erlangc.py

#!/usr/bin/env python

from decimal import Decimal, getcontext
from math import factorial

#a = float(500000) # total traffic offered
#n = 10 # number of servers


# 500000 per day
# Ts = 2 seconds per crash
# lambda = 5.78 crashes per second

# (a, n) pairs
test_values = [ (48, 55, 240), (11.56, 10, 2), (115.6, 10, 2), (117.4, 30, 2), (117.4, 50, 2) ]


getcontext().prec = 50

for test in test_values:

    u, m, t = test
    u = Decimal(u)
    m = Decimal(m)
    sum = 0

    print "traffic intensity (u): ", u
    print "number of agents (m): ", m
    print "average processing duration (in seconds): ", t
    agent_occupancy =  u / m
    print "agent occupancy:  %0.6f" % agent_occupancy

    for i in range(0, int(m)-1):
        sum += ( u**i / factorial(i) )

    p = (u**m / factorial(m)) / ((u**m / factorial(m)) + ((1 - agent_occupancy) * sum))


    print "probability that an arriving crash will need to queue: %0.8f" % (p * 100)

    x = (p * t ) / (m * (1-agent_occupancy))

    print "average waiting time for %s servers: %0.6f" % (m,x)
    print