21,716 research outputs found
A Modular Formalization of Reversibility for Concurrent Models and Languages
Causal-consistent reversibility is the reference notion of reversibility for
concurrency. We introduce a modular framework for defining causal-consistent
reversible extensions of concurrent models and languages. We show how our
framework can be used to define reversible extensions of formalisms as
different as CCS and concurrent X-machines. The generality of the approach
allows for the reuse of theories and techniques in different settings.Comment: In Proceedings ICE 2016, arXiv:1608.0313
Solving the At-Most-Once Problem with Nearly Optimal Effectiveness
We present and analyze a wait-free deterministic algorithm for solving the
at-most-once problem: how m shared-memory fail-prone processes perform
asynchronously n jobs at most once. Our algorithmic strategy provides for the
first time nearly optimal effectiveness, which is a measure that expresses the
total number of jobs completed in the worst case. The effectiveness of our
algorithm equals n-2m+2. This is up to an additive factor of m close to the
known effectiveness upper bound n-m+1 over all possible algorithms and improves
on the previously best known deterministic solutions that have effectiveness
only n-log m o(n). We also present an iterative version of our algorithm that
for any is both
effectiveness-optimal and work-optimal, for any constant . We
then employ this algorithm to provide a new algorithmic solution for the
Write-All problem which is work optimal for any
.Comment: Updated Version. A Brief Announcement was published in PODC 2011. An
Extended Abstract was published in the proceeding of ICDCN 2012. A full
version was published in Theoretical Computer Science, Volume 496, 22 July
2013, Pages 69 - 8
Formal modelling for Ada implementations: tasking Event-B
This paper describes a formal modelling approach, where Ada code is automatically generated from the modelling artefacts. We introduce an implementation-level specification, Tasking Event-B, which is an extension to Event-B. Event-B is a formal method, that can be used to model safety-, and business-critical systems. The work may be of interest to a section of the Ada community who are interested in applying formal modelling techniques in their development process, and automatically generating Ada code from the model. We describe a streamlined process, where the abstract modelling artefacts map easily to Ada language constructs. Initial modelling takes place at a high level of abstraction. We then use refinement, decomposition, and finally implementation-level annotations, to generate Ada code. We provide a brief introduction to Event-B, before illustrating the new approach using small examples taken from a larger case study
Rethinking State-Machine Replication for Parallelism
State-machine replication, a fundamental approach to designing fault-tolerant
services, requires commands to be executed in the same order by all replicas.
Moreover, command execution must be deterministic: each replica must produce
the same output upon executing the same sequence of commands. These
requirements usually result in single-threaded replicas, which hinders service
performance. This paper introduces Parallel State-Machine Replication (P-SMR),
a new approach to parallelism in state-machine replication. P-SMR scales better
than previous proposals since no component plays a centralizing role in the
execution of independent commands---those that can be executed concurrently, as
defined by the service. The paper introduces P-SMR, describes a "commodified
architecture" to implement it, and compares its performance to other proposals
using a key-value store and a networked file system
- …