Question

The jobs listed below need to be completed. Assume that it is now day 140. If the jobs are sequenced according to the shortest processing time rule and earliest due date rule,

a. what is the job processing sequence for each rule?

b. what is the average flow time for each rule?

c. what is the utilization for each rule?

d. what is the average job lateness for each rule?

e. what is the average number of jobs in a system?

Job	Processing Time (days)(PT)	Job due date (days) (DD)
A	20	180
B	30	200
C	10	175
D	16	230
E	18	210

Answer 1

SPT

JOB	PROCESSING TIME	DUE TIME	FLOW TIME	JOB LATENESS
C	10	35	0 + 10 = 10
D	16	90	10 + 16 = 26
E	18	70	26 + 18 = 44
A	20	40	44 + 20 = 64	24
B	30	60	64 + 30 = 94	34

TOTAL FLOW TIME = 10 + 26 + 44 + 64 + 94 = 238

AVERAGE COMPLETION TIME = FLOW TIME / N = 238 / 5 = 47.6

AVERAGE JOB LATENESS = TOTAL JOB LATENESS / N = 58 / 5 = 11.6

UTILIZATION METRIC = (TOTAL PROCESSING TIME / TOTAL FLOW TIME) * 100 = 94 / 238 * 100 = 39.5

AVERAGE JOBS IN THE SYSTEM = TOTAL FLOW TIME / TOTAL PROCESSING TIME = 238 / 94 = 2.53

EDD

JOB	PROCESSING TIME	DUE TIME	FLOW TIME	JOB LATENESS
C	10	35	0 + 10 = 10
A	20	40	10 + 20 = 30
B	30	60	30 + 30 = 60	0
E	18	70	60 + 18 = 78	8
D	16	90	78 + 16 = 94	4

TOTAL FLOW TIME = 10 + 30 + 60 + 78 + 94 = 272

AVERAGE COMPLETION TIME = FLOW TIME / N = 272 / 5 = 54.4

AVERAGE JOB LATENESS = TOTAL JOB LATENESS / N = 12 / 5 = 2.4

UTILIZATION METRIC = (TOTAL PROCESSING TIME / TOTAL FLOW TIME) * 100 = 94 / 272 * 100 = 34.56

AVERAGE JOBS IN THE SYSTEM = TOTAL FLOW TIME / TOTAL PROCESSING TIME = 272 / 94 = 2.89

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