Publications de Rachid Guerraoui

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A failure detector is a fundamental abstraction in distributed computing. This paper surveys this abstraction through two dimensions. First we study failure detectors as building blocks to simplify the design of reliable distributed algorithms. In particul ...

The notion of adversary is a staple of distributed computing. An adversary typically models “hostile” assumptions about the underlying distributed environment, e.g., a network that can drop messages, an operating system that can delay processes or an attac ...

We present Abstract (ABortable STate mAChine replicaTion), a new abstraction for designing and reconfiguring generalized replicated state machines that are, unlike traditional state machines, allowed to abort executing a client's request if "something goes ...

Causal consistency is an attractive consistency model for geo-replicated data stores. It is provably the strongest model that tolerates network partitions. It avoids the long latencies associated with strong consistency, and, especially when using read-onl ...

The success of Bitcoin largely relies on the perception of a fair underlying peer-to-peer protocol: blockchain. Fairness here essentially means that the reward (in bitcoins) given to any participant that helps maintain the consistency of the protocol by mi ...

This paper studies obstruction-free software transactional memory systems (OFTMs). These systems are appealing, for they combine the atomicity property of transactions with a liveness property that ensures the commitment of every transaction that eventually encounters no contention. We precisely define OFTMs and establish two of their fundamental properties. First, we prove that the consensus number of such systems is 2. This indicates that OFTMs cannot be implemented with plain read/write shared memory, on

This paper describes an event dissemination algorithm that implements a topic-based publish/subscribe abstraction in mobile ad-hoc networks (MANETs). Our algorithm relies on (1) the mobility of the processes and (2) the validity period of the events to ensure the reliability of the dissemination (under reasonable conditions) with a thrifty usage of the memory. The algorithm is inherently portable and does not assume any specific routing protocol. Old events are collected to save the memory and the energy co

Synchronous distributed algorithms are easier to design and prove correct than algorithms that tolerate asynchrony. Yet, in the real world, networks experience asynchrony and other timing anomalies. In this paper, we address the question of how to efficien ...

A priori, locking seems easy: To protect shared data from concurrent accesses, it is sufficient to lock before accessing the data and unlock after. Nevertheless, making locking efficient requires fine-tuning (a) the granularity of locks and (b) the locking ...

LEAF, the Lean and Extensible Architectural Framework, is an enhancement wrapper for J2EE implementations. Basically, LEAF fixes some identified J2EE issues and extends, as well as simplifies, the use of the J2EE by providing several incremental improvements. These improvements are seamlessly integrated, include an additional component type, allow the same interfaces for local and remote service implementations, offer better J2EE implementation compatibility and ORB interceptors, and encompass several new t

In this paper, we study the wireless synchronization prob- lem which requires devices activated at different times on a congested single-hop radio network to synchronize their round numbering. We assume a collection of n synchronous devices with access to ...

The present application concerns a computer-implemented method for training a machine learning model in a distributed fashion, using Stochastic Gradient Descent, SGD, wherein the method is performed by a first computer in a distributed computing environmen ...

It is considered good distributed computing practice to devise object implementations that tolerate contention, periods of asynchrony and a large number of failures, but perform fast if few failures occur, the system is synchronous and there is no contenti ...

This paper presents elastic transactions, a variant of the transactional model. Upon conflict detection, an elastic transaction might drop what it did so far within a separate transaction that immediately commits, and initiate a new transaction which might itself be elastic. Elastic transactions are a complementary alternative to traditional transactions, particularly appealing when implementing search structures. Both forms of transactions can safely be combined within the same application. We implemented

We prove that no fully transactional system can provide fast read transactions (including read-only ones that are considered the most frequent in practice). Specifically, to achieve fast read transactions, the system has to give up support of transactions ...

The present invention concerns a method of determining an effect of a user action taken with respect to an item in a communication network. The item is associated with data content in the communication network. The method comprises: (a) determining (31) pu ...

The k-set-agreement problem consists for a set of n processes to agree on less than k among n possibly different Values, each initially known to only one process. The problem is at the heart of distributed computing and generalizes the celebrated consensus ...

Decades of research in distributed computing have led to a variety of perspectives on what it means for a concurrent algorithm to be efficient, depending on model assumptions, progress guarantees, and complexity metrics. It is therefore natural to ask whether one could compose algorithms that perform efficiently under different conditions, so that the composition preserves the performance of the original components when their conditions are met. In this paper, we evaluate the cost of composing shared-memory

Set agreement is a fundamental problem in distributed computing in which processes collectively choose a small subset of values from a larger set of proposals. The impossibility of fault-tolerant set agreement in asynchronous networks is one of the seminal ...

Rachid Guerraoui

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The Failure Detector Abstraction

The Universal Gossip Fighter

The Next 700 BFT Protocols

Causal Consistency and Latency Optimality: Friend or Foe?

On the Unfairness of Blockchain

On Obstruction-Free Transactions

Mobility Friendly Publish/Subscribe

Generating Fast Indulgent Algorithms

Locking Made Easy

The LEAF Platform: Incremental Enhancements for the J2EE

The Wireless Synchronization Problem

Byzantine tolerant gradient descent for distributed machine learning with adversaries

Refined Quorum Systems

Elastic Transactions

Distributed Transactional Systems Cannot Be Fast

Utility and privacy effects of a user action in a communication system

A Topological Treatment of Early-Deciding Set-Agreement

Generating Fast Indulgent Algorithms

On the cost of composing shared-memory algorithms

Of Choices, Failures and Asynchrony: The Many Faces of Set Agreement