Chapter-01-Slides

SimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide1of23Chapter1WhatisSimulation?LastrevisionJune7,2003SimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide2of23SimulationIs…•Simulation–verybroadterm–methodsandapplicationstoimitateormimicrealsystems,usuallyviacomputer•Appliesinmanyfieldsandindustries•Verypopularandpowerfulmethod•BookcoverssimulationingeneralandtheArenasimulationsoftwareinparticular•Thischapter–generalideas,terminology,examplesofapplications,good/badthings,kindsofsimulation,softwareoptions,how/whensimulationisusedSimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide3of23Systems•System–facilityorprocess,actualorplannedExamplesabound…–Manufacturingfacility–Bankoperation–Airportoperations(passengers,security,planes,crews,baggage)–Transportation/logistics/distributionoperation–Hospitalfacilities(emergencyroom,operatingroom,admissions)–Computernetwork–Freewaysystem–Businessprocess(insuranceoffice)–Criminaljusticesystem–Chemicalplant–Fast-foodrestaurant–Supermarket–Themepark–Emergency-responsesystemSimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide4of23WorkWiththeSystem?•Studythesystem–measure,improve,design,controlMaybejustplaywiththeactualsystem–Advantage—unquestionablylookingattherightthingButit’softenimpossibletodosoinrealitywiththeactualsystem–Systemdoesn’texist–Wouldbedisruptive,expensive,ordangerousSimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide5of23Models•Model–setofassumptions/approximationsabouthowthesystemworksStudythemodelinsteadoftherealsystem…usuallymucheasier,faster,cheaper,saferCantrywide-rangingideaswiththemodel–Makeyourmistakesonthecomputerwheretheydon’tcount,ratherthanforrealwheretheydocountOften,justbuildingthemodelisinstructive–regardlessofresultsModelvalidity(anykindofmodel…notjustsimulation)–Careinbuildingtomimicrealityfaithfully–Levelofdetail–Getsameconclusionsfromthemodelasyouwouldfromsystem–MoreinChapter13SimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide6of23TypesofModels•Physical(iconic)modelsTabletopmaterial-handlingmodelsMock-upsoffast-foodrestaurantsFlightsimulators•Logical(mathematical)modelsApproximationsandassumptionsaboutasystem’soperationOftenrepresentedviacomputerprograminappropriatesoftwareExercisetheprogramtotrythings,getresults,learnaboutmodelbehaviorSimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide7of23StudyingLogicalModels•Ifmodelissimpleenough,usetraditionalmathematicalanalysis…getexactresults,lotsofinsightintomodelQueueingtheoryDifferentialequationsLinearprogramming•ButcomplexsystemscanseldombevalidlyrepresentedbyasimpleanalyticmodelDangerofover-simplifyingassumptions…modelvalidity?TypeIIIerror–workingonthewrongproblem•Often,acomplexsystemrequiresacomplexmodel,andanalyticalmethodsdon’tapply…whattodo?SimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide8of23ComputerSimulation•Broadlyinterpreted,computersimulationreferstomethodsforstudyingawidevarietyofmodelsofsystemsNumericallyevaluateonacomputerUsesoftwaretoimitatethesystem’soperationsandcharacteristics,oftenovertime•Canbeusedtostudysimplemodelsbutshouldnotuseitifananalyticalsolutionisavailable•Realpowerofsimulationisinstudyingcomplexmodels•Simulationcantoleratecomplexmodelssincewedon’tevenaspiretoananalyticalsolutionSimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide9of23PopularityofSimulation•Consistentlyrankedasthemostuseful,populartoolinthebroaderareaofoperationsresearch/managementscience1978:M.S.graduatesofCWRUO.R.Department…aftergraduation1.Statisticalanalysis2.Forecasting3.SystemsAnalysis4.Informationsystems5.Simulation1979:Survey137largefirms,whichmethodsused?1.Statisticalanalysis(93%usedit)2.Simulation(84%)3.FollowedbyLP,PERT/CPM,inventorytheory,NLP,…SimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide10of23PopularityofSimulation(cont’d.)1980:(A)IIEO.R.divisionmembers–Firstinutilityandinterest—simulation–Firstinfamiliarity—LP(simulationwassecond)1983,1989,1993:Longitudinalstudyofcorporatepractice1.Statisticalanalysis2.Simulation1989:Surveyofsurveys–HeavyuseofsimulationconsistentlyreportedSimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide11of23AdvantagesofSimulation•Flexibilitytomodelthingsastheyare(evenifmessyandcomplicated)Avoidlookingwherethelightis(amoralityplay):•Allowsuncertainty,nonstationarityinmodelingTheonlythingthat’sforsure:nothingisforsureDangerofignoringsystemvariabilityModelvalidityYou’rewalkingalonginthedarkandseesomeoneonhandsandkneessearchingthegroundunderastreetlight.You:“What’swrong?CanIhelpyou?”Otherperson:“Idroppedmycarkeysandcan’tfindthem.”You:“Oh,soyoudroppedthemaroundhere,huh?”Otherperson:“No,Idroppedthemoverthere.”(Pointsintothedarkness.)You:“Thenwhyareyoulookinghere?”Otherperson:“Becausethisiswherethelightis.”SimulationwithArena,3rded.Chapter1–WhatIsSimulation?Slide12of23AdvantagesofSimulation(cont’d.)•Advancesincomputing/costratiosEstimatedthat75%ofcomputingpowerisusedforvariouskindsofsimulationsDedicatedmachines(e.g.,real-timeshop-floorcontrol)•Advancesinsimulationsoftwa