an introduction to agent-based modeling8.pdf · an introduction to agent-based modeling unit 8:...
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BillRand AssistantProfessorofBusinessManagement
PooleCollegeofManagementNorthCarolinaStateUniversity
An Introduction to Agent-Based Modeling
Unit 8: History of ABM and Classic Models
Unit8Overview
• CellularAutomata• GeneticAlgorithmsandCAS• Logo• Object-OrientedProgramming• Parallelism• Graphics
JohnvonNeumann
• Helpeddeveloponeofthefirstcomputers,ENIAC
• Wantedtodevelopself-replicatingmachines
• CollaboratingwithStanislawUlamcreateCellularAutomata
• developedtheUniversalConstructorwith29states
JohnConwayandtheGameofLife
• UsedaGoboardtoinvestigateCA• GameofLife:
1. Ifacellhasthreeneighborsitbecomesalive(birth)
2. Ifithastwoorthreeneighborsitstaysalive(persistence)
3. Anyothercombinationmeansthecelldies(overcrowdingorloneliness)
• Self-reproducingandUniversalComputer
ArthurW.BurksandStephenWolfram
• ArthurW.BurkscarriedonvonNeumann’swork
• TheoryofSelf-ReproducingAutomata(1966)
• StephenWolfram• Conductedacensusofthe1-DCAruleswithradius=1
• uniform,random,cyclical,andcomplex
• madetheclaimthatthewholeworldcouldbemodeledusingCA
• AlsocreatedMathematica
RelationshipbetweenCAandABM
• DevelopersofearlyABMwereawareofCA• NoevidencethatearlyABMersthoughoftheirmodelsasCA
• Thesetupsaresimilar• eachcellcanbeviewedasanagent• vonNeumann’smodelswerefirstcomputationalmodelsofbiologicalsystems
• CAschedulerissimilar• Wolfram’sclassificationissimilartocurrentattemptstoclassifycomplexsystems
JohnHolland• InspiredbyHebb’sideasaboutneuronsandRosenblatt’sworkontheperceptron,Hollanddecidedtobuildacomputationalmodelofevolutionaryadaptation
• In1975publishedAdaptationinNaturalandArtificialSystems,describingtheGeneticAlgorithm
• HollandwasalsoinfluencedbySamuel’sworkoncheckers,andstartedtothinkabouthowtocreateadaptiveagents
EarlySFIandEconomicModeling• HollandbecameinvolvedintheSantaFeInstitutearound1985
• In9/1987,hepresentedsomeofhisideasaboutadaptiveagentsatameetingoftheeconomyasacomplexadaptivesystem
• workedwithBrianArthur,BlakeLeBaron,RichardPalmer,andPaulTaylertocreatetheSantaFeArtificialStockMarket
• in8/1986,JohnReed,CEOofCiticorpmetatSFIwithKenArrow,BrianArthur,andJohnHollandtogethertothinkaboutnewwaystomodeleconomics,ledtoSwarm
• JohnMillerandJohnHollandpublishthe1991paperon“ArtificialAdaptiveAgentsinEconomicTheory”
• ManyofthesemodelswereinspiredbyHerbertSimon’sworkonBoundedRationality
HerbertSimon
TheBACHGroup
• HollandwasalsoamemberofagroupofresearchersatMichiganknownastheBACHgroup:• ArthurBurks,RobertAxelrod,MichaelCohenandJohnHolland
• Thisgroupalsoinspiredtwoprominentgraduatestudentswhocontinuedtoworkinthisspace:• MelanieMitchellandStephanieForrest
HollandandHiddenOrder
• Workingwiththisgroup,Hollandstartedtodeveloptheclassifiersystem
• Thisledtotheideaofaworldwherenever-endingnoveltycouldevolve,Echo
• ThiswasdescribedinaStanislawUlamlecture,whichbecamethebook,HiddenOrder(1993)
SeymourPapertandLogo
• StudiedwithPiagetinSwitzerland
• Inthelate1960s,SeymourPapertwasappointedco-directorofMIT’sArtificialIntelligenceLabwithMarvinMinsky
• Papert,Feurzeig,BorrowandSolomoncreatedLogoin1969
• LogoisbasedonLisp,butwasdesignedtogivechildrenaccesstoprogramming
TheTurtle• Theturtlewasdevelopedpost-Logotoaidstudentsinlearningthelanguage
• Theturtleisa“body-syntonic”object• Theearlyturtlesweremechanicalandtetheredtothecomputer,butsoonbecamevirtualandvisual
• Logowasintroducedtoschoolsandmillionsofchildrenparticipatedinusingit
