122 research outputs found
Solitonization of a dispersive wave
International audienceWe report the observation of a nonlinear propagation scenario in which a dispersive wave is transformed into a fundamental soliton in an axially-varying optical fiber. The dispersive wave is initially emitted in normal dispersion region and the fiber properties change longitudinally so that the dispersion becomes anomalous at the dispersive wave wavelength, which allows it to be transformed into a soliton. The solitonic nature of the field is demonstrated by solving the direct Zakharov-Shabat scattering problem. Experimental characterization performed in spectral and temporal domains show evidence of the solitonizatin process in an axially-varying photonic crystal fiber
Lazy Abstraction-Based Controller Synthesis
We present lazy abstraction-based controller synthesis (ABCS) for
continuous-time nonlinear dynamical systems against reach-avoid and safety
specifications. State-of-the-art multi-layered ABCS pre-computes multiple
finite-state abstractions of varying granularity and applies reactive synthesis
to the coarsest abstraction whenever feasible, but adaptively considers finer
abstractions when necessary. Lazy ABCS improves this technique by constructing
abstractions on demand. Our insight is that the abstract transition relation
only needs to be locally computed for a small set of frontier states at the
precision currently required by the synthesis algorithm. We show that lazy ABCS
can significantly outperform previous multi-layered ABCS algorithms: on
standard benchmarks, lazy ABCS is more than 4 times faster
Efficient and Generalized Decentralized Monitoring of Regular Languages
Part 2: Monitoring and TestingInternational audienceThis paper proposes an efficient and generalized decentralized monitoring algorithm allowing to detect satisfaction or violation of any regular specification by local monitors alone in a system without central observation point. Our algorithm does not assume any form of synchronization between system events and communication of monitors, uses state machines as underlying mechanism for efficiency, and tries to keep the number and size of messages exchanged between monitors to a minimum. We provide a full implementation of the algorithm with an open-source benchmark to evaluate its efficiency in terms of number, size of exchanged messages, and delay induced by communication between monitors. Experimental results demonstrate the effectiveness of our algorithm which outperforms the previous most general one along several (new) monitoring metrics
A Map-Reduce Parallel Approach to Automatic Synthesis of Control Software
Many Control Systems are indeed Software Based Control Systems, i.e. control
systems whose controller consists of control software running on a
microcontroller device. This motivates investigation on Formal Model Based
Design approaches for automatic synthesis of control software.
Available algorithms and tools (e.g., QKS) may require weeks or even months
of computation to synthesize control software for large-size systems. This
motivates search for parallel algorithms for control software synthesis.
In this paper, we present a Map-Reduce style parallel algorithm for control
software synthesis when the controlled system (plant) is modeled as discrete
time linear hybrid system. Furthermore we present an MPI-based implementation
PQKS of our algorithm. To the best of our knowledge, this is the first parallel
approach for control software synthesis.
We experimentally show effectiveness of PQKS on two classical control
synthesis problems: the inverted pendulum and the multi-input buck DC/DC
converter. Experiments show that PQKS efficiency is above 65%. As an example,
PQKS requires about 16 hours to complete the synthesis of control software for
the pendulum on a cluster with 60 processors, instead of the 25 days needed by
the sequential algorithm in QKS.Comment: To be submitted to TACAS 2013. arXiv admin note: substantial text
overlap with arXiv:1207.4474, arXiv:1207.409
Interrupt Timed Automata: verification and expressiveness
We introduce the class of Interrupt Timed Automata (ITA), a subclass of
hybrid automata well suited to the description of timed multi-task systems with
interruptions in a single processor environment. While the reachability problem
is undecidable for hybrid automata we show that it is decidable for ITA. More
precisely we prove that the untimed language of an ITA is regular, by building
a finite automaton as a generalized class graph. We then establish that the
reachability problem for ITA is in NEXPTIME and in PTIME when the number of
clocks is fixed. To prove the first result, we define a subclass ITA- of ITA,
and show that (1) any ITA can be reduced to a language-equivalent automaton in
ITA- and (2) the reachability problem in this subclass is in NEXPTIME (without
any class graph). In the next step, we investigate the verification of real
time properties over ITA. We prove that model checking SCL, a fragment of a
timed linear time logic, is undecidable. On the other hand, we give model
checking procedures for two fragments of timed branching time logic. We also
compare the expressive power of classical timed automata and ITA and prove that
the corresponding families of accepted languages are incomparable. The result
also holds for languages accepted by controlled real-time automata (CRTA), that
extend timed automata. We finally combine ITA with CRTA, in a model which
encompasses both classes and show that the reachability problem is still
decidable. Additionally we show that the languages of ITA are neither closed
under complementation nor under intersection
Computing Nash Equilibrium in Wireless Ad Hoc Networks: A Simulation-Based Approach
This paper studies the problem of computing Nash equilibrium in wireless
networks modeled by Weighted Timed Automata. Such formalism comes together with
a logic that can be used to describe complex features such as timed energy
constraints. Our contribution is a method for solving this problem using
Statistical Model Checking. The method has been implemented in UPPAAL model
checker and has been applied to the analysis of Aloha CSMA/CD and IEEE 802.15.4
CSMA/CA protocols.Comment: In Proceedings IWIGP 2012, arXiv:1202.422
Robust Model-Checking of Linear-Time Properties in Timed Automata
International audienceFormal verification of timed systems is well understood, but their \emphimplementation is still challenging. Recent works by Raskin \emphet al. have brought out a model of parameterized timed automata that can be used to prove \emphimplementability of timed systems for safety properties. We define here a more general notion of robust model-checking for linear-time properties, which consists in verifying whether a property still holds even if the transitions are slightly delayed or expedited. We provide PSPACE algorithms for the robust model-checking of Büchi-like and LTL properties. We also verify bounded-response-time properties
Parametric timed model checking for guaranteeing timed opacity
Information leakage can have dramatic consequences on systems security. Among
harmful information leaks, the timing information leakage is the ability for an
attacker to deduce internal information depending on the system execution time.
We address the following problem: given a timed system, synthesize the
execution times for which one cannot deduce whether the system performed some
secret behavior. We solve this problem in the setting of timed automata (TAs).
We first provide a general solution, and then extend the problem to parametric
TAs, by synthesizing internal timings making the TA secure. We study
decidability, devise algorithms, and show that our method can also apply to
program analysis.Comment: This is the author (and extended) version of the manuscript of the
same name published in the proceedings of ATVA 2019. This work is partially
supported by the ANR national research program PACS (ANR-14-CE28-0002), the
ANR-NRF research program (ProMiS) and by ERATO HASUO Metamathematics for
Systems Design Project (No. JPMJER1603), JS
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