Shortest Processing Time
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Shortest Processing Time

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    Shortest Processing Time (SPT) :
            The shortest job are handled first and completed.

           The step for using this rule are:

Firstly, the user will input the number of jobs, the job names,the processing time and the due date of each job or use the data values given at the starting point.
The second step is sorting out the shortest processing time among the jobs.
Thirdly, calculate the flow time of each job by using the processing time. the flow time is the accummulations of processing time each job by each job.
The delays is calculated from the flow time and due date. The formula is:
Delay = Flow time - due date
However, there are two conditions for calculating the delays although apply the formula already:

    If the delays calculated is less than flow time, then the delays = zero.
    If the delays calculated is more than flow time, then the delays =
          the value of (flow time - due date).
The next step is calculating the total processing time, total flow time and total delays from the accummulations processing time, the accummulations flow time and the accummulations delays.
Then, using the total flow time, total processing time, and total delays for calculating the average completion time, the utilisation, the average number of jobs in the system and the average job delays.
The formulas for calculation are below:

    Average completion time = sum of total flow / no. of jobs
    Utilisation = total processing time / sum of total flow
    Average no. of jobs  = total flow time / total processing time
    Average job delays = total delays / no. of jobs
These above are the steps for using the SPT priority rules.

face2.gif (615 bytes)    Demo Using SPT in Example

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