COMS10003-packet-arrival-simulator

__author__ = 'ross'
import random

repeats = 10000
intervals_per_repeat = 1000

packet_types = [128,256]
input_links = ['a','b']

def get_packet_size(input_link):  # return a packet in the form ('a', 256)
    if input_link == 'a':
        prob_256 = 75
    elif input_link == 'b':
        prob_256 = 64
    if random.randint(1,100) <= prob_256:
        return 256
    else:
        return 128


def get_packet_stream(num_pairs):

    packets = []

    for i in range(num_pairs):
        first_link = random.choice(input_links)
        if first_link == 'a':
            second_link = 'b'
        else:
            second_link = 'a'

        first_packet = (first_link, get_packet_size(first_link))
        second_packet = (second_link, get_packet_size(second_link))

        packets.append(first_packet)
        packets.append(second_packet)
    return packets


def get_adjacent_pair(packet_stream):  # return an adjacent pair of packets from anywhere in the stream
    packet_index = random.randint(0,len(packet_stream)-2)
    packet_2_index = packet_index+1

    return [packet_stream[packet_index], packet_stream[packet_2_index]]

def run(num_repeats):
    counter_ordered_packets = 0     # counter for the number of packet pairs which are in the correct order (256-byte then 128-byte)
    counter_from_right_links = 0    # counter for the number of ordered packet pairs which also arrived on the correct links
    for i in range(num_repeats):
        stream = get_packet_stream(intervals_per_repeat)
        packets = get_adjacent_pair(stream)
        (link_1, size_1) = packets[0]
        (link_2, size_2) = packets[1]

        if size_1 == 256 and size_2 == 128:
            counter_ordered_packets += 1
            if link_1 == 'a' and link_2 == 'b':
                counter_from_right_links += 1

    print('prob from right links given in right order: ')
    print(counter_from_right_links/counter_ordered_packets)