  The study of robotic flocking has received considerable attention in the past
twenty years. As we begin to deploy flocking control algorithms on physical
multi-agent and swarm systems, there is an increasing necessity for rigorous
promises on safety and performance. In this paper, we present an overview the
literature focusing on optimization approaches to achieve flocking behavior
that provide strong safety guarantees. We separate the literature into cluster
and line flocking, and categorize cluster flocking with respect to the
system-level objective, which may be realized by a reactive or planning control
algorithm. We also categorize the line flocking literature by the energy-saving
mechanism that is exploited by the agents. We present several approaches aimed
at minimizing the communication and computational requirements in real systems
via neighbor filtering and event-driven planning, and conclude with our
perspective on the outlook and future research direction of optimal flocking as
a field.
