2 research outputs found
An Algorithmic Approach to the Asynchronous Computability Theorem
The asynchronous computability theorem (ACT) uses concepts from combinatorial
topology to characterize which tasks have wait-free solutions in read-write
memory. A task can be expressed as a relation between two chromatic simplicial
complexes. The theorem states that a task has a protocol (algorithm) if and
only if there is a certain chromatic simplicial map compatible with that
relation.
While the original proof of the ACT relied on an involved combinatorial
argument, Borowsky and Gafni later proposed an alternative proof that relied on
a algorithmic construction, termed the "convergence algorithm". The description
of this algorithm was incomplete, and presented without proof. In this paper,
we give the first complete description, along with a proof of correctness.Comment: 16 pages, 2 figure
On Decidability of 2-process Affine Models
An affine model of computation is defined as a subset of iterated
immediate-snapshot runs, capturing a wide variety of shared-memory systems,
such as wait-freedom, t-resilience, k-concurrency, and fair shared-memory
adversaries. The question of whether a given task is solvable in a given affine
model is, in general, undecidable. In this paper, we focus on affine models
defined for a system of two processes. We show that the task computability of
2-process affine models is decidable and presents a complete hierarchy of the
five equivalence classes of 2-process affine models