Swiftier Swift, Swiftly

Everybody wants their Swift programs to run swiftier, right? In case you haven’t stumbled across it so far, The Canonical List Of Recommended Ways To Do That is found right in the Swift github repo:

Writing High-Performance Swift Code

So you should go read that at the first opportunity and keep an eye on edits too!

Follow that up with this excellently accessible talk:

Real World Swift Performance

Lots of things can make your application slow. In this talk we’re going to explore application performance from the bottom. Looking at the real world performance impact of Swift features (Protocols, Generics, Structs, and Classes) in the context of data parsing, mapping, and persistence, we will identify the key bottlenecks as well as the performance gains that Swift gives us…

Here’s a couple more illuminating posts on instruction level speediness:

Unowned or Weak? Lifetime and Performance

os_unfair_lock is the new synchronization hotness!

Mind you, it’s quite likely that for many of you the most compelling thing that springs to mind on reading the headline there is not swiftier execution, but swiftier compilation, amirite? Here’s some backgrounders and tips on that:

Profiling your Swift compilation times

Guarding Against Long Compiles

Speeding Up Slow Swift Build Times

Regarding Swift build time optimizations

After I read @nickoneill’s excellent post Speeding Up Slow Swift Build Times last week, it’s hard not to look at Swift code in a slightly different light. A single line of what could be considered clean code now raises a new question — should it be refactored to 9 lines to please the compiler? (see the nil coalescing operator example further down) What is more important? Concise code or compiler friendly code? Well, it depends on project size and developer frustration.

Before getting to some examples, let me first mention that going through log files manually is very time consuming. Someone came up with a terminal command to make it easier but I took it a step further and threw together an Xcode plugin

Also check out Swift build time optimizations — Part 2 for followup.

And you’re probably vaguely aware that XCTest does performance these days but haven’t adopted it wholeheartedly yet, right? Check out

measure(): How to optimize our slow code and adjust the baseline

XCTest makes performance testing extraordinarily easy: you give it a closure to run, and it will execute that code 10 times in a row. You’ll then get a report back of how long the call took on average, what the standard deviation was (how much variance there was between runs), and even how fast each of those 10 runs performed if you want the details…

Kinda handy to be able to get hard numbers for your refactoring efforts that easily, indeed.

Any other compilation or execution tips, tricks, and tradeoffs to share, Dear Readers?


Improving Swift compile times

Swift one-line type-checking lasting 27s

How we cut our iOS app’s launch time in half (with this one cool trick)

A record-breaking story of boosting the launch time of Mail.Ru’s email app for iOS

Swift Performance

Alex | December 11, 2016

Leave a Reply