class Disk(Process):
mean_service_time = 0.02 # Mean service time for one IO request.
def reset(self):
self.state = TSeries(numeric=False, time_fnc=self.sim.clock.get)
self.state.collect("Idle")
@Chain
def initialize(self):
sim = self.sim
queue = sim.members["Queue"]
while True:
if queue.size.get() == 0:
self.state.collect("Idle")
yield Poll.greater_than(0, queue.size)
self.state.collect("Busy")
io_request = queue.get()
io_request.service = sim.time
yield sample.nonnegative(sim.rng.expovariate, 1.0 / Disk.mean_service_time)
io_request.departure = self.sim.time
queue.collect(io_request)
def finalize(self):
queue = self.sim.members["Queue"]
if queue.running:
queue.stop() # Make sure to finalize the queue before the disk.
self.state.collect(self.state.last_value())
self.state.pareto_chart(axes=queue.plotter, title=self.name)
print self, "utilization:", self.state.wrel_frequency("Busy")
class WorkStation(Process):
"""Configuration parameters:
initial_workers :: int
throughput_fnc :: callable(int) -> float
changeover :: {(from, to): float}
setup :: {product: float}
"""
state = TSeries()
workers = Checkable(0)
throughput = 0.0
current = None
initial_workers = 0
changeover = {}
setup = {}
def set_workers(self, workers):
"""This method is used by the line balancer to adjust the number of workers in each
assembly line and/or the workbenches, and update their throughput."""
self.throughput = self.throughput_fnc(workers)
self.workers.set(workers)
def throughput_fnc(self, workers):
raise NotImplementedError()
def status(self):
return "%d workers (throughput=%f) - %s - %s" % \
(self.workers.get(), self.throughput, self.state.last_value(), self.current)
def reset(self):
if "queue" not in self:
self["queue"] = Store()
self["queue"].content.clear()
self.state = TSeries(storing=False, numeric=False, time_fnc=self.sim.clock.get)
self.workers = Checkable(self.initial_workers)
self.throughput = self.throughput_fnc(self.initial_workers)
self.current = None
self.previous = None
@Chain
def initialize(self):
queue = self["queue"]
while True:
yield self.fetch(queue)
yield self.prepare(self.current.product)
yield self.process(self.current)
self.previous = self.current.product
self.current.action.succeed()
self.current = None
@Chain
def fetch(self, queue):
"""Get the order with minimum preparation time and maximum process time from the queue."""
self.state.collect(IDLE)
if len(queue.content) == 0:
self.current = (yield queue.content.get()).result
else:
best_score = None
best_order = None
for order in queue.content:
changeover = self.changeover.get((self.previous, order.product), 0.0)
setup = self.setup.get(order.product, 0.0)
ptime = order.quantity * order.product.complexity[self.name]
score = (-(changeover + setup), +ptime)
if score > best_score:
best_score = score
best_order = order
queue.content.remove(best_order)
self.current = best_order
self.current.location = self.name
@Chain
def prepare(self, product):
"""Prepare the workstation for processing the specified product. This may include a
changeover if the product is different from the one previously processed, and a setup
time for preparing the machinery to start working."""
self.state.collect(CHANGEOVER)
yield self.changeover.get((self.previous, product), 0.0)
self.state.collect(SETUP)
yield self.setup.get(product, 0.0)
@Chain
def process(self, order):
"""Simulate the processing of 'order' with a possibly variable number of workers."""
self.state.collect(BUSY)
remaining = order.quantity
while True:
if self.workers.get() == 0:
self.state.collect(NO_WORKERS)
yield Poll.greater_than(0, self.workers)
self.state.collect(BUSY)
rate = self.throughput / order.product.complexity[self.name]
process = Delay(remaining / rate)
yield Renege(process, Poll.not_equal_to(self.workers.get(), self.workers))
remaining -= process.elapsed_time * rate
if process.succeeded():
raise Chain.success()
def finalize(self):
self.state.collect(self.state.last_value())
self.state.pareto_chart(axes=self.sim.plotter, title=self.name)