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CMSC 330: Organization of
Programming Languages
Project 5
CMSC 330 2
Multithreaded Simulation
Goal
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Implement multithreaded Metro simulation in Ruby
Separate threads for trains, passengers
Monitors to avoid data races
Conditions to efficiently acquire locks
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Implement simulation verifier in Ruby
Examine log file of simulation
Determine whether simulation output is consistent
CMSC 330 3
Metro Simulation
You are given
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List of metro lines & stations on each line
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List of passengers & their stops
You need to simulate
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One train per metro line
Train goes up & down line, stopping at each station
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Passengers
Passengers board & leave trains
CMSC 330 4
Metro Simulation
Multithreading
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One thread per train
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One thread per passenger
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Only one train at a metro station at any time
Simulation outputs
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Train <color> entering <station>
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Train <color> leaving <station>
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<Passenger> boarding train <color> at <station>
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<Passenger> leaving train <color> at <station>
CMSC 330 5
Simulation Verifier
Analyze simulation output for feasibility
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Trains start at their initial station
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Trains move forward and backward along their lines
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Trains enter a station before they leave it
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2 trains are not at the same station at the same time
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Passengers follow their path as given in input
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Passengers only board & leave train when in station
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Passengers get to where they're going
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No extra passengers on trains
CMSC 330 6
Simulation Output
Example
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Train green leaving Fort Totten
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Train blue entering L'Enfant Plaza
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Train red entering Fort Totten
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Train yellow entering Pentagon
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Paul boarding train yellow at Pentagon
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Train green entering Gallery Place
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Train red leaving Fort Totten
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Train blue leaving L'Enfant Plaza
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Train yellow leaving Pentagon
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Train green leaving Gallery Place