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Explain Job sequencing with deadline for the given instance.

Mumbai University > Computer Engineering > Sem 4 > Analysis of Algorithm

Marks: 10M

Year: May 2015

1 Answer
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  • We are given n jobs. Associated with each job i there is an integer deadline di and a profit pi where di>0 & pi>0.
  • For any job i, the corresponding profit is earned if the job is completely by its deadline. To complete the job one has to process a job on a machine and only one machine is available for processing jobs.
  • Each jobs requires only one unit of time for its processing.
  • A feasible solution for this problem is a subset j of jobs such that each job in this subset can be completed by its deadline. The value of this feasible solution j is the sum of profits of jobs in j or ⅀pi. An optimal solution is a feasible solution with maximum value. Hence again, since the problem involves the identification of a subset, it fits the subset paradigm.

Problem:

Feasible solution and there values are:

Sr. No Feasible solution Frequenting,sequence Values
1 (1,2) 1,2 or 2,1 35
2 (1,3) 1,3 30
3 (1,4) 1,4 25
4 (1,5) 1,5 23
5 (1,2,4) 1,2,4 or 2,1,4 40
6 (1,3,4) 3,1,4 35
7 (2,3,4) 3,2,4 30
8 (1,2,5) 1,2,5 or 2,1,5 38
9 (1,3,5) 3,1,5 33
10 (2,3,5) 3,2,5 28
11 (2,3) 3,2 25
12 (2,4) 2,4 20
13 (2,5) 2,5 18
14 (4,5) 4,5 or 5,4 8
  • Solution 5 is optimal. In this solution, job 1, 2, 4 are processed and the value is 40.
  • These jobs can be processed in order 1, 2 and then 4 or 2, 1 and then 4.
  • The processing of job 1 or 2 begins at time zero and is completed at time 2 and that of job 4 is completed at time 3.

Why do we make subsets of two or three jobs ? Please explain in detail


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