204 lines
7.8 KiB
Python
204 lines
7.8 KiB
Python
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"""
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Taxi simulator
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==============
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Driving a taxi from the console::
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>>> from taxi_sim import taxi_process
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>>> taxi = taxi_process(ident=13, trips=2, start_time=0)
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>>> next(taxi)
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Event(time=0, proc=13, action='leave garage')
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>>> taxi.send(_.time + 7)
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Event(time=7, proc=13, action='pick up passenger')
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>>> taxi.send(_.time + 23)
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Event(time=30, proc=13, action='drop off passenger')
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>>> taxi.send(_.time + 5)
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Event(time=35, proc=13, action='pick up passenger')
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>>> taxi.send(_.time + 48)
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Event(time=83, proc=13, action='drop off passenger')
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>>> taxi.send(_.time + 1)
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Event(time=84, proc=13, action='going home')
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>>> taxi.send(_.time + 10)
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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StopIteration
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Sample run with two cars, random seed 10. This is a valid doctest::
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>>> main(num_taxis=2, seed=10)
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taxi: 0 Event(time=0, proc=0, action='leave garage')
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taxi: 0 Event(time=5, proc=0, action='pick up passenger')
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taxi: 1 Event(time=5, proc=1, action='leave garage')
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taxi: 1 Event(time=10, proc=1, action='pick up passenger')
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taxi: 1 Event(time=15, proc=1, action='drop off passenger')
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taxi: 0 Event(time=17, proc=0, action='drop off passenger')
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taxi: 1 Event(time=24, proc=1, action='pick up passenger')
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taxi: 0 Event(time=26, proc=0, action='pick up passenger')
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taxi: 0 Event(time=30, proc=0, action='drop off passenger')
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taxi: 0 Event(time=34, proc=0, action='going home')
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taxi: 1 Event(time=46, proc=1, action='drop off passenger')
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taxi: 1 Event(time=48, proc=1, action='pick up passenger')
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taxi: 1 Event(time=110, proc=1, action='drop off passenger')
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taxi: 1 Event(time=139, proc=1, action='pick up passenger')
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taxi: 1 Event(time=140, proc=1, action='drop off passenger')
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taxi: 1 Event(time=150, proc=1, action='going home')
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*** end of events ***
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See longer sample run at the end of this module.
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"""
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import argparse
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import collections
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import random
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import queue
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DEFAULT_NUMBER_OF_TAXIS = 3
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DEFAULT_END_TIME = 180
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SEARCH_DURATION = 5
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TRIP_DURATION = 20
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DEPARTURE_INTERVAL = 5
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Event = collections.namedtuple('Event', 'time proc action')
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# tag::TAXI_PROCESS[]
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def taxi_process(ident, trips, start_time=0): # <1>
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"""Yield to simulator issuing event at each state change"""
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time = yield Event(start_time, ident, 'leave garage') # <2>
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for i in range(trips): # <3>
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time = yield Event(time, ident, 'pick up passenger') # <4>
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time = yield Event(time, ident, 'drop off passenger') # <5>
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yield Event(time, ident, 'going home') # <6>
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# end of taxi process # <7>
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# end::TAXI_PROCESS[]
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# tag::TAXI_SIMULATOR[]
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class Simulator:
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def __init__(self, procs_map):
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self.events = queue.PriorityQueue()
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self.procs = dict(procs_map)
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def run(self, end_time): # <1>
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"""Schedule and display events until time is up"""
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# schedule the first event for each cab
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for _, proc in sorted(self.procs.items()): # <2>
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first_event = next(proc) # <3>
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self.events.put(first_event) # <4>
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# main loop of the simulation
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sim_time = 0 # <5>
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while sim_time < end_time: # <6>
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if self.events.empty(): # <7>
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print('*** end of events ***')
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break
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current_event = self.events.get() # <8>
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sim_time, proc_id, previous_action = current_event # <9>
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print('taxi:', proc_id, proc_id * ' ', current_event) # <10>
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active_proc = self.procs[proc_id] # <11>
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next_time = sim_time + compute_duration(previous_action) # <12>
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try:
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next_event = active_proc.send(next_time) # <13>
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except StopIteration:
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del self.procs[proc_id] # <14>
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else:
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self.events.put(next_event) # <15>
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else: # <16>
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msg = '*** end of simulation time: {} events pending ***'
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print(msg.format(self.events.qsize()))
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# end::TAXI_SIMULATOR[]
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def compute_duration(previous_action):
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"""Compute action duration using exponential distribution"""
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if previous_action in ['leave garage', 'drop off passenger']:
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# new state is prowling
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interval = SEARCH_DURATION
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elif previous_action == 'pick up passenger':
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# new state is trip
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interval = TRIP_DURATION
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elif previous_action == 'going home':
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interval = 1
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else:
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raise ValueError(f'Unknown previous_action: {previous_action}')
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return int(random.expovariate(1 / interval)) + 1
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def main(end_time=DEFAULT_END_TIME, num_taxis=DEFAULT_NUMBER_OF_TAXIS,
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seed=None):
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"""Initialize random generator, build procs and run simulation"""
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if seed is not None:
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random.seed(seed) # get reproducible results
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taxis = {i: taxi_process(i, (i + 1) * 2, i * DEPARTURE_INTERVAL)
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for i in range(num_taxis)}
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sim = Simulator(taxis)
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sim.run(end_time)
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if __name__ == '__main__':
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parser = argparse.ArgumentParser(
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description='Taxi fleet simulator.')
