Python Queue Similation (Python COMPSCI Coursework)

Python_FINAL

import sys, os
import math
import random

def nextTime(mean):

	from random import choice
	
	# Giving x a random number from 0 to 1
	x = random.random()
	
	# return -alpha ln(1-x)
	# where (mean = alpha) (ln = math.log)
	return -mean * math.log(1-x)

	
#Checking code works:

# Create an empty variable to store average      
# Add value of nextTime to average
# Hence making nt_average = nextTime
# Divide total by number of runs to get the value
# Print result
# Loop this loop 5 times for accuracy (hence total of 50,000 simulations)

nt_average = 0.0

print "Q1.(a). Where mean = 1"
for i in range (5):
        for i in range (10000):
                nt_average += nextTime(1)
        nt_average = nt_average/10000
#for i in range (5):
        print "Result:  %s" % nt_average
        
print " "
print "Q1.(a). Where mean = 10"  
for i in range (10000):
        nt_average += nextTime(10)
nt_average = nt_average/10000
for i in range (5):
        print "Result:  %s" % nt_average

print " "
print "Q1.(a). Where mean = 50"  
for i in range (10000):
        nt_average += nextTime(50)
nt_average = nt_average/10000
for i in range (5):
        print "Result:  %s" % nt_average
        
print " "
print "Q1.(a). Where mean = 100"  
for i in range (10000):
        nt_average += nextTime(100)
nt_average = nt_average/10000
for i in range (5):
        print "Result:  %s" % nt_average

print " "
print " "


def SingleQueueSimulation(alpha, beta, time):

# alpha is average time for arival
# beta is average time for service

# c = curent time in mins
# ta = time to the next customer arival
# ts = time until current customer is served
# q = current length of queue

        new_q = 0.0
        c = 0.0
        ta = 0.0
        ts = 0.0
        q = 1.0
        


        while c < time:
                
                if ta < ts:
                        ts -= ta
                        c = c + ta
                        q += 1
                        ta = nextTime(alpha)
                
                else:
                        ta -= ts
                        c += ts
                        q -= 1
                        ts = nextTime(beta)

                if q == 0:
                        c = c + ta
                        q += 1
                        ta = nextTime(alpha)

        # If queue length becomes bigger than the initial queue length
        # Then make the initial queue length become this new length
        # Don't need else on "if q ==0" because if q != 0 then the loop repeats
                if q > new_q:
                        new_q = q
        return new_q



# Testing test data (email) (20 experiements)
#   alpha 20, beta 5, time 480...expected ~2.85
#   alpha 20, beta 10, time 480...expected ~4.55

# Testing data from question (10,000 experiments)
#   alpha 10, beta 4, time 480
#   alpha 10, beta 2, time 480
#   alpha 5, beta 4, time 480
#   alpha 5, beta 2, time 480

sqs_average = 0.0

print "Q1.(b). Where (alpha = 20), (beta = 5), (time = 480), 20 experiments only" 
for i in range (5):
        for i in range (20):
                sqs_average += SingleQueueSimulation(20, 5, 480)
        sqs_average = sqs_average/20
        print "Result:  %s" % sqs_average
        
print " "
print "Q1.(b). Where (alpha = 20), (beta = 10), (time = 480), 20 experiments only" 
for i in range (5):
        for i in range (20):
                sqs_average += SingleQueueSimulation(20, 10, 480)
        sqs_average = sqs_average/20
        print "Result:  %s" % sqs_average
        
print " "
print "Q1.(b). Where (alpha = 10), (beta = 4), (time = 480)" 
for i in range (5):
        for i in range (10000):
                sqs_average += SingleQueueSimulation(20, 5, 480)
        sqs_average = sqs_average/10000
        print "Result:  %s" % sqs_average
        
print " "
print "Q1.(b). Where (alpha = 10), (beta = 2), (time = 480)" 
for i in range (5):
        for i in range (10000):
                sqs_average += SingleQueueSimulation(20, 5, 480)
        sqs_average = sqs_average/10000
        print "Result:  %s" % sqs_average
        
print " "
print "Q1.(b). Where (alpha = 5), (beta = 2), (time = 480)" 
for i in range (5):
        for i in range (10000):
                sqs_average += SingleQueueSimulation(20, 5, 480)
        sqs_average = sqs_average/10000
        print "Result:  %s" % sqs_average
        
print " "
print "Q1.(b). Where (alpha = 20), (beta = 5), (time = 480)" 
for i in range (5):
        for i in range (20):
                sqs_average += SingleQueueSimulation(20, 5, 480)
        sqs_average = sqs_average/20
        print "Result:  %s" % sqs_average