Part of the NumSim compiler epic: #28.
Summary
Lower the Material IR's time-evolving + LNS structure into concrete generated code: replace Dt(α) = f(...) with a discrete time-stepping rule (Backward Euler default) and emit a Newton iteration loop that solves the resulting algebraic system at each call.
Scope
3a.1 — TimeIntegrationPass
- Schemes:
BackwardEuler (default), ForwardEuler, BDF2
- Lowers
Dt(α) = f(α, ε) → (α_new − α_old)/dt − f(α_new, ε) = 0 using CAS's existing substitute()
- Adds
α_new and α_old as IR state-variable nodes if not already present
3a.2 — LocalNewtonLoweringPass
- Builds residual vector
R(x, ε) from each LocalNewtonSystem's residual list
- Computes
∂R/∂x symbolically via existing tensor_differentiation
- Emits a Newton iteration loop with:
- Configurable convergence tolerance + max iterations
- Residual-norm criterion (energy norm later)
- Divergence detection (NaN check, residual growth)
- Non-singular-Jacobian fallback (minor diagonal regularisation)
- Line search: none initially (flagged for follow-up; see plan)
Acceptance
- J2 plasticity recipe with
StateVariable ε_p lowers through TimeIntegrationPass + LocalNewtonLoweringPass to produce a working stress update
- At uniaxial tension, matches an analytic reference for σ within 1e-6
- The 1D spike from Phase 1.3 is now production code (no longer throwaway)
Files affected
- New:
include/numsim_codegen/passes/TimeIntegrationPass.h
- New:
include/numsim_codegen/passes/LocalNewtonLoweringPass.h
- Test recipes:
tests/goldens/J2PlasticityFull.cpp
Dependencies
- Phase 2 (Material IR with
StateVariable, Dt, LocalNewtonSystem)
Part of the NumSim compiler epic: #28.
Summary
Lower the Material IR's time-evolving + LNS structure into concrete generated code: replace
Dt(α) = f(...)with a discrete time-stepping rule (Backward Euler default) and emit a Newton iteration loop that solves the resulting algebraic system at each call.Scope
3a.1 — TimeIntegrationPass
BackwardEuler(default),ForwardEuler,BDF2Dt(α) = f(α, ε)→(α_new − α_old)/dt − f(α_new, ε) = 0using CAS's existingsubstitute()α_newandα_oldas IR state-variable nodes if not already present3a.2 — LocalNewtonLoweringPass
R(x, ε)from eachLocalNewtonSystem's residual list∂R/∂xsymbolically via existingtensor_differentiationAcceptance
StateVariable ε_plowers throughTimeIntegrationPass + LocalNewtonLoweringPassto produce a working stress updateFiles affected
include/numsim_codegen/passes/TimeIntegrationPass.hinclude/numsim_codegen/passes/LocalNewtonLoweringPass.htests/goldens/J2PlasticityFull.cppDependencies
StateVariable,Dt,LocalNewtonSystem)