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from random import normalvariate, seed
from SimPy.Simulation import (Level, Process, activate, get, initialize, hold,
now, put, simulate)
class Deliver(Process):
def deliver(self): # an "offeror" PEM
while True:
lead = 10.0 # time between refills
delivery = 10.0 # amount in each refill
yield put, self, stock, delivery
print('at %6.4f, add %6.4f units, now amount = %6.4f' %
(now(), delivery, stock.amount))
yield hold, self, lead
class Demand(Process):
stockout = 0.0 # initialize initial stockout amount
def demand(self): # a "requester" PEM
day = 1.0 # set time-step to one day
while True:
yield hold, self, day
dd = normalvariate(1.20, 0.20) # today's random demand
ds = dd - stock.amount
# excess of demand over current stock amount
if dd > stock.amount: # can't supply requested amount
yield get, self, stock, stock.amount
# supply all available amount
self.stockout += ds
# add unsupplied demand to self.stockout
print('day %6.4f, demand = %6.4f, shortfall = %6.4f' %
(now(), dd, -ds))
else: # can supply requested amount
yield get, self, stock, dd
print('day %6.4f, supplied %6.4f, now amount = %6.4f' %
(now(), dd, stock.amount))
stock = Level(monitored=True) # 'unbounded' capacity and other defaults
seed(99999)
initialize()
offeror = Deliver()
activate(offeror, offeror.deliver())
requester = Demand()
activate(requester, requester.demand())
simulate(until=49.9)
result = (stock.bufferMon.mean(), requester.stockout)
print('')
print('Summary of results through end of day %6.4f:' % int(now()))
print('average stock = %6.4f, cumulative stockout = %6.4f' % result)
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