4QA3 F12 Week 11 Lecture Notes

In dynamic scheduling jobs are not available

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Unformatted text preview: ob 1 Job 2 Makespan 4QA3 F12 A. Gandomi 9 ●  Difference between completion time and due date (may be negative). ●  The positive difference between the completion time and the due date. ●  In static scheduling, jobs are all available for processing right at time t = 0 when the processing starts. In dynamic scheduling, jobs are not available all at time t = 0. ●  In deterministic scheduling, the job characteristics such as ready time, processing time and due date are all known with certainty. In stochastic scheduling, some of the job characteristics are uncertain. 4QA3 F12 A. Gandomi 10 ●  o  Sequential Processing: Machines are distinguishable, and different operations are performed by different machines. o  Parallel processing: The machines are identical, and any job can be processed on any machine. Job A M3 M4 A. Gandomi M1 M2 Job B M2 Job B 4QA3 F12 M1 Job A M3 M4 11 ●  First Come First Served (FCFS): Jobs processed in the order they come to the shop. ●  Shortest Processing Time (SPT): Jobs with the shortest processing time are scheduled 5irst. ●  Earliest Due Date (EDD): Jobs are sequenced according to their due dates. ●  Critical Ratio (CR): Compute the ratio of remaining time until the due date to processing time of the job. Schedule the job with the smallest CR value next (in case of a tie or more than one negative value then schedule with SPT). Due Date - Current time CR = Processing Time 4QA3 F12 A. Gandomi 12 Job A B C D E FCFS Sequence A B C D E 4QA3 F12 Start Time 0 11 40 71 72 Processing Time 11 29 31 1 2 Due Date 61 45 31 33 32 Processing Completion Time Time 11 29 31 1 2 11 40 71 72 74 Due Date Tardiness 61 45 31 33 32 0 0 40 39 42 Mean Flow Time: (11 + 40 + 71 + 72 + 74) / 5 = 53.4 Average tardiness=(40 + 39 + 42) / 5 = 24.2 A. Gandomi Number of tardy jobs = 3 13 Job Processing Time Due Date A B C D E 11 61 29 45 31 31 1 33 2 32 SPT DUE SPT START PProcessing COMPLETION Due Start ROCESSING Completion SEQUENCE Time TIME TIME TIME DATE Tardiness Sequence Time Time Date TARDINESS D 0 1 1 33 0 E 1 2 3 32 0 A 3 11 14 61 0 B 14 29 43 45 0 C 43 31 74 31 43 Mean 5low time = 27, Average tardiness = 8.6, Number of tardy jobs=1 4QA3 F12 A. Gandomi 14 Job Due Date A B C D E EDD Sequence C E D B A Processing Time 11 29 31 1 2 61 45 31 33 32 Start Time 0 31 33 34 63 Processing Completion Time Time 31 31 2 33 1 34 29 63 11 74 Due Date Tardiness 31 0 32 1 33 1 45 18 61 1 Flow time = 47.0, Average tardiness = 6.6, Number of tardy jobs=4 4QA3 F12 A. Gandomi 15 Job Processing Time Due Date A B C D E 11 29 31 1 2 61 45 31 33 32 CR Sequence C B D E A Start Time 0 31 60 61 63 Due Date - Current time CR = Processing Time Processing Completion Time Time 31 31 27 60 1 61 2 63 11 74 Due Date 31 45 33 32 61 Tardiness 0 15 28 31 13 Mean Flow time = 57.8, Average...
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