Evan Schwartz has six jobs waiting to be processed through his machine. Processi
ID: 429445 • Letter: E
Question
Evan Schwartz has six jobs waiting to be processed through his machine. Processing time (in days) and due date information for each job are as follows:
Job Processing Time Due Date
a 2 3
b 1 2
c 4 12
d 3 4
e 4 8
f 5 10
Sequence the jobs by FCFS, SPT, SLACK, and DDATE. Calculate the mean ow time and mean tardiness of the six jobs under each sequencing rule. Which rule would you recommend? Please show all work. Thank you!
Explanation / Answer
FCFS: Process the jobs in order of their arrival, A, B, C, D, E.
Job
Processing time
Flow time
Due date
Tardiness
a
2
2
3
0
b
1
3
2
1
c
4
7
12
0
d
3
10
4
6
e
4
14
8
6
f
5
19
11
8
55
21
Mean flow time = total flow time/ no. of jobs
= 55/6 = 9.17
Mean Tardiness = total tardiness/ no. of jobs
= 21/6 = 3.50
SPT: Sequence the jobs by smallest processing time.
Job
Processing time
Flow time
Due date
Tardiness
b
1
1
2
0
a
2
3
3
0
d
3
6
4
2
c
4
10
12
0
e
4
14
8
6
f
5
19
11
8
53
16
Mean flow time = 53/6 = 8.83
Mean Tardiness = 16/6 = 2.67
SLACK: Sequence the jobs by minimum slack. The slack for each job is calculated as: (due date - today's date) - remaining processing time.
Job
Processing time
Due date
Slack
a
2
3
0
b
1
2
0
c
4
12
7
d
3
4
0
e
4
8
3
f
5
11
5
Job
Processing time
Flow time
Due date
Tardiness
a
2
2
3
0
b
1
3
2
1
d
3
6
4
2
e
4
10
8
2
f
5
15
11
4
c
4
19
12
7
55
16
Mean flow time = 55/6 = 9.17
Mean Tardiness = 16/6 = 2.67
DDATE: Sequence the jobs by earliest due date
Job
Processing time
Flow time
Due date
Tardiness
b
1
1
2
0
a
2
3
3
0
d
3
6
4
2
e
4
10
8
2
f
5
15
11
4
c
4
19
12
7
54
15
Mean flow time = 54/6 = 9
Mean Tardiness = 15/6 = 2.50
Process DDate method is recommended as it has the lowest Mean tardiness.
Job
Processing time
Flow time
Due date
Tardiness
a
2
2
3
0
b
1
3
2
1
c
4
7
12
0
d
3
10
4
6
e
4
14
8
6
f
5
19
11
8
55
21
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.