The following jobs are waiting to be processed at the machine center. They are r
ID: 464676 • Letter: T
Question
The following jobs are waiting to be processed at the machine center. They are ready to be scheduled today, which is day 20 (day 20 is a work day).
Job
Processing Time
Date job is due
A
5
25
B
3
30
C
4
32
D
6
28
E
8
34
F
6
32
Complete the following table. (Show your supporting calculations.
Average flow time
Which dispatching rule has the best score for flow time?
Which dispatching rule has the best score for utilization metric?
Which dispatching rule has the best score for lateness?
Note: When determining the job due date be sure to take into account that starting day number is 20, i.e., work can be done on day 20. In other words, number of days till due date for job A = 25 – 20 + 1 = 6.
Please show all work! Partial answer key was given {Average flow time: SPT = 16, EDD = 17.333, CR = 20.167}
Job
Processing Time
Date job is due
A
5
25
B
3
30
C
4
32
D
6
28
E
8
34
F
6
32
Explanation / Answer
Average lateness: total late days/number of jobs
SPT: Shortest Processing Time
EDD: Earliest Due Date
CR:Time remaining before due date/Remaining processing time
CR for process A = Time to due/processing time= 6/5=1.2
CR for process B =11/3=3.67
CR for process C =13/4=3.25
CR for process D=9/6 = 1.5
CR for process E=15/8=1.87
CR for process F=13/6=2.16
Average no. Of jobs = Total flow time / Makespan
Makespan =total time needed to finish a group of jobs
Average no. Of jobs=96/32=3
create a sequence on the basis of lowest time to due
Average no. Of jobs=104/32=3.25
create a sequence on the basis of lowest CR
Average no. Of jobs=121/32=3.78
Lowest Mean flow time from above table is 16 and that is for SPT.Thus dispatching rule has the best score for flow time
minimum lateness from above tables is 6 and that is for EDD.Thus dispatching rule has the best score for lateness.
SPT seq. Processing Time Flow Time Time To due Lateness B 3 3 11(30-20+1) 0 C 4 7(3+4) 13(32-20+1) 0 A 5 12(7+5) 6(25-20+1) 6 D 6 18(12+6) 9 (28-20+1) 9 F 6 24(18+6) 13(32-20+1) 11 E 8 32(24+8) 15(34-20+1) 17 Total 96 43 Mean 16 7.16Related Questions
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