Combinational LEC: Key-Point Matching and Structural Normalization: Design Space

Design space exploration

For Combinational LEC: Key-Point Matching and Structural Normalization, teams balance model realism, convergence, and signoff risk.

Option A - conservative

• Conservative modeling: helps high soundness

• Risk: slower closure

• Validate with: high-risk interfaces

Option B - balanced

• Balanced setup: helps good throughput

• Risk: needs strict review

• Validate with: daily CI operations

Option C - aggressive

• Aggressive abstraction: helps runtime reduction

• Risk: higher misuse risk

• Validate with: expert-owned proof clusters

Option D - refactor

• Refactor properties: helps better debug isolation

• Risk: initial migration cost

• Validate with: stalled convergence buckets

DESIGN SPACE - Combinational LEC: Key-Point Matching and Structural Normalization
model realism <-> convergence speed <-> debug clarity <-> signoff confidence

Design pitfalls

• Trading away legal behavior for runtime without documenting risk.

• Combining abstraction and assumption changes in one uncontrolled step.

Formal deep dive

Equivalence confidence comes from transformation-aware setup and rapid first-divergence diagnosis.

Concept diagram

EQUIVALENCE WORKFLOW

golden and revised design -> mapping and alignment -> mismatch triage -> closure evidence

Metric graph

LEC/SEC DEBUG SIGNALS

setup mismatches        █████
real behavioral deltas  ███
resolved divergences    ███████

Metrics and artifacts to collect

• compare-point match quality

• SEC latency-alignment success

• RTL-to-gate variant coverage

• ECO mismatch root-cause aging

Mini case study

A late ECO mismatch was traced to clock-gating setup, then closed with repeatable SEC alignment rules.

Debug branches

• Classify mismatch source before editing waiver sets.

• Use SEC when latency movement is intentional.

• Replay first divergence in simulation for cross-validation.

Senior review question

Ask: which requirement intent is proven, under which assumptions, and what residual risk remains?

Key takeaways

• Tie each proof claim to assumption boundaries and reachability evidence.

• Prefer minimal reversible fixes and preserve legal behavior visibility.

Common pitfalls

• Treating runtime reduction as proof-quality improvement without audits.

• Declaring closure while critical covers remain unreachable.

• Using broad waivers instead of first-divergence root-cause ownership.

Principal formal review addendum

Combinational LEC: Key-Point Matching and Structural Normalization should be reviewed as a requirement-evidence workflow, not a single status report.

Use non-vacuous closure rate, counterexample turnaround time, and requirement-level residual risk trend as the monitoring lens and formal closure packet: assumptions audit, proof status matrix, counterexample classification, and requirement traceability as closure proof.

Equivalence closure quality depends on transformation-aware setup and first-divergence debug discipline. Strong teams preserve legal reachability while improving convergence.