shortest processing time

**Shortest processing time** is the **dispatch rule that prioritizes jobs with the smallest operation time to reduce average queue and flow time** - it is effective for throughput velocity but can starve long jobs. **What Is Shortest processing time?** - **Definition**: Scheduling policy that selects the lot with minimal estimated processing duration. - **Primary Objective**: Minimize average waiting and completion time across queued jobs. - **Operational Character**: Increases number of completed jobs per interval under stable conditions. - **Known Limitation**: Long-duration lots may wait excessively without fairness controls. **Why Shortest processing time Matters** - **Queue Reduction**: Quickly clears many short operations, lowering average congestion. - **Cycle-Time Benefit**: Often improves mean flow time in high-mix dispatch environments. - **Throughput Efficiency**: Raises apparent movement rate at bottleneck resources. - **Tradeoff Awareness**: Can worsen tail latency and due-date misses for long jobs. - **Policy Design Value**: Useful component in hybrid multi-objective dispatch schemes. **How It Is Used in Practice** - **Eligibility Filtering**: Apply SPT within constraint-compliant candidate sets. - **Fairness Safeguards**: Add aging penalties or max-wait constraints to prevent starvation. - **Scenario Tuning**: Use simulation to determine where SPT improves or harms business metrics. Shortest processing time is **a strong queue-efficiency heuristic with known fairness risks** - combining it with guardrails can preserve speed benefits while avoiding excessive delay for long operations.