UE4 using a single core on multi-core pc

Development Programming & Scripting C++
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1

Hello, I have a 14-core workstation, however when I compile my ue4 c++ project, it will use maybe 5% utilization on a single cpu. I read comments that all cpu’s are used by default, but I don’t see this on my box.

I am running Engine Version 4.21.2 It appears some of what I read online around the issue is obsolete now since 2.19.

I have attempted to modify the BuildConfiguration.xml by adding the ProcessorCountMultiplier=2 and MaxProcessorCount=4 as an example with no effect. I’m not sure if I did this correctly. Below is my modified BuildConfiguration.

<?xml version="1.0" encoding="utf-8" ?>
<Configuration xmlns="https://www.unrealengine.com/BuildConfiguration">
  <LocalExecutor>
    <ProcessorCountMultiplier>1</ProcessorCountMultiplier>
    <MaxProcessorCount>4</MaxProcessorCount>
  </LocalExecutor>
  <ParallelExecutor>
    <ProcessorCountMultiplier>1</ProcessorCountMultiplier>
    <MaxProcessorCount>4</MaxProcessorCount>
  </ParallelExecutor>
  <SNDBS>
    <ProcessorCountMultiplier>4</ProcessorCountMultiplier>
    <MaxProcessorCount>4</MaxProcessorCount>
  </SNDBS>
</Configuration>

I also attempted to modify my build.cs with
bFasterWithoutUnity = true;
however this caused build errors.

I was unable to add the bFasterWithoutUnity = false to the BuildConfiguration.xml as it also caused build errors.

Any help is greatly appreciated.

2

You are aware that it simply runs compiler on X number of cpp files? in order to actully use 14 cores you need at least 14 files to be compiling. post you compilation log, also try removing buildconfiguration.xml

3

Thanks for responding ,

My project has 61 .cpp files and about 17,000 lines of code, but I’m usually only working in a single file at any one time. I tried making edits to several .cpp files and the build still focused on one core.

I removed the BuildConfiguration.xml file that I edited earlier, from C:\Users\User\AppData\Roaming\Unreal Engine\UnrealBuildTool\ but no change.

I notice on my quad core laptop, the same project will compile in about 59 seconds (24% cpu utilization across all four cores) after editing a single .cpp.

On my 14-core i9 it takes about 39 seconds (7% cpu utilization - actually 1 core at 100% utilization). I would expect the 14-core to be much faster than the 4-core, but also the 4-core laptop should be a lot quicker than 59 seconds I would think. Both are 16gb ram, SSD drives.

I can’t help but think I’m missing some compile flag somewhere. My laptop and workstation are both running vanilla 4.21.2

4

I don’t think it missing flag, can you show compilation log? you can cover up cpp file names and project name

5

Compiling on VS, the Output Log looks like this:

1>------ Skipped Build: Project: UE4, Configuration: BuiltWithUnrealBuildTool Win32 ------
1>Project not selected to build for this solution configuration
2>------ Build started: Project: VGS, Configuration: Development_Editor x64 ------
2>Using ‘git status’ to determine working set for adaptive non-unity build (F:\VGS_UNREAL).
2>Creating makefile for hot reloading VGSEditor (source directory changed)
2>Compiling game modules for hot reload
2>Using Visual Studio 2017 14.16.27023 toolchain (C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.16.27023) and Windows 10.0.16299.0 SDK (C:\Program Files (x86)\Windows Kits\10).
2>Building 3 actions with 28 processes…
2> [1/3] Module.VGS.cpp
2> [2/3] UE4Editor-VGS-3012.lib
2> Creating library F:\VGS_UNREAL\Intermediate\Build\Win64\UE4Editor\Development\VGS\UE4Editor-VGS-3012.lib and object F:\VGS_UNREAL\Intermediate\Build\Win64\UE4Editor\Development\VGS\UE4Editor-VGS-3012.exp
2> [3/3] UE4Editor-VGS-3012.dll
2> Creating library F:\VGS_UNREAL\Intermediate\Build\Win64\UE4Editor\Development\VGS\UE4Editor-VGS-3012.suppressed.lib and object F:\VGS_UNREAL\Intermediate\Build\Win64\UE4Editor\Development\VGS\UE4Editor-VGS-3012.suppressed.exp
2>Deploying VGSEditor Win64 Development…
2>Total build time: 38.50 seconds (Parallel executor: 31.71 seconds)
========== Build: 1 succeeded, 0 failed, 0 up-to-date, 1 skipped ==========

Compiling from the Editor, the Compiler Log is as the image attached. Couldn’t find an option in the Editor to copy/paste the text so i took a screen grab.

269479-compiler-log.jpg
269479-compiler-log.jpg1641×408 70.1 KB

6

I solved this issue. I modified the BuildConfiguration.xml in C:\Users\User\AppData\Roaming\Unreal Engine\UnrealBuildTool\

mine looks like this

<?xml version="1.0" encoding="utf-8" ?>
<Configuration xmlns="https://www.unrealengine.com/BuildConfiguration">
  <ParallelExecutor>
	<MaxProcessorCount>32</MaxProcessorCount>
	<ProcessorCountMultiplier>32</ProcessorCountMultiplier>
  </ParallelExecutor>
  
  <LocalExecutor>
	<MaxProcessorCount>32</MaxProcessorCount>
	<ProcessorCountMultiplier>32</ProcessorCountMultiplier>
  </LocalExecutor>
</Configuration>

I deleted the following folders from my Unreal project
.vs
Binaries
DerivedDataCache
Intermediate

I deleted IncrediBuild from Visual Studio Installer ← This is really important to do. Otherwise the project will build on a single core.

Run the project in Unreal.
In Ureal go to File → Refresh Visual Studio Project
In Unreal go to File → Open Visual Studio Project
Rebuild the entire solution

Results

Rebuild started...
1>------ Rebuild All started: Project: mvp, Configuration: Development_Editor x64 ------
2>------ Skipped Rebuild All: Project: UE4, Configuration: BuiltWithUnrealBuildTool Win32 ------
2>Project not selected to build for this solution configuration 
1>Cleaning mvpEditor and UnrealHeaderTool binaries...
1>Using 'git status' to determine working set for adaptive non-unity build (E:\repos\mvp).
1>Creating makefile for mvpEditor (no existing makefile)
1>Parsing headers for mvpEditor
1>  Running UnrealHeaderTool "E:\repos\mvp\mvp.uproject" "E:\repos\mvp\Intermediate\Build\Win64\mvpEditor\Development\mvpEditor.uhtmanifest" -LogCmds="loginit warning, logexit warning, logdatabase error" -Unattended -WarningsAsErrors -abslog="C:\Users\Vivi-Desktop\AppData\Local\UnrealBuildTool\Log_UHT.txt" -installed
1>LogInit: Display: Loading text-based GConfig....
1>Reflection code generated for mvpEditor in 3.7518003 seconds
1>Building mvpEditor...
1>Using Visual Studio 2022 14.31.31104 toolchain (C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.31.31103) and Windows 10.0.18362.0 SDK (C:\Program Files (x86)\Windows Kits\10).
1>Building 21 actions with 32 processes...
1>  [1/21] Default.rc2
1>  [2/21] SharedPCH.Engine.ShadowErrors.cpp
1>  Detected compiler newer than Visual Studio 2019, please update min version checking in WindowsPlatformCompilerSetup.h
1>  [3/21] mvp.cpp
1>  [4/21] MovingPlatform.cpp
1>  [5/21] NPCStandStill.cpp
1>  [6/21] mvpGameModeBase.cpp
1>  [7/21] NPC_Interactable.cpp
1>E:\repos\mvp\Source\mvp\RaynorScripts\NPC\NPC_Interactable.cpp(27): warning C4996: 'UTextRenderComponent::SetText': Passing text as FString is deprecated, please use FText instead (likely via a LOCTEXT). Please update your code to the new API before upgrading to the next release, otherwise your project will no longer compile.
1>  [8/21] NPCStandStill.gen.cpp
1>  [9/21] mvp.init.gen.cpp
1>  [10/21] mvpGameModeBase.gen.cpp
1>  [11/21] MvpCharacter.gen.cpp
1>  [12/21] FriendlyNPC_AnimInstance.gen.cpp
1>  [13/21] MovingPlatform.gen.cpp
1>  [14/21] NPC_Interactable.gen.cpp
1>  [15/21] MvpCharacter.cpp
1>  [16/21] FriendlyNPC_AnimInstance.cpp
1>  [17/21] FriendlyNPC.cpp
1>E:\repos\mvp\Source\mvp\NPC\FriendlyNPC.cpp(25): warning C4996: 'UTextRenderComponent::SetText': Passing text as FString is deprecated, please use FText instead (likely via a LOCTEXT). Please update your code to the new API before upgrading to the next release, otherwise your project will no longer compile.
1>  [18/21] FriendlyNPC.gen.cpp
1>  [19/21] UE4Editor-mvp-0001.lib
1>     Creating library E:\repos\mvp\Intermediate\Build\Win64\UE4Editor\Development\mvp\UE4Editor-mvp-0001.lib and object E:\repos\mvp\Intermediate\Build\Win64\UE4Editor\Development\mvp\UE4Editor-mvp-0001.exp
1>  [20/21] UE4Editor-mvp-0001.dll
1>     Creating library E:\reposmvp\Intermediate\Build\Win64\UE4Editor\Development\mvp\UE4Editor-mvp-0001.suppressed.lib and object E:\repos\mvp\Intermediate\Build\Win64\UE4Editor\Development\mvp\UE4Editor-mvp-0001.suppressed.exp
1>  [21/21] mvpEditor.target
1>Total time in Parallel executor: 28.84 seconds
1>Total execution time: 34.85 seconds
1>Done building project "mvp.vcxproj".
========== Rebuild All: 1 succeeded, 0 failed, 1 skipped ==========

As you can see it says Building 21 actions with 32 processes…

I have a 1950X CPU

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