Process Scheduler Simulation

Building a preemptive scheduler with aging in Python

This is a hard coding problem that tests your ability to simulate a realistic operating-system scheduler. It combines discrete-event thinking, priority queue management, and careful state tracking — all under tight specification. Firms like DE Shaw care deeply about scheduler behaviour because jitter in thread scheduling directly impacts latency-sensitive trading systems.

The core challenge is managing preemption correctly. You must detect when a newly arrived or aged process has better priority than the currently running one, interrupt it mid-burst, and swap in the new process. At the same time, you need to track when aging occurs (at fixed time boundaries), apply it only to waiting processes, and re-evaluate scheduling immediately after. Edge cases include tie-breaking by arrival time and PID, handling processes that arrive simultaneously, and ensuring that priority never goes below zero.

• Discrete-event simulation and timeline management
• Priority-based scheduling with preemption logic
• State transitions (ready, running, waiting) and process lifecycle
• Correct application of aging to waiting processes only
• Tie-breaking rules and deterministic ordering