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parser.add_argument('-e', '--end-time', type=int,
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default=DEFAULT_END_TIME,
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help='simulation end time; default = %s'
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% DEFAULT_END_TIME)
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parser.add_argument('-t', '--taxis', type=int,
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default=DEFAULT_NUMBER_OF_TAXIS,
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help='number of taxis running; default = %s'
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% DEFAULT_NUMBER_OF_TAXIS)
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parser.add_argument('-s', '--seed', type=int, default=None,
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help='random generator seed (for testing)')
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args = parser.parse_args()
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main(args.end_time, args.taxis, args.seed)
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"""
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Sample run from the command line, seed=3, maximum elapsed time=120::
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# tag::TAXI_SAMPLE_RUN[]
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$ python3 taxi_sim.py -s 3 -e 120
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taxi: 0 Event(time=0, proc=0, action='leave garage')
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taxi: 0 Event(time=2, proc=0, action='pick up passenger')
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taxi: 1 Event(time=5, proc=1, action='leave garage')
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taxi: 1 Event(time=8, proc=1, action='pick up passenger')
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taxi: 2 Event(time=10, proc=2, action='leave garage')
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taxi: 2 Event(time=15, proc=2, action='pick up passenger')
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taxi: 2 Event(time=17, proc=2, action='drop off passenger')
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taxi: 0 Event(time=18, proc=0, action='drop off passenger')
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taxi: 2 Event(time=18, proc=2, action='pick up passenger')
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taxi: 2 Event(time=25, proc=2, action='drop off passenger')
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taxi: 1 Event(time=27, proc=1, action='drop off passenger')
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taxi: 2 Event(time=27, proc=2, action='pick up passenger')
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taxi: 0 Event(time=28, proc=0, action='pick up passenger')
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taxi: 2 Event(time=40, proc=2, action='drop off passenger')
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taxi: 2 Event(time=44, proc=2, action='pick up passenger')
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taxi: 1 Event(time=55, proc=1, action='pick up passenger')
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taxi: 1 Event(time=59, proc=1, action='drop off passenger')
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taxi: 0 Event(time=65, proc=0, action='drop off passenger')
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taxi: 1 Event(time=65, proc=1, action='pick up passenger')
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taxi: 2 Event(time=65, proc=2, action='drop off passenger')
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taxi: 2 Event(time=72, proc=2, action='pick up passenger')
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taxi: 0 Event(time=76, proc=0, action='going home')
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taxi: 1 Event(time=80, proc=1, action='drop off passenger')
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taxi: 1 Event(time=88, proc=1, action='pick up passenger')
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taxi: 2 Event(time=95, proc=2, action='drop off passenger')
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taxi: 2 Event(time=97, proc=2, action='pick up passenger')
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taxi: 2 Event(time=98, proc=2, action='drop off passenger')
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taxi: 1 Event(time=106, proc=1, action='drop off passenger')
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taxi: 2 Event(time=109, proc=2, action='going home')
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taxi: 1 Event(time=110, proc=1, action='going home')
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*** end of events ***
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# end::TAXI_SAMPLE_RUN[]
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"""
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