みなさま，

東京大学の蓮尾研究室M1の森谷です． 蓮尾研究室では明日30日（直前で申し訳ないのですが）に Salzburg 大学の Ana Sokolova さん， 11月9日に Jan Rutten さんをお迎えしてご講演いただきます．

事前の登録等不要です．ご興味のある方はぜひお越しください！

========================================================== Tue 30 October 2012, 16:40-18:10 Ana Sokolova (U. Salzburg), Quantitative relaxations of concurrent data structures 理学部7号館1階 102教室 Room 102, School of Science Bldg. No. 7

This talk is about our recent work on relaxing the semantics of concurrent data structures, in a quantitative way, so that they allow better-performing implementations. By their nature, data structures are bottlenecks in the presence of concurrency, e.g. the top pointer of a stack is a point of contention for which all threads compete. As a consequence, implementations of concurrent data structures often show negative scalability. Recent trends in concurrency show that relaxing the semantics may be the way to better performance. In this work we provide a framework for quantitative relaxations of concurrent data structures, where the allowed``error" from the perfect semantics is quantified by a distance. During the talk, we will use a stack as a running example. Also we present new concurrent implementation of a quantitatively relaxed stack that performs well and shows positive scalability.

(joint work with Thomas A. Henzinger, Christoph M. Kirsch, Hannes Payer, and Ali Sezgin)

========================================================== Fri 9 November 2012, 10:30-12:00 Jan Rutten (CWI Amsterdam & Radboud Univ. Nijmegen), The method of coalgebra--an overview 理学部7号館地下１階 007教室 Room 007 (on the underground floor), School of Science Bldg. No. 7

Since the early nineties, coalgebra has become an active area of research in which one tries to understand all kinds of infinite data types, automata, transition systems and dynamical systems from a unifying perspective. The focus of coalgebra is on observable behaviour and one uses coinduction as a central methodology, both for behavioural specifications and to prove behavioural equivalences. These days, one uses coalgebraic techniques in a wide variety of areas, ranging from automata theory to software engineering to ecology. In this talk, we shall illustrate the coalgebraic approach by discussing a number examples, including streams, automata and circuits.