[Tutorial] Boost Compile Times


After building for quite some time I put together some notes on how to boost compile times for the engine and your game projects. I was able to go from 36 minutes on a complete rebuild to 23 minutes, which is quite a lot by applying only a few tweaks.

You can find the tutorial on the wiki and as post on my blog.

Holy ****! Thanks for posting it.

I don’t have a direct comparison at hand, but it made a ridiculous difference on a test scene that had extreme values set in the lightmass.ini. Made it probably 5-10x faster for me.

Pretty confident the difference on low build settings will be rather small, but with extreme settings the speedup seems to quadruple.

Every thing that is IO bound will benefit from the same approach. Nice that it helped! You could also add your numbers into the wiki post :smiley:

I honestly cannot find the UnrealBuildTool , I’ve looked everywhere , searched on all my drives.
There is only one I’ve found in C:\Users\Robbie\AppData\Roaming\Unreal Engine\UnrealBuildTool\BuildConfiguration.xml but this only contains : " <?xml version=“1.0” encoding=“UTF-8”?>

-<Configuration xmlns=“https://www.unrealengine.com/BuildConfiguration”>

<BuildConfiguration> </BuildConfiguration>


Can anyone help?

Check UE4/Engine/Programs/UnrealBuildTool directory. Probably it will be generated when you’ll build your engine.

Much like Robbie222, I am unable to find the BuildTool config. I too have a xml file in AppData\Roaming\Unreal Engine\UnrealBuildTool\ which with zero configuration parameters in it.

Additionally, I do not have a “documents” but I do have a “My Documents”, in which there is only an Unreal Projects folder (which is empty).

For 4.10, on a Windows 7 system, where in the world is the engine installed at? Bear in mind I installed the engine from a supplied executable from the site, not a build from source.

Bump, I cant find the file either, was it switched to somewhere else, or does unreal automatically use all cores to build now, or whats the deal.

It’s in Engine/Saved/UnrealBuildTool/BuildConfiguration.xml

EDIT: I’ve checked UBT source code, it seems you can control number of parallel tasks (upper value) with BuildConfiguration.xml, “MaxProcessorCount” property.

Hi All,

I can’t do that in version 4.22. Is “boost” still available?

I would like to know that as well.

I guess yes, just check if the BuildConfiguration.xml has the same variables or it might changed in some way.

Is a compiled version from source required in order to make this work?
I can’t find the xml file you are refering to.

The file might be in different places depending on the engine version. But I guess you are right, on installed builds you can not specify it => https://github.com/EpicGames/UnrealEngine/blob/6c20d9831a968ad3cb156442bebb41a883e62152/Engine/Source/Programs/UnrealBuildTool/System/XmlConfig.cs#L205

is there anything update? now i’m using UE 2.24 and i still fould the config.xml C:\Users&lt;my user name>\AppData\Roaming\Unreal Engine\UnrealBuildTool\BuildConfiguration.xml

From the source code it seams that it moved: https://github.com/EpicGames/UnrealEngine/blob/6c20d9831a968ad3cb156442bebb41a883e62152/Engine/Source/Programs/UnrealBuildTool/System/XmlConfig.cs#L223

Now it should be here: AppData/Unreal Engine/UnrealBuildTool