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| [[Image:Grus grus flocks.jpg|thumb|200px|right|Two flocks of [[Common Crane]]s]]
| | My name: Genesis Frei<br>Age: 31<br>Country: Switzerland<br>Home town: Kandersteg <br>ZIP: 3718<br>Street: Forrenbohlstrasse 59<br><br>Here is my page :: [http://safedietsthatwork.wordpress.com/ diet plans] |
| '''Flocking''' behavior is the behavior exhibited when a group of birds, called a [[Flock (birds)|flock]], are [[foraging]] or in flight. There are parallels with the [[Shoaling and schooling|shoaling]] behavior of fish, the [[swarm]]ing behavior of insects, and [[herd behavior]] of land animals.
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| Computer simulations and mathematical models which have been developed to emulate the flocking behaviors of birds can generally be applied also to the "flocking" behavior of other species. As a result, the term "flocking" is sometimes applied, in computer science, to species other than birds.
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| This article is about the modelling of flocking behavior. From the perspective of the mathematical modeller, "flocking" is the collective motion of a large number of self-propelled entities and is a [[collective animal behavior]] exhibited by many living beings such as [[flock (birds)|bird]]s, [[fish]], [[bacteria]], and [[insect]]s.<ref>{{cite journal | arxiv = cond-mat/9811336| title = Alternating steady state in one-dimensional flocking | journal = Journal of Physics A}}</ref> It is considered an [[emergence|emergent]] behavior arising from simple rules that are followed by individuals and does not involve any central coordination.
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| Flocking behavior was first simulated on a computer in 1986 by [[Craig Reynolds (computer graphics)|Craig Reynolds]] with his simulation program, [[Boids]]{{cn|date=January 2014}}. This program simulates simple agents (boids) that are allowed to move according to a set of basic rules. The result is akin to a [[Flock (birds)|flock]] of [[bird]]s, a [[Shoaling and schooling|school]] of [[fish]], or a [[swarm]] of [[insects]].
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| ==Flocking rules==
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| Basic models of flocking behavior are controlled by three simple rules:
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| #Separation - avoid crowding neighbors (short range repulsion)
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| #Alignment - steer towards average heading of neighbors
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| #Cohesion - steer towards average position of neighbors (long range attraction)
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| With these three simple rules, the flock moves in an extremely realistic way, creating complex motion and interaction that would be extremely hard to create otherwise.
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| The basic model has been extended in several different ways since Reynolds proposed it. For instance, Delgado-Mata et al.
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| <ref>{{cite journal
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| |author= Delgado-Mata C, Ibanez J, Bee S, ''et al.''
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| |title= On the use of Virtual Animals with Artificial Fear in Virtual Environments
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| |journal= New Generation Computing
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| |volume=25 |issue=2 |pages= 145–169
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| |year=2007
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| |doi= 10.1007/s00354-007-0009-5}}</ref>
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| extended the basic model to incorporate the effects of fear. Olfaction was used to transmit emotion between animals, through pheromones modelled as particles in a free expansion gas. Hartman and Benes
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| <ref>{{cite journal
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| |author= Hartman C, Benes B
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| |title= Autonomous boids
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| |journal= Computer Animation and Virtual Worlds
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| |volume=17 |issue=3-4 |pages= 199–206
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| |year=2006
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| |doi= 10.1002/cav.123}}</ref>
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| introduced a complementary force to the alignment that they call the change of leadership. This steer defines the chance of the bird to become a leader and try to escape.
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| Hemerlijk and Hildenbrandt
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| <ref>{{cite journal
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| |author= Hemelrijk, C. K., Hildenbrandt, H.
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| |title= Some Causes of the Variable Shape of Flocks of Birds
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| |journal= PLoS ONE
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| |volume=6 |issue=8 |year=2011
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| |doi= 10.1371/journal.pone.0022479 }}</ref>
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| used attraction, alignment and avoidance and extended this with a number of traits of real starlings: first, birds fly according to fixed wing aerodynamics, while rolling when turning (thus losing lift), second they coordinate with a limited number of interaction neighbours of 7 (like in real starlings), third, they try to stay above a sleeping site (like starlings do at dawn) and when they happen to move outwards the sleeping site, they return to it by turning, fourth, they move at relative fixed speed. The authors showed that the specifics of flying behaviour as well as large flocksize and low number of interaction partners were essential to the creation of the variable shape of flocks of starlings.
