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Changing UBT config to limit max CPUs

Hey Guys

I would like to know if there is an option, or line of code I can edit, to limit the amount of CPU cores it uses to build the project. I only have 8 Gig RAM and run out of RAM during compilation, thus the build fails. I have to build it multiple times in order to complete the build process, each times it builds a little bit at a time.

I have limited the CPUs in Visual Studio, but I know UBT builds the source on it's own, so that's probably why it didn't work.

Any advice ? Except for buying more RAM :-)

Product Version: Not Selected
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asked Sep 01 '14 at 12:18 PM in C++ Programming

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You can try tweak:

 /// <summary>
 /// Processor count multiplier for local execution. Can be below 1 to reserve CPU for other tasks.
 /// </summary>
 public static double ProcessorCountMultiplier;

 // When using the local executor (not XGE), run a single action on each CPU core.  Note that you can set this to a larger value
 // to get slightly faster build times in many cases, but your computer's responsiveness during compiling may be much worse.
 ProcessorCountMultiplier = 1.0;




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answered Sep 01 '14 at 03:34 PM

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avatar image Ad3ViLl Sep 01 '14 at 03:55 PM

Nope, didnt work. Thanks for the help though.

avatar image Pierdek Sep 01 '14 at 04:27 PM

Ok, find


then find this line of code:

if (Utils.IsRunningOnMono)

and before this line put MaxActionsToExecuteInParallel = 2; or something

avatar image Ad3ViLl Sep 01 '14 at 04:34 PM

Ahhh, awesome thanks, that worked !!

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With latest master (4.6, didn't make it to 4.5) there's an option. Add MaxProcessorCount tag to Engine/Saved/UnrealBuildTool/BuildConfiguration.xml. Something like this:

 <Configuration xmlns="https://www.unrealengine.com/BuildConfiguration">
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answered Sep 26 '14 at 06:39 PM

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avatar image Pierdek Sep 26 '14 at 07:30 PM

huh six month of waiting;)

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