1,790 research outputs found
Minimizing Message Size in Stochastic Communication Patterns: Fast Self-Stabilizing Protocols with 3 bits
This paper considers the basic model of communication, in
which in each round, each agent extracts information from few randomly chosen
agents. We seek to identify the smallest amount of information revealed in each
interaction (message size) that nevertheless allows for efficient and robust
computations of fundamental information dissemination tasks. We focus on the
Majority Bit Dissemination problem that considers a population of agents,
with a designated subset of source agents. Each source agent holds an input bit
and each agent holds an output bit. The goal is to let all agents converge
their output bits on the most frequent input bit of the sources (the majority
bit). Note that the particular case of a single source agent corresponds to the
classical problem of Broadcast. We concentrate on the severe fault-tolerant
context of self-stabilization, in which a correct configuration must be reached
eventually, despite all agents starting the execution with arbitrary initial
states.
We first design a general compiler which can essentially transform any
self-stabilizing algorithm with a certain property that uses -bits
messages to one that uses only -bits messages, while paying only a
small penalty in the running time. By applying this compiler recursively we
then obtain a self-stabilizing Clock Synchronization protocol, in which agents
synchronize their clocks modulo some given integer , within rounds w.h.p., and using messages that contain bits only.
We then employ the new Clock Synchronization tool to obtain a
self-stabilizing Majority Bit Dissemination protocol which converges in time, w.h.p., on every initial configuration, provided that the
ratio of sources supporting the minority opinion is bounded away from half.
Moreover, this protocol also uses only 3 bits per interaction.Comment: 28 pages, 4 figure
08371 Abstracts Collection -- Fault-Tolerant Distributed Algorithms on VLSI Chips
From September the , 2008 to September the
, 2008 the Dagstuhl Seminar 08371 ``Fault-Tolerant
Distributed Algorithms on VLSI Chips \u27\u27 was held in Schloss
Dagstuhl~--~Leibniz Center for Informatics. The seminar was devoted to
exploring whether the wealth of existing fault-tolerant distributed
algorithms research can be utilized for meeting the challenges of
future-generation VLSI chips. During the seminar, several participants
from both the VLSI and distributed algorithms\u27 discipline, presented
their current research, and ongoing work and possibilities for
collaboration were discussed. Abstracts of the presentations given
during the seminar as well as abstracts of seminar results and ideas
are put together in this paper. The first section describes the
seminar topics and goals in general. Links to extended abstracts or
full papers are provided, if available
Compact Deterministic Self-Stabilizing Leader Election: The Exponential Advantage of Being Talkative
This paper focuses on compact deterministic self-stabilizing solutions for
the leader election problem. When the protocol is required to be \emph{silent}
(i.e., when communication content remains fixed from some point in time during
any execution), there exists a lower bound of Omega(\log n) bits of memory per
node participating to the leader election (where n denotes the number of nodes
in the system). This lower bound holds even in rings. We present a new
deterministic (non-silent) self-stabilizing protocol for n-node rings that uses
only O(\log\log n) memory bits per node, and stabilizes in O(n\log^2 n) rounds.
Our protocol has several attractive features that make it suitable for
practical purposes. First, the communication model fits with the model used by
existing compilers for real networks. Second, the size of the ring (or any
upper bound on this size) needs not to be known by any node. Third, the node
identifiers can be of various sizes. Finally, no synchrony assumption, besides
a weakly fair scheduler, is assumed. Therefore, our result shows that, perhaps
surprisingly, trading silence for exponential improvement in term of memory
space does not come at a high cost regarding stabilization time or minimal
assumptions
On the Runtime of Chemical Reaction Networks Beyond Idealized Conditions
This paper studies the (discrete) chemical reaction network (CRN) computational model that emerged in the last two decades as an abstraction for molecular programming. The correctness of CRN protocols is typically established under one of two possible schedulers that determine how the execution advances: (1) a stochastic scheduler that obeys the (continuous time) Markov process dictated by the standard model of stochastic chemical kinetics; or (2) an adversarial scheduler whose only commitment is to maintain a certain fairness condition. The latter scheduler is justified by the fact that the former one crucially assumes "idealized conditions" that more often than not, do not hold in real wet-lab experiments. However, when it comes to analyzing the runtime of CRN protocols, the existing literature focuses strictly on the stochastic scheduler, thus raising the research question that drives this work: Is there a meaningful way to quantify the runtime of CRNs without the idealized conditions assumption?
