MIE360 4SimFlow - MIE360 Computer Modeling and Simulation...

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MIE360 Computer Modeling and Simulation Lecture Notes Daniel Frances © 2010 1 MIE360 Lecture 4. A Generic Simulation Flow Chart Most systems modelled with DES consist of a network of waiting lines. Items wait in line waiting for service, after which they come somewhere else to wait some more, etc. .., until the process is completed and they exit the system. That was the case for the roommate, continually waiting, first to wake up, then to use the washroom, then to complete, then to eat, then for the bus and finally for the subway. If one were to develop software for this situation, you would find that if you write it general enough you could use it to model other systems in other domains. This possibility is what gave rise to general purpose simulation languages such as SIMUL8. When using such packages it is important to have some idea of how they work. Let’s introduce a general purpose flow chart for DES. The approach shown below is the Next Event Advance Approach (NEAA). Let’s attempt to define the terms used in the order the blocks are invoked, starting with INIT. 1. Clock – a variable in a simulation model that gives the current value of simulated time. 2. Counters – variables necessary to calculate the statistics of interest to the study. E.g. the total numbers of customers that have arrived in the system by some Clock time. Start MAIN 1. Invoke INIT 2. Invoke TIME 3. Invoke EVENT of Type i 4. If Clock < T Max go to 2 5. Invoke REPORT INIT 1. Set Clock=0 2. Initialize Counters 3. Initialize State 4. Initialize Event List 5. Return EVENT of Type i 1. Update Counters 2. Update State 3. Generate Future Events 4. Append to Event List 5. Return T I M E 1. Determine next event time t and type i 2. Determine time since last event t 3. Clock = t 4. Return REPORT 1. Compute Estimates of Interest 2. Report 3. Return End Invoked once Invoked repeatedly Invoked once Invoked repeatedly
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MIE360 Computer Modeling and Simulation Lecture Notes Daniel Frances © 2010 2 3. State – collection of variables necessary to describe a system at a particular time relative to the
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This note was uploaded on 09/20/2011 for the course MIE 360 taught by Professor D.frances during the Fall '10 term at University of Toronto.

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MIE360 4SimFlow - MIE360 Computer Modeling and Simulation...

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