BOURNAT Marjorie

PhD graduated
Team : DELYS
Departure date : 08/31/2019

Supervision : Franck PETIT

Co-supervision : DUBOIS Swan, DIEUDONNÉ Yoann

Graceful Degradation and Speculation for Robots in Highly Dynamic Environments

Distributed systems are systems composed of multiple communicant processes cooperating to solve a common task. This is a generic model for numerous real systems as wired or mobile networks, shared-memory multiprocessor systems, and so on. From an algorithmic point of view, it is well-known that strong assumptions (as asynchronism or mobility) on such systems lead often to impossibility results or high lower bounds on complexity. In this thesis, we study algorithms that adapt themselves to their environment (i.e., the union of all assumptions on the system) by focusing on the two following approaches. Graceful degradation circumvents impossibility results by degrading the properties offered by the algorithm as the environment become stronger. Speculation allows to bypass high lower bounds on complexity by optimizing the algorithm only on more probable environments.
Robot networks are a particular case of distributed systems where processes are endowed with sensors and able to move from a location to another. We consider dynamic environments in which this ability may evolve with time. This thesis answers positively to the open question whether it is possible and attractive to apply gracefully degrading and speculative approaches to robot networks in dynamic environments. This answer is obtained through contributions on gracefully degrading gathering (where all robots have to meet on the same location in finite time) and on speculative perpetual exploration (where robots must visit infinitely often each location).

Defence : 06/27/2019

Jury members :

Ralf Klasing, Directeur de recherche CNRS au LaBRI [Rapporteur]
Roger Wattenhofer, Full Professor at Swiss Federal Institute of Technology in Zurich [Rapporteur]
Lélia Blin, Maîtresse de conférences (HDR) à Sorbonne Université
Sylvie Delaët, Maîtresse de conférences (HDR) à Université Paris Sud
Carole Delporte, Professeure des universités à Université Paris Diderot
Yoann Dieudonné, Maître de conférences à l'Université de Picardie Jules Verne
Swan Dubois, Maître de conférences à Sorbonne Université
Franck Petit, Professeur des universités à Sorbonne Université

Departure date : 08/31/2019

2015-2019 Publications