339 lines
9.6 KiB
Python
339 lines
9.6 KiB
Python
# -*- coding: Latin-1 -*-
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## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ##
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# trafficLight.py --- simple Traffic Light example
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# --------------------------------
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# October 2005
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# Hans Vangheluwe
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# McGill University (Montréal)
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# --------------------------------
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## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ##
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# Add the directory where pydevs lives to Python's import path
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import sys
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# Import code for DEVS model representation:
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from pypdevs.infinity import *
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from pypdevs.DEVS import *
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# Import for uniform random number generators
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from random import uniform
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from random import randint
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# ====================================================================== #
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class TrafficLightMode:
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"""Encapsulates the system's state
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"""
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###
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def __init__(self, current="red"):
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"""Constructor (parameterizable).
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"""
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self.set(current)
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def set(self, value="red"):
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self.__colour=value
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def get(self):
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return self.__colour
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def __str__(self):
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return self.get()
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class TrafficLight(AtomicDEVS):
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"""A traffic light
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"""
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###
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def __init__(self, name=None):
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"""Constructor (parameterizable).
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"""
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# Always call parent class' constructor FIRST:
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AtomicDEVS.__init__(self, name)
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# STATE:
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# Define 'state' attribute (initial sate):
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self.state = TrafficLightMode("red")
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# PORTS:
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# Declare as many input and output ports as desired
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# (usually store returned references in local variables):
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self.INTERRUPT = self.addInPort(name="INTERRUPT")
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self.OBSERVED = self.addOutPort(name="OBSERVED")
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###
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def extTransition(self, inputs):
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"""External Transition Function."""
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# Compute the new state 'Snew' based (typically) on current
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# State, Elapsed time parameters and calls to 'self.peek(self.IN)'.
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#input = self.peek(self.INTERRUPT)
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input = inputs[self.INTERRUPT][0]
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state = self.state.get()
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if input == "toManual":
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if state == "manual":
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# staying in manual mode
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return TrafficLightMode("manual")
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if state in ("red", "green", "yellow"):
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return TrafficLightMode("manual")
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else:
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raise DEVSException(\
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"unknown state <%s> in TrafficLight external transition function"\
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% state)
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if input == "toAutonomous":
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if state == "manual":
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return TrafficLightMode("red")
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else:
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raise DEVSException(\
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"unknown state <%s> in TrafficLight external transition function"\
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% state)
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raise DEVSException(\
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"unknown input <%s> in TrafficLight external transition function"\
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% input)
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###
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def intTransition(self):
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"""Internal Transition Function.
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"""
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state = self.state.get()
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if state == "red":
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return TrafficLightMode("green")
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elif state == "green":
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return TrafficLightMode("yellow")
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elif state == "yellow":
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return TrafficLightMode("red")
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else:
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raise DEVSException(\
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"unknown state <%s> in TrafficLight internal transition function"\
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% state)
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###
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def outputFnc(self):
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"""Output Funtion.
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"""
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# A colourblind observer sees "grey" instead of "red" or "green".
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# BEWARE: ouput is based on the OLD state
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# and is produced BEFORE making the transition.
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# We'll encode an "observation" of the state the
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# system will transition to !
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# Send messages (events) to a subset of the atomic-DEVS'
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# output ports by means of the 'poke' method, i.e.:
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# The content of the messages is based (typically) on current State.
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state = self.state.get()
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if state == "red":
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return {self.OBSERVED: ["grey"]}
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#self.poke(self.OBSERVED, "grey")
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# NOT self.poke(self.OBSERVED, "grey")
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elif state == "green":
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return {self.OBSERVED: ["yellow"]}
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#self.poke(self.OBSERVED, "yellow")
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# NOT self.poke(self.OBSERVED, "grey")
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elif state == "yellow":
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return {self.OBSERVED: ["grey"]}
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#self.poke(self.OBSERVED, "grey")
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# NOT self.poke(self.OBSERVED, "yellow")
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else:
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raise DEVSException(\
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"unknown state <%s> in TrafficLight external transition function"\
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% state)
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###
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def timeAdvance(self):
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"""Time-Advance Function.
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"""
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# Compute 'ta', the time to the next scheduled internal transition,
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# based (typically) on current State.
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state = self.state.get()
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if state == "red":
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return 3
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elif state == "green":
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return 2
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elif state == "yellow":
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return 1
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elif state == "manual":
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return INFINITY
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else:
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raise DEVSException(\
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"unknown state <%s> in TrafficLight time advance transition function"\
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% state)
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# ====================================================================== #
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class PolicemanMode:
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"""Encapsulates the Policeman's state
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"""
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###
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def __init__(self, current="idle"):
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"""Constructor (parameterizable).
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"""
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self.set(current)
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def set(self, value="idle"):
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self.__mode=value
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def get(self):
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return self.__mode
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def __str__(self):
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return self.get()
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class Policeman(AtomicDEVS):
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"""A policeman producing "toManual" and "toAutonomous" events:
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"toManual" when going from "idle" to "working" mode
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"toAutonomous" when going from "working" to "idle" mode
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"""
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###
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def __init__(self, name=None):
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"""Constructor (parameterizable).
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"""
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# Always call parent class' constructor FIRST:
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AtomicDEVS.__init__(self, name)
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# STATE:
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# Define 'state' attribute (initial sate):
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self.state = PolicemanMode("idle")
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# ELAPSED TIME:
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# Initialize 'elapsed time' attribute if required
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# (by default, value is 0.0):
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self.elapsed = 0
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# PORTS:
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# Declare as many input and output ports as desired
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# (usually store returned references in local variables):
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self.OUT = self.addOutPort(name="OUT")
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###
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# Autonomous system (no input ports),
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# so no External Transition Function required
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#
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###
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def intTransition(self):
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"""Internal Transition Function.
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The policeman works forever, so only one mode.
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"""
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state = self.state.get()
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if state == "idle":
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return PolicemanMode("working")
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elif state == "working":
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return PolicemanMode("idle")
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else:
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raise DEVSException(\
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"unknown state <%s> in Policeman internal transition function"\
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% state)
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###
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def outputFnc(self):
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"""Output Funtion.
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"""
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# Send messages (events) to a subset of the atomic-DEVS'
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# output ports by means of the 'poke' method, i.e.:
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# The content of the messages is based (typically) on current State.
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state = self.state.get()
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if state == "idle":
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return {self.OUT: ["toManual"]}
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#self.poke(self.OUT, "toManual")
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elif state == "working":
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return {self.OUT: ["toAutonomous"]}
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#self.poke(self.OUT, "toAutonomous")
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else:
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raise DEVSException(\
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"unknown state <%s> in Policeman output function"\
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% state)
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###
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def timeAdvance(self):
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"""Time-Advance Function.
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"""
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# Compute 'ta', the time to the next scheduled internal transition,
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# based (typically) on current State.
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state = self.state.get()
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if state == "idle":
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return 200
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elif state == "working":
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return 100
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else:
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raise DEVSException(\
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"unknown state <%s> in Policeman time advance function"\
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% state)
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# ====================================================================== #
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class TrafficSystem(CoupledDEVS):
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def __init__(self, name=None):
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""" A simple traffic system consisting of a Policeman and a TrafficLight.
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"""
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# Always call parent class' constructor FIRST:
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CoupledDEVS.__init__(self, name)
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# Declare the coupled model's output ports:
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# Autonomous, so no output ports
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#self.OUT = self.addOutPort(name="OUT")
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# Declare the coupled model's sub-models:
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# The Policeman generating interrupts
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self.policeman = self.addSubModel(Policeman(name="policeman"))
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# The TrafficLight
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self.trafficLight = self.addSubModel(TrafficLight(name="trafficLight"))
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# Only connect ...
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self.connectPorts(self.policeman.OUT, self.trafficLight.INTERRUPT)
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#self.connectPorts(self.trafficLight.OBSERVED, self.OUT)
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def select(self, immList):
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"""Give the Policeman highest priority.
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Note how the technique used below can
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be generalized to encode priorities based on model type.
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To distinguish between models of the same type,
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the name or unique ID should be used.
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"""
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# return the first Policeman instance in the immList
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for i in range(len(immList)):
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#if immList[i].__class__ == TrafficLight:
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if immList[i].__class__ == Policeman:
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return immList[i]
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# if no Policeman instances found, return the last entry
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return immList[-1]
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# Alternative: randomly choose among imminent submodels
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#return immList[randint(0,len(immList))]
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# If the select method is not defined, the immList[0]
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# will be chosen by default.
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# ====================================================================== #
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