[jcelerier]

> Fast: also yes. Usually about 2x or 3x the run time of C/C++ code, some times even less.

not commenting on the Java part as I believe it's usually faster than that (though not so sure when you see the years of hoops that Minecraft java had to go through to stop being so damn slow all the time...) , but it's kinda frustrating to be fighting for microseconds almost daily and then hear people saying that 2x slower is fast... 2x slower means going from 100fps to 50fps which ... well, gets you fired ?

[saagarjha]

I know this thread is about game development, but not everyone has hard deadlines to churn out frames. The comparison is useful because it separates Java from many other languages that are possibly 10x slower, which make them unsuitable for a huge number of domains where Java can still be useful.

[pjmlp]

While Java isn't perfect, it was more lack of skills of Minecraft developers than anything else.

Using classes for everything with a full OOP approach, instead of DOA and ECS, with tons of new in hot paths, no wonder it had performance isuses.

This was discussed in some Minecraft forums,

https://www.reddit.com/r/programming/comments/2jsrif/optifin...

It basically boils down to

> Why is 1.8 allocating so much memory? This is the best part - over 90% of the memory allocation is not needed at all. Most of the memory is probably allocated to make the life of the developers easier.

HFT is as high demanding as games and it makes use of Java, however I think that Java developers with such skills rather have a HFT salary than what game devs earn on average.

[jstimpfle]

How would avoiding GC even work? As far as I know that Valhalla thing still isn't there - wonder if it ever comes. Last I used it, you could only have "structs" together with GC. Maybe there is just no practical way to do this? What prominent examples are there?

I remember a story of a HFT trading software written in Java. Supposedly it had big issues with GC. That's why they built a system where multiple threads would attempt the same operation, and the first thread wins. This approach reduces the likelyhood of a GC ruining the timings. Funny story.

My bachelor's thesis involved writing a software in Java that would manage dozens or hundreds of millions of small objects. These objects were all instances of the same class; the contained only three ints. It was very slow, and especially in an OOM situation the GC would work for more than a minute before finally giving up. I changed the software to use SOA instaed of AOS - moving from a huge array of these objects to three int[] arrays. Since ints aren't boxed, that left me with only 3 objects instead of many millions. The code was uglier for it, but the performance was another world. Unfortunately, such a change is not practical if you have many classes.

That was 5 years ago with Java 8. Disclaimer: I haven't followed Java since then. I know next to nothing about it.

[pjmlp]

But that is exactly what you do when going after performance in game development, even in C and C++, and it isn't less ugly by using those languages instead of Java.

There is an EA available for Valhalla and there is now the roadmap to incrementally bring such features into the platform. Java 14 has a new native memory support as experimental and it might reach stable already by 15.

https://jdk.java.net/valhalla/

https://cr.openjdk.java.net/~briangoetz/valhalla/sov/01-back...

https://openjdk.java.net/jeps/370

The problem why it is taking so long is engineering effort to keep ABI compatibility, namely how to keep 20 year old jars running in a post Valhala world, while at the same time migrate value like classes into real value types.

Java's biggest mistake, from my point of view, was to ignore the GC enabled systems languages that had value types, non traced references, and AOT compilation from the get go, then again I guess no one on the team imagined that 25 years later the language would be one of the choices in enterprise computing.

Back to Minecraft, the game isn't Crysis or Fortnight in hardware requirements, so a language like Java is quite alright for such game, what isn't alright is what the new development team apparently lacking experience eventually ended up doing to the game engine.

If one is to believe a couple of posts like the one I referred to.

[jstimpfle]

In C and C++ you don't need to make int-arrays. You can group data that is accessed together in structs and keep arrays of these structs.

With regards to performance, there must be some fine art in splitting structs into smaller structs, and keep them as parallel arrays, but there is also a limit to it. At some point you will need too many pointers to point at the same position in all these arrays.

I've never cared to split a lot, since it makes code harder to read. My guideline has always been to optimize for modularization: In OOP there tend to be large objects containing links to "all" related information. That violates the rule of separation of concerns. With parallel arrays you get perfect separation of concerns. One parallel array doesn't even need to know that there are others.

> Back to Minecraft, the game isn't Crysis or Fortnight in hardware requirements, so a language like Java is quite alright for such game, what isn't alright is what the new development team apparently lacking experience eventually ended up doing to the game engine.

I'm not in a position to judge, and I've never even played it, but it seems to me that Minecraft has a lot of voxels to maintain. Also massive multiplayer requirements?

[pjmlp]

Fair enough, however regarding massive multiplayer requirements most game shops are anyway using Java or .NET on their backends, as you can easily check going over their job adverts.

As on the client side, proper coding plus offloading stuff into shaders already goes quite far.

And even in the debatable point that Java isn't the best language for any kind of game development, well maybe Mojang would never have taken off if Markus had decided to prototype the same in something else.

Nowadays the Java version is only kept around due to the modding community, as the C++ version is found lacking in this area.

[pjmlp]

Just to add something that I forgot to mention on my previous comment that I think it is worthwhile mentioning.

Naturally at some level you will have a class full of native methods as FFI to OS APIs or libraries written in C or C++.

From that point of view, I consider Java still a better option as game engine scripting language as Python/Lua/JavaScript, because you get strong typing, there is still dynamic loading, a good set of AOT/JIT/GC infrastructure and more control over memory layout than those languages allow for.

Naturally that is a matter of personal taste.