• TheLogoturtlemayhavebeenthefirstcomputationalagentinwideuse
NetLogoandLogo
• NetLogotookmuchofitssyntaxfromLogo• Alsoborrowedtheslogan,“lowthreshold,highceiling”
• TheinfluenceofLogoisnotonlyinNetLogo,butmanyABMlanguages
• Theideaofvisualizingagentsmovingarounda2-DspaceisdrawnfromLogo
TheExpansionoftheFunction
• Afunctioninaprogramminglanguagewasoriginallysomethingthattookanumberasaninputandgaveanumberasanoutput
• JohnMcCarthy’sworkonLisp(1958)expandedthenotionoffunction,buildinguponAlonzoChurch’slambdacalculus(1932)byallowingfunctionstotakeotherfunctionsasinputs
• However,Lispstillkeptfunctionsanddataseparate,e.g.,youneededdifferentadditionoperatorsfordifferentdatatypes
TheCreationofObject-OrientedProgramming
• DahlandNygaarddevelopedsimulationsformaritimeships,andcreatedthenotionofa“class”,whichwasanobjectthatcombineddataandfunctionsinthelanguageSimula
• Buttheterm“object-orientedprogramming”wasnotuseduntilthedevelopmentofSmalltalkbyAlanKayandcolleagues(1972) AlanKay
OOandABM
• Agentsareofteninstantiatedasclasses(orwhatNetLogocallsbreeds)
• Thenotionofobject-orientedprogrammingisthattheseclassescancontaindifferentdatafields,anddifferentfunctionscanbeappliedtothem
ActorModel• CarlHewittatIBM(1973)developedtheActormodelofprogramming(formalizedbyBishopandSteiger)
• ThismodelsimplifiedSmalltalkandSimulaandwasinfluencedbyPapert’sworkonbody-syntonicreasoningandKay’sworkonOO
• Actorscanonlydoafewthings:send/receivemessages,createotheractors,manipulatemessages
• Eachactorhasanaddresstheonlywaytomessageanactoristoknowtheiraddress
• Eachactorhasalimitednumberofaddressesitcanknow
• Actorsareinherentlyconcurrent
OOProgramming
• EventuallyallofthisresultedinthemodernOOlanguages• C++,Objective-C,CocoaandtheABMplatforms
• ActorsinfluencedABMinmanyways:• anemphasisonconcurrentcomputation• localinteractions• boundedinteractionspaces• dynamic• thenotionofbehaviorsandpropertiesofindependententities
Parallelism
• Inthe1980sDannyHillisdevelopedanarchitectureforaparallelcomputerhecalleda“connectionmachine”
• UnliketraditionalvonNeumannmachinestherewasn’tasingleCPU,butinsteadthousandsoflow-cost,low-capacityprocessorsconnectedtogether
• UsedaframeworkknownasSingleInstruction,MultipleData(SIMD)
• HillisfoundedThinkingMachinestocommercializethisproduct
ParallelProgrammingLanguages
• Bytheendofthe80sspecialprogramminglanguages,suchasStarLispandC-Starweredevelopedtoprogramthismachine
• CM-2had65,536processors• Datawasspreadacrosstheprocessors• Documentretrievalandobjectrecognitionwereearlysuccesses
• Veryusefulforcellularautomata• StarLogo(anearlyformofABM)waswritteninStarLisp
ParticleSystems
• Earlyonincomputergraphics,visualizationswereaccomplishedbyusinglargeflatsurfacesandtextures
• Butsurfacesdon’tworkwellforsmoke,stars,light,orevenbirds
• Neededapointrepresentation(Reeves,1983),whichcametobeknownasparticlesystems
RelationshiptoABM
• Particlessystemsalsoexhibitemergentphenomenon
• Theyexhibitagentinteractioninthesensethatwhenmanyparticlescometogetheritlookslikeanobject
Boids
• ParticleSystemspartiallyinspiredCraigReynoldstodeveloptheBoidsmodel
• Threesimplerulescreatetheflockingpatterns
• ShortlyafterReynoldspresentedBoidsatSIGGRAPH’87,ChrisLangtonheldthefirstorganizedworkshoponArtificialLife
• ArtificialLifehasthegoalofcreatinglife-likeobjectsinacomputeranddrawsonBoids,CA,andGAs
Unit8Overview
• CellularAutomata• AdaptiveAgentsandGeneticAlgorithms
• LogoandtheTurtle• Object-OrientedProgramming
• Parallelism
• ParticleSystems• Unit8Slides• Unit8Test