Dane Sabo 9fc4afb611 julia-port: parallel plant model; sanity sim matches MATLAB, reach is stub
Port pke_params, pke_th_rhs, pke_linearize, and all five controllers
to Julia. sim_sanity.jl reproduces the MATLAB main.m operation-mode
scenario (100%->80% Q_sg step) and matches final state to 3 decimals
across n, T_f, T_avg, T_cold, u.

reach_operation.jl is a stub: ReachabilityAnalysis.jl (LGG09, GLGM06,
BFFPSV18) numerically explodes on the raw stiff system — envelopes of
1e14 K to 1e37 K instead of the known-tight 0.03 K. Almost certainly
a state-scaling issue: precursors C_i ~ 1e5, temperatures ~ 300,
eigvals span 5000x. Diagonal scaling + retry is planned; left for the
next pass since the hand-rolled MATLAB reach already discharges the
operation-mode obligation.

Project.toml pins OrdinaryDiffEq >= 6.111 (the one that precompiled
cleanly on first instantiate). Manifest gitignored.

Hacker-Split: Julia path open, reach side needs a scaling pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-04-17 12:52:57 -04:00

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# Julia port
Parallel implementation of the plant model (`../plant-model/`) in Julia,
intended as an eventual landing spot for reachability if we outgrow the
MATLAB / hand-rolled tooling.
## Status
- `src/pke_params.jl`, `src/pke_th_rhs.jl`, `src/pke_linearize.jl`
functional, match MATLAB term-for-term.
- `controllers/controllers.jl` — all five modes ported
(null, shutdown, heatup, operation, scram). LQR factory included via
MatrixEquations.jl.
- `scripts/sim_sanity.jl` — closed-loop simulation matches MATLAB to 3
decimals on the 100% → 80% `Q_sg` step. ✅ passing.
- `scripts/reach_operation.jl` — ❌ stub. ReachabilityAnalysis.jl
algorithms blow up on this stiff, badly-conditioned system. See the
file header for diagnosis and planned fix (state rescaling).
## When to prefer Julia over MATLAB
Today: nowhere. The sanity path exists so we don't regret the eventual
port.
Once the reach scaling is resolved:
- Nonlinear reach for the P controller in operation mode (CORA /
JuliaReach territory where MATLAB's linearization doesn't suffice).
- Heatup reach with its time-varying reference.
- Parametric studies where MATLAB license fees / CI friction matter.
## Running
```bash
cd julia-port
julia --project=. -e 'using Pkg; Pkg.instantiate()'
julia --project=. scripts/sim_sanity.jl
```
First run will precompile the dependency stack (OrdinaryDiffEq,
ReachabilityAnalysis, LazySets — a few minutes).