If by parallel you mean across multiple threads in some map-reduce algorithm, the compiler will not do that automatically since that would be both extremely surprising behavior and in most cases, would make performance worse (it'd be interesting to see just how many shapes you'd need to iterate over before you start seeing performance benefits from map-reduce). If you're referring to vectorization, then the Rust compiler does automatically do that in some cases, and I imagine it depends on how the area is calculated and whether the implementation can be inlined.