C++ Newbie - Please judge my C++ code.

[NegInfinity]

@.Richards;413147

I have to ask, what is a premature optimization?

Any attempt to improve speed of any piece of code without profiling it first.
Worrying about function speed when you don’t know how many millions of times it will be called is also premature optimization.

The term was probably coined by Donald Knuth. You can google it.

@.Richards;413147

Reducing the number of statements is an optimization. Keeping functionality centralized is an optimization. I guess in your mind then these are premature too.

No, that’s readability and that one is done specifically to reduce maintenance cost.

You’re appear to be trying to turn that into semantic argument by shifting meaning of “optimization”. Please don’t do that. In this context “optimizations” refers to “performance optimization” only.

The reason why premature optimization is bad is because person performing it wastes development time without getting tangible benefit. Humans make mistakes. If you think that “this will be slow”, but you haven’t measured it, then you’re wrong by default.

@Gigantoad;413160

So use RoundToFloat (which admittedly is just a cast RoundToInt). Are you going to ignore most of the stuff in FMath and use your own thing instead or are you going to heed your own advice and keep code clean and readable for other devs doing it the UE4 way?

Anything that is part of the language is not “my thing”. It is part of the language. Feature available in language takes precedence over feature available in framework, which takes precedence over feature created by you, unless there is a good reason. Type like FString and FName has a good reason to use it. However, that does not necessarily apply to FMath functions.

Now, what is a good reason to avoid round() function from cmath?

The first person for which code readability is important is you, because in few weeks or months you’ll forget what this subroutine is doing. Then it is your team. “Other unreal devs” only enter the picture if you’re planning to share the code OR preparing engine patch for submission.

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I don’t like the tone this thread is taking. Is the point where we start insulting each other due to having different programming opinions?

[Jamendxman3]

@NegInfinity;412797

I advise to review my previously posted code snippet.

FVector snap(FVector arg, float gridSize){
	auto f = &](float val){
		return gridSize ? (float)round(val/gridSize)*gridSize: val;		
	};
	return FVector{f(arg.X), f(arg.Y), f(arg.Z)};
}

First, code duplication should be eliminated in almost all cases. You have three if/else branches doing the same thing, but on different fields of the structure. This stuff belong to another function or lambda. Duplication results in bugs and increases maintenance costs.

Also, cmath library has round() function, which rounds float/double value to the nearest integer.
Your code does the same thing as this builtin function, so you’re reinventing the wheel. That is a bad practice.

Using round(), you can replace convoluted if/else with

snappedValue = (float)round(val/gridSize)*gridSize;

I am having a very hard time understanding what that code is doing, is there a name for what is happening?

[anonymous_user_689e935a]

You can have opinions all you want. The fact remains UE4 uses a customized C++ implementation. If you include cmath then it shows only one thing: you haven’t truely arrived in UE4 yet. There’s no problem with that unless you give tips to to other UE4 devs and are being adamant about your solution being better than those already in UE4. At that point I think someone has to at least mention that this isn’t the way that most UE4 devs do it.

[BrUnO_XaVIeR]

@NegInfinity;413123

STL stands for Standard Template Library. There’s no STL, only standard library currently, mathematical functions are not templated.

Hmm… They are pretty much the same thing. STL is just an old parent of what “The C++ Standard Library” is today, the std namespace. Old ppl still call it STL and they have no intention to change it seems. Std still makes use of Stl containers and all that stuff.

[anonymous_user_689e935a]

@Jamendxman3;413206

I am having a very hard time understanding what that code is doing, is there a name for what is happening?

It’s a lambda expression.

C++11 - Lambda Closures, the Definitive Guide - Cprogramming.com

[BrUnO_XaVIeR]

Also, code duplication isn’t good as pointed out already… But as always, everybody ignores the fact that excessive indirections can hit your overall game performance; splitting everything into functions isn’t great idea either.
When games, huge as they are nowadays, are calling 80.000~300.000 functions every frame, there’s a performance hit in there. So you don’t necessarily wan’t everything formatted to a generic function call.
I don’t see any problem with the way he wrote his original code then; at the end of day if he doesn’t need to create a function call for it so be it.

[NegInfinity]

@Jamendxman3;413206

I am having a very hard time understanding what that code is doing, is there a name for what is happening?

Lambdas, “auto” keyword and uniform intiialization syntax.

@Gigantoad;413208

The fact remains UE4 uses a customized C++ implementation.

No, this is false and misleading.

“Customized C++ implementation” would require custom compiler. There’s no company in the world insane enough try to do something like that for their product, especially with multiple platforms to support. C++ is the wrong language for this kind of stunt.

UE4 acts pretty much in the same way as Qt with its metaobject system. Few extra preprocessor directives that are handled in special fashion and generate code behind the scenes. There’s nothing special aside from that. If you meant build system, then build system is not part of the language.

Anyway, I’m done with this, since there’s no point in discussing it further.

[Chyros]

At the end of the day, everyone has a point:

• Balance readability/maintainability vs performance
• Don’t do premature optimization. Do some profiling before optimizing anything.
• Use UE4 libraries over the standard ones (i.e., FMath). There is a good reason for it: UE4 Libraries You Should Know About - Unreal Engine
• If you’re aiming for high perfomance code, avoid using blueprint nodes on those. And convert blueprints to C++ code.
• Attend DevCon such as GDC talk and learn from the other experts. No single developer has figured everything out anyways.
• And oh, write clean and quality code. Your teammate/co-workers will love you for it.
• And some things that I’ve missed.

[anonymous_user_689e935a]

@NegInfinity;413348

Lambdas, “auto” keyword and uniform intiialization syntax.

No, this is false and misleading.

“Customized C++ implementation” would require custom compiler. There’s no company in the world insane enough try to do something like that for their product, especially with multiple platforms to support. C++ is the wrong language for this kind of stunt.

UE4 acts pretty much in the same way as Qt with its metaobject system. Few extra preprocessor directives that are handled in special fashion and generate code behind the scenes. There’s nothing special aside from that. If you meant build system, then build system is not part of the language.

Anyway, I’m done with this, since there’s no point in discussing it further.

Fine, I guess I worded it wrong but I don’t know how else to say it (or you’re just arguing semantics). UE4 uses a lot of custom types, macros, its own reflection system, its own build system, its own naming conventions etc. That’s why you don’t use a lot of stuff from the standard library. Epic has created their own engine-specific library instead and the bottom line is you should use it.