Neighborhood best (nbest) is the best position found by the particles in a selected neighborhood. When that neighborhood contains only a few particles, it is called the local best (lbest); when it contains the entire swarm, it is the global best (gbest). section 9.2
Use neighborhood best in particle swarm optimization to share useful information without requiring every particle to follow the entire swarm:
- Evaluate each particle’s fitness and update its personal best when the current position improves on its previous best. section 9.2.2
- Update each neighborhood’s best position, then use nbest or lbest in place of gbest when calculating particle motion. section 9.2.2 section 9.2.1
- In synchronous PSO, particles use a common update stage; in asynchronous PSO, each particle can use the most recent neighborhood information during its update. section 9.2.2
Restricted versus whole-swarm neighborhoods
A particle swarm divided into small neighborhoods uses each neighborhood’s lbest to guide motion. Replacing those restricted neighborhoods with the whole swarm makes nbest identical to gbest. section 9.2 section 9.2.2
Figure 9.4 Synchronous and asynchronous PSO
Compare synchronous and asynchronous PSO update flow, including where the neighborhood-best update occurs. section 9.2.2
