰ͋ΕϞσϧ ͷਫ਼៛ԽΛߦ͍ͬͯ͘͜ͱඞཁͰ͋Ζ͏ɽͦΕ ୯ʹརಘؔΛదʹઃఆ͢Δ͚͔ͩ͠Εͳ͍ ͠ɼͬͱϞσϧͷࠜװͷ෦Λม͍͑ͯ͘ඞཁ͕ ͋Δ͔͠Εͳ͍ɽ Ϟσϧͷਫ਼៛Խʹؔ͢ΔҰͭͷྫͱͯ͠ɼϓϨΠ Ϡʔͷݶఆ߹ཧੑ(bounded rationality)͓Αͼඇ ߹ཧੑ(irrationality)ͷϞσϧԽͱ͍͏Ξϓϩʔ ν͕ڍ͛ΒΕΔɽຊߘͰऔΓѻͬͨϓϨΠϠʔɼ શͯશ߹ཧతͰ͋Δ͜ͱΛԾఆ͍ͯ͠Δɽ͢ͳΘ ͪɼݱࡏͷঢ়گશͯ؍ଌՄೳͰ͋Δ͠ɼऔಘͨ͠ ঢ়گͷԼͰࣗʹͱͬͯ࠷దͳઓུΛ͍ͭͰબͼද1: ಈֶతNWܗήʔϜϞσϧʹ͓͚ΔظPoAͱطଘͷ2ࢦඪͷҧ͍ʹ͍ͭͯࣔͨ͠8ϊʔυͷ ࣮ྫɽஶऀΒͷҰ෦ʹΑΔจݙ(Imai and Tanaka 2013)[6]ͷTable.1Λमਖ਼ͯ͠࡞ɽ
͜ͷྫͰશ෦Ͱ12ݸͷର҆ఆղ͕͋Γɼपظղଘࡏ͠ͳ͍ɽͦΕͧΕͷղʹ͓͍ͯɼNWτϙϩ δɼརಘͷ૯Ͱ༩͑ΒΕΔࣾձతޮੑɼҾ͖ࠐΈྖҬͷαΠζ͕ه͞Ε͍ͯΔɽର҆ఆղͷ͏ͪɼࣾ ձతޮੑͷ࠷ѱͱ࠷ྑͦΕͧΕs5ͷͱ͖ͷ5.81ɼs3ͷͱ͖ͷ27.11Ͱ͋Δɽޮղsˆର҆ ఆղʹؚ·Ε͓ͯΒͣɼදͷ࠷ޙͷ෦ʹهࡌ͞Ε͓ͯΓɼޮղͷࣾձతޮੑͷ30.22ɽ͜ͷ ྫͰɼPoAͷ30.22/5.81≈ 5.20ɼPoSͷ30.22/27.11≈ 1.11ɼظPoAͷ2.03ͱ ͳΔɽ ղ NWτϙϩδ ࣾձతޮੑ ղ NWτϙϩδ ࣾձతޮੑ Ҿ͖ࠐΈྖҬͷ Ҿ͖ࠐΈྖҬͷ αΠζ αΠζ s1 7.83 s8 21.21 106,966,207 177,032 s2 21.82 s9 25.41 69,057,682 1,522,866 s3 27.11 s10 20.01 6,745,020 14,864,197 s4 24.29 s11 25.18 841,521 8,107,411 s5 5.81 s12 23.16 23,915,112 735,093 s6 20.63 31,149,583 s7 26.15 ˆ s 30.22 4,353,732 –
