Phase 4 — Verification framework + material drivers + report generation #36

Part of the NumSim compiler epic: #28.

Summary

Every generated material must be verifiable on its own; the project must produce human-readable documentation of what was generated.

Scope

4.1 — TangentCheckPass

• Generates a small driver per recipe
• Compares algorithmic tangent (from Phase 3b) against forward-FD (σ(ε+h) − σ(ε))/h
• Per-region tolerance scheme (per the plan):
  • Tight (1e-6) on smooth regimes
  • Looser through elastic-plastic transitions, kinematic-hardening reverse loading, multi-surface corners
• Runs in CI on the entire golden recipe set
• Failure breaks the build

4.2 — Material drivers

A small library of standard load paths (tests/drivers/ or own lib):

• Uniaxial tension / compression
• Simple shear
• Plane stress / plane strain
• Biaxial loading
• Cyclic loading

Each takes a generated compute() function and produces (ε, σ, internal variables) traces. Used by verification and reports.

4.3 — Report generator

A pass that consumes the verified IR + driver results and emits:

• HTML (MathJax for equations, embedded plots)
• PDF (LaTeX path)
• Markdown (lightweight)

Report contents per the spec § 23: model metadata, rendered equations, state variables table, tangent verification results, driver plots, generated targets summary.

Acceptance

• TangentCheckPass runs in CI; every golden recipe passes
• Driver suite is wired into the standalone backend
• Report renders cleanly for J2 + NeoHookean + Drucker-Prager
• Edge-case loading paths (transition, reverse, multi-surface corner) are explicitly in the verification matrix

Files affected

• New: include/numsim_codegen/passes/TangentCheckPass.h
• New: tests/drivers/ library
• New: include/numsim_codegen/passes/ReportPass.h
• New: templates/report/ (HTML/MD/LaTeX templates)

Dependencies

• Phase 3b (algorithmic tangent must exist before it can be verified)