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Paper Abstract and Keywords
Presentation 2015-06-25 09:30
Online Density Estimation of Bradley-Terry Models
Issei Matsumoto (Toyota), Kohei Hatano, Eiji Takimoto (Kyushu U.) IBISML2015-21
Abstract (in Japanese) (See Japanese page) 
(in English) We consider an online density estimation problem for Bradley-Terry models that determine the probability of a match result between any pair in a set of $n$ teams. However, in this context, the loss function is not convex. A standard solution to avoid this non-convexity is to change variables such that the new loss function w.r.t.~new variables is convex. However, the
radius $K$ of the new domain may then become huge or infinite. When $K$ is considered a constant, standard algorithms OGD and ONS have regret
bounds $O(n^{frac{1}{2}}(ln K)sqrt{T})$ and $O(n^{frac{3}{2}}Kln T)$, respectively. We derive a $Theta(T^{n-1})$ bound of the radius $K$ of the reparameterized convex domain under a mild assumption. The bound implies a worst case where the regret bounds of OGD and ONS are $O(n^{frac{3}{2}}sqrt{T}ln T)$ and $tilde{O}(n^{frac{3{2}}(T)^{n-1})$, respectively. We then propose a version of Follow the Regularized Leader, whose regret bound is close to the minimum of those of OGD and ONS. Therefore, the proposed algorithm is competitive both when $K$ is constant or $O(T^{n-1})$. With an appropriate parameter, the proposed algorithm achieves a better regret bound $O(n^{frac{5}{2}}T^{frac{1}{3}} ln T)$ in the worst case. In addition, the proposed algorithm works without knowledge of the radius, which is a practical advantage.
Keyword (in Japanese) (See Japanese page) 
(in English) online density estimation / Bradley-Terry model / ranking / / / / /  
Reference Info. IEICE Tech. Rep., vol. 115, no. 112, IBISML2015-21, pp. 173-180, June 2015.
Paper # IBISML2015-21 
Date of Issue 2015-06-16 (IBISML) 
ISSN Print edition: ISSN 0913-5685    Online edition: ISSN 2432-6380
Copyright
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reproduction
All rights are reserved and no part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher. Notwithstanding, instructors are permitted to photocopy isolated articles for noncommercial classroom use without fee. (License No.: 10GA0019/12GB0052/13GB0056/17GB0034/18GB0034)
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Conference Information
Committee NC IPSJ-BIO IBISML IPSJ-MPS  
Conference Date 2015-06-23 - 2015-06-25 
Place (in Japanese) (See Japanese page) 
Place (in English) Okinawa Institute of Science and Technology 
Topics (in Japanese) (See Japanese page) 
Topics (in English) Machine Learning Approach to Biodata Mining, and General 
Paper Information
Registration To IBISML 
Conference Code 2015-06-NC-BIO-IBISML-MPS 
Language English (Japanese title is available) 
Title (in Japanese) (See Japanese page) 
Sub Title (in Japanese) (See Japanese page) 
Title (in English) Online Density Estimation of Bradley-Terry Models 
Sub Title (in English)  
Keyword(1) online density estimation  
Keyword(2) Bradley-Terry model  
Keyword(3) ranking  
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1st Author's Name Issei Matsumoto  
1st Author's Affiliation Toyota Motor Corporation (Toyota)
2nd Author's Name Kohei Hatano  
2nd Author's Affiliation Kyushu University (Kyushu U.)
3rd Author's Name Eiji Takimoto  
3rd Author's Affiliation Kyushu University (Kyushu U.)
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Speaker Author-2 
Date Time 2015-06-25 09:30:00 
Presentation Time 25 minutes 
Registration for IBISML 
Paper # IBISML2015-21 
Volume (vol) vol.115 
Number (no) no.112 
Page pp.173-180 
#Pages
Date of Issue 2015-06-16 (IBISML) 


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