[tarentel]

That's true between a debug build and just running it as a script I believe. But a release version will be optimized, I imagine if they compared a debug build to the scripted version they'd perform similarly.

[nicky0]

Can confirm, Debug build runs in similar time to script.

[Someone]

Difference is that Release builds do whole-module optimization in Swift 3.

That allows for more aggressive code specialization and inlining and can remove more reference count updates (https://swift.org/blog/whole-module-optimizations/)