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Building from source on Windows quickly

With the rapid expansion of the engine footprint, my Windows PC is taking about 73 minutes to build the 4.24.1 engine from clean. This is too slow so I am investigating upgrading my hardware to build faster. I’ve done some timing studies in various configurations that might interest others. Note, I recommend excluding your development disk area from Windows Defender since this sometimes has a big impact, although it only makes about a 2% difference for me building 4.24.1.

Generally, the build scales really well with real cores. Hyperthreading only makes an incremental difference of 8% or so. Fast IO seems to help the per-core scaling. I would love to see the performance of the new AMD 32-core Threadripper 3970 system compared to this, especially with 4 M2 SSD’s in RAID 0 to see if bandwidth or NTFS is the limiting factor.

Unreal Engine 4.24.1 complete build, (Clean Solution, then Rebuild Solution in Visual Studio 19 Version 16.4.0)
Intel(R) Xeon(R) W-2133 CPU @ 3.60GHz (6 real cores)
Samsung SSD 860 QVO 4TB

12 processes: 73 minutes
6 processes: 77 minutes
5 processes: 83 minutes
4 processes: 85 minutes
3 processes: 97 minutes
2 processes: 127 minutes
1 process: 234 minutes

New iMac Pro doing Mac build:
18/36 2.3 Ghz Intel CPU
2TB custom Apple PCIE SSD

iMac Pro 18/36, 36 processes - 20 minutes
iMac Pro 18/36, 24 processes - 20.8 minutes
iMac Pro 18/36, 18 processes - 21.7 minutes
iMac Pro 18/36, 17 processes - 22.3 minutes
iMac Pro 18/36, 16 processes - 23.2 minutes
iMac Pro 18/36, 15 processes - 24.3 minutes
iMac Pro 18/36, 12 processes - 28.7 minutes
iMac Pro 18/36, 9 processes - 36 minutes
iMac Pro 18/36, 8 processes - 39 minutes
iMac Pro 18/36, 6 processes - 49.8 minutes
iMac Pro 18/36, 4 processes - 71.8 minutes
iMac Pro 18/36, 3 processes - 93.6 minutes
iMac Pro 18/36, 2 processes - 136 minutes
iMac Pro 18/36, 1 process - 263 minutes

The same iMac Pro doing the Windows build using Parallels:

18 processes 45 minutes 30 seconds
16 processes 48 minutes
14 processes 52 minutes
6 processes 97 minutes

Forgot to mention I had to apply this update to get 4.24.1 to build (The Datasmith external dependencies issue), this may impact build times:

https://github.com/EpicGames/UnrealEngine/commit/7f18f950b0f415c2b74b8316e84910c0a9b4d793