Vassos Hadzilacos

On the impossibility of group membership

We prove that the primary-partition group membership problem cannot be solved in asynchronous systems with crash failures, even if one allows the removal or killing of non-faulty processes that are erroneously suspected to have crashed.

The weakest failure detector for solving consensus

We determine what information about failures is necessary and sufficient to solve Consensus in asynchronous distributed systems subject to crash failures. In [CT91], we proved that

A theory of reliability in database systems

\Diamond\cal W

Using failure detectors to solve consensus in asynchronous shared-memory systems

, a failure detector that provides surprisingly little information about which processes have crashed, is sufficient to solve Consensus in asynchronous systems with a majority of correct processes. In this paper, we prove that to solve Consensus, any failure detector has to provide at least as much information as

A note on group mutual exclusion

\Diamond\cal W

Abortable and query-abortable objects and their efficient implementation

. Thus,

A scheme for load balancing in heterogenous distributed hash tables

\Diamond\cal W

A first-come-first-served mutual-exclusion algorithm with small communication variables

is indeed the weakest failure detector for solving Consensus in asynchronous systems with a majority of correct processes.

Constant-RMR implementations of CAS and other synchronization primitives using read and write operations

Reliable concurrent processing of transactions in a database system is examined. Since serializability, the conventional concurrency control correctness criterion, is not adequate in the presence of common failures, another theory of correctness is proposed, involving the concepts of commit serializability, recoverability, and resiliency.

Generalized Irreducibility of Consensus and the Equivalence of t -Resilient and Wait-Free Implementations of Consensus

An illuminable wrench of the ratchet type in which the tool handle defines a receptacle for battery cells. A lamp or bulb is retained in the head of the tool and is connected in a circuit to the batteries and may be actuated to illuminate a work area. In one embodiment of the present invention, the bulb is secured in a rotatable assembly adjacent the head so the bulb may be rotatably positioned to direct illumination to the desired work area. In still another embodiment, the battery housing and light are adapted to be detachably secured to a conventional wrench.