Timing becomes clean after a broad false path. What is the correct response?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Assume the improvement is unproven until exact membership and functional justification show that only impossible paths were removed.
Technical Explanation
Treat this as a readiness check. It should produce named objects and a result that another engineer can repeat from the same handoff.
What To Check
• Warning sign: WNS improves dramatically and path counts collapse after a wildcard exception. • Inspect: Keep at least two possible causes open, then use one named object and the active mode or scenario to separate them. • Correct: Report the exception and ignored/dominant interactions, narrow it with the STA owner, and restore analysis of valid paths.
Command Checks & Actions
• report_exceptions: shows timing exceptions and their scope
• report_exceptions -ignored: shows timing exceptions and their scope
• report_timing: shows a path and its timing calculation
Run the commands in order. Each line answers a separate part of the check.Healthy, Suspicious & Hard-stop Results
• Expected: Assume the improvement is unproven until exact membership and functional justification show that only impossible paths were removed. • Investigate: WNS improves dramatically and path counts collapse after a wildcard exception. • Stop before floorplanning when required logic or timing coverage is missing or unexplained. Report the exception and ignored/dominant interactions, narrow it with the STA owner, and restore analysis of valid paths.
Common Mistake
Do not assume the check passed just because ICC2 continued: WNS improves dramatically and path counts collapse after a wildcard exception. Fix or narrowly justify the named objects, then rerun the same command.
What The Interviewer Is Testing
Be ready to explain why this matters before floorplanning: WNS improves dramatically and path counts collapse after a wildcard exception.
Follow-up Question & Model Response
Model response: “I would save the report, inspect one affected object in the correct block and scenario, and make or request this correction: Report the exception and ignored/dominant interactions, narrow it with the STA owner, and restore analysis of valid paths. Then I would reopen the clean checkpoint and rerun the same evidence.”
Practical Example
Symptom: WNS improves dramatically and path counts collapse after a wildcard exception. Corrective path: Report the exception and ignored/dominant interactions, narrow it with the STA owner, and restore analysis of valid paths.
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