Correct Answer - Option 4 : 8
Answer: 4
Concept:
Shortest Processing Time (SPT): Sequence of the job is based on ascending order of processing time.
Processing time: The time spent by a job on machine.
Due date: Expected completion time of a job.
Flow time: Time spend by a job on shop floor. Cumulative addition of Processing time.
Make span: Time interval between starting of 1st job & coming out of last job in all machine.
Earliness/Tardiness: Time difference between Flow time and Due date time.
-
Earliness: When time difference is negative i.e. Job comes out before due date.
-
Tardiness: When time difference is positive i.e. Job comes out after due date.
Calculation:
Job
|
Processing Time
|
Flow Time
|
Due date
|
Tardiness
|
3
|
2
|
2
|
19
|
0
|
1
|
4
|
6
|
6
|
0
|
2
|
7
|
13
|
9
|
4
|
4
|
8
|
21
|
17
|
4
|
∴ Total tardiness = 4 + 4 = 8.
Important Points:
Method
|
Definition
|
First Come First Serve (FCFS)
|
Jobs are arranged as per they arrived
|
Shortest Processing Time (SPT)
|
Jobs are arranged as per the ascending order of Processing Time.
|
Earliest Due Date (EDD)
|
Jobs are arranged as per the ascending order of Due date.
|
Critical Ratio (CR)
|
\(C.R = \frac{{Due\;date}}{{Procesisng\;Time}}\)
Jobs are arranged as per the ascending order of Critical Ratio.
|