Script Performance Questions

Questions & Answers
1

Hello there, the Eldars of Unity Community,

 After a year of coding, now I have enough experience but if you know
 more, you realise you need to know alot more so I have few questions:

  1. I use Javascript and I work on IOS so I need performance, do I have to use C++ in some of the calculations to improve the performance?

  2. I have a lot of coding from previous projects and I want to update them. I know most of the tricks for performance but scripting tricks I am lack of. I have many codes like if(a==b && b==c && c==d && d==e) and it can be changed like if(a==b){if(b==c && c==d && d==e)} so it can be optimised but is this performance optimisation important or is it such a small gain that I do not need to change it?

  3. And it would be easier for me to use if statements alot but if I work on them I can make some shorter with extra effort and smarter coding, I had some ugly coding at past but the performance will change in a way that I would care? Is the if statement very fast?, in this way I mean there are some crazy expensive stuff like FindObject, in compare with those, is if statement expensive in this means or not, like for example is it 10 times cheaper than FindObject or 100 times cheaper? I would calculate my performance needs better if I would have some data, some stuff you cannot learn efficiently from profile, I hope you got what I mean.

Thank you community, sorry for my English and hope for an answer from a person with exact knowledge.

2
  1. You can’t script in C++.
  2. That’s not an optimization at all. && short-circuits, unlike &.
  3. An if statement is a vital part of coding and you’re not going to get rid of it. Write as much code as you need to; if statements are going to have to be a large part of that. if statement are not likely to be bottlenecks.
3

Understanding and predicting performance isn’t easy in general, and a managed environment like Mono makes it even harder. But IMHO the best thing you can do is improve your knowledge of computer hardware and runtime environments. Learn to read assembly language (at least x86), and then get the Mono source code. Look at the IL output from the compiler, then look at how that is JITed into x86 by the Mono runtime. Learn about calling conventions, stack variables vs. heap variables, return results, etc. Get the intel developers guide Intel® 64 and IA-32 Architectures Software Developer Manuals . This may sound like a lot, and it is, but this kind of understanding will serve you throughout your entire career.

4

complementing Jessy and helicats answer, there is a lot of optimization that can be done, and much of it needs further studying and technics. A good place to start is http://unity3d.com/support/documentation/Manual/Optimizing%20Graphics%20Performance.html
a tip would be to use getcomponents instead of findGameObjects, but you can find lots of good learning material on the forum or answers from more seasoned developers like Jessy, Erich5h5, Duck, DaveA, Statement, skovacs1, etc that discuss more in depth stuff, just browse their answered questions through the profile and you can learn a lot, I do that once in a while :wink: