13,120 research outputs found
Modelling and Simulation of Asynchronous Real-Time Systems using Timed Rebeca
In this paper we propose an extension of the Rebeca language that can be used
to model distributed and asynchronous systems with timing constraints. We
provide the formal semantics of the language using Structural Operational
Semantics, and show its expressiveness by means of examples. We developed a
tool for automated translation from timed Rebeca to the Erlang language, which
provides a first implementation of timed Rebeca. We can use the tool to set the
parameters of timed Rebeca models, which represent the environment and
component variables, and use McErlang to run multiple simulations for different
settings. Timed Rebeca restricts the modeller to a pure asynchronous
actor-based paradigm, where the structure of the model represents the service
oriented architecture, while the computational model matches the network
infrastructure. Simulation is shown to be an effective analysis support,
specially where model checking faces almost immediate state explosion in an
asynchronous setting.Comment: In Proceedings FOCLASA 2011, arXiv:1107.584
Fearless asynchronous communications with timed multiparty session protocols
Session types using affinity and exception handling mechanisms have been developed to ensure the
communication safety of protocols implemented in concurrent and distributed programming languages.
Nevertheless, current affine session types are inadequate for specifying real-world asynchronous
protocols, as they are usually imposed by time constraints which enable timeout exceptions to prevent
indefinite blocking while awaiting valid messages. This paper proposes the first formal integration
of affinity, time constraints, timeouts, and time-failure handling based on multiparty session types for
supporting reliability in asynchronous distributed systems. With this theory, we statically guarantee
that asynchronous timed communication is deadlock-free, communication safe, while being fearless ā
never hindered by timeout errors or abrupt terminations.
To implement our theory, we introduce MultiCrustyT
, a Rust toolchain designed to facilitate the
implementation of safe affine timed protocols. MultiCrustyT
leverages generic types and the time
library to handle timed communications, integrated with optional types for affinity. We evaluate
MultiCrustyT by extending diverse examples from the literature to incorporate time and timeouts.
We also showcase the correctness by construction of our approach by implementing various real-world
use cases, including protocols from the Internet of Remote Things domain and real-time systems
Performance Analysis of Distributed and Asynchronous Systems using Probabilistic Timed Actors
Many real-time distributed applications exhibit probabilistic and non-deterministic behaviors. In this paper, we introduce Probabilistic Timed Rebeca (PTRebeca) as an actor-based language for modeling probabilistic distributed real-time systems with asynchronous message passing. We propose the semantics of PTRebeca model in Timed Markov Decision Process (TMDP), the integral semantics of probabilistic timed automaton (PTA) with one digital clock. To analyze PTRebeca models, we develop a tool set to automatically generate a TMDP model from a PTRebeca model in the form of the input language of PRISM model checker. We use PRISM for performance analysis of PTRebeca models against expected reachability and probabilistic reachability properties. We show the applicability of our approach using a few case studies and experimental results
Timed Implementation Relations for the Distributed Test Architecture
In order to test systems that have physically distributed interfaces, called ports, we might use a distributed approach in which there is a separate tester at each port. If the testers do not synchronise during testing then we cannot always determine the relative order of events observed at different ports and this leads to new notions of correctness that have been described using corresponding implementation relations. We study the situation in which each tester has a local clock and timestamps its observations. If we know nothing about how the local clocks relate then this does not affect the implementation relation while if the local clocks agree exactly then we can reconstruct the sequence of observations made. In practice, however, we are likely to be between these extremes: the local clocks will not agree exactly but we have some information regarding how they can differ. We start by assuming that a local tester interacts synchronously with the corresponding port of the system under test and then extend this to the case where communications can be asynchronous, considering both the first-in-first-out (FIFO) case and the non-FIFO case. The new implementation relations are stronger than implementation relations for distributed testing that do not use timestamps but still reflect the distributed nature of observations. This paper explores these alternatives and derives corresponding implementation relations
Area/latency optimized early output asynchronous full adders and relative-timed ripple carry adders
This article presents two area/latency optimized gate level asynchronous full
adder designs which correspond to early output logic. The proposed full adders
are constructed using the delay-insensitive dual-rail code and adhere to the
four-phase return-to-zero handshaking. For an asynchronous ripple carry adder
(RCA) constructed using the proposed early output full adders, the
relative-timing assumption becomes necessary and the inherent advantages of the
relative-timed RCA are: (1) computation with valid inputs, i.e., forward
latency is data-dependent, and (2) computation with spacer inputs involves a
bare minimum constant reverse latency of just one full adder delay, thus
resulting in the optimal cycle time. With respect to different 32-bit RCA
implementations, and in comparison with the optimized strong-indication,
weak-indication, and early output full adder designs, one of the proposed early
output full adders achieves respective reductions in latency by 67.8, 12.3 and
6.1 %, while the other proposed early output full adder achieves corresponding
reductions in area by 32.6, 24.6 and 6.9 %, with practically no power penalty.
Further, the proposed early output full adders based asynchronous RCAs enable
minimum reductions in cycle time by 83.4, 15, and 8.8 % when considering
carry-propagation over the entire RCA width of 32-bits, and maximum reductions
in cycle time by 97.5, 27.4, and 22.4 % for the consideration of a typical
carry chain length of 4 full adder stages, when compared to the least of the
cycle time estimates of various strong-indication, weak-indication, and early
output asynchronous RCAs of similar size. All the asynchronous full adders and
RCAs were realized using standard cells in a semi-custom design fashion based
on a 32/28 nm CMOS process technology
Properties of Distributed Time Arc Petri Nets
In recent work we started a research on a distributed-timed extension of Petri nets where time parameters are associated with tokens and arcs carry constraints that qualify the age of tokens required for enabling. This formalism enables to model e.g. hardware architectures like GALS. We give a formal definition of process semantics for our model and investigate several properties of local versus global timing: expressiveness, reachability and coverability
Generalized Asynchronous Systems
The paper is devoted to a mathematical model of concurrency the special case
of which is asynchronous system. Distributed asynchronous automata are
introduced here. It is proved that the Petri nets and transition systems with
independence can be considered like the distributed asynchronous automata. Time
distributed asynchronous automata are defined in standard way by the map which
assigns time intervals to events. It is proved that the time distributed
asynchronous automata are generalized the time Petri nets and asynchronous
systems.Comment: 8 page
Towards a Notion of Distributed Time for Petri Nets
We set the ground for research on a timed extension of Petri nets where time parameters are associated with tokens and arcs carry constraints that qualify the age of tokens required for enabling. The novelty is that, rather than a single global clock, we use a set of unrelated clocks --- possibly one per place --- allowing a local timing as well as distributed time synchronisation. We give a formal definition of the model and investigate properties of local versus global timing, including decidability issues and notions of processes of the respective models
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