User:Lou Montana/Sandbox

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This page is an intended replacement for Code Optimisation. It is obviously a WORK-IN-PROGRESS.

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Code Optimisation

Introduction

This article will try to be a general guide about improving your code and its performance.

Rules

In the domain of development, any rule is a rule of thumb. If a rule states for example that it is better that a line of code doesn't go over 80 characters, it doesn't mean that any line must not go over 80 characters; sometimes, the situation needs it. If you have a good structure, do not change your code to enforce a single arbitrary rule. If you break many of them, you may have to change something. Again, this is according to your judgement.

With that being said, here are the three basic rules to get yourself in the clear:

1. Make it work
2. Make it readable
3. Optimise then

Make it work

Your first goal when coding is to make your code do what you want it does. A good way to reach this objective is to read and getting inspired by other people's code. If you understand it by reading it once, it is probably a good source of inspiration.
When starting from scratch if you know what you want but miss the specific steps to get to your point, it is a good practice to write down in your native language what you want to do. E.g Get all the units near the city, and for each west soldier in them, add damage.

Make it readable

Whether you are cleaning your code or a different person's, you must understand the code without twisting your brain:

• While SQF is impacted by variable name length, this should not take precedence on the fact that code must be readable by a human being. Variables like _u instead of _uniform should not be present.
• One-lining (putting everything in one statement) memory improvement is not worth the headache it gives when trying to read it. Don't overuse it.
• Indentation is important for the human mind, and space is too. Space is free, use it.
• Finally, camel-casing (namingLikeThis) your variables and commands will naturally make the code more readable, especially for long names.

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_i is an accepted variable standard for a for..do iteration

See the following code: _w=[];{_w pushbackunique primaryweapon _x}foreach((allunits+alldeadmen)select{_x call bis_fnc_objectside==east});

The same example is far more readable with proper spacing, good variable names and intermediate results: _weaponNames = []; _allUnitsAliveAndDead = allUnits + allDeadMen; _allEastAliveAndDead = _allUnitsAliveAndDead select { _x call BIS_fnc_objectSide == east }; { _weaponNames pushBackUnique primaryWeapon _x } forEach _allEastAliveAndDead;

• if you have a lot of if..else, you may want to look at a switch condition, or again break your code in smaller functions.

Optimise then

Once you know what is what, you can understand your code better.

• You were iterating multiple times on the same array?
  • You should be able to spot your issue now.
• Do you see the same code, but with different parameters?
  • Time to write a function.
• Are you using execVM on the same file, many times?
  • Store your function in memory to avoid file reading every call with _myFunction = compile preprocessFileLineNumbers "myFile.sqf";
• Is your function code far too long?
  • Split it in understandable-sized bites, for your own sanity.
• Is your variable name far too long?
  • Find a smaller name, according to the variable scope:

e.g

{ _opforUnitUniform = uniform _x; systemChat _opforUnitUniform; } forEach _allOpforUnits

becomes

{ _uniform = uniform _x; systemChat _uniform; } forEach _allopforUnits

Code optimisation

Successive condition check

In SQF the following code will check all and every condition, even if one fail:

if (condition1 && condition2 && condition3) then { /* thenCode */ };

e.g:

if (alive unit1 && not alive aPvehicle && daytime > 5) then { /* thenCode */ };

This code will check if unit1 is alive, and if it is not not alive aPvehicle && daytime > 5 will execute anyway. To avoid this behaviour, you can either imbricate ifs or use lazy evaluation such as the following:

if (alive unit1 && { not alive aPvehicle } && {{ daytime > 5}}) then { /* thenCode */ };

This lazy evaluation will stop code execution on the first false statement.

Using lazy evaluation is not always the best way as it could speed up the code as well as slow it down, depending on the current condition being evaluated:

[true  || {false} || {false}] call BIS_fnc_codePerformance;	// fastest
[true  ||  false  ||  false ] call BIS_fnc_codePerformance;	// normal
[false ||  false  ||  false ] call BIS_fnc_codePerformance;	// normal
[false || {false} || {false}] call BIS_fnc_codePerformance;	// slowest

Adding large strings together

-No code provided- works fine for small strings, however the bigger the string gets the slower this becomes:

s = ""; for "_i" from 1 to 10000 do {s = s + "123"}; // 30000 chars @ 290ms

The solution is to use a string array that you will concatenate later:

strings = []; for "_i" from 1 to 10000 do {strings pushBack "123"}; strings = strings joinString ""; // 30000 chars @ 30ms

Multiplayer recommendations

TODO

• no publicVariable or public setVariable at high frequency
• the server is supposed to have a lot of memory, use it

createSimpleObject vs createVehicle

TODO create at [0,0,0]

Equivalent commands performance

if

Use:

if (condition1) then { /* thenCode */ } else { /* elseCode */ }; // faster

Instead of:

if (condition1) then [{ /* thenCode */ }, { /* elseCode */ }]; // slower

for

Use:

for "_i" from 0 to 100 do { /* forCode */ }; // faster

Instead of:

for [{_i = 0}, {_i < 100}, {_i = _i + 1}] do { /* forCode */ }; // slower

forEach vs count

Both commands will step through supplied array of elements one by one and both commands will contain reference to current element in the _x variable. However, count loop is a little faster than forEach loop, but it does not have _forEachIndex variable.
Also, there is a limitation as the code inside count expects Boolean or Nothing while itself returns Number.

