Correct Answer Explanation: B. SPT: shortest processing time

The correct answer is B. SPT (Shortest Processing Time) because it is a dispatching rule that tends to minimize job flow time by prioritizing jobs with the shortest processing times. Let’s explore in detail why this answer is correct and then analyze why the other options are not suitable for minimizing job flow time.

SPT, or Shortest Processing Time, is an effective dispatching rule for minimizing job flow time. This rule works on the principle of completing the job that will take the least amount of time first.

By doing this, it reduces the time jobs spend in the system and allows faster turnover. Minimizing job flow time is crucial in scenarios where you want to optimize throughput, reduce lead times, and improve overall operational efficiency.

Here’s a detailed explanation of why SPT is the correct choice:

• Minimizing Completion Times: SPT focuses on completing the shortest jobs first, which minimizes the time each job spends in the system. This, in turn, reduces the overall job flow time.
• Reducing Waiting Times: By addressing short jobs first, SPT helps prevent longer jobs from causing delays to the entire process. This minimizes the waiting time for jobs with longer processing times.
• Optimal Resource Utilization: SPT ensures that resources are allocated to shorter tasks first, making the most efficient use of resources and allowing for faster turnover of jobs.

Explanation of Why the Other Options are Incorrect

Now, let’s examine why the other options are not suitable for minimizing job flow time:

A. FCFS (First Come, First Served):

FCFS prioritizes jobs based on their arrival order, without considering their processing times. This means that longer jobs may be processed before shorter ones, potentially leading to higher job flow times.

If there are long jobs at the beginning of the queue, they can create significant delays for shorter jobs that arrive later, resulting in a longer overall job flow time. It doesn’t take into account the actual time required to complete each job, which can lead to suboptimal resource utilization.

C. EDD (Earliest Due Date):

EDD prioritizes jobs based on their due dates, rather than their processing times. While this rule ensures that deadlines are met, it doesn’t necessarily minimize job flow time.

A job with a shorter processing time but a later due date may be delayed in favor of a longer job with an earlier due date. This can lead to longer job flow times for shorter tasks.

D. LPT (Longest Processing Time)

LPT prioritizes longer jobs, which can lead to higher job flow times. This rule is not suitable for minimizing job flow time because it doesn’t consider the length of the jobs in the queue.

Shorter jobs may be kept waiting for extended periods while longer jobs are processed first, leading to suboptimal flow time.

E. FCLS (First Come, Last Served):

FCLS prioritizes the first-arriving job but processes it last. This approach can lead to longer job flow times because jobs are processed in a non-optimal order.

Shorter jobs may be delayed in favor of longer ones, which can increase the overall job flow time and reduce operational efficiency.

In summary, while each dispatching rule has its own strengths and applications, they may not be as effective as SPT when the primary objective is to minimize job flow time. SPT’s focus on processing shorter jobs first ensures that resources are utilized efficiently, waiting times are reduced, and overall job flow time is minimized.

This makes SPT a highly effective strategy for improving operational efficiency and throughput in scenarios where minimizing job flow time is a critical objective.