Rayon for data parallelism with par_iter

Rayon makes data parallelism trivial: replace .iter() with .par_iter(), and your loop runs in parallel across all CPU cores. It uses a work-stealing scheduler to balance load automatically. I use rayon for CPU-bound tasks like image processing, data transformations, or batch computations. The API mirrors standard iterators (.map(), .filter(), .reduce()), so it's easy to adopt. Rayon handles thread pools internally, so you don't manage threads manually. The key is ensuring your closure is Send and doesn't have shared mutable state (use atomics or reduction). For embarrassingly parallel workloads, rayon can give near-linear speedups. It's one of the easiest wins for performance in Rust.