# 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).