Thu 11 Jan 2018 13:40 - 14:05 at Watercourt - Outside the box Chair(s): Lars Birkedal

Concurrent separation logics have helped to significantly simplify correctness proofs for concurrent data structures. However, a recurring problem in such proofs is that data structure abstractions that work well in the sequential setting are much harder to reason about in a concurrent setting due to complex sharing and overlays. To solve this problem, we propose a novel approach to abstracting regions in the heap by encoding the data structure invariant into a local condition on each individual node. This condition may depend on a quantity associated with the node that is computed as a fixpoint over the entire heap graph. We refer to this quantity as a \emph{flow}. Flows can encode both structural properties of the heap (e.g. the reachable nodes from the root form a tree) as well as data invariants (e.g. sortedness). We then introduce the notion of a \emph{flow interface}, which expresses the relies and guarantees that a heap region imposes on its context to maintain the local flow invariant with respect to the global heap. Our main technical result is that this notion leads to a new semantic model of separation logic. In this model, flow interfaces provide a general abstraction mechanism for describing complex data structures. This abstraction mechanism admits proof rules that generalize over a wide variety of data structures. To demonstrate the versatility of our approach, we show how to extend the logic RGSep with flow interfaces. We have used this new logic to prove linearizability and memory safety of nontrivial concurrent data structures. In particular, we obtain parametric linearizability proofs for concurrent dictionary algorithms that abstract from the details of the underlying data structure representation. These proofs cannot be easily expressed using the abstraction mechanisms provided by existing separation logics.

Thu 11 Jan

Displayed time zone: Tijuana, Baja California change

13:40 - 15:20
Outside the boxResearch Papers at Watercourt
Chair(s): Lars Birkedal Aarhus University
13:40
25m
Talk
Go with the Flow: Compositional Abstractions for Concurrent Data Structures
Research Papers
Siddharth Krishna New York University, Dennis Shasha New York University, Thomas Wies New York University
14:05
25m
Talk
Parametricity versus the Universal Type
Research Papers
Dominique Devriese KU Leuven, Marco Patrignani Saarland University, CISPA, Frank Piessens KU Leuven
14:30
25m
Talk
Linearity in Higher-Order Recursion Schemes
Research Papers
Pierre Clairambault CNRS & ENS Lyon, Charles Grellois INRIA Sophia Antipolis & Aix-Marseille Université, Andrzej Murawski University of Oxford
14:55
25m
Talk
Symbolic Types for Lenient Symbolic Execution
Research Papers
Stephen Chang Northeastern University, Alex Knauth Northeastern University, Emina Torlak University of Washington