ReNunney/docs/TRACK2_RUST.md

Track 2 Rust Plan

Updated: 2026-04-11

Purpose

This note defines the initial Rust entry point for Track 2 in renunney.

Track 2 is not a line-by-line translation of Nunney's published threshold heuristic. It is the modern path: explicit threshold definitions, clearer simulation contracts, and a performant kernel.

Why Rust

Rust is the preferred Track 2 kernel language because it directly addresses the main engineering problems revealed by Track 1:

• heavy repeated stochastic simulation,
• threshold sweeps over many independent jobs,
• need for clear data structures and reproducible binaries,
• and a likely future need for Python bindings or service backends.

Initial Scope

The first Rust step is intentionally narrow:

• create a Rust workspace,
• define a Track 2 core crate,
• and encode threshold-centered abstractions rather than immediately porting the entire biological simulator.

This is the correct order because Track 2 should start from a clean statement of what is being estimated.

Current Crate

The initial crate is:

• rust/track2-core

Current contents:

• ExtinctionCount
• ThresholdPoint
• ThresholdBracket
• ThresholdEstimate
• bracket_threshold(...)
• midpoint_threshold(...)

These are placeholders for a modern threshold-estimation path where:

• extinction probability is explicit,
• bracketing is explicit,
• and the estimator is separate from the simulation kernel.

Next Rust Steps

1. Add a simulation-state model for Track 2.
2. Add a trait or function contract for producing extinction probabilities from repeated stochastic runs.
3. Add a threshold search strategy that consumes those estimates.
4. Add serialization-friendly input/output structs for orchestration.
5. Only then start porting heavy simulation loops from Python.

Operational Targets

The repo Makefile should treat Rust as a first-class build/test surface:

• make rust-test
• make rust-check

That keeps Track 2 visible in daily workflow from the start.