Comment by throwaway17_17
2 days ago
I see that there is a section (relatively short) on real time GC. But for anyone who has read the Handbook, how much emphasis is placed on GC in constrained environments. I have fought the urge to implement a 3D, modern AA game with GC just to prove it is viable outside all but the most resource poor platforms or the most AAAAA, cutting edge, every cycle counted, hyper optimized game. But I am transitioning to a slightly less focused area of responsibility at work and may have some free time to prototype and this may be how I spend my winter and spring free time.
I think you would be hard-pressed to find a modern AA game that does not already use a GC. The major game engines Unreal and Unity are garbage collected - although they use manual memory management for some of their internals, the exposed API surface (including the C++ API) is designed with garbage collection in mind.
Notably, the popular-with-hobbyists Godot Engine does not use a garbage collector. It uses reference counting with some objects, but does not provide cycle detection, thus requires all objects to be laid out in a tree structure (which the engine is built around).
Reference counting is chapter 5 on the linked book.
I said "a GC", that is, "a garbage collector". Even if you consider reference counting as technically being garbage collection, purely reference counted systems do not have a distinct entity that can be identified as "a" garbage collector. So I'm technically correct here even in face of this pedantry.
Not that I think it's a reasonable approach to language to be pedantic on this. RC being GC is, of course, true from an analytic approach to language: a garbage collection system is defined as a system that collects and frees objects that are unreachable and thus dead; a reference counting pointer collects and frees objects that are unreachable and thus dead; therefore, reference counting is garbage collection.
One problem with this is the vagueness: now, the use of a call stack is garbage collection; after all, returning from a function collects and frees the objects in the stack frame. Leaking memory all over the place and expecting the operation system to clean up when you call `exit()` likewise is "garbage collection".
But more importantly, it's just not how anyone understands the word. You understood perfectly well what I meant when I said "you would be hard-pressed to find a modern AA game that does not already use a GC"; in other words, you yourself don't even understand the word differently. You merely feel an ethical imperative to understand the word differently, and when you failed to do so, used my comment as a stand-in to work through the emotions caused by your own inability to live up to this unfulfilled ethic.
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Reference counting isn’t garbage collection.
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US navy has weapons targeting systems on some battleships implemented in Java with realtime GC, equally France has missile tracking systems, also implemented in Java with realtime GC, courtesy of PTC and Aonix.
https://www.militaryaerospace.com/defense-executive/article/...
https://www.lockheedmartin.com/en-us/products/aegis-combat-s...
https://vita.militaryembedded.com/1670-aonix-uss-bunker-hill...
Not all GC are born alike, and in real life there isn't "insert credit to continue".
Minecraft is the best selling game of all time, uses GC, and is an indie game.
There's a bunch of caveats to that story. At one point (in one patch I recall) they got tired of passing around 3 floats separately for x, y, and z all the time, so they did what any reasonable programmer would do and created a "coordinate" structure.
This created one of the worst performing partches of the game ever, and they had to back all the way out. They ended up just passing the separate floats around again.
My takeaway is that GC doesn't have to be slow, it just imposes a bunch of new constraints on what can be fast.
The problem there is probably that Java cannot pass objects by value [1]. That incurs an additional layer of indirection when accessing the individual members of the struct, tanking performance.
That's not a necessity, though - you can use a GC in languages that allow you to control whether structs get allocated on the heap or on the stack, and then you don't have this issue. For example, in Go, structs can be allocated on the stack and passed by value, or they can be allocated on the heap and passed by reference, and this is under the control of the application programmer [2].
[1]: Actually, according to the Java spec, Java does not have pass-by-reference, and objects are always passed by value. However, that's just strange nomenclature - in Java parlance, "object" names the reference, not the actual range of memory on the heap.
[2]: The language spec does not guarantee this, so this is technically implementation-defined behavior. But then, there's really only one implementation of the Go compiler and runtime.
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Value types would solve that issue flawlessly.
That’s not the GC’s fault. If you wrote C++ code that malloced a vector object every time you wanted to create a new vector, it would be even worse.
That’s Java’s fault for not having value types (though that’s changing soon maybe).
Yeah but it’s a game category where is that’s viable
What do you mean? A 3D game with a dynamic environment doesn't sound like the best category for GC. Or do you just mean that it was a game that didn't write extreme performance optimizations.
Unreal Engine has a GC for its internal object graph, so GC is already in use in a ton of games.
Not much. The book mostly covers theory and not platform-specific details. The explanations on various real-time gc algorithms are very thorough though.
Unreal has an incremental GC
Wouldn't all the popular games based on Unity and written in C# count?