5.9 Performance Considerations

Different numeric types in Rust come with distinct performance trade-offs:

  • i32/u32: Often optimal on both 32-bit and 64-bit CPUs; i32 is Rust’s default.
  • i64/u64: Generally efficient on 64-bit architectures but potentially heavier on 32-bit ones.
  • i128/u128: Not natively supported on most CPUs; the compiler typically emits multiple instructions for 128-bit arithmetic, making it slower than 64-bit arithmetic.
  • f64: Often faster than f32 on modern hardware due to double-precision support.
  • Smaller types (i8, i16): Can save space in large arrays or embedded contexts but may introduce extra overhead for overflow checks or upcasting.

For large datasets, using smaller numeric types may improve cache efficiency, but you should balance that against overflow risks and the cost of additional conversions. Rust can also leverage SIMD instructions and concurrency in a safe manner, so paying attention to data alignment, cache usage, and avoiding unnecessary type conversions can yield performance gains.