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| == Measurement ==
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| Measurements of bird flocking have been made<ref>{{ cite journal | last =Feder | first =Toni | authorlink = |date=October 2007 | title =Statistical physics is for the birds | journal = Physics Today| volume =60 | issue =10 | pages =28–30 | id = | url = | accessdate = | quote = | doi =10.1063/1.2800090 }}</ref> using high-speed cameras, and a computer analysis has been made to test the simple rules of flocking mentioned above. It is found that they generally hold true in the case of bird flocking, but the long range attraction rule (cohesion) applies to the nearest 5-10 neighbors of the flocking bird and is independent of the distance of these neighbors from the bird. In addition, there is an [[anisotropy]] with regard to this cohesive tendency, with more cohesion being exhibited towards neighbors to the sides of the bird, rather than in front or behind. This is no doubt due to the field of vision of the flying bird being directed to the sides rather than directly forward or backward.
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| Another recent study is based on an analysis of high speed camera footage of flocks above Rome, and uses a computer model assuming minimal behavioural rules.<ref>Hildenbrandt H, Carere C and Hemelrijk CK (2010) [http://beheco.oxfordjournals.org/content/21/6/1349.full "Self-organized aerial displays of thousands of starlings: a model"] ''Behavioral Ecology'', '''21''' (6): 1349–1359. {{doi|10.1093/beheco/arq149}}</ref><ref>Hemelrijk CK and Hildenbrandt H (2011) [http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0022479 "Some causes of the variable shape of flocks of birds"] ''PloS one'', '''6''' (8): e22479. {{doi|10.1371/journal.pone.0022479}}</ref><ref>[http://www.rug.nl/sciencelinx/exhibits/swarming/index Project Starflag]</ref><ref>[http://www.rug.nl/fmns-research/beso/_people/hemelrijk Swarm behaviour model by University of Groningen]</ref>
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| ==Algorithmic complexity==
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| In flocking simulations, there is no central control; each bird behaves autonomously. In other words, each bird has to decide for itself which flocks to consider as its environment. Usually environment is defined as a circle (2D) or sphere (3D) with a certain radius (representing reach).
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| A basic implementation of a flocking algorithm has complexity <math>O(n^2)</math> - each bird searches through all other birds to find those which fall into its environment.
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| Possible improvements:
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| * bin-[[Square lattice|lattice]] spatial subdivision. Entire area the flock can move in is divided into a large number of bins. Each bin stores which birds it contains. Each time a bird moves from one bin to another, lattice has to be updated.
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| ** Example: 2D(3D) grid in a 2D(3D) flocking simulation.
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| ** Complexity: <math>O(n k)</math>, k is number of surrounding bins to consider; just when bird's bin is found in <math>O(1)</math>
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| Lee Spector, Jon Klein, Chris Perry and Mark Feinstein studied the emergence of collective behavior in evolutionary computation systems.<ref>{{cite web | url=http://hampshire.edu/lspector/gecco2003-collective.html | author=Spector, L. | coauthors=Klein, J.; Perry, C.; and Feinstein, M. | year=2003 | title=Emergence of Collective Behavior in Evolving Populations of Flying Agents | work=Proceedings of the Genetic and Evolutionary Computation Conference (GECCO-2003) | publisher=Springer-Verlag | accessdate=2007-05-01}}</ref>
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| ==Applications==
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| In Cologne, Germany, two biologists from the University of Leeds demonstrated a flock like behavior in humans. The group of people exhibited a very similar behavioral pattern to that of a flock, where if 5% of the flock would change direction the others would follow suit. When one person was designated as a predator and everyone else was to avoid him, the flock behaved very much like a school of fish.<ref>"http://psychcentral.com/news/2008/02/15/herd-mentality-explained/1922.html". Retrieved on October 31st 2008.</ref>
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| Flocking has also been considered as a means of controlling the behavior of Unmanned Air Vehicles (UAVs).
