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Comment by munificent | Hacker News Reader

> Both are technically possible in Java, but I've never seen them used commonly (though in fairness I've never written performance critical Java.)

I don't know about the Java world, but in C#—especially in games written in Unity—object pooling is very common.

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Writing High Performance .NET Code (https://www.writinghighperf.net/) has a chapter on this. In C#, time spent collecting depends on the number of still-living objects. That means you want objects you allocate to be short-lived (dead by the time GC happens) or to live forever (they go to the gen 2 heap and stay there). The book suggests object pooling when the lifetime of objects is between those two extremes, or when objects are big enough for the Large Object Heap.

But at the end of the section, the book says:

  I do not usually run to pooling as a default solution. As a general-purpose mechanism, it is clunky and error-prone. However, you may find that your application will benefit from pooling of just a few types.

What kind of things do you pool in Unity?

Ideally you would pool anything you might need to dynamically allocate during a level. You want to avoid allocations during game play entirely, if possible.

Unity itself will pool most media assets. Any given texture asset is shared between all object instances that use that texture. The programmer will end up pooling instances of their objects or just use structs and such. It can be tedious but I wouldn't call it more clunky than explicit memory management.

Large collections are actually not a problem at all in games as long as you only run the collection during a load screen.

Unity aside, I believe it's useful in a lot of areas of gamedev.

Anecdotally, in a lower-level game engine I wrote at one point in C#, object pooling significantly reduced memory overhead (and IIRC increased framerates on complex scenes) when I scaled well past 1000 dynamic, moderately-lived entities. Particles, objects, projectiles, bad guys, etc. I believe can all benefit from pooling, assuming they aren't long-lived.

I do agree it can be error prone, but I'm convinced it's worth it for several places in gaming.

I've seen it on a large site written in c#. Object pools of stream objects for serializing and deserializing data. This was 10 years ago.

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