Why logical clocks are easy

Logical Physical Clocks

There is a gap between the theory and practice of distributed systems in terms of the use of time. The theory of distributed systems shunned the notion of time, and introduced “causality tracking” as a clean abstraction to reason about concurrency. The practical systems employed physical time (NTP) information but in a best effort manner due to the difficulty of achieving tight clock synchroniz...

Virtual Time CSMA: Why Two Clocks Are Better than One

A new carrier sense multiple access (CShiA) algorithm, called virtual time CSMA, is described and analyzed. This algorithm uses a novel approach to granting access to the shared broadcast channel based on variable-rate clocks. Unlike other CSMA algorithms, the operation of virtual time CSMA reduces to the ideal case in the zero propagation time limit: a work-conserving, first-come first-served ...

Plausible Clocks: Constant Size Logical Clocks for Distributed Systems

Why almost all k-CNF formulas are easy

Finding a satisfying assignment for a k-CNF formula (k ≥ 3), assuming such exists, is a notoriously hard problem. In this work we consider the uniform distribution over satisfiable k-CNF formulas with a linear number of clauses (clause-variable ratio greater than some constant). We rigorously analyze the structure of the space of satisfying assignments of a random formula in that distribution, ...

Why almost all satisfiable k-CNF formulas are easy

Finding a satisfying assignment for a k-CNF formula (k ≥ 3), assuming such exists, is a notoriously hard problem. In this work we consider the uniform distribution over satisfiable k-CNF formulas with a linear number of clauses (clause-variable ratio greater than some constant). We rigorously analyze the structure of the space of satisfying assignments of a random formula in that distribution, ...