When you're using a programming language that naturally steers you to write slow code you can't only blame the programmer.

I was listening to someone say they write fast code in Java by avoiding allocations with a PoolAllocator that would "cache" small objects with poolAllocator.alloc(), poolAllocator.release(). So just manual memory management with extra steps. At that point why not use a better language for the task?

I decompiled Project Zomboid (written in Java) a while back, because I was curious about the performance issues I was having with the game. (Very laggy on my 10 year old laptop, while looking like The Sims 1.) I figured, best case scenario I find some easy bottlenecks and I can patch in a fix.

Well, the whole thing was standard Java OOP, except they also had a bunch of functional programming stuff on top of that. I can relate to that -- I think they were university students when they started, and I definitely had an OOP and FP phase. But then they just... kept it, 10+ years later.

So while it's true that you can write C in any language... those kind of folks don't tend to use Java in the first place ;)

--

(Except Notch? Well, his code looks like C, not sure if it's actually fast! I really enjoyed his 4 kilobyte java games back in the day, I think he published the source for each one too.)

EDIT: Found it!

https://web.archive.org/web/20120317121029/http://www.mojang...

Edit 2: This one has a download, still works!

https://web.archive.org/web/20120301015921/http://www.mojang...

This point gets raised every single time managed languages and low latency development come up together. The trade off is running "fast" all of the time, even when you don't have to, vs running slow most of the time and tinkering when you need to go fast.

I've spent a fair few years developing lowish (10-20us wire to wire) latency trading systems and the majority of the code does not need to go fast. It's just wasted effort, a debugging headache, and technical debt. So the natural trade off is a bit of pain to make the hot path fast through spans, unsafe code, pre-allocated object pools, etc and in return you get to use a safe and easy programming language everywhere else.

In C# low latency dev is not even that painful, as there are a lot of tools available specifically for this purpose by the runtime.

I saw something like that being suggested when working with GIS data with many points as classes in Java, the object overhead for storing XYZ doubles is quite crazy. The optimization was to build a global double array and use "pointers" to get and set the number in the array.

Even JavaScript is much better for this, much, much better.

You might have an application for which speed is not important most of the time. Only one or two processes might require allocation-free code. For such a case, why would you burden all of the other code with the additional complexity? Calling out to a different language then may come with baggage you'd rather avoid.

A project might also grow into these requirements. I can easily imagine that something wasn't problematic for a long time but suddenly emerged as an issue over time. At that point you wouldn't want to migrate the whole codebase to a better language anymore.

Java doesn't steer you into object pools. I wrote Java code for 20 years and never used a cache to avoid allocating objects, and never saw a colleague use one. The person you were talking to doesn't know what he's doing.

TBH, I do not see how Java as a language steers anyone to use one those shotguns. E.g. the knowledge about algorithmic complexity is foundational, the StringBuilder is junior-level basic knowledge.

The problem with comments like these is that guessing what "better language" a commentator has in mind is always an exercise left up to the reader. And that tends to be by design—it's great for potshots and punditry, because it means not having make a concrete commitment to anything that might similarly be confronted and torn apart in the replies—like if the "better language" alluded to is C (and it generally is)—the language where the standard library "steers" you towards quadratic string operations because the default/natural way to refer to a string's length is O(n).

> So just manual memory management with extra steps

This is actually the perfect situation: you are allowed to do it carefully and manually for 1% of code on the hot path, but you don't have to worry about it for the 99% of the code that's not.

Bad idea. I've made a pool allocator before, but that was for expensive network objects and expensive objects dealing with JNI.

Doing it to avoid memory pressure generally means you simply have a bad algorithm that needs to be tweaked. It's very rarely the right solution.

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