Swarm behaviour

The term swarm behavior refers to the behavior of fish, birds, insects or other animals, to aggregations of individuals - usually the same type and size - unite. Often they move together in one direction. However, it can also form mixed flocks of animals of different species and size. Advantages of swarm formation arise in the search for food and protection from potential predators, such as through collective vigilance. Typical swarm of animals, for example, herring, starlings and locusts. The physiological basis, which enables the individuals of a swarm to move in the observable synchronicity is suspected in the mirror neurons.

In land mammals, it is called with a similar behavior of a herd, at higher speeds from a stampede.

The phenomenon is studied not only in different biological disciplines, but also for example in computer science. Applications are in computer graphics, optimization, and in the military.

Rules for the formation of swarms

Interesting results brought computer simulations of swarms that were actually modeled in 1986 by Craig Reynolds for the first time. The principle is based on three rules that respect the individual agents ( individuals / Boids ):

As a result of these rules to individual level results in a total structure, namely the swarm. We speak of emergence.

A group of scientists from the University of Leeds by Jens Krause explored that a structural memory in fish and flocks of birds ensures that a specific swarm formation is always a very specific next follows. So they first arrange themselves in a disorderly chaotic swarm like mosquito swarms and form next a torus.

Physicist and ornithologist Andrea Cavagna from Rome stated in an EU research project that birds be based on the seven neighboring birds, which is the highest number that can distinguish the birds. Generally they hold at least a wingspan distance. When changing direction of the swarm is not necessarily the swarm peak responding, each individual can cause a change in direction and the whole swarm is organized around this way. At the approach of birds of prey condenses the swarm, to complicate the targeting of an individual. Sometimes even the bird of prey from the swarm is enclosed so that it must be possible to drop flightless. Disturb a bird of prey to swarm -resolution approach to roost, the swarm again rises, often to the onset of darkness.

Many species of migratory birds, however, do not fly in flocks, but in V-shaped trains or, like the cranes, also in long chains diagonally in a row. Computer modeling of swarm behavior have long failed to calculate such V- formations of a swarm of randomly arranged, auffliegender of soil animals. Valmir Barbosa and Andre Nathan ( Universidade Federal do Rio de Janeiro ) reported in early 2007 that it had resolved the problem: By combining only two requirements for each animal:

These model calculations were swarms of up to 35 animals, and regardless of the original arrangement of these animals eventually was always a decent lineup.

Algorithmic complexity

In an application that simulates swarm behavior, there is no central control for the individuals. The next position must be calculated separately for each individual. This is an O ( n ²) is given by the O- notation - algorithm with a computation time of at n individuals. There are various approaches in order to keep the processing time at a varying number of individuals constant or at least the processing time of an O ( n ²) - to reduce the algorithm.

Already Reynolds tried to implement for this purpose a 3D lattice, in which his Boids are distributed based on their position in the container. About this latticework the Boids can quickly check the container in their environment to neighbors, which reduces the running time of the algorithm.

Application in the military

The U.S. Air Force began in 1998 with the exploration of an autonomous drone system, called LOCAAS ( Low Cost Autonomous Attack System). This drone system uses an algorithm based on the model developed by Craig Reynolds to fly as a swarm can. As soon be thrown up to 192 drones from a stealth bomber, they begin to communicate electronically with each other and engage enemy troops to swarm.