How do you compare two floorplans without cherry-picking metrics?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Use one scorecard with declared definitions and identical methods for area/utilisation, usable rows, macro legality, channels, pins, congestion, PG reservation, voltage areas, early timing, and change risk.
Technical Explanation
A fair comparison fixes the measuring stick before seeing the winner. Mark hard stops separately from quality risks. Record measurement settings, evidence links, owners, and sensitivity to expected design growth.
Formula Or Decision Rule
Decision rule: reject hard stops, then choose the lower owned risk across project priorities.
What To Check
• Warning sign: Each advocate reports only the metric their option wins. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Recompute the full scorecard and require explanations for every material delta.
Command Checks & Actions
• report_design -floorplan: reports the floorplan state understood by the tool
• report_congestion -mode summary: reports routing demand, capacity, overflow, or hot spots
• estimate_timing: performs early virtual timing estimation
• report_timing: reports timing paths in the active analysis context
Run only the commands needed for this question. Save the report with the floorplan version and analysis context.Healthy, Suspicious & Hard-stop Results
• Healthy: Use one scorecard with declared definitions and identical methods for area/utilisation, usable rows, macro legality, channels, pins, congestion, PG reservation, voltage areas, early timing, and change risk. • Suspicious: Each advocate reports only the metric their option wins. • Hard stop: required legality or physical feasibility is missing or unexplained. Recompute the full scorecard and require explanations for every material delta.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. Each advocate reports only the metric their option wins.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How do you compare two floorplans without cherry-picking metrics?” to measurable physical evidence and an owned correction.
Follow-up Question & Model Response
Follow-up probe: What would make you change your decision? Model response: “I would change it if the same controlled rerun shows that each advocate reports only the metric their option wins. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: Each advocate reports only the metric their option wins. Corrective path: Recompute the full scorecard and require explanations for every material delta.
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