Formal Verification · All levels

Combinational LEC: Key-Point Matching and Structural Normalization: Worked Example

Worked Example for Combinational LEC: Key-Point Matching and Structural Normalization.

Worked example

Worked Example for Combinational LEC: Key-Point Matching and Structural Normalization is anchored on non-vacuous closure rate, counterexample turnaround, and residual-risk trend by requirement class. Convert outcomes into assumption-aware, evidence-backed actions.

A regression appears in non-vacuous closure rate, counterexample turnaround, and residual-risk trend by requirement class. Strong closure isolates first divergence, proves mechanism, applies one reversible fix, and validates blast radius before signoff.

Execution lens

diagram

FORMAL EXECUTION FLOW - Combinational LEC: Key-Point Matching and Structural Normalization

requirement intent and risk class
      |
      v
property and assumption modeling
      |
      v
proof engine exploration and trace extraction
      |
      v
counterexample classification and fix hypothesis
      |
      v
re-proof, coverage audit, and signoff decision

Decision matrix

diagram

EVIDENCE MATRIX - Combinational LEC: Key-Point Matching and Structural Normalization

+-----------------------------+--------------------------------+--------------------------------+---------------------------+
| Evidence                    | Tells you                      | Does not prove                 | Next action               |
+-----------------------------+--------------------------------+--------------------------------+---------------------------+
| property status by class    | closure shape by requirement   | model realism                  | pair with cover reachability |
| vacuity and trigger checks  | assertion meaningfulness       | full legal-path exploration    | inspect assumptions       |
| counterexample traces       | concrete divergence path       | complete bug-space closure     | classify and replay       |
| assumption audit trail      | model boundary confidence      | implementation correctness     | review spec traceability  |
| before/after trend packet   | mitigation movement quality    | long-window stability          | run broader matrix        |
+-----------------------------+--------------------------------+--------------------------------+---------------------------+

Formal deep dive

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

Concept diagram

diagram

EQUIVALENCE WORKFLOW

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

Metric graph

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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.

Worked-example reasoning

Start from requirement intent and map every trace event back to modeled obligations.

Close with smallest fix that preserves legal scenario reachability.

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