PowerPoint Presentation

INTRODUCTION TO SYSTEMS MODELING AND SIMULATIONWEEK 1IEG3L3 Simulasi Komputer Dan Praktikum1

Ari Yanuar RidwanIndustrial Engineering Study ProgramSchool of Industrial And System EngineeringTelkom UniversityV1.0 (2015)

Basics of Modeling and SimulationIEG3L3 Simulasi Komputer Dan Praktikum2What is simulation? How to study a system?When to use simulations?Application areas of simulationTerminology system, state, eventsModel classificationTypes of simulationSteps in a simulation studyAdvantages, disadvantages, and pitfalls in a simulation study

What is a simulation?IEG3L3 Simulasi Komputer Dan Praktikum3Simulation is imitation of the operation of a facility or process, usually using a computerFacility being simulated is also called a systemAssumptions/approximations, both logical and mathematical, are made about how the system worksThese assumptions form a model of the system3How to study a system?IEG3L3 Simulasi Komputer Dan Praktikum4

4When to use simulations?IEG3L3 Simulasi Komputer Dan Praktikum5Simulations can be used:To study complex system, i.e., systems where analytic solutions are infeasible.To compare design alternatives for a system that doesnt exist.To study the effect of alterations to an existing system. Why not change the system??To reinforce/verify analytic solutions.Simulations should not be used: If model assumptions are simple such that mathematical methods can be used to obtain exact answers (analytical solutions)

5Application AreasIEG3L3 Simulasi Komputer Dan Praktikum6Design and performance evaluation of computer systemsDetermining hardware requirements or protocols for communications networksStudying CPU Scheduling algorithmsEvaluation of Web caching policiesDesign and analysis of manufacturing systemsOperation of a production line Evaluating designs for service organizationsStudy call centers, fast-food restaurants, hospitals, and post officesEvaluating military weapons systems or their logistics requirementsDesigning and operating transportation systems such as airports, freeways, ports, and subwaysAnalyzing financial or economic systems6TerminologyIEG3L3 Simulasi Komputer Dan Praktikum7System: A collection of objects that act and interact together toward some logical end E.g. Determine number of cashiers needed to provide express service to customers with 10 or less item at a superstore system consists of express cashiers and customers with 10 or less itemsState of a system: Collection of variables and their values necessary to characterize a system at a particular timeMight depend on desired objectives, performance measuresSS Example: # of express cashiers, time of arrival of customers with 10 or less items, etc.Event: A change in system stateCustomer arrival, start of service, and customer departure

7Model ClassificationIEG3L3 Simulasi Komputer Dan Praktikum8Continuous-time vs. discrete-time modelsContinuous-event vs. discrete-event modelsDeterministic vs. probabilistic modelsStatic vs. dynamic modelsLinear vs. non-linear modelsOpen vs. closed models[Jain91]8Continuous and Discrete-time models9IEG3L3 Simulasi Komputer Dan PraktikumNumber of cust. in queueTimeNumber of students in cpsc 531Time(a) Continuous-time(b) Discrete-time9Continuous and Discrete-event models10IEG3L3 Simulasi Komputer Dan PraktikumDistancetraveled by planeTime(a) Continuous-event(b) Discrete-eventNumber of cust. in queueTime10Deterministic and Stochastic ModelsIEG3L3 Simulasi Komputer Dan Praktikum11Deterministic models produce deterministic resultsStochastic or probabilistic models are subject to random effectsTypically, they have one or more random inputs (e.g., arrival of customers, service time etc.).Outputs from stochastic models are estimates of the true characteristics of the systemNeed to repeat experiments number of timesNeed to have confidence in the results11More on modelsIEG3L3 Simulasi Komputer Dan Praktikum12Static and dynamic modelsStatic models system state independent of timeDynamic models - system state change with timeLinear and non-linear modelsLinear models output is a linear function of input parametersOpen and closed models(a) Open Model(b) Closed Model12Types of Simulation (1/2)IEG3L3 Simulasi Komputer Dan Praktikum13Monte Carlo simulationNo time element (usually)Used for evaluating non-probabilistic expressions (e.g., an integral) using probabilistic methodsWide variety of mathematical problemsTrace-driven simulationExtensively used in computer systems performance evaluation; e.g., paging algorithmsAdvantages: credibility, easy validation, less randomness, accurate workloadDisadvantages: complexity, only a snap-shot, representative?, single point of validation

13Types of Simulation (2/2)IEG3L3 Simulasi Komputer Dan Praktikum14Monte Carlo simulationTrace-driven simulationDiscrete-event simulation: a simulation using a discrete-event (also called discrete-state) model of the systemE.g., Widely used for studying computer systemsContinuous-event simulation: uses a continuous-state modelsE.g., Widely used in chemical/pharmaceutical studiesOur focus will be on discrete-event systems.14Steps in a Simulation StudyIEG3L3 Simulasi Komputer Dan Praktikum15

15Advantages, disadvantages, and pitfalls in a simulation studyIEG3L3 Simulasi Komputer Dan Praktikum16AdvantagesSimulation allows great flexibility in modeling complex systems, so simulation models can be highly validEasy to compare alternativesControl experimental conditionsCan study system with a very long time frameDisadvantagesStochastic simulations produce only estimates with noiseSimulation models can be expensive to developSimulations usually produce large volumes of output need to summarize, statistically analyze appropriatelyPitfallsFailure to identify objectives clearly up frontInappropriate level of detail (both ways)Inadequate design and analysis of simulation experimentsInadequate education, training16Any Question ?Thank You17IEG3L3 Simulasi Komputer Dan Praktikum