On the Mailbox Problem

TL;DR

This paper presents a new mailbox algorithm that reduces the size of flag registers from 14 to 6 and 4, improving efficiency in distributed communication systems.

Contribution

It introduces a novel mailbox algorithm with significantly smaller flag values, addressing an open problem from prior research.

Findings

Reduces flag register sizes from 14 to 6 and 4

Provides a constructive algorithm for the mailbox problem

Improves efficiency in distributed message passing

Abstract

The Mailbox Problem was described and solved by Aguilera, Gafni, and Lamport in their 2010 DC paper with an algorithm that uses two flag registers that carry 14 values each. An interesting problem that they ask is whether there is a mailbox algorithm with smaller flag values. We give a positive answer by describing a mailbox algorithm with 6 and 4 values in the two flag registers.