[rookie]

My guess it is all of the string converting back and forth to character arrays.

[rookie]

Yep, replaced string with Int array and now it is much faster.

https://gist.github.com/rookie/3d9a848c6fefacc4254da921da79b...

It now runs faster (when compiled, optimized) than the python code.

    xcrun -sdk macosx swiftc -O gen.swift

[nicky0]

Ooh yeah, 0m0.363s for 1000 iterations on mine. So the slowness was in the string manipulation and character conversion operations.

[SOLAR_FIELDS]

I've learned from years of working on making code more performant that the biggest code smells to look at first are string operations.