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| Flocking is a common technology in [[screensaver]]s, and has found its use in animation. Flocking has been used in many films<ref>{{cite journal | last = Gabbai | first = J. M. E. | authorlink = Jonathan Gabbai | title = Complexity and the Aerospace Industry: Understanding Emergence by Relating Structure to Performance using Multi-Agent Systems | year = 2005 | publisher = University of Manchester Doctoral Thesis | place = Manchester|url=http://www.gabbai.com/academic/complexity-and-the-aerospace-industry-understanding-emergence-by-relating-structure-to-performance-using-multi-agent-systems/}}</ref> to generate crowds which move more realistically. [[Tim Burton]]'s ''[[Batman Returns]]'' (1992) featured flocking bats, and [[Walt Disney Pictures|Disney]]'s ''[[The Lion King]]'' (1994) included a [[wildebeest]] [[stampede]].
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| Flocking behaviour has been used for other interesting applications. It has been applied to automatically program Internet multi-channel radio stations
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| <ref>{{cite conference
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| | title = DJ-boids: emergent collective behavior as multichannel radio station programming
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| | author = Ibanez J, Gomez-Skarmeta A F, Blat J
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| | year = 2003
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| | booktitle = Proceedings of the 8th international conference on Intelligent User Interfaces
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| | pages = 248–250
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| | doi = 10.1145/604045.604089
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| }}</ref>
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| . It has also been used for visualizing information
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| <ref>{{cite conference
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| | title = Time-Varying Data Visualization Using Information Flocking Boids
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| | author = Moere A V
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| | year = 2004
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| | booktitle = Proceedings of the IEEE Symposium on Information Visualization
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| | pages = 97–104
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| | doi = 10.1109/INFVIS.2004.65
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| }}</ref>
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| and for optimization tasks
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| <ref>{{cite journal
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| |author= Cui Z, Shi Z
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| |title= Boid particle swarm optimisation
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| |journal= International Journal of Innovative Computing and Applications
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| |volume=2 |issue=2 |pages= 77–85
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| |year=2009
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| |doi= 10.1504/IJICA.2009.031778}}</ref>
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| ==See also==
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| *[[Crowd]]
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| ==References==
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| {{Reflist}}
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| ==Other sources==
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| * {{ cite journal | last =Cucker | first =Felipe | authorlink = | coauthors =[[Stephen Smale|''Steve Smale'']] | year =2007 | month = | title =The Mathematics of Emergence | journal = Japanese Journal of Mathematics | volume = 2| issue = | pages = 197| id = | url =http://ttic.uchicago.edu/~smale/papers/math-of-emergence.pdf |format=PDF| accessdate = 2008-06-09 | quote =| doi =10.1007/s11537-007-0647-x }}
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| * {{ cite journal | last =Shen | first =Jackie (Jianhong) | authorlink = | coauthors = | year =2008 | month = | title =Cucker–Smale Flocking under Hierarchical Leadership | journal =SIAM J. Applied Math. | volume =68 | issue =3 | pages = 694| id = | url =http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=SMJMAP000068000003000694000001&idtype=cvips&gifs=yes | accessdate = 2008-06-09 | quote =| doi =10.1137/060673254 }}
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| ==External links==
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| {{Commons category|Flocking}}
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| *[http://www.red3d.com/cwr/boids/ Craig Reynolds' Boids page]
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| *[http://lrss.fri.uni-lj.si/people/ilbajec/publications.htm Iztok Lebar Bajec's fuzzy logic based flocking publications]
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| *[http://hal.elte.hu/~vicsek/flocking page on flocking maintained by T. Vicsek]
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| *[http://black-square.github.io/BirdFlock/ Live In-Browser 3D Simulation of Bird Flocking Behavior in Unity3D] - Open Source implementation for Windows, Linux and Mac
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| *[http://vufa.tdsb.on.ca/~sam.scott/flock/index.html Another Flocking Simulator] - A simple flocking applet which lets you control a number of parameters to create flocks that behave like birds, insects, bacteria, etc.
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| *[http://ccl.northwestern.edu/netlogo NetLogo], a free software for multi-agent modeling, simulation, and the like, including a flocking simulation.
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| *[http://www.visualbots.com/index.htm VisualBots] - Freeware multi-agent simulator in Microsoft Excel - Visual Basic syntax
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| * [http://www.dcs.shef.ac.uk/~paul/publications/boids/index.html 3D Java Boids demonstrating bird flocking (Paul Richmond)]
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| * [http://vimeo.com/31158841 Murmurations of starlings]
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| {{collective animal behaviour}}
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| {{DEFAULTSORT:Flocking (Behavior)}}
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| [[Category:Artificial life]]
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