56,863 research outputs found
Deductive Verification of Parallel Programs Using Why3
The Message Passing Interface specification (MPI) defines a portable
message-passing API used to program parallel computers. MPI programs manifest a
number of challenges on what concerns correctness: sent and expected values in
communications may not match, resulting in incorrect computations possibly
leading to crashes; and programs may deadlock resulting in wasted resources.
Existing tools are not completely satisfactory: model-checking does not scale
with the number of processes; testing techniques wastes resources and are
highly dependent on the quality of the test set.
As an alternative, we present a prototype for a type-based approach to
programming and verifying MPI like programs against protocols. Protocols are
written in a dependent type language designed so as to capture the most common
primitives in MPI, incorporating, in addition, a form of primitive recursion
and collective choice. Protocols are then translated into Why3, a deductive
software verification tool. Source code, in turn, is written in WhyML, the
language of the Why3 platform, and checked against the protocol. Programs that
pass verification are guaranteed to be communication safe and free from
deadlocks.
We verified several parallel programs from textbooks using our approach, and
report on the outcome.Comment: In Proceedings ICE 2015, arXiv:1508.0459
Unforgeable Noise-Tolerant Quantum Tokens
The realization of devices which harness the laws of quantum mechanics
represents an exciting challenge at the interface of modern technology and
fundamental science. An exemplary paragon of the power of such quantum
primitives is the concept of "quantum money". A dishonest holder of a quantum
bank-note will invariably fail in any forging attempts; indeed, under
assumptions of ideal measurements and decoherence-free memories such security
is guaranteed by the no-cloning theorem. In any practical situation, however,
noise, decoherence and operational imperfections abound. Thus, the development
of secure "quantum money"-type primitives capable of tolerating realistic
infidelities is of both practical and fundamental importance. Here, we propose
a novel class of such protocols and demonstrate their tolerance to noise;
moreover, we prove their rigorous security by determining tight fidelity
thresholds. Our proposed protocols require only the ability to prepare, store
and measure single qubit quantum memories, making their experimental
realization accessible with current technologies.Comment: 18 pages, 5 figure
Dynamical entanglement purification using chains of atoms and optical cavities
In the framework of cavity QED, we propose a practical scheme to purify
dynamically a bipartite entangled state using short chains of atoms coupled to
high-finesse optical cavities. In contrast to conventional entanglement
purification protocols, we avoid CNOT gates, thus reducing complicated pulse
sequences and superfluous qubit operations. Our interaction scheme works in a
deterministic way, and together with entanglement distribution and swapping,
opens a route towards efficient quantum repeaters for long-distance quantum
communication.Comment: 13 pages, 6 figures, revised version with incorporated erratu
Parameterized Concurrent Multi-Party Session Types
Session types have been proposed as a means of statically verifying
implementations of communication protocols. Although prior work has been
successful in verifying some classes of protocols, it does not cope well with
parameterized, multi-actor scenarios with inherent asynchrony. For example, the
sliding window protocol is inexpressible in previously proposed session type
systems. This paper describes System-A, a new typing language which overcomes
many of the expressiveness limitations of prior work. System-A explicitly
supports asynchrony and parallelism, as well as multiple forms of
parameterization. We define System-A and show how it can be used for the static
verification of a large class of asynchronous communication protocols.Comment: In Proceedings FOCLASA 2012, arXiv:1208.432
On Global Types and Multi-Party Session
Global types are formal specifications that describe communication protocols
in terms of their global interactions. We present a new, streamlined language
of global types equipped with a trace-based semantics and whose features and
restrictions are semantically justified. The multi-party sessions obtained
projecting our global types enjoy a liveness property in addition to the
traditional progress and are shown to be sound and complete with respect to the
set of traces of the originating global type. Our notion of completeness is
less demanding than the classical ones, allowing a multi-party session to leave
out redundant traces from an underspecified global type. In addition to the
technical content, we discuss some limitations of our language of global types
and provide an extensive comparison with related specification languages
adopted in different communities
A Modular Toolkit for Distributed Interactions
We discuss the design, architecture, and implementation of a toolkit which
supports some theories for distributed interactions. The main design principles
of our architecture are flexibility and modularity. Our main goal is to provide
an easily extensible workbench to encompass current algorithms and incorporate
future developments of the theories. With the help of some examples, we
illustrate the main features of our toolkit.Comment: In Proceedings PLACES 2010, arXiv:1110.385
Parameterised Multiparty Session Types
For many application-level distributed protocols and parallel algorithms, the
set of participants, the number of messages or the interaction structure are
only known at run-time. This paper proposes a dependent type theory for
multiparty sessions which can statically guarantee type-safe, deadlock-free
multiparty interactions among processes whose specifications are parameterised
by indices. We use the primitive recursion operator from G\"odel's System T to
express a wide range of communication patterns while keeping type checking
decidable. To type individual distributed processes, a parameterised global
type is projected onto a generic generator which represents a class of all
possible end-point types. We prove the termination of the type-checking
algorithm in the full system with both multiparty session types and recursive
types. We illustrate our type theory through non-trivial programming and
verification examples taken from parallel algorithms and Web services usecases.Comment: LMCS 201
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