Code Optimisation
Make it work.
No need to worry about making it work at light speed if it doesn't even do what it is supposed to. Focus on getting a working product first.
Make it fast.
Optimisation is everything when running lots of instances, with low delays. However, there is such thing as premature optimisation.
""Excessive cleverness" is doing something in a really clever way when actually you could have done it in a much more straightforward but slightly less optimal manner. You've probably seen examples of people who construct amazing chains of macros (in C) or bizarre overloading patterns (in C++) which work fine but which you look at an go "wtf"? EC is a variation of premature-optimisation. It's also an act of hubris - programmers doing things because they want to show how clever they are rather than getting the job done." - sbsmac
3. Make it pretty.
Documentation, readability, and all that jazz. Clean code is good code.
Written it twice? Put it in a function
Pre-compilation by the game engine can save up 20x the amount of time processing, even if the initial time is slightly lengthened. If you've written it twice, or if there is a kind of loop consistently being compiled (perhaps a script run by execVM), make it into a function (FUNCVAR =compile preprocessfilelinenumbers "filename.sqf").
Adding elements to an array
- set is 56x faster than binary addition (_a set [count _a,_v] vs _a = _a + [_v])
Getting position
10,000 Iterations Limit in Loops
Doesn't exist in scheduled environments, only in non - scheduled (only where the 0.3ms delay does not exist).
Loops
These first two loop types are identical in speed (+/- 10%), and are more than 2x as fast the proceeding two loop types.
- for "_y" from 0 to (count [0,0,0,0] - 1) step 1 do { ... };
- { ... } foreach [0,0,0,0];
Where as these two loops are much slower, and for maximum performance, avoided.
- _y=0; while {_y = _y + 1; _y < count [0,0,0,0]} do { ... };
- for [{_y=0},{_y<(count [0,0,0,0])},{_y=_y+1}] do { ... }
Avoid O(n^2)!!
Commonly you may set up foreach foreach's. 'For' example:
- { { ... } foreach [0,0,0]; } foreach [0,0,0];
This example is of the order (n^2) (3^2 = 9 iterations). For each element you add to this, it will increase the processing exponentially. Which can lead to poor performance in snap functions.
Avoiding the 0.3ms delay
Many times you may want to avoid the 0.3 ms delay (not 3ms!), and there a few tricks around how to do it...
- Triggers are inside what we call the 'non-scheduled' environment.
- All pre-init code executions are without scheduling.
- FSM conditions are without scheduling
Measuring Velocity Scalar
Sure we can just use Pythagorean theorem to calculate the magnitude from a velocity vector, but a command native to the engine runs much faster (over 10x faster) than the math.
- VECTOR distance [0,0,0]
Works for 2D vectors as well.