45,942 research outputs found
The Dafny Integrated Development Environment
In recent years, program verifiers and interactive theorem provers have
become more powerful and more suitable for verifying large programs or proofs.
This has demonstrated the need for improving the user experience of these tools
to increase productivity and to make them more accessible to non-experts. This
paper presents an integrated development environment for Dafny-a programming
language, verifier, and proof assistant-that addresses issues present in most
state-of-the-art verifiers: low responsiveness and lack of support for
understanding non-obvious verification failures. The paper demonstrates several
new features that move the state-of-the-art closer towards a verification
environment that can provide verification feedback as the user types and can
present more helpful information about the program or failed verifications in a
demand-driven and unobtrusive way.Comment: In Proceedings F-IDE 2014, arXiv:1404.578
Fast and Accurate Mining of Correlated Heavy Hitters
The problem of mining Correlated Heavy Hitters (CHH) from a two-dimensional
data stream has been introduced recently, and a deterministic algorithm based
on the use of the Misra--Gries algorithm has been proposed by Lahiri et al. to
solve it. In this paper we present a new counter-based algorithm for tracking
CHHs, formally prove its error bounds and correctness and show, through
extensive experimental results, that our algorithm outperforms the Misra--Gries
based algorithm with regard to accuracy and speed whilst requiring
asymptotically much less space
Concurrent Data Structures Linked in Time
Arguments about correctness of a concurrent data structure are typically
carried out by using the notion of linearizability and specifying the
linearization points of the data structure's procedures. Such arguments are
often cumbersome as the linearization points' position in time can be dynamic
(depend on the interference, run-time values and events from the past, or even
future), non-local (appear in procedures other than the one considered), and
whose position in the execution trace may only be determined after the
considered procedure has already terminated.
In this paper we propose a new method, based on a separation-style logic, for
reasoning about concurrent objects with such linearization points. We embrace
the dynamic nature of linearization points, and encode it as part of the data
structure's auxiliary state, so that it can be dynamically modified in place by
auxiliary code, as needed when some appropriate run-time event occurs. We name
the idea linking-in-time, because it reduces temporal reasoning to spatial
reasoning. For example, modifying a temporal position of a linearization point
can be modeled similarly to a pointer update in separation logic. Furthermore,
the auxiliary state provides a convenient way to concisely express the
properties essential for reasoning about clients of such concurrent objects. We
illustrate the method by verifying (mechanically in Coq) an intricate optimal
snapshot algorithm due to Jayanti, as well as some clients
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