Suppose that the following jobs are waiting to be processed at a work center. Fu

Question

Suppose that the following jobs are waiting to be processed at a work center. Further suppose that today is day 120. Which of the three schedules is the best for (a) minimizing WIP and (b) which is the best for minimizing lateness? Consider only SPT, EDD and CR schedules. You must show all the work 3. Duration 60 35 25 45 Job Day job is due 219 185 150 180 200 195 40 Note: When determining the job due date be sure to take into account that the today day number is available as a production day. In other words, if day job is due 120, we have one day to complete the job, not zero SPT EDD CR Average flow time Average lateness

Explanation / Answer

EDD (earliest due date)

The order of job sequence using due dates taken in ascending order

Average no. of jobs = total flow time/duration time

= 805/260=3.096

Average job lateness =total late days/no. of jobs

= 401/6 = 66.8

Lateness = flowtime- due date starting from 121

= 0 if negative

Average flow time = total flow time/no. of jobs

= 805/6 = 134.16

Utilization metric= total duration time/ total flow time

= 260/805= 32.29%

SPT- shortest processing time

Sequence of job selection by using SPT is taken first and rest of the jobs are taken in an ascending order.

Average no. of jobs = 790/260= 3.038

Average flow time= 790/6= 131.66

Average job lateness= 391/6= 65.16

Utilization metric= 260/790= 32.91%

CR-Critical ratio

Sequence of job is by smallest critical ratio

CR= time remaining before due date/duration time

Job along with critical ratio

A=3.65

B=5.28

C=6

D=4

E=3.63

F=4.8

Sequence as per smallest critical path first

Average no. of jobs= 1025/260 = 3.94

Average flow time= 1025/6= 170.83

Average job lateness = 260/1025 =106.83

Utilization= 260/1025= 25.36%

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