Yes, your Godot game runs faster with static types

🔗 Wednesday, 14 February 2024 • Cariad Eccleston • @cariad@gamedev.lgbt

Static typing is one of the easiest and most rewarding disciplines you can add to your game development.

GDScript is a dynamically-typed language. A GDScript variable’s type can change from line to line.

For example, here’s a variable that starts with a string, then gets a floating-point number, and ends up with a vector:

var a = "hello"
a = 1.2
a = Vector2.ZERO

That’s entirely valid GDScript, and it’ll happily do what you’re asking it to do.

But you can–and I’d argue that you should–use static types.

Here, I’m telling GDScript that I want a variable to be statically, unchangingly, unwaveringly and for evermore typed as a string:

var a: String = "hello"

With that type annotation in place, GDScript won’t let me assign a floating-point number, and I’ll get a warning in the Godot Editor as soon as I type it:

var a: String = "hello"
a = 1.2  # ERROR: Cannot assign a value of type "float" as "String".

Now, look: I think static typing is a Good Thing™ for consistency, readability and maintainability – but that’s just, like, my opinion, man.

But did you know static typing improves your code’s performance?

Performance

Here are a couple of loops that increment a couple of variables. One’s dynamically-typed, and the other is statically-typed as an integer:

const ITERATIONS: int = 1000000000

var _untyped = 0
var _typed: int = 0

for i in range(ITERATIONS):
  _untyped += 1

for i in range(ITERATIONS):
  _typed += 1

Which of these loops do you reckon runs the fastest?

Well, I mean, it’s obviously going to be the statically-typed loop given the conceit of the blog, but how much faster do you reckon?

I hacked up a quick test project to run 1,000,000,000 iterations on my M2 Max, and the results speak for themselves:

Ain’t that grand! According to GDScript progress report: Typed instructions, static typing allows the interpreter to take shortcuts – and it shows, too.

I added a multiplication test and saw roughly the same performance improvement. And then I added vector calculations, and that blew me away:

Bloody hell! Vector operations just scream when they’re statically-typed!

You’ve got nothing to lose by adding static type annotations, and potential double-digit math performance increases to gain. There’s no good reason to not.

And if you want to verify my numbers, my test project’s on GitHub at cariad/gdscript-typed-performance.

Working with type annotations in the Godot editor

You don’t need to change any settings to use static types–you can just start adding type annotations and away you go–but I do recommend that you enable text_editor/completion/add_type_hints in the Godot editor to automatically pre-fill known annotations.

For example, when overriding _physics_process, you’ll get:

func _physics_process(delta: float) -> void:

…instead of just:

func _physics_process(delta):

You can also keep an eye out for grey line numbers, like 294 here:

This indicates an “unsafe” line that the editor can’t guarantee will work at runtime.

In this case, the editor can’t be sure that a and b will hold values that + can operate on, so the line is flagged for review. We can reassure the editor by statically-typing a and b as types that can be added:

But of course, why statically-type just two lines when you could fix all three?

Have fun! ❤️