Code Review

Purpose

Review code for correctness, performance, and maintainability with attention to the specific concerns of scientific/numerical Julia code.

Review Checklist

Correctness

• Logic is correct and handles edge cases (singularities, zero vectors, degenerate orbits)
• Numerical stability: no catastrophic cancellation, overflow, or division by near-zero
• Units are consistent (km, km/s, radians) and conversions are correct
• Frame conventions are respected (J2000 ECI, ECEF, body-fixed)
• Mathematical formulation matches cited reference (paper, textbook)

Performance

• Hot-path functions return SVector/SMatrix, not heap-allocated arrays
• No unnecessary allocations (verify with @check_allocs or @allocated)
• @inline on performance-critical functions
• No type instabilities (@code_warntype clean)
• Promotion via promote_type rather than implicit conversion

AD Compatibility

• No mutation of arrays that AD needs to track (return new values instead)
• No branching on floating-point values in differentiable paths
• Uses promote_type(T, V) for mixed numeric types
• Safe handling of norm-near-zero (no NaN gradients)
• Tested with ForwardDiff at minimum; ideally multiple backends

Style & Maintainability

• using/import only in module file or runtests.jl, not in include-d files
• export at the top of the file where symbols are defined
• Packages added via Pkg.jl, not by editing Project.toml directly
• Docstrings with # Arguments, # Returns, # References
• Functions are focused (single responsibility)
• Consistent naming: PascalCase types, snake_case functions, Unicode for physics

Testing

• Correctness tests against known reference values
• Edge cases tested (circular, equatorial, hyperbolic, near-singularity)
• AD tests comparing against FiniteDiff
• Allocation tests on hot-path functions

Feedback Format

Categorize each finding:

• Critical: Must fix -- correctness bug, numerical instability, or silent wrong answer
• Performance: Allocation, type instability, or avoidable overhead
• Suggestion: Improvement to clarity, style, or maintainability
• Nitpick: Minor style preference, optional

For each finding, provide:

1. The specific location (file and line)
2. What the issue is
3. A concrete fix or alternative