Mission Optimisation

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This page is about Mission Optimisation. For scripting optimisation, see Code Optimisation.

Introduction

This article will try to be a general guide about improving your mission's performance.
As usual, moderation is the key; do not expect to find on this page a magical solution that makes it possible to run thousands of AI at 144 FPS. Everything comes at a cost, the tweaks here will simply allow you to locate issues and calibrate your mission properly.

Before anything

Before optimising anything, make sure you do not have any performance issue running the game itself:

• Read Arma 3: Performance Optimisation
• Open the editor, place a unit in the area you like and test your computer.
  • You can get current FPS in Arma 3 by going into video options or using diag_fps
  • Steam allows you to display FPS in a screen corner, in Settings > In game > FPS Counter
• Use (unofficial) Performance Guides to get better performances:
  • Arma 3 performance guide
  • Arma 2 performance guide
  • Armed Assault performance guide
• Play your mission in singleplayer. If your mission runs fine, its network messages might very well be the issue. See Multiplayer Scripting for good practice tips.
• Usual bottlenecks:
  • Lower your graphical settings (resolution, textures). If you get way better performances, at least your GPU limits you.
  • If the game keeps having low FPS when running @ 1024×768/low textures then your CPU is most likely the issue. Mission scripts may be performance-hogging too.

⚠

Please note that view distance (among other settings) impacts both GPU and CPU!

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View distance can be separately set for each clients independently from the server's value through scripting.
This can make or break performance for the client.

Creating your mission

• Be sure to create your scripts with the latest available commands and functions.
  • In Arma 3 use remoteExec / remoteExecCall and DITCH BIS_fnc_MP FOR GOOD! See Arma 3: Remote Execution for more information.
  • In Arma 2 network communication is done using the Arma 2: Multiplayer Framework.
• Use the available frameworks and functions for each topic, unless you replace them by third-party ones:
  • Arma 3: Respawn
  • Arma 3: Revive
  • Arma 3: Task Framework
  • Arma 3 Animated Briefing
  • Arma 3 Animated Opening
  • Arma 3: Dynamic Groups
  • Arma 3 Key Frame Animation
  • and most importantly: Functions

Performance impact table

ⓘ

means a heavy impact on performance

means an average impact

means little to no performance impact.

Topic	CPU	GPU	Net- work	Solution
AI unit quantity				Use Agents whenever possible The more units there are, the more network updates there will be - hence the impact on both CPU and network. If a client has a low-end machine, they shouldn't lead a group of many AIs as these would then be locally computed. Arma 3: Dynamic Simulation allows you to freeze AI that are distant from players. Many distance settings should be set according to the mission. ⓘ If you own more than one average computer, you could consider Headless client to offload AI from the server.
Object quantity				The less objects, the more FPS you will have. Lower the quantity of objects in the mission, such as: AI units, agents vehicles, simple objects weapon attachments (their proxies are attachedTo) headgear, clothing, vests, backpacks head-mounted devices (NVGs, etc.) Lower viewDistance Lower terrain details Lower the Dynamic Simulation treshold Use Simple Objects Use Garbage Collection in order to automatically delete bodies and wreckages: Arma 3's Eden-integrated Garbage Collection Arma 2's Garbage Collector Take On Helicopters's BIS_fnc_GC ⓘ Only the on-screen objects will strongly impact GPU.
General script mistakes				Having too many scripts running is a cause for severe performance issues and execution delays in singleplayer as well as multiplayer. You can track the number of running scripts using diag_activeScripts; you can also use: diag activeSQFScripts diag activeSQSScripts diag activeMissionFSMs A common bad practice is to spawn a function for each units that need it; the good practice would be to have a single script working with an array of units, array that is edited (unit added/removed) whenever needed: { _x spawn _myCode; } forEach _units; // bad _units spawn _myCode; // good You can use diag_activeSQFScripts to ensure you are not clogging your CPU with multiple instances of the same script. Not compiling your scripts: running multiple times the same script with execVM will make the game read the file every single time; This is an issue, especially if you execute it frequently. while { sleep 5; alive player } do { player execVM "myScript.sqf"; }; // bad private _myScript = compile preprocessFileLineNumbers "myScript.sqf"; while { sleep 5; alive player } do { player spawn _myScript; }; // good
High-frequency scripts				Checking a condition too often is usually a source of poor performance. Does your code execution need to be frame-perfect, or can you afford a delay of a few seconds? A while-loop checking without a minimum loop-sleep time is usually a sign of bad conception. while { true } // bad if you don't know what you are doing while { alive player } // better while { sleep 1 ; alive player } // perfect Triggers check their set condition every 0.5 second (hardcoded value). If a large area is covered or condition code is too complex, this can become an issue; the triggers should then be converted to scripts if possible. Triggers can be made Server-Side only to save clients' resources. ⚠ All of the mission-related calculation (objectives, completion distance, etc.) must be done server-side. Local effects should be calculated client-side.
High-frequency network messages				Use publicVariable wisely; for specific cases, consider publicVariableServer / publicVariableClient Creating units/vehicles globally implies a network synchronisation, keep them to a minimum / at one-point in the mission. Keep global effect commands to a minimum: e.g a setPos will synchronise the unit position to every client, a good practice is to use these commands punctually. If you need a frequent "set position" you may want to look at attachTo depending on your usage. global marker commands always send all the marker's information. If you are creating/updating many markers e.g server-side, edit them with local commands, except the last one (that will be global) to send the whole marker's status over the network, once. Lower client's view distance in order to lessen its object position update requests
Unscheduled code				Unscheduled code can have a high impact on the framerate, as such code is not subject to the scheduler's management (as its name suggests) and will run without limitation. Cyclic unscheduled low-performance code can make the game unplayable, up to freezing it. As only time-critical scripts should run unscheduled, spawn any other code from unscheduled environment once you have the required results: (...) // unscheduled code [_var1, _var2] spawn TAG_fnc_MyFunction; (...) // other unscheduled code ⓘ See also Where code starts unscheduled.

What else?

If you have applied all these recommendations and your mission still doesn't run well in multiplayer (but does in singleplayer), it might be caused by mods that you are running which could be badly, or not at all, optimised.

If you want to be sure, run the same mission with and without mods. If you have a big difference in performance, look no further.

Performance Diagnostic tools

Server commands

• #monitor 5
  • Shows performance information of the server. Interval 0 means to stop monitoring.
• #monitords 5
  • Shows performance information in the dedicated server console. Interval 0 means to stop monitoring. (since Arma 3 v1.64)

Diagnostic commands

• Diag. commands only available in Diagnostic Branch
• Diag. command available in all builds

See also

• Multiplayer Scripting
• Code Optimisation
• Code Best Practices
• Performance Profiling
• Dedmen's ArmaScriptProfiler (forum post)