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Question 15.SP.3: The Dallas firm in Solved Problem 15.2 also wants to conside...

The Dallas firm in Solved Problem 15.2 also wants to consider job sequencing by the SPT priority rule. Apply SPT to the same data, and provide a recommendation.

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SPT has the sequence D–F–A–E–B–C.

JOB
SEQUENCE		 JOB
PROCESSING
TIME		 FLOW TIME DUE DATE JOB LATENESS
D 2 2 18 0
F 4 6 34 0
A 6 12 22 0
E 10 22 25 0
B 12 34 14 20
C 14 48 30 18
48 124 38

1. Average completion time = 124/6 = 20.67 days
2. Average number of jobs in system = 124/48 = 2.58 jobs
3. Average job lateness = 38/6 = 6.33 days
4. Utilization = 48/124 = 38.7%

SPT is superior to FCFS in this case on all four measures. If we were to also analyze EDD, we would, however, find its average job lateness to be lowest at 5.5 days. SPT is a good recommendation. SPT’s major disadvantage is that it makes long jobs wait, sometimes for a long time.

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