Skip to content (access key 's')
Logo of Technion
Logo of CS Department
Logo of CS4People
Events

The Taub Faculty of Computer Science Events and Talks

Theory Seminar: An Adaptive Step Toward the Multiphase Conjecture
event speaker icon
Omri Weinstein (Columbia University)
event date icon
Monday, 23.12.2019, 12:30
event location icon
Taub 301 Taub Bld.
In 2010, Patrascu proposed the Multiphase problem, as a candidate for proving polynomial lower bounds on the operational time of dynamic data structures. Patrascu conjectured that any data structure for the Multiphase problem must make n cell-probes in either the update or query phase, and showed that this would imply similar unconditional lower bounds on many important dynamic data structure problems. Alas, there has been almost no progress on this conjecture in the past decade since its introduction.

We show an ~\Omega(\sqrt{n}) cell-probe lower bound on the Multiphase problem for data structures with general (adaptive) updates, and queries with unbounded but "layered" adaptivity. This result captures all known set-intersection data structures and significantly strengthens previous Multiphase lower bounds, which only captured non-adaptivedata structures. Our main technical result is a communication lower bound on a 4-party variant of Patrascu's Number-On-Forehead Multiphase game, using information complexity techniques.

Joint work with Young Kun Ko.