Here is my project setup:
As you can see I have setted up a lightmass importance volume and the stage is pretty small , with only 2 lights:
Error <None> === Lightmass crashed: ===
Fatal error: [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.7\Engine\Source\Programs\UnrealLightmass\Private\Lighting\LightingSystem.cpp] [Line: 1324]
Static lighting thread exception:
Fatal error: [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.7\Engine\Source\Runtime\Core\Private\GenericPlatform\GenericPlatformMemory.cpp] [Line: 54]
Ran out of memory allocating 16384 bytes with alignment 0
KERNELBASE.dll!UnknownFunction (0x000007fefcb3940d) + 0 bytes [UnknownFile:0]
UnrealLightmass-Core.dll!UnknownFunction (0x000007fec70444f4) + 0 bytes [UnknownFile:0]
UnrealLightmass-Core.dll!UnknownFunction (0x000007fec6f22754) + 0 bytes [UnknownFile:0]
UnrealLightmass-Core.dll!UnknownFunction (0x000007fec6e37867) + 0 bytes [UnknownFile:0]
UnrealLightmass-Core.dll!UnknownFunction (0x000007fec6e33ebd) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!operator new<TChunkedArray<Lightmass::FTexelToCorners,16384>::FChunk,FDefaultAllocator>() (0x000000013fc6793a) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!Lightmass::FTexelToCornersMap::FTexelToCornersMap() (0x000000013fc8085d) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!Lightmass::FStaticLightingSystem::ProcessTextureMapping() (0x000000013fd369a5) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!Lightmass::FStaticLightingSystem::ThreadLoop() (0x000000013fcee9d7) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!Lightmass::FMappingProcessingThreadRunnable::Run() (0x000000013fce5639) + 0 bytes [UnknownFile:0]
UnrealLightmass-Core.dll