{diag_log _x} count [1,2,3,4,5,6,7,8,9]; // faster {diag_log _x} forEach [1,2,3,4,5,6,7,8,9]; // slower

Usage: _someoneIsNear = {_x distance [0,0,0] < 1000} count allUnits > 0;

_someoneIsNear = {
	if (_x distance [0,0,0] < 1000) exitWith { true };
	false
} forEach allUnits;

TODO: findIf?

+ and format

When concatenating more than two strings, format is faster than +. Use:

format ["%1%2%3%4%5", "string1", "string2", "string3", "string4", "string5"]; // faster

Instead of:

"string1" + "string2" + "string3" + "string4" + "string5"; // slower

select and if

Use:

result = ["false result", "true result"] select _condition; // faster

Instead of the lazy-evaluated if:

result = if (_condition) then { "true result"; } else { "false result"; }; // slower

private

Use:

private _a = 1;
private _b = 2;
private _c = 3;
private _d = 4; 
// 0.0023 ms

Instead of:

private ["_a", "_b", "_c", "_d"];
_a = 1;
_b = 2;
_c = 3;
_d = 4; 
// 0.0040 ms

However:

for "_i" from 1 to 100 do
{
	private _a = 1; private _b = 2; private _c = 3; private _d = 4;
};
// 0.186776 ms

is slower than:

private ["_a", "_b", "_c", "_d"];
for "_i" from 1 to 100 do
{
	_a = 1;
	_b = 2;
	_c = 3;
	_d = 4;
};
// 0.146327 ms

The reason behind this is that in the first example variables are created, assigned and deleted in each loop.
In the second example the variables are only created/deleted once and changed often.

objectParent and vehicle

isNull objectParent player // 0.0013 ms, slightly faster vehicle player == player // 0.0022 ms

nearEntities and nearestObjects

• nearEntities is much faster than nearestObjects given on range and amount of object(s) which are within the given range.

If a range was set to more thean 100 meters it is highly recommend to use nearEntities instead of nearestObjects.

Note: nearEntities only searches for objects which are alive. Killed units, destroyed vehicles, static objects and buildings will be ignored by the nearEntities command.

Config path delimiter

>> is slightly faster than / when used in config path with configFile or missionConfigFile:

configFile >> "CfgVehicles" // 0.0019 ms

is (very slighlty) faster than

configFile / "CfgVehicles" // 0.0023 ms

getPos* and setPos*

getPosWorld			// 0.0015 ms
getPosASL			// 0.0016 ms
getPosATL			// 0.0016 ms
getPos				// 0.0020 ms
position			// 0.0020 ms
getPosVisual		// 0.0021 ms
visiblePosition		// 0.0021 ms
getPosASLW			// 0.0023 ms

setPosWorld			// 0.0060 ms
setPosASL			// 0.0060 ms
setPosATL			// 0.0060 ms
setPos				// 0.0063 ms
setPosASLW			// 0.0068 ms
setVehiclePosition	// 0.0077 ms "CAN_COLLIDE"
					// 0.0390 ms "NONE"

Conversion from earlier versions

Each iteration of Bohemia games (Operation Flashpoint, Arma, Arma 2, Take On Helicopters, Arma 3) brought their own new commands, especially Arma 2 and Arma 3.
For that, if you are converting scripts from older versions of the engine, some aspects should be reviewed:

Loops

• forEach loops, depending on the situation, can be replaced by:
  • apply
  • count
  • findIf
  • select

Array operations

• Adding an item: myArray + [element] and myArray set [count myArray, element] have been replaced by pushBack
• Selecting a random item: BIS_fnc_selectRandom has been replaced by selectRandom
• Removing items: myArray set [1, objNull]; myArray - [objNull] has been replaced by deleteAt and deleteRange
• Concatenating: myArray = myArray + [element] has been reinforced by append: if you don't need the original array to be modified, use +
• Comparing: use isEqualTo instead of BIS_fnc_areEqual or a custom comparison function
  • count myArray == 0 is pretty fast, but direct comparison with isEqualTo is still a little faster: myArray isEqualTo []
• Finding common items: in forEach loop has been replaced by arrayIntersect
• Condition filtering: forEach can be replaced by select (alternative syntax)

result = []; { if (_x % 2 == 0) then { result pushBack _x; }; } forEach arrayOfNumbers; // 2.57 ms

result = (arrayOfNumbers select { _x % 2 == 0 }); // 1.55 ms

String operations

String manipulation has been simplified with the following commands:

• string select index
• toArray and toString have been reinforced with splitString and joinString

Multiplayer

• BIS_fnc_MP has been replaced by remoteExec and remoteExecCall