ORIGINAL COMPANY-CONTEXT PRACTICE
Evaluate a chamber-scheduling policy with a transparent simulation
Original practice scenario: A hypothetical wafer-processing tool has several chambers, setup times and product restrictions. A team claims a scheduling change improves throughput. Design an evaluation before assuming the simulation is trustworthy.
Written for independent practice using company context; this is not a verified question from a company interview.
A REASONED APPROACH
Model answer.
Validate the simulation's representation before comparing policies. Throughput gains can arise from omitted setup, downtime or eligibility constraints rather than a genuinely better schedule.
Work through it
- Define lots, processing stages, chamber capabilities and setup transitions, checking conservation of work-in-progress and resource occupancy on small hand-worked cases.
- Calibrate timing inputs from appropriate evidence and replay a held-out workload, comparing queue lengths, completion times and bottlenecks with observed or independently specified behavior.
- Run policies under identical demand and random seeds where appropriate, varying uncertain inputs and reporting tail delays and starvation alongside throughput.
Tradeoffs to discuss
- Detailed simulation improves realism but requires more uncertain parameters; a simpler model is easier to audit while omitting interactions.
Common pitfalls
- Do not let a policy select a chamber that the product cannot use.
- A simulation comparison is conditional evidence and does not authorize real equipment control.