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Swarm Intelligence Book Chapter n n n “the swarm seems more intelligent than the individual in it”; insects: “the swarm exhibits behavior that individual members cannot” Stigmergy: indirect communication (using signs or clues placed in the environment) SWI: Cooperative efforts of groups of agents…. • • • n n Agents are autonomous and operate in parallel Little or no centralized control Stigmergy (indirect communication) Usually use simple rules … Learning from foraging: http: //en. wikipedia. org/wiki/Foraging Stigmergy: • • • Ch. Eick: SWI Book Chapter Stimulating material triggers response in the termite workers; as the configuration changes, this change triggers a different response Pheromone (already covered before) Nest-building: The Structure influences the actions of the individual that reads it
Swarm Intelligence Book Chapter II n Natural Clustering 1. Ant cemeteries; ant eggs and micro larvae are sorted in rings by age 2. Simple Agent Rule for clustering (as witnessed in the Net. Logo Program): a. Pick up single corpse b. Move away c. Find an area with high density corpses n Termites build highly complex structures. How do they do it • • • n Micro rules Patterns observed by termites and other sensual input act as sigmergic trigger I did not quite understand Figure 4? Did you? Swarm robots: Small simple robots furnished with relatively nonsophisticated ways to communicate. Ch. Eick: SWI Book Chapter
Swarm Intelligence Book Chapter III n Foraging • • • Ch. Eick: SWI Book Chapter “Get food without wasting too much energy” Bacterial Foraging: – Chemotaxis: Movement along a chemical gradient – Bacterium has two kind of movements: Tumble and run – When encountering an increasing gradient more running – Additionally, bacteria secrete chemicals that attract each other like in particle swarms – In summary uses some combination of exploration and exploitation Bee Foraging: – Waggle dance (http: //www. youtube. com/watch? v=-7 ij. I-g 4 j. Hg ) • Straightline Movement tells where the food is • Duration of dance tells “quality/quantity of food source” • Bees are allowed to sample the nectar (not during the dance) • Depending on the quality of the dance other bees are or are not recruited in exploring the food source • If the food source is good multiple bees will be performing the same dance.
Swarm Intelligence Book Chapter IV n Flocking (already covered) n PSO (already covered). Simple version: New Vector (speed + direction) is computed dependent on • Current Vector • Personal Best multiplied by a random number in [0, 2] • Global Best multiplied by a random number in [0, 2] and the position of the particle is updated by adding this vector to the current position • PSO provides a significant contribution to optimization practice Current Trends: • Hybrid algorithms • A lot of new paper that approach optimization and multiobjective optimization using Multiple Swarms • Some work that borrows ideas from bacterial foraging algorithms n Ch. Eick: SWI Book Chapter