SJF or Shortest Job First is the optimal algorithm for process scheduling but it can be beaten by First come First serve in the following scenarios -
- When all processes have equal burst times. In this case unnecessary time will be wasted by SJF sorting algorithm. Hence, it will lead to more overhead.
- When all inputs are already sorted in ascending order. This again follows from the complexity of sorting algorithm.
- Another possibility could arise when α isn't balanced between τ and t. This will lead to wrong predictions for the next process.