IE 383
Assignment 10 Solution
Note: always bear in mind you can only schedule a job when it arrives. And we use
the scheduling principle such as SPT, EDD etc only when multiple jobs are competing
for the same resource at the same time. For example, in problem 1c) at time 0 there
are only job A, E and F are competing for the same resource not all of the jobs.
Problem 1 (Please carefully follow the instructions and answer questions in order,
otherwise 5 points will be deducted.)
Job
A
B
C
D
E
F
G
H
I
Proc Time
5
6
7
14
4
8
3
3
9
Due Date
65
48
40
45
55
28
20
25
40
a)
Assuming that all jobs arrive at time 0, generate a schedule that minimizes mean
flow time using a table and a Gantt chart. Break ties with job index. Also determine
the following measurements.
mean flow time
mean tardiness
maximum tardiness
Job
A
B
C
D
E
F
G
H
I
Arr Time
0
42
20
20
0
5
0
12
13
b)
Given the arrival time above, generate a schedule based on EDD using a table and a
Gantt chart, and determine
mean flow time
mean tardiness
maximum tardiness
Break ties with job index.
c)
Given the arrival time above, generate a schedule based on Critical Ratio using a
table and a Gantt chart, and determine
mean flow time
mean tardiness
maximum tardiness
Break ties with job index
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Answer:
1
a) To minimize MFT, sort jobs in the order of increasing processing time.
Job
G
H
E
A
B
C
F
I
D
Proc Time
3
3
4
5
6
7
8
9
14
Due Date
20
25
55
65
48
40
28
40
45
Arr Time
0
0
0
0
0
0
0
0
0
End time=Start time+Proc Time
3
6
10
15
21
28
36
45
59
Tardiness=max {0, End timeDue Date}
0
0
0
0
0
0
8
5
14
Mean flow time=sum of (end timearr. time)/# of jobs=24.78
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 Spring '08
 Leyla,O
 Harshad number, Triangular number, M3 Halftrack, World War II American infantry weapons

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