Slide 8: Introduction to Simulation Consider a simple example Simulation of a single server processing system(e. g an M/M/1 queuing system) o System components and their relations(needs for abstraction) e System states and constraints o Problem statement (goal of the study: what output/performance measures to be collected or computed?)
Consider a simple example: Simulation of a single server processing system (e.g., an M/M/1 queuing system) ⚫ System components and their relations (needs for abstraction) ⚫ System states and constraints ⚫ Problem statement (goal of the study: what output/performance measures to be collected or computed?) Slide 8: Introduction to Simulation
Slide 9: Introduction to Simulation A graphical model of a M/M/1 system erver A rivals Departures Waiting line (queue Arrival time and service time are random variables
Slide 9: Introduction to Simulation A graphical model of a M/M/1 system Arrivals Waiting line (queue) Server Departures Arrival time and service time are random variables
Slide 10: Introduction to simulation Elements of a simulation model g Entities: items being processed by and flow through the system, e.g. parts, cars, customers e Attributes: properties/characteristics assigned to entities, e.g. part types, time arrived in a queue ariables: changeable quantities defined to reflect the characteristics of the system, e.g. we may define two state variables for a M/M/1 system o Server status(states): idle or busy Number of items waiting in queue
Elements of a simulation model: Entities: items being processed by and flow through the system, e.g. parts, cars, customers Attributes: properties/characteristics assigned to entities, e.g. part types, time arrived in a queue Variables: changeable quantities defined to reflect the characteristics of the system, e.g. we may define two state variables for a M/M/1 system: ⚫ Server status (states): idle or busy ⚫ Number of items waiting in queue Slide 10: Introduction to Simulation
Slide 11: Introduction to Simulation s Events: an event is an occurrence of something that changes the state of the system(e.g. arrival or departure of a customer in a M/M/1 system) c Resources: means by which to process entities(e. g machines, operators, fork-trucks s Queues(buffers, waiting lines ): storage space for entities waiting for required resource) c Activities/processes: an activity is a period of time during which an entity(entities)is serviced (e.g processed or transferred). The duration of an activity is known a priori, and can be scheduled(e.g processing time, transfer time
Events: an event is an occurrence of something that changes the state of the system (e.g. arrival or departure of a customer in a M/M/1 system) Resources: means by which to process entities (e.g. machines, operators, fork-trucks) Queues (buffers, waiting lines): storage space for entities waiting for required resource) Activities/processes: an activity is a period of time during which an entity (entities) is serviced (e.g. processed or transferred). The duration of an activity is known a priori, and can be scheduled (e.g. processing time, transfer time) Slide 11: Introduction to Simulation
Slide 12: Introduction to simulation e Statistical accumulators: variables that collect and keep track of statistics during the progress of simulation to obtain required output performance measures c Simulation clock: a mechanism to keep track of current(simulated) time in a simulation. It lurches from the time of one event to the time of next event arrival arrival departure l Jumps of simulation clock
Statistical accumulators: variables that collect and keep track of statistics during the progress of simulation to obtain required output performance measures. Simulation clock: a mechanism to keep track of current (simulated) time in a simulation. It lurches from the time of one event to the time of next event. Slide 12: Introduction to Simulation arrival2 arrival3 departure1 t1 t2 t3 Jumps of simulation clock