औΔ͜ͱ͕Ͱ͖Δɽ͜ͷԾఆෆࣗવͰɼݱ࣮ʹҙ ࢥܾఆΛ͢ΔϓϨΠϠʔ௨ৗɼ؍ଌೳྗʹ࠷ద Խೳྗʹݶք͕͋Δ(ݶఆ߹ཧੑ)ɽ2અͰड़ ͨΑ͏ʹɼಈֶతϞσϧʹ͓͍ͯϓϨΠϠʔʹ՝͞ ΕΔ߹ཧੑɼ੩ֶతϞσϧͷͦΕʹൺܰݮ͞ Ε͍ͯΔɽ͜Εݶఆ߹ཧੑͷϞσϦϯάͷҰͭ ͷࢼΈͰͰ͋Δ͕ɼ͜Ε͕ʮదͳʯϞσϦϯά Ͱ͋Δ͔Ͳ͏͔ɼٞͷ༨͕͋ΔͩΖ͏ɽݱ࣮ ͷNWΛϞσϧԽ͢ΔࡍʹɼϞσϧԽͷରͷ NWͷΓཱͪͳͲΛ౿·͑ͯɼΑΓదͳݶఆ߹ ཧੑͷϞσϧԽΛબ͢Δํ͕ྑ͍߹͕͋ΔͩΖ ͏ 10 ɽ·ͨɼͦͦਓؒৗʹ߹ཧతʹৼ ͏ͱݶΒͳ͍ (͢ͳΘͪඇ߹ཧతͰ͋Δ)ͱ͍ ͏ࢦఠ͕͋Γ(ΧʔωϚϯ 2012)[2]ɼϓϨΠϠʔͷ ඇ߹ཧੑΛϞσϧʹΈೖΕΔ͜ͱ͕ඞཁ͔͠Ε ͳ͍ɽ࣮ࡍͷNWΛϞσϧԽ͢Δࡍʹɼ͜ͷΑ ͏ͳݶఆ߹ཧతɾඇ߹ཧతͳҙࢥܾఆͷ؍͔Βɼ ϞσϧΛਫ਼៛Խ͍ͯ͘͜͠ͱඞཁͰ͋Ζ͏ɽ·ͨ ͜ΕΒͷϞσϧΛݱ࣮ͷNWͱൺֱ͠ݕূΛ͢Δ ࡍʹɼൺֱରͷNWͱಉنͷେنNWγ ϛϡϨʔγϣϯ͕ඞਢͱͳΔɽ ࠷ޙʹɼϝΧχζϜσβΠϯͳͲͷΞϓϩʔν͔ Βͷτϙϩδ࠷దԽ͕ڍ͛ΒΕΔɽݱ࣮ʹݟΒΕΔ NWτϙϩδ͕࣋ͭಛੑɼྫ͑εέʔϧϑϦʔ ੑͳͲɼඞͣ͠ʮ·͍͠ʯಛੑͱݴ͑ͳ ͍ɽྫ͑௨৴NWͷτϙϩδ͕εέʔϧϑϦʔ Ͱ͋ͬͨͱ͖ʹɼߴ͍௨৴ͷޮੑΛ࣋ͭ໘ɼ ϋϒʹର͢Δબత߈ܸʹରͯ͠੬ऑͰ͋Δͱ͍ͬ ͨෆ߹ͳಛੑΛ࣋ͭͨΊɼඞͣ͠ʮ·͍͠ʯ ͱݴ͑ͳ͍͔͠Εͳ͍ɽԿΛ࣋ͬͯʮ·͠ ͍ʯͱ͢Δ͔ɼ୭ʹͱͬͯͷʮ·͠͞ʯͳͷ͔ ͱ͍͍ͬͨ͠ΛؚΉ͕ɼগͳ͘ͱݱঢ়Λύ Ϩʔτվળ 11 ͢ΔNWτϙϩδɼݱঢ়ͷ NWτϙϩδΑΓʮ·͍͠ʯͱͯ͠ྑ͍Ͱ͋Ζ ͏ɽ͜ͷΑ͏ʹɼԿΒ͔ͷܗͰʮ·͠͞ʯ͕ఆٛ ͞Εͨͱ͖ɼଟͷརݾతͳओମʹΑͬͯߏ͞Ε ΔNWΛʮ·͍͠ʯͷʹ͍ͯ͘͠ʹɼͲ͏ ͢Ε͍͍ͷͩΖ͏͔ɽ ήʔϜཧͰɼϝΧχζϜσβΠϯͱݺΕΔ ݚڀ͕͋Δɽ͜ΕɼήʔϜͷ݁ՌΛࣾձతʹ ·͍͠ͷʹ੍ޚ͢ΔͨΊͷํ๏Ͱ͋Γɼطʹ ΦʔΫγϣϯͷઃܭͳͲͰՌΛڍ͍͛ͯΔɽۙ ͰɼܭࢉՊֶऀͱήʔϜཧֶऀΒͷਚྗʹΑͬ ͯɼଟਓήʔϜʹ͓͚ΔϓϨΠϠʔͷݶఆ߹ཧੑ ใͷඇରশੑΛѻͬͨܭࢉతϝΧχζϜσ βΠϯͱ͍͏ຄڵͭͭ͋͠Δɽ͜ΕΒͷՌ ΛಈֶతNWܗήʔϜϞσϧʹΑΔNWܗͷ ʹԉ༻͢Δ͜ͱʹΑͬͯɼকདྷతʹNWτϙ ϩδΛ࠷దԽ͢ΔͨΊͷํ๏ཱ͕֬͞ΕΔ͜ͱ͕ ظͰ͖Δɽ ͜ΕΒΛഎܠͱͯ͠ɼ͜͜Ͱਤ4ͷྫΛͬ ͯʮ·͍͠ʯNWτϙϩδܗΛଅ͢2ͭͷΞϓ ϩʔνΛհ͢Δ(ਤ6)ɽ͜ͷέʔεͰɼਤ6(a) ʹࣔ͢Α͏ʹɼݱࡏͷঢ়ଶg2Ͱ͋Γɼ͜ͷ·· ࠷ऴతʹ౸ୡ͢Δঢ়ଶg3(རಘͷ૯3.82)ͱ ͳΔ͕ɼΑΓʮ·͍͠ʯঢ়ଶg5(ಉ4.42)Ͱ͋ Δɽ͜ΕΛվળ͢ΔͨΊͷҰͭͷํ๏ɼΠϯη ϯςΟϒઃܭͷΞϓϩʔνͰ͋Δɽ͜Ε͍ΘΏ ΔʮΞϝͱϜνʯͰ͋Γɼࣾձతʹ·͘͠ͳ͍ؼ ݁ΛͨΒ͢ߦಈʹରͯ͠੫ۚΛ՝͠ɼࣾձతʹ ·͍͠ؼ݁ΛͨΒ͢ߦಈʹରͯ͠ิॿۚΛ༩ ͑Δͱ͍ͬͨΞϓϩʔνͰ͋Δɽਤ6(b)Ͱɼa ͱcͷؒͷϦϯΫͷίετcca= cacͷίετΛ ্͛ͯ͠acؒͷϦϯΫΛܗ͠ʹ͘͘͢Δ͜ͱʹ Αͬͯɼ·͍͠ؼ݁g5౸ୡ͢ΔΑ͏ʹ͍ͯ͠ ΔɽΠϯηϯςΟϒઃܭɼήʔϜͷઃܭΛ͢͠ τοϓμϯܕͷΞϓϩʔνͰ͋ΓɼඇৗʹڧྗͰ ͋Δ͕ɼͦͷ࣮ߦओମɼαʔϏεͷӡӦऀ ͱ͍ͬͨެڞతن੍Λ͔͚Δ͜ͱͷͰ͖Δ৫ʹݶ ΒΕΔɽ·ͨɼطʹଟͷεςʔΫϗϧμʔ͕͍Δ தͰɼήʔϜͷϧʔϧΛ్த͔Βมߋ͢Δ͜ͱ͋ ·Γݱ࣮తͰͳ͍ͱݴ͑ΔɽҰํɼਤ6(c)ʹ ࣔ͢ೋͭͷํ๏Ͱɼaͱc͕݁ୗͯ͠ڧ੍తʹ g0ભҠ͢Δ͜ͱʹΑͬͯɼ࠷ऴతʹ౸ୡ͢Δঢ় ଶΛg5ʹมߋ͢Δɽ͜Εɼ݁ୗऀaͱcʹͱͬ ͯҰ࣌తʹརಘΛݮগͤ͞ΔߦಈͰ͋Δ͕ɼԿ ͠ͳ͔ͬͨͱ͖ͷ࠷ऴతͳঢ়ଶg3ͱൺͯɼมߋ ޙͷg5ͷঢ়ଶ݁ୗʹࢀՃͨ͠aͱcͷͲͪΒʹ ͱͬͯརಘΛվળͤ͞ΔͷͱͳΔɽ͜ͷ݁ୗ͠ ͨϓϨΠϠʔͷಋೖɼϓϨΠϠʔͷݸਓ߹ཧੑΛ อͪͳ͕ΒࣾձతޮԽΛਤΔ͜ͱ͕Ͱ͖ΔϘτϜ ΞοϓܕͷΞϓϩʔνͰ͋Γɼঢ়ଶۭ͕ؒଟʹ ׂ͞ΕΔ͜ͱΛར༻ͨ͠ͷͰɼҰ෦ͷϓϨΠϠʔ ʹͷΈհೖ͢Ε͍͍ͱ͍͏ҙຯͰɼ࣮ߦՄೳੑ ͕ߴ͍ɽ͔݁͠͠ୗ͢ΔҰ෦ͷϓϨΠϠʔͷ߹ཧੑ ͱࣾձతޮੑ͕Ұக͢Δ߹ʹͷΈ༗ޮͰ͋Δͱ [ [ ] ]
(a)ʮ·͍͠ʯNWτϙϩδʹ౸ୡͰ͖ͳ͍ έʔε (b)ΠϯηϯςΟϒઃܭ(ิॿۚͱ੫ۚ) (c) Ұ෦ͷϓϨΠϠʔͷ݁ୗʹΑΔঢ়ଶͷඈ༂ తભҠ ਤ6: ʮ·͍͠ʯNWτϙϩδܗΛଅ͢2 ͭͷΞϓϩʔνɽ (a)ݱࡏͷঢ়ଶg2Ͱ͋Γɼ͜ͷ··࠷ऴతʹ ౸ୡ͢Δঢ়ଶg3(རಘͷ૯3.82)Ͱ͋Δ ͕ɼΑΓʮ·͍͠ʯঢ়ଶg5(ಉ4.42)ɽ(b) aͱcͷؒͷϦϯΫίετΛ0.5্͛Δͱɼg2 ͔Βg5౸ୡ͢ΔΑ͏ʹͳΔɽ(c) aͱc͕݁ ୗͯ͠ڧ੍తʹg0ભҠ͢Δͱɼg5౸ୡͰ ͖Δɽ͜ΕaͱcͷͲͪΒʹͱͬͯརಘΛ վળͤ͞Δɽ ͍͏ҙຯͰɼ࣮ߦՄೳͳ໘͕ଟ͘ͳ͍ͱ͍͏໘Λ ࣋ͭɽ Ҏ্ɼNWܗͷؼ݁ΛΑΓʮ·͍͠ʯͷʹ ͢ΔͨΊͷΞϓϩʔνʹ͍ͭͯड़͕ͨɼ͜ΕΒͷ ٞ·ͩඇৗʹૉͰɼߥΓͰ͋Δɽࠓޙɼ͜ ΕΒ͕ήʔϜཧ͓ΑͼϛΫϩܦࡁֶͷݟΛੜ͔ ͯ͠ཧɾચ࿅͞Εɼ͞Βʹൃల͞ΕΔ͜ͱ͕ظ ͞ΕΔɽ
6
͓ΘΓʹ
