algorithm to compute waiting time for FCFS scheduling in python

Question

Consider the following code that takes input processes and their arrival times and sort them according to FCFS algorithm, so i\'ve been thinking about algorithms to compute avg

Answer 1

# Author:Geraldo Braho
process_queue = []
total_wtime = 0
n = int(raw_input('Enter the total numbers of processes: '))
for i in xrange(n):
    process_queue.append([])#append a list object to the list
    process_queue[i].append(raw_input('Enter process name: '))
    process_queue[i].append(int(raw_input('Enter process arrival Time : ')))
    total_wtime += process_queue[i][1]
    process_queue[i].append(int(raw_input('Enter Process CPU bustTime : ')))
    print ''

process_queue.sort(key = lambda process_queue:process_queue[1])

print 'ProcessName\tArrivalTime\tBurstTime'
for i in xrange(n):
    print process_queue[i][0],'\t\t',process_queue[i][1],'\t\t',process_queue[i][2]

print 'Total waiting time: ',total_wtime
print 'Average waiting time: ',(total_wtime/n)

Answer 2

Concept: https://www.geeksforgeeks.org/program-fcfs-scheduling-set-2-processes-different-arrival-time/

processes = [
    {"pid": "P0", "burst_time": 5, "arrival_time": 0, "service_time": None, "waiting_time": None},
    {"pid": "P1", "burst_time": 3, "arrival_time": 1, "service_time": None, "waiting_time": None},
    {"pid": "P2", "burst_time": 8, "arrival_time": 2, "service_time": None, "waiting_time": None},
    {"pid": "P3", "burst_time": 6, "arrival_time": 3, "service_time": None, "waiting_time": None}
]

# No waiting time for first process
processes[0]["waiting_time"] = 0
# Service_time of the first process is it's arrival time
processes[0]["service_time"] = processes[0]["arrival_time"]

for i in range(1, len(processes)):
    # Case where process comes when processor is in idle state
    if processes[i]["arrival_time"] > (processes[i - 1]["service_time"] + processes[i - 1]["burst_time"]):
        processes[i]["service_time"] = processes[i]["arrival_time"]
    else:
        processes[i]["service_time"] = processes[i - 1]["service_time"] + processes[i - 1]["burst_time"]

    processes[i]["waiting_time"] = processes[i]["service_time"] - processes[i]["arrival_time"]

total_waiting_time = 0

for process in processes:
    total_waiting_time += process["waiting_time"]

avg_waiting_time = total_waiting_time / len(processes)

print("Average Waiting Time:", avg_waiting_time)

Answer 3

process_queue[i].append(int(list1[i])

you are appending the i'th element of list1 to the process_queue list , You should note that list1[i] is not a list but an integer . and in next line you are trying to access

total_wtime += process_queue[i][1]

1st element of the process_queue[i] but it is not a 2d array

total_wtime += process_queue[i]

should work .