Glossary · System coordination, integration and orchestration
Shortest processing time (SPT)
Also known as: SPT rule, Shortest job first
German: Kürzeste Bearbeitungszeit (SPT)
In production scheduling, shortest processing time (SPT) is a priority rule that always selects, from the jobs waiting at a resource, the job with the shortest processing time; on a single resource it minimizes average flow time and the average number of waiting jobs.
- System integration
In one sentence
Shortest processing time (SPT) is a priority rule that selects the waiting job with the shortest processing time next.
Example
At a test bench, the dispatcher applies SPT: a two-minute function test runs before a twenty-minute endurance test that arrived earlier.
How it applies
- Planning: SPT is simple and effective for reducing average waiting and work in progress. Its weakness is that long jobs can wait indefinitely when short jobs keep arriving, and due dates are ignored.
- Engineering: In practice, SPT is combined with other criteria, such as due dates or a maximum waiting time, to prevent long jobs from being starved.
- Operation: Planners and operators should know which rule is active, so the order of jobs is understandable; unexplained reordering creates mistrust.
- Documentation: State the rule and any modifications in the dispatching documentation, including how operators can override it for urgent jobs.
SPT vs. earliest due date (EDD)
SPT minimizes average flow time; earliest due date minimizes maximum lateness. Which one fits depends on whether throughput and low work in progress or delivery reliability matters more.