In: Operations Management
Average flow and average delay based on FCFS, EDD, and SPT
Job |
Job time (days) |
Due date (days from now) |
A |
12 |
15 |
B |
6 |
24 |
C |
14 |
20 |
D |
3 |
8 |
1. FIRST COME FIRST SERVE
JOB |
PROCESSING TIME |
DUE TIME |
FLOW TIME |
JOB LATENESS |
A |
12 |
15 |
0 + 12 = 12 |
|
B |
6 |
24 |
12 + 6 = 18 |
|
C |
14 |
20 |
18 + 14 = 32 |
12 |
D |
3 |
8 |
32 + 3 = 35 |
27 |
TOTAL FLOW TIME = 12 + 18 + 32 + 35 = 97
AVERAGE COMPLETION TIME = FLOW TIME / N = 97 / 4 = 24.25
AVERAGE JOB LATENESS = TOTAL JOB LATENESS / N = 39 / 4 = 9.75
2. EARLIEST DUE DATE
JOB |
PROCESSING TIME |
DUE TIME |
FLOW TIME |
JOB LATENESS |
D |
3 |
8 |
0 + 3 = 3 |
|
A |
12 |
15 |
3 + 12 = 15 |
0 |
C |
14 |
20 |
15 + 14 = 29 |
9 |
B |
6 |
24 |
29 + 6 = 35 |
11 |
TOTAL FLOW TIME = 3 + 15 + 29 + 35 = 82
AVERAGE COMPLETION TIME = FLOW TIME / N = 82 / 4 = 20.5
AVERAGE JOB LATENESS = TOTAL JOB LATENESS / N = 20 / 4 = 5
3. SHORTEST PROCESSING TIME
JOB |
PROCESSING TIME |
DUE TIME |
FLOW TIME |
JOB LATENESS |
D |
3 |
8 |
0 + 3 = 3 |
|
B |
6 |
24 |
3 + 6 = 9 |
|
A |
12 |
15 |
9 + 12 = 21 |
6 |
C |
14 |
20 |
21 + 14 = 35 |
15 |
TOTAL FLOW TIME = 3 + 9 + 21 + 35 = 68
AVERAGE COMPLETION TIME = FLOW TIME / N = 68 / 4 = 17
AVERAGE JOB LATENESS = TOTAL JOB LATENESS / N = 21 / 4 = 5.25
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