FlatTape

A recorded tape copied into flat parallel arrays, once, at compile time.

Every host engine walks the same tape millions of times. Calling op(int) and friends per node per scenario costs a bounds check and a field load that no amount of JIT will hoist out of the scenario loop, so each engine used to flatten the tape into its own set of arrays in its own constructor. This is that copy, written once.

Fields are final arrays rather than accessors deliberately: the sweeps read them in their innermost loop, and a plain array read is what C2 turns into a single load.

Public only so the engine modules can use it; not part of the supported API.