What is Shortest-Job-First (SJF) Scheduling  

Other name of this algorithm is Shortest-Process-Next (SPN).

Shortest-Job-First (SJF) is a non-preemptive discipline in which waiting job (or process) with the smallest estimated run-time-to-completion is run next. In other words, when CPU is available, it is assigned to the process that has smallest next CPU burst.

The SJF scheduling is especially appropriate for batch jobs for which the run times are known in advance. Since the SJF scheduling algorithm gives the minimum average time for a given set of processes, it is probably optimal.

The SJF algorithm favors short jobs (or processors) at the expense of longer ones.

The obvious problem with SJF scheme is that it requires precise knowledge of how long a job or process will run, and this information is not usually available.

The best SJF algorithm can do is to rely on user estimates of run times.

In the production environment where the same jobs run regularly, it may be possible to provide reasonable estimate of run time, based on the past performance of the process. But in the development environment users rarely know how their program will execute.

Like FCFS, SJF is non preemptive therefore, it is not useful in timesharing environment in which reasonable response time must be guaranteed.
http://www.person al.kent.edu/~rmuhamma/OpSystem s/Myos/sjfSchedule.htm

Answered by Nishu's , an ibibo Master, at 4:01 PM on October 29, 2008

In Data-processing, SJF is the acronym of Shortest Job First (“shorter process in first”). It indicates a method of scheduling process.

It is about a algorithm of scheduling, i.e. of a algorithm being used to choose which several processes will be treated in first by the Processeur. The choice is done according to the execution time estimated of the process. Thus, the ordonnancor will let pass initially shortest from the processes of the queue.

There exist two versions of this algorithm: a préemptive version , and a nonpréemptive version. In the latter, a process having taken control of CPU leaves it only once the finished gust.

The préemptive version, so called SRIF , Shortest Remaining Time First (“shorter time remaining in first”), is more flexible. If a process whose execution time is shorter than the remainder of the execution time of the process in the course of treatment enters the queue, then it will take its place. There is then a commutation of context, and the treatment of the stopped process will begin again later there or it had been left.

SJF proves one of the most profitable algorithms with regard to the reduction of the time spent in the queue of the processes. However it is seldom used in-outside specialized environments, because it on standby requires a precise evaluation of the execution time of all the processes of treatment.

Answered by Sanjeev , an ibibo Advisor, at 3:41 PM on October 28, 2008

Well Ashish! Shortest-Job-First (SJF) is a non-preemptive discipline in which waiting job (or process) with the smallest estimated run-time-to-completion is run next. In other words, when CPU is available, it is assigned to the process that has smallest next CPU burst.

Other name of this algorithm is Shortest-Process-Next (SPN).

The SJF scheduling is especially appropriate for batch jobs for which the run times are known in advance. Since the SJF scheduling algorithm gives the minimum average time for a given set of processes, it is probably optimal.

The SJF algorithm favors short jobs (or processors) at the expense of longer ones.

The obvious problem with SJF scheme is that it requires precise knowledge of how long a job or process will run, and this information is not usually available.

The best SJF algorithm can do is to rely on user estimates of run times.

In the production environment where the same jobs run regularly, it may be possible to provide reasonable estimate of run time, based on the past performance of the process. But in the development environment users rarely know how their program will execute.

Like FCFS, SJF is non preemptive therefore, it is not useful in timesharing environment in which reasonable response time must be guaranteed.

http://www.personal. kent.edu/~rmuhamma/OpSystems/Myos/s jfSchedule.htm

Answered by Kumaar , an ibibo Master, at 2:46 PM on October 28, 2008

Shortest-Job-First (SJF) is a non-preemptive discipline in which waiting job (or process) with the smallest estimated run-time-to-completion is run next. In other words, when CPU is available, it is assigned to the process that has smallest next CPU burst.

The SJF scheduling is especially appropriate for batch jobs for which the run times are known in advance. Since the SJF scheduling algorithm gives the minimum average time for a given set of processes, it is probably optimal.

The SJF algorithm favors short jobs (or processors) at the expense of longer ones.

The obvious problem with SJF scheme is that it requires precise knowledge of how long a job or process will run, and this information is not usually available.

The best SJF algorithm can do is to rely on user estimates of run times.

Answered by NIVEDITA , an ibibo Master, at 12:40 PM on October 28, 2008

Other name of this algorithm is Shortest-Process-Next (SPN).

Shortest-Job-First (SJF) is a non-preemptive discipline in which waiting job (or process) with the smallest estimated run-time-to-completion is run next. In other words, when CPU is available, it is assigned to the process that has smallest next CPU burst.

The SJF scheduling is especially appropriate for batch jobs for which the run times are known in advance. Since the SJF scheduling algorithm gives the minimum average time for a given set of processes, it is probably optimal.

The SJF algorithm favors short jobs (or processors) at the expense of longer ones.

The obvious problem with SJF scheme is that it requires precise knowledge of how long a job or process will run, and this information is not usually available.

The best SJF algorithm can do is to rely on user estimates of run times.

In the production environment where the same jobs run regularly, it may be possible to provide reasonable estimate of run time, based on the past performance of the process. But in the development environment users rarely know how their program will execute.

Like FCFS, SJF is non preemptive therefore, it is not useful in timesharing environment in which reasonable response time must be guaranteed.

Answered by jaivir , an ibibo Master, at 9:10 AM on October 28, 2008