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Compiling a game - cpu or gpu

With the advent of UE4 are we still compiling our game strictly on CPU or has Epic started utilizing the GPU to help offset the demands of creating large executables?

If it is strictly CPU, is UE4 multi-threaded and will it take advantage of all cores and all threads in a dual-CPU configuration?

GPU is only used for gameplay, it’s not used for building lighting or compiling. I don’t know if the compiling is multi-threaded, I would think so.

Why does building lighting not use the GPU? Wouldn’t that make more sense?

In some ways, but game levels can end up being quite large, you need to be able to load the entire level when you build lighting and most GPU’s only have 2GB of memory unless you buy a card specifically to have more, even at 6GB which is the maximum for today’s cards you could easily fill it up.

So if we were to build a large scale sandbox type environment that would be quite populated with 100’s if not 1000’s of lights with a ton of geometry spread over a number of square kilometers, what kind of server config should we be looking at?

I’m currently leaning towards a dual-cpu Xeon 10-core 20-thread config with between 64 and 128GB of RAM - but if this were overkill, I could save a lot of money. I need some guidance from Epic.

A Tim Sweeney quote from a recent Gamasutra article](http://www.gamasutra.com/view/news/213647/Epics_Tim_Sweeney_lays_out_the_case_for_Unreal_Engine_4.php) might help:

I can’t say if this also applies to lighting builds, but perhaps someone official could chime in?

I am trying to offload lighting to Amazon EC2 but I can’t seem to get Swarm working locally even yet. Will dig through the source code when I get time to work out why.
I think a 55 core Compute Intensive machine is about $0.48/hour.

The kind of utterly huge sandbox game you described, lightmaps are not advisable choice. Dynamic lights are probably the most practical solution, the performance boost isn’t that large that the time baking Vs the performance tradeoff are worth it for lightmaps, the loss would arguably be GI, but the realtime GI solution is around the corner for UE4 so even then.

With deferred lighting/shading dynamic lights are cheaper than they have ever been

Thanks for shedding light on this Chronichol, super helpful. I’ll be keeping my eyes open for what’s going on with dynamic lights :slight_smile: