268 research outputs found
A Certified Universal Gathering Algorithm for Oblivious Mobile Robots
We present a new algorithm for the problem of universal gathering mobile
oblivious robots (that is, starting from any initial configuration that is not
bivalent, using any number of robots, the robots reach in a finite number of
steps the same position, not known beforehand) without relying on a common
chirality. We give very strong guaranties on the correctness of our algorithm
by proving formally that it is correct, using the COQ proof assistant. To our
knowledge, this is the first certified positive (and constructive) result in
the context of oblivious mobile robots. It demonstrates both the effectiveness
of the approach to obtain new algorithms that are truly generic, and its
managability since the amount of developped code remains human readable
Certified Universal Gathering in for Oblivious Mobile Robots
We present a unified formal framework for expressing mobile robots models,
protocols, and proofs, and devise a protocol design/proof methodology dedicated
to mobile robots that takes advantage of this formal framework. As a case
study, we present the first formally certified protocol for oblivious mobile
robots evolving in a two-dimensional Euclidean space. In more details, we
provide a new algorithm for the problem of universal gathering mobile oblivious
robots (that is, starting from any initial configuration that is not bivalent,
using any number of robots, the robots reach in a finite number of steps the
same position, not known beforehand) without relying on a common orientation
nor chirality. We give very strong guaranties on the correctness of our
algorithm by proving formally that it is correct, using the COQ proof
assistant. This result demonstrates both the effectiveness of the approach to
obtain new algorithms that use as few assumptions as necessary, and its
manageability since the amount of developed code remains human readable.Comment: arXiv admin note: substantial text overlap with arXiv:1506.0160
On the Energetics of the HCO + C CH + CO Reaction and Some Astrochemical Implications
We explore the energetics of the titular reaction, which current
astrochemical databases consider open at typical dense molecular (i.e., dark)
cloud conditions. As is common for reactions involving the transfer of light
particles, we assume that there are no intersystem crossings of the potential
energy surfaces involved. In the absence of any such crossings, we find that
this reaction is endoergic and will be suppressed at dark cloud temperatures.
Updating accordingly a generic astrochemical model for dark clouds changes the
predicted gas-phase abundances of 224 species by greater than a factor of 2. Of
these species, 43 have been observed in the interstellar medium. Our findings
demonstrate the astrochemical importance of determining the role of intersystem
crossings, if any, in the titular reaction.Comment: Accepted for publication in ApJ; 14 pages, 2 figures, and 1 tabl
Certified Impossibility Results for Byzantine-Tolerant Mobile Robots
We propose a framework to build formal developments for robot networks using
the COQ proof assistant, to state and to prove formally various properties. We
focus in this paper on impossibility proofs, as it is natural to take advantage
of the COQ higher order calculus to reason about algorithms as abstract
objects. We present in particular formal proofs of two impossibility results
forconvergence of oblivious mobile robots if respectively more than one half
and more than one third of the robots exhibit Byzantine failures, starting from
the original theorems by Bouzid et al.. Thanks to our formalization, the
corresponding COQ developments are quite compact. To our knowledge, these are
the first certified (in the sense of formally proved) impossibility results for
robot networks
Impossibility of Gathering, a Certification
Recent advances in Distributed Computing highlight models and algorithms for
autonomous swarms of mobile robots that self-organise and cooperate to solve
global objectives. The overwhelming majority of works so far considers handmade
algorithms and proofs of correctness. This paper builds upon a previously
proposed formal framework to certify the correctness of impossibility results
regarding distributed algorithms that are dedicated to autonomous mobile robots
evolving in a continuous space. As a case study, we consider the problem of
gathering all robots at a particular location, not known beforehand. A
fundamental (but not yet formally certified) result, due to Suzuki and
Yamashita, states that this simple task is impossible for two robots executing
deterministic code and initially located at distinct positions. Not only do we
obtain a certified proof of the original impossibility result, we also get the
more general impossibility of gathering with an even number of robots, when any
two robots are possibly initially at the same exact location.Comment: 10
Vibrational state distribution of 2-Na^+ ions created in ultracold collisions
The vibrational distribution P(v) of 2-Na^+ ions created in
ultracold collisions in a magneto-optical trap has been deter-
mined. Only two vibrational states with v = 2 and 3 are popu-
lated and we find P(2)=0.29±0.02 and P(3)=0.71±0.02. The
results provide conclusive evidence that the ionization mech-
anism is photo-associative autoionization,and not photo-
associative photoionization and will form a fundamental test
for the theoretical description of the process
Certified Impossibility Results for Byzantine-Tolerant Mobile Robots
We propose a framework to build formal developments for robot networks using the COQ proof assistant, to state and to prove formally various properties. We focus in this paper on impossibility proofs, as it is natural to take advantage of the COQ higher order calculus to reason about algorithms as abstract objects. We present in particular formal proofs of two impossibility results forconvergence of oblivious mobile robots if respectively more than one half and more than one third of the robots exhibit Byzantine failures, starting from the original theorems by Bouzid et al.. Thanks to our formalization, the corresponding COQ developments are quite compact. To our knowledge, these are the first certified (in the sense of formally proved) impossibility results for robot networks
Comment s'assurer de garder le contact (et nos distances)
International audienceNous étudions le problème du maintien de connexion dans les réseaux de robots mobiles. On considère un robot incontrôlable (la « cible ») et une flotte de robots volumiques autonomes se déplaçant dans le plan réel et munis de capteurs et transmetteurs à portée limitée. Le problème consiste à maintenir à tout moment une connexion entre un point fixe connu au départ et la cible. Cette situation est par exemple instanciée dans le cas d'une équipe de recherche (la cible) en cours d'exploration et qui doit conserver une liaison avec la base des secours (le point fixe). Dans un tel cas où des vies sont en jeu, le problème devient critique : il est impératif d'avoir les plus fortes garanties de correction possibles sur les protocoles candidats. Nous définissons formellement ce problème et proposons une famille de protocoles que nous prouvons correcte grâce à l'assistant de preuve Coq et la bibliothèque PACTOLE. Nous illustrons en particulier l'utilité de cet outil formel ainsi que de la démarche associée, de la réflexion préliminaire sur un problème à la production d'une solution certifiée
Modular & Incremental Automated Termination Proofs
International audienc
- …