The main conceptual contribution of the current paper is to answer this question in the affirmative, formulating a new runtime measure for CRN protocols that does not rely on idealized conditions. This runtime measure is based on an adapted (weaker) fairness condition as well as a novel scheme that enables partitioning the execution into short rounds and charging the runtime for each round individually (inspired by definitions for the runtime of asynchronous distributed algorithms). Following that, we turn to investigate various fundamental computational tasks and establish (often tight) bounds on the runtime of the corresponding CRN protocols operating under the adversarial scheduler. This includes an almost complete chart of the runtime complexity landscape of predicate decidability tasks
Engineering Resilient Collective Adaptive Systems by Self-Stabilisation
Collective adaptive systems are an emerging class of networked computational
systems, particularly suited in application domains such as smart cities,
complex sensor networks, and the Internet of Things. These systems tend to
feature large scale, heterogeneity of communication model (including
opportunistic peer-to-peer wireless interaction), and require inherent
self-adaptiveness properties to address unforeseen changes in operating
conditions. In this context, it is extremely difficult (if not seemingly
intractable) to engineer reusable pieces of distributed behaviour so as to make
them provably correct and smoothly composable.
Building on the field calculus, a computational model (and associated
toolchain) capturing the notion of aggregate network-level computation, we
address this problem with an engineering methodology coupling formal theory and
computer simulation. On the one hand, functional properties are addressed by
identifying the largest-to-date field calculus fragment generating
self-stabilising behaviour, guaranteed to eventually attain a correct and
stable final state despite any transient perturbation in state or topology, and
including highly reusable building blocks for information spreading,
aggregation, and time evolution. On the other hand, dynamical properties are
addressed by simulation, empirically evaluating the different performances that
can be obtained by switching between implementations of building blocks with
provably equivalent functional properties. Overall, our methodology sheds light
on how to identify core building blocks of collective behaviour, and how to
select implementations that improve system performance while leaving overall
system function and resiliency properties unchanged.Comment: To appear on ACM Transactions on Modeling and Computer Simulatio
Polymer Chain Generation for Coarse-Grained Models Using Radical-Like Polymerization
International audienceThis paper presents major improvements in the efficiency of the so-called Radical-Like Polymerization (RLP) algorithm proposed in ”Polymer chain generation for coarse-grained models using radical-like polymerization” [J. Chem. Phys. 128 (2008)]. Three enhancements are detailed in this paper: (1) the capture radius of a radical is enlarged to increase the probability of finding a neighboring monomer; (2) between each growth step, equilibration is now performed with increasing the relaxation time depending on the actual chain size; (3) the RLP algorithm is now fully parallelized and proposed as a “fix” within the “Lammps” molecular dynamics simulation suite
Diagnostics and Correction of Pre-Competition Psychological Readiness of Judoists of Dif-ferent Qualifications
The paper contains experimental materials on diagnostics and correction of pre-competition
psychological readiness of judoists of different qualifications. The diagnostics of pre-competition
psychological readiness is carried out during the whole pre-competition mesocycle - at the beginning
and at the end of every micro cycle. The results of the diagnostics underlie the development of individual
contents of correctional work for every sportsman.
The contents of the correctional work can have substantial differences depending on the sport
qualifications of a judoist and the completeness of separate components of his/her mental
preparation.
In order to verify the effectiveness of the developed contents of correctional work we have carried out
three pedagogical experiments with judo sportsmen of different sport qualifications. The correctional
work has been done with judo sportsmen of different sport qualifications during these three competition
periods; it allowed us to achieve the completeness of each structural component of mental preparation,
which in its turn contributed to the achievement of optimal pre-competition psychological state of
judoists; adequate reactions during the fight; improvement of the judoists` performance.В статье представлены экспериментальные материалы диагностики и коррекции
предсоревновательной психологической подготовленности дзюдоистов различной
квалификации. Диагностика предсоревновательной психологической подготовленности
проводится на протяжении всего предсоревновательного мезоцикла - в начале и после
окончания каждого микроцикла. Полученные результаты диагностики служат основой для
разработки индивидуального содержания коррекционной работы для каждого спортсмена.
Содержание коррекционной работы имеет существенные отличия в зависимости от
спортивной квалификации дзюдоиста и сформированности отдельных компонентов
психологической подготовленности. Для проверки эффективности разработанного
содержания коррекционной работы было проведено три педагогических эксперимента с
дзюдоистами различной спортивной квалификации. Проведение коррекционной работы с
дзюдоистами различной квалификации в течение трех соревновательных этапов позволило
добиться желаемой сформированности каждого структурного компонента психологической
подготовленности. Это, в свою очередь, способствовало созданию оптимального
предстартового состояния дзюдоистов; адекватному реагированию в процессе ведения
схватки, повышению результативности соревновательной деятельности дзюдоистов
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