What causes "excluded from unity build"?

Development Programming & Scripting C++
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1

I’m using wwise and I’ve noticed in the last few months, my compile times suddenly got a lot longer.

Every time I compile, I get the following message:

2>[Adaptive unity build] Disabling PCH for excluded files. Set bAdaptiveUnityDisablesPCH to false in BuildConfiguration.xml to change this behavior.
2>[Adaptive unity build] Excluded from AkAudio unity file: AkAcousticTexture.cpp, AkAmbientSound.cpp, AkAudioBank.cpp, AkAudioEvent.cpp, AkAudioInputComponent.cpp, AkAudioInputManager.cpp, AkAudioModule.cpp, AkAudioStyle.cpp, AkBankManager.cpp, AkCustomVersion.cpp, AkGameplayTypes.cpp, AkReverbVolume.cpp, AkSpatialAudioVolume.cpp, AkSpotReflector.cpp, AkSurfaceReflectorSetComponent.cpp, AkWaapiCalls.cpp, AkWaapiFieldNames.cpp, AkWaapiFieldNamesCustomization.cpp, AkWaapiJsonManager.cpp, AkWaapiUri.cpp, AkWaapiUriCustomization.cpp, AkSSlider.cpp, AkBoolPropertyToControlCustomization.cpp, AkCheckBox.cpp, AkItemBoolProperties.cpp, AkItemProperties.cpp, AkPropertyToControlCustomization.cpp, AkSlider.cpp, AkWwiseObjectDetailsStructCustomization.cpp, AkWwiseTree.cpp, ... (continues for another 50+ files)
  • What might be causing this?
  • Does this make compile time slower like I suspect?
  • How can I fix it? It mentions buildconfiguration.xml but that seems to be superceded by Build.cs
  • The setting for PCH I have in my ModuleRules is PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;
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What is PCH and bAdaptiveUnityDisablesPCH?
2

I find that if you have the files modified then they get excluded. I assume that this makes the incremental build times much smaller while maintaining main performance win of the unity build system.

Do you have a bunch of writable files?

3

Yes they’re writable, but they haven’t been changed.

You think Unreal checks whether a file is writable or not, rather than whether the file has been changed or not?

4

I’m not sure the rules as I only just noticed this. With git as source control there’s a print out saying using git status, in perforce I’m not sure. Fallback might be file modification times but then I’m not sure what criteria it uses to decide to fallback to a full unity build again.

5

Worst case you can probably do a clean build to reset everything.

8

afaik, no, it makes it faster by compiling them in parallel.

uba (i think) detects that only a some files have changed.

it can be controlled in build.cs i think.

can also be changed on build.cs

note that disabling pch on adaptive unity, and adaptive unity are two different features.

9

Nice necro! :smiley:

The unity build uses the selected version control’s changelist (i.e the things you see listed in git status for git). See for yourself: Commit everything, and suddenly no file will be excluded.

It is NOT whether the file is writable, nor is it UE/UBT “guessing” anything. This is a much simpler/dumber system.

It makes sense that this would trigger eggregious behaviors in the case where you’ve started using a plugin: That’s a piece of code that will live in your project folder, but that you don’t want to commit. If you don’t cleanly setup your version control tool to ignore the wwise folder, it will force UE to keep assuming that you are in the process of modifying these plugin files.

10

Adding more context to already necroed but interesting topic :smiley:
From the TargetRules.cs we can read:

/// <summary>
/// Use a heuristic to determine which files are currently being iterated on and exclude them from unity blobs. This results in faster
/// incremental compile times. For Perforce repositories, the current implementation uses the read-only flag to distinguish the working
/// set, assuming that files will be made writable by the source control system if they are being modified. For Git repositories, the
/// implementation uses the git status command. Source code archives downloaded from Git as .zip files are not supported.
/// </summary>
[CommandLine("-DisableAdaptiveUnity", Value = "false")]
[XmlConfigFile(Category = "BuildConfiguration")]
public bool bUseAdaptiveUnityBuild { get; set; } = true;

So it checks if file is writable, but only if you use Perforce as a source control.

For git it works as @Altrue says.

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