We present a preliminary investigation of state partition and high-level dynamics for the hierarchical supervisory control of an automaton with disableable and undisableable events. Conditions are determined on partitions ensuring that state-feedback control of transitions between aggregated blocks, combined with local control, will yield target state (non-blocking) accessibility .

1 Consensus from read/write registers In this section we prove that wait-free consensus for 2 processes or more cannot be implemented from (multi-reader/multi-writer) registers. We actually prove that even the more restricted binary consensus object cannot be implemented in a wait-free manner from registers. In all the discussion that follows we assume that 2 or more processes share the consens...

We present two wait-free algorithms for simulating an `-bit single-writer register from k-bit single-writer registers, for any k ≥ 1. Our first algorithm has Θ(`/k) step complexity for both Read and Write and uses Θ(4`−k) registers. An interesting feature of the algorithm is that Read operations do not write to shared variables. Our second algorithm has Θ(`/k+ (logn)/k) step complexity for both...

In a shared-memory system, n independent asynchronous processes, with distinct names in the range f0;:: : ; N ? 1g, communicate by reading and writing to shared registers. An algorithmis wait-free if a process completes its execution regardless of the behaviorof other processes. This paper considers wait-free algorithms whose complexity adjusts to the level of contention in the system: An algor...

Causal consistency has been introduced to increase wait-free concurrent accesses to a shared memory. Contrarily to sequential consistency, causal consistency allows independent write operations, with respect to the causality relation, to be executed in different orders at each distinct process. This paper introduces a protocol for fully replicated settings which exploits the writing semantic an...

Concurrent data structures are the data sharing side of parallel programming. Data structures give the means to the program to store data, but also provide operations to the program to access and manipulate these data. These operations are implemented through algorithms that have to be efficient. In the sequential setting, data structures are crucially important for the performance of the respe...

! " # $ % & '% &( % & # ) % & % & !

In this paper, we describe a novel algorithm to create a concurrent wait-free stack. To the best of our knowledge, this is the first wait-free algorithm for a general purpose stack. In the past, researchers have proposed restricted wait-free implementations of stacks, lock-free implementations, and efficient universal constructions that can support wait-free stacks. The crux of our wait-free im...

We introduce the first process algebra with non-blocking reading actions for modelling con-current asynchronous systems, and we do it in two different ways: one is more flexible, the otheris simpler since it needs only one type of transitions. We study the impact this new kind ofactions have on fairness, liveness and the timing of systems, using Dekker’s mutual exclusionalgo...

In this paper, we propose a distributed data storage framework that supports unrestricted offline access. The system does not explicitly distinguish between connected and disconnected states. Its design is based on a lock-free distributed framework that avoids update conflicts through file versioning. We propose an algorithm for replica synchronization. The feasibility of this framework is conf...