ήʔϜతNWܗͷݚڀΛਐΊΔʹɼ৭ʑ ͳࠔ͕͖ͭ·ͱ͏ɽୈҰʹɼήʔϜతNWܗ ɼֶज़తʹෳࡶNWՊֶɾήʔϜཧɾ ܭࢉՊֶͷ3 ͭͷֶज़ͷަࠩʹҐஔ͠ɼֶ ࡍతͰ͋Δͱ͍͏ಛΛ࣋ͭɽͦͷͨΊɼಛʹଔۀ จʹऔΓΉΑ͏ͳֶੜʹͱͬͯɼݚڀΛ࢝Ί Δ·ͰʹֶͿ͖͜ͱ͕ଟ͘ɼݚڀͷϋʔυϧ ͕ߴ͘ͳͬͯ͠·͍ͬͯΔɽୈೋʹɼͦͦήʔ ϜతNWܗΛݚڀ͍ͯ͠Δݚڀऀɼಛʹࠃ ʹ͋·Γଟ͘ͳ͍Α͏Ͱ͋Δɽͦͷوॏͳݚڀ ऀϛΫϩܦࡁֶɾήʔϜཧΛόοΫάϥϯυ ͱͨ͠ݚڀऀ͕ଟ͘ɼͦͷͨΊݚڀର͕ൺֱతখ نͷͷ͕ଟ͘ͳΓ͕ͪͰɼචऀΒ͕ࢦ͢Δେ نෳࡶNWͱͷؔੑʹ͍ͭͯऔΓΜͰ͍Δ ݚڀऀΛݟ͚ͭΔ͜ͱɼ͔ͳΓࠔʹͳ͍ͬͯ ΔɽͦͷͨΊɼͷݚڀऀ͕ू·ͬͯٞΛ͢Δ ͕ଟ͘औΕͣɼݚڀൃදଞͷઐͷݚڀձ ෝ͖ɼଞྲྀࢼ߹Λ͢Δ͔͠ͳ͍ͷ͕ݱঢ়ͷΑ͏Ͱ ͋Δɽ ͜ͷΑ͏ͳࠔ͕͋ΔҰํͰɼήʔϜత NW ܗͷݚڀʹେ͖ͳັྗ͕͋ΔɽຊߘͰड़͖ͯ ͨΑ͏ʹɼήʔϜతNWܗͷΈɼଟओ ମʹΑͬͯߏ͞ΕΔNWܗͷΈΛɼNW ߏʹࢀՃ͢Δओମͷݸਓ߹ཧੑʹج͍ͮͯ໌Β͔ ʹ͠Α͏ͱ͢ΔऔΓΈͰ͋Δɽ͜ͷΑ͏ͳཱ͔ Βͷݚڀɼ೦ͳ͕Βະͩେ͖ͳΛूΊ͍ͯͳ͍ͷͷɼಛʹଟओମʹΑΔNWܗΛ· ͍͠ํ੍ޚ͠Α͏ͱͨ͠ͱ͖ʹɼ͜ͷΑ͏ͳ ࢹ͔Βͷݚڀຊ࣭తͰɼආ͚ͯ௨Εͳ͍ͷͱ ͳΖ͏ɽ ·ͨɼԣஅతɾֶࡍతͱ͍͏͜ͱɼ֤ ͷݚڀऀ͕ࣗͷͷݟΛར༻ͯ͠ɼݚڀΛൃ లͤ͞Δ͜ͱ͕Ͱ͖Δͱ͍͏͜ͱͰ͋Δɽ֤ ʹ͓͚ΔݟΛҟͳΔʹదԠͯ͠ΈΔ͜ͱ ݟͷҰൠԽΛࢼΈΔͱ͍͏͜ͱͰ͋Γɼద༻ઌͷ ͷൃలʹߩݙ͢ΔͷΈͳΒͣɼݩͷΛ૬ରత ʹଊ͖͔͚͑ͬ͢ͱͳΔɽ͜ΕΒͷ͜ͱɼݚ ڀͷ໘നΈͷ࠶ൃݟͱͳΖ͏ɽ ݱࡏ·Ͱͷͱ͜ΖɼήʔϜతNWܗͷ ΈͰେنෳࡶNWܗΛϞσϧԽ͢ΔऔΓΈ ɼ5અʹڍ͛ͨΑ͏ʹɼ·ͩ·ͩະ౿ͷ෦͕ଟ ͘ɼ໌Β͔ʹͳ͖͍ͬͯͯΔݟʹ͍ͭͯɼ·ͩ ࡶଟͳͷ͕ଟ͘ݟΒΕΔɽݴ͏ͳΕɼߥͷ҉ ҋʹ͍͔ͭ͘ͷ౮Ր͕ࡏ࢝͠Ίͨஈ֊Ͱ͋Δɽ͜ ΕΒΛཧ͠ɼચ࿅͞Εͨݟʹ·ͱΊ্͍͛ͯ͘ ͜ͱɼ҉ҋʹࢄࡏ͢Δ౮ՐΛܨ͛ͯ໌Δ͍֗ಓΛ ࡞Δͱݴ͏͜ͱͰ͋Γɼେ͍ʹҙٛਂ͍ࣄͱͳ ΔͩΖ͏ɽ·ͨࣾձΛ͘ݟͤɼଟͷओମʹ Αͬͯࣗݾ৫తʹߏ͞ΕͨNWଟ͘ݟΒ ΕΔɽഎܠ͕େ͖͘ҟͳΔ͜ΕΒͷNWΛ؏͘ ݟΛಘΔ͜ͱ͕Ͱ͖Δͱ͢ΕɼͦΕతح৺ Λຬͨ͢ͱ͍͏ҙຯͰݚڀͱͯ͠ͷେ͖ͳັྗͰ͋ ΓɼͦΕΒͷݟ·ͨɼࣾձతʹൃల͕ظ͞ ΕΔॏཁͳٕज़ͱͳ͍ͬͯͩ͘Ζ͏ɽ ͜ͷΑ͏ʹචऀΒɼήʔϜతNWܗͷݚ ڀΛॏཁͰɼ໘ന͘ɼকདྷతʹେ͍ʹൃల͢Δ༨ ͷ͋ΔݚڀͰ͋Δͱߟ͍͑ͯΔɽຊߘͷಡऀॾ ܑ࢞ʹɼήʔϜతNWܗʹ͍ͭͯڵຯΛ࣋ͪɼ ݚڀͷൃలʹਚྗ͍͚ͯͨͩ͠Δํ͕ݱΕΔ͜ ͱΛظ͍ͨ͠ɽຊߘ͕ͦͷ͖͔͚ͬͱͳͬͯ͘Ε ΕɼචऀΒʹͱͬͯେ͖ͳتͼͰ͋Δɽ
ँࣙ
ຊ ݚ ڀ JSPS Պ ݚ අ 26870856 ͓ Α ͼ 30236567ͷॿΛड͚ͨͷͰ͋Δɽ·ͨຊݚڀ ͷҰ෦HPCIγεςϜར༻ݚڀ՝ͷՌʹΑ ΔͷͰ͋Γɼւಓେֶใج൫ηϯλʔͷܭࢉ ࢿݯΛར༻ͨ͠ͷͰ͋Δʢ՝൪߸:hp140070ʣɽ ʲʳ 1 ͕࣍ϕΩʹै͏͜ͱͰಛ͚ͮΒ ΕΔɽ 2 ϊʔυʹର͠খ͍͞ฏۉ࠷ܦ࿏ͱɼେ ͖ͳΫϥελϦϯάʹΑͬͯಛ͚ͮΒ ΕΔɽ 3 NW ܗήʔϜʹɼຊߘͰऔΓ্͛Δ JacksonͱWolinskyͷํϞσϧͷ΄͔ ʹɼBalaͱGoyal͕ఏҊͨ͠ҰํϞσϧ(Bala and Goyal 2000)[1]͕͋ΔɽJackson
ͱWolinskyͷϞσϧͰϦϯΫͷܗʹ྆ ͷϓϨΠϠʔͷ߹ҙ͕ඞཁͰ͋Δͷʹର ͠ɼBalaͱGoyalͷϞσϧͰยํͷϓϨ ΠϠʔͷఏҊͷΈͰϦϯΫ͕ܗ͞ΕΔͱ ͍͏ҧ͍͕͋Δɽޙऀղͷ֓೦ͱͯ͠φο γϡۉߧ͕͑Δ͜ͱ͔Βɼͪ͜ΒͷϞσϧ ͷੳΜʹߦΘΕ͍ͯΔɽ 4 ͜ͷޮ༻ؔdistance-based utilityͱݺ Εɼ͜ͷޮ༻ؔΛ༻͍ͨ੩ֶతNWܗ ήʔϜ࿈݁Ϟσϧ(connections model) ͱݺΕΔɽͳ͓ɼҰఆҎ্Εͨڑʹ͋ Δϊʔυ͔ΒͷརಘΛແࢹ͢ΔϞσϧΓ ࣺͯ͋Γͷ࿈݁Ϟσϧ (truncated connec-tions model)ͱݺΕΔɽ 5 ϖΞϫΠζ҆ఆɼϖΞʹؔͯ҆͠ఆͱݺ ΕΔɽ 6 ৄ ͠ ͘ Jackson ʹ Α Δ ஶ ॻ (Jackson 2008)[7]ͷ11.1અΛࢀরɽ 7 Jackson ʹΑΔஶॻ (Jackson 2008)[7] ͷ 6.2અʹղઆ͕͋Δɽ 8 PoAݩʑɼܭࢉػՊֶͷจ຺Ͱࢄܕॲ ཧͷ݁Ռͷूதܕॲཧͷ݁Ռʹର͢Δޮੑ Λࣔͨ͢Ίʹ 1999ʹ Koutsoupias and PapadimitriouʹΑͬͯఏҊ͞Εͨ (Kout-soupias and Papadimitriou 1999)[11]ͷ Ͱ͋Δ͕ɼݱࡏͰήʔϜͷؼ͕݁ͨΒ͢ ඇޮੑͱͯ͘͠ΒΕ͍ͯΔɽ 9 ήʔϜʹ͓͚ΔࣾձతޮੑΛଌΔؔͱ ͯ͠ɼϓϨΠϠʔͷརಘͷ߹ܭ࠷େͳ Ͳ͕༻͍ΒΕΔ͜ͱ͕ଟ͍ɽ 10 ͔͠͠ͳ͕ΒɼҰൠʹʮదͳʯݶఆ߹ཧੑ ΛϞσϦϯά͢ΔࢼΈɼଟ͘ͷݚڀऀΒ ʹΑΔઓʹؔΘΒͣɼ·ͩਖ਼͍͠ํ Λݟ͍͍ͩͤͯͳ͍Α͏Ͱ͋Γ(Rubinstein 2008)[14]ɼ͍͠Ͱ͋Δɽ 11 ୭ͷརಘΛԼͤ͞Δ͜ͱͳ͘ɼগͳ͘ͱ 1ਓͷརಘΛ্ͤ͞Δ͜ͱ͕Ͱ͖ΔΑ͏ͳ ঢ়ଶมߋͷ͜ͱɽ [ [ [ [ [ [ [ [ [ [ [ ] ] ] ] ] ] ] ] ] ] ]
ʲҾ༻จݙʳ
[1] Bala, V. and Goyal, S., “A Nonco-operative Model of Network Forma-tion,”Econometrica, 68(5), pp. 1181– 1229 (2000).
[2] ΧʔωϚϯ, D.,ʰϑΝετ&εϩʔ ্: ͋ ͳͨͷҙࢥͲͷΑ͏ʹܾ·Δ͔?ʱɼଜҪষ ࢠ༁ɼૣॻ(2012).
[3] Dezs˝o, B., J¨uttner, A., and Kov´acs, P., “LEMON – an Open Source C++ Graph Template Library,”Electronic Notes in Theoretical Computer Science, 264(5), pp. 23 – 45 (2011).
[4] Imai, T. and Tanaka, A., “A Game The-oretic Model for AS Topology Formation with the Scale-Free Property,”IEICE Transactions on Information and Sys-tems, E93.D(11), pp. 3051–3058 (2010). [5] Imai, T. and Tanaka, A., “Weighted
Price of Anarchy for the Multi-Agent based Dynamic Network Formation Game,” in Proceedings of the 2nd Inter-national Joint Agent Workshop & Sym-posium (iJAWS2011), 2011–18 (2011). [6] Imai, T. and Tanaka, A., “Expected
Price of Anarchy for the Dynamic Net-work Formation Game Model,”Journal of Information Processing, 21(1), pp. 2-8 (2013).
[7] Jackson, M. O., Social and Economic Networks, Princeton University Press:
Princeton University Press (2008). [8] Jackson, M. O. and Rogers, B. W., “The
economics of small worlds,”Journal of the European Economic Association, 3(2), pp. 617–627 (2005).
[9] Jackson, M. O. and Watts, A., “The Evolution of Social and Economic Net-works,”Journal of Economic Theory, 106(2), pp. 265–295 (2002).
[10] Jackson, M. O. and Wolinsky, A., “A Strategic Model of Social and Economic Networks,”Journal of Economic Theory, 71(1), pp. 44–74 (1996).
[11] Koutsoupias, E. and Papadimitriou, C., “Worst-case equilibria,” in Proceed-ings of the 16th annual conference on Theoretical aspects of computer science, STACS’99, pp. 404–413: Springer-Verlag
(1999).
[12] Murase, Y., Uchitane, T., and Ito, N., “A Tool for Parameter-space Explo-rations,”Physics Procedia, 57, pp. 73 – 76 (2014).
[13] Myerson, R. B., “Graphs and Coop-eration in Games,” Discussion Papers 246, Northwestern University, Center for Mathematical Studies in Economics and Management Science (1976). [14] Rubinstein, A.,ʰݶఆ߹ཧੑͷϞσϦϯ άʱɼ݉ాහ೭ɾಙӬ݈Ұ༁ɼڞཱग़൛(2008). [15] Տ߁ࢤɾٱ,ʮແடংͷঈͱ҆ఆ ੑͷঈ(ಛू ͡ΊΑ͏ήʔϜཧ)ʯɼ ʰΦϖϨʔγϣϯζɾϦαʔνʱ, 60(6), pp. 337–342 (2015). [16] ࠓҪɾాதರ,ʮεέʔϧϑϦʔੑΛ࣋ ͭASτϙϩδܗͷͨΊͷήʔϜཧత ϞσϧͷఏҊͱͦͷܗτϙϩδͷௐࠪʯɼ ʰୈ29ճຊγϛϡϨʔγϣϯֶձେձൃ දจूʱ, pp. 451–454 (2010). [17] ࠓҪɾాதರ,ʮརݾతɾࢄతͳଟओ ମʹΑΔෳࡶωοτϫʔΫܗϞσϧͷฒ ྻܭࢉٕज़ʹΑΔେنԽ͚ͨධՁʯɼ ʰୈ10ճωοτϫʔΫੜଶֶγϯϙδϜ ༧ߘूʱɼP26 (2013). [18] ࡾ্,ʮઓུతωοτϫʔΫܗʯɼࡉߐ कلɾଜాলࡾɾݪʢฤʣʰήʔϜͱใ ͷܦࡁֶʱɼႻॻɼୈ13ষ, pp. 297–324 (2006). [19] ૿ࢁҰ,ʮωοτϫʔΫήʔϜͱܦࡁωο τϫʔΫͷࣾձతޮੑʯɼ࢈ۀܦࡁݚڀॴ