Implement thread parallelism

[jlogan03]

0.10.0 2026-01-10

Added

• Rust
  • Add top-level interpn, interpn_alloc and interpn_serial methods along with supporting enums for selecting methods
  • Add par feature, enabled by default, that enables parallelism with rayon in interpn function

Changed

• Rust
  • Update deps
• Python
  • !Refactor interpn function
    • Combine check_bounds: bool and bounds_check_atol: float to check_bounds_with_atol: float | None
    • Replace assume_regular input with optional grid_kind to allow assuming either regular or rectilinear, or making no assumption
    • Add max_threads: int | None input to allow manually limiting parallelism
    • Use rust top-level interpn function as backend for method selection, bounds checks, and parallelism

[jlogan03]

@neutrinoceros I recall you had tried threading at the python level and didn't see any benefit. This update adds threading to the backend for the interpn convenience function, and has some heuristics that should almost-always prevent it from being slower than single-threaded.

Example case that roughly reflects a 10-megapixel image shows nearly linear speedup for all interpolant and grid kinds:

[neutrinoceros]

Thanks for the ping ! This is pretty exciting to hear, I'll drop you a line whatever the impact I see in my applications !