The Swift compiler swiftc provides options such as -O, -Osize, and -Ounchecked to build code with optimizations turned on. Use optimizations such as -Osize to target small code size and the -Ounchecked to remove runtime safety checks.
The example below creates an array of size n that contains random numbers in the range from 1 to 10. The sum of the array is calculated then information about the result is printed to the screen.
// main.swift
let n = 2_000_000
let x = (1...n).map { _ in Float.random(in: 1...10) }
let s = x.reduce(0, +)
print("first item \(x[0])")
print("last item \(x[n-1])")
print("sum \(s)")
Compiling without optimizations and timing the code execution is shown below. The execution time is 1.84 seconds on a 2019 MacBook Pro with a 2.6 GHz Intel CPU and 32 GB of RAM.
swiftc main.swift
time ./main
Compiling with optimizations and timing the code execution is shown below. The execution time is 0.26 seconds. The code executes about 7 times faster when it is compiled with optimizations.
swiftc main.swift -Ounchecked -o main_opt
time ./main_opt
Gavin Wiggins © 2024