Séminaire du thème IC :

From Turing to the Clouds (or what can be computed in a distributed system)

Le 15 Février 2013 à 10h30

Intervenant

Michel Raynal
Pr
IRISA

E-mail : michel.raynal@irisa.fr

Lieu

LAAS-CNRS - Salle de Conférences

7 avenue du Colonel Roche

31077 TOULOUSE Cedex 4

Résumé

One of the main issues addressed in A. Turing's work was about computability, namely,
his Holy Grail Quest was to answser the question "What can be mechanically computed?". Since the definition of the Turing machine and the statement of the Turing-Church thesis, a lot of great technological advances have modified our view of what is a "computing device".

Among them, distributed systems -sometimes called "cloud computing"- are among the most pervasive, and force us to think again to the computability power of such systems. The talk will present several models of distributed computing and will introduce the notion of a task, which is the distributed counterpart of a mathematical function. It will focus on the consensus task, which is the most central task as soon as cooperating entities have to agree. It will also show that (contrarily to what one could hope) the computability power of an asynchronous distributed system prone to process failures is weaker than the one of a Turing machine (hence, from a computability point of view, a "cloud" is less powerful than a Turing machine).

Biographie : Michel Raynal is a professor of computer science at the University of Rennes, France. He is a senior member of "Institut Universitaire de France". His main research interests are the basic principles of distributed computing systems. He is the author of numerous papers on distributed computing (more than 130 in journals) and is well-known for his books on distributed computing. He has chaired the program committee of the major conferences on the topic, has served on the program committees of many international conferences, and is the recipient of several "Best Paper" awards (e.g., ICDCS 1999, 2000 and 2001, SSS 2009, Europar 2010, DISC 2010). Michel Raynal is regularly invited by universities all over the world to give lectures on distributed computing. Very recently (2013) he has published a book devoted to concurrent objects, titled "Concurrent Programming: Algorithms, Principles, and Foundations" (515 pages, Springer, ISBN ISBN 978-3-642-32027-9).





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