Here is a comparison between the Shortest Job First (SJF) and Longest Job First (LJF) scheduling algorithms in operating systems in tabular form with 15 points of differentiation:
| Feature | Shortest Job First (SJF) | Longest Job First (LJF) |
|---|---|---|
| Purpose | Selects the job with the shortest expected execution time to complete next | Selects the job with the longest expected execution time to complete next |
| Objective | Minimize waiting time for all jobs | Minimize turnaround time for all jobs |
| Performance | Lower average waiting time | Lower average turnaround time |
| Predictability | Requires knowledge of the expected execution time of each job | Does not require knowledge of expected execution time |
| Throughput | Higher | Lower |
| Predictability of completion time | High | Low |
| Starvation | May occur for long jobs | Avoided for long jobs |
| Load balancing | Even distribution of workload among all the processes | Uneven distribution of workload |
| CPU utilization | Higher | Lower |
| Response time | Faster for short jobs | Slower for short jobs |
| Fairness | Unfair to long jobs | Fair to long jobs |
| Context switching overhead | Lower | Higher |
| Memory requirements | Moderate | Higher |
| Preemptive or Non-Preemptive | Can be either preemptive or non-preemptive | Typically non-preemptive |
| Suitability | Suitable for real-time systems with predictable execution times | Suitable for batch systems with unpredictable execution times |
Note that the exact performance and behavior of the SJF and LJF algorithms can vary based on the specific implementation and the workload being scheduled. Both algorithms have their own strengths and weaknesses and the choice between them depends on the requirements and constraints of the specific operating system.
