Time-space trade-offs in population protocols for the majority problem

Population protocols are a model for distributed computing that is focused on simplicity and robustness. A system ofnidentical agents (finite state machines) performs a global task like electing a unique leader or determining the majority opinion when each agent has one of two opinions. Agents communicate in pairwise interactions with randomly assigned communication partners. Quality is measured in two ways: the number of interactions to complete the task and the number of states per agent. We present protocols for the majority problem that allow for a trade-off between these two measures. Compared to the only other trade-off result (Alistarh et al. in Proceedings of the 2015 ACM symposium on principles of distributed computing, Donostia-San Sebastian, 2015), we improve the number of interactions by almost a linear factor. Furthermore, our protocols can be made uniform (working correctly without any information on the population sizen), yielding the first uniform majority protocols that stabilize in a subquadratic number of interactions.

Automated summary

Population protocols are a model for distributed computing that emphasizes simplicity and robustness. Agents communicate in pairwise interactions to complete global tasks like choosing a leader or determining majority opinion. Protocols for the majority problem allow for a trade-off between the number of interactions and the number of states per agent.