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DevsModel.py
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DevsModel.py
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# Copyright 2014 Modelling, Simulation and Design Lab (MSDL) at
# McGill University and the University of Antwerp (http://msdl.cs.mcgill.ca/)
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import sys
# Import code for DEVS model representation:
from pypdevs.DEVS import *
from pypdevs.infinity import INFINITY
class TrafficLightMode:
"""
Encapsulates the system's state
"""
def __init__(self, current="red"):
"""
Constructor (parameterizable).
"""
self.set(current)
def set(self, value="red"):
self.__colour=value
def get(self):
return self.__colour
def __str__(self):
return self.get()
class TrafficLight(AtomicDEVS):
"""
A traffic light
"""
def __init__(self, name=None):
"""
Constructor (parameterizable).
"""
# Always call parent class' constructor FIRST:
AtomicDEVS.__init__(self, name)
# STATE:
# Define 'state' attribute (initial sate):
self.state = TrafficLightMode("red")
# ELAPSED TIME:
# Initialize 'elapsed time' attribute if required
# (by default, value is 0.0):
# self.elapsed = 1.5
# with elapsed time initially 1.5 and initially in
# state "red", which has a time advance of 60,
# there are 60-1.5 = 58.5time-units remaining until the first
# internal transition
# PORTS:
# Declare as many input and output ports as desired
# (usually store returned references in local variables):
self.INTERRUPT = self.addInPort(name="INTERRUPT")
self.OBSERVED = self.addOutPort(name="OBSERVED")
self.ta = {
'red' : 80, #60,
'green' : 30, #50,
'yellow' : 10, #10,
'manual' : INFINITY
}
self.generated = 0
def updateTa(self, color, timeAdvance):
print("Warning: time advance updated")
self.ta[color] = timeAdvance
def updateAllTa(self, timeAdvance):
self.ta['red'] = timeAdvance[0]
self.ta['green'] = timeAdvance[1]
self.ta['yellow'] = timeAdvance[2]
def extTransition(self, inputs):
"""
External Transition Function.
"""
# Compute the new state 'Snew' based (typically) on current
# State, Elapsed time parameters and calls to 'self.peek(self.IN)'.
input = inputs.get(self.INTERRUPT)
state = self.state.get()
if input == "toManual":
if state == "manual":
# staying in manual mode
return TrafficLightMode("manual")
elif state in ("red", "green", "yellow"):
return TrafficLightMode("manual")
elif input == "toAutonomous":
if state == "manual":
return TrafficLightMode("red")
elif state in ("red", "green", "yellow"):
# If toAutonomous is given while still autonomous, just stay in this state
return self.state
raise DEVSException(\
"unknown state <%s> in TrafficLight external transition function"\
% state)
def intTransition(self):
"""
Internal Transition Function.
"""
state = self.state.get()
if state == "red":
return TrafficLightMode("green")
elif state == "green":
return TrafficLightMode("yellow")
elif state == "yellow":
return TrafficLightMode("red")
else:
raise DEVSException(\
"unknown state <%s> in TrafficLight internal transition function"\
% state)
def outputFnc(self):
"""
Output Funtion.
"""
# A colourblind observer sees "grey" instead of "red" or "green".
# BEWARE: ouput is based on the OLD state
# and is produced BEFORE making the transition.
# We'll encode an "observation" of the state the
# system will transition to !
# Send messages (events) to a subset of the atomic-DEVS'
# output ports by means of the 'poke' method, i.e.:
# The content of the messages is based (typically) on current State.
self.generated += 1
state = self.state.get()
if state == "red":
return {self.OBSERVED: "grey"}
elif state == "green":
return {self.OBSERVED: "yellow"}
elif state == "yellow":
return {self.OBSERVED: "grey"}
else:
raise DEVSException(\
"unknown state <%s> in TrafficLight external transition function"\
% state)
def timeAdvance(self):
"""
Time-Advance Function.
"""
# Compute 'ta', the time to the next scheduled internal transition,
# based (typically) on current State.
state = self.state.get()
if state == "red":
return self.ta['red']
elif state == "green":
return self.ta['green']
elif state == "yellow":
return self.ta['yellow']
elif state == "manual":
return self.ta['manual']
else:
raise DEVSException(\
"unknown state <%s> in TrafficLight time advance transition function"\
% state)
class PolicemanMode:
"""
Encapsulates the Policeman's state
"""
def __init__(self, current="idle"):
"""
Constructor (parameterizable).
"""
self.set(current)
def set(self, value="idle"):
self.__mode=value
def get(self):
return self.__mode
def __str__(self):
return self.get()
class Policeman(AtomicDEVS):
"""
A policeman producing "toManual" and "toAutonomous" events:
"toManual" when going from "idle" to "working" mode
"toAutonomous" when going from "working" to "idle" mode
"""
def __init__(self, name=None):
"""
Constructor (parameterizable).
"""
# Always call parent class' constructor FIRST:
AtomicDEVS.__init__(self, name)
# STATE:
# Define 'state' attribute (initial sate):
self.state = PolicemanMode("idle")
# ELAPSED TIME:
# Initialize 'elapsed time' attribute if required
# (by default, value is 0.0):
self.elapsed = 0
# PORTS:
# Declare as many input and output ports as desired
# (usually store returned references in local variables):
self.OUT = self.addOutPort(name="OUT")
def intTransition(self):
"""
Internal Transition Function.
The policeman works forever, so only one mode.
"""
state = self.state.get()
if state == "idle":
return PolicemanMode("working")
elif state == "working":
return PolicemanMode("idle")
else:
raise DEVSException(\
"unknown state <%s> in Policeman internal transition function"\
% state)
def outputFnc(self):
"""
Output Funtion.
"""
# Send messages (events) to a subset of the atomic-DEVS'
# output ports by means of the 'poke' method, i.e.:
# The content of the messages is based (typically) on current State.
state = self.state.get()
if state == "idle":
return {self.OUT: "toManual"}
elif state == "working":
return {self.OUT: "toAutonomous"}
else:
raise DEVSException(\
"unknown state <%s> in Policeman output function"\
% state)
def timeAdvance(self):
"""
Time-Advance Function.
"""
# Compute 'ta', the time to the next scheduled internal transition,
# based (typically) on current State.
state = self.state.get()
if state == "idle":
return 200
elif state == "working":
return 100
else:
raise DEVSException(\
"unknown state <%s> in Policeman time advance function"\
% state)
class TrafficSystem(CoupledDEVS):
def __init__(self, name=None):
"""
A simple traffic system consisting of a Policeman and a TrafficLight.
"""
# Always call parent class' constructor FIRST:
CoupledDEVS.__init__(self, name)
# Declare the coupled model's output ports:
# Autonomous, so no output ports
# Declare the coupled model's sub-models:
# The Policeman generating interrupts
self.policeman = self.addSubModel(Policeman(name="policeman"))
# The TrafficLight
self.trafficLight = self.addSubModel(TrafficLight(name="trafficLight"))
# Only connect ...
self.connectPorts(self.policeman.OUT, self.trafficLight.INTERRUPT)
def select(self, immChildren):
"""
Choose a model to transition from all possible models.
"""
# Policeman has priority over the traffic light
if self.policeman in immChildren:
return self.policeman
else:
# Doesn't really matter, as they don't influence each other
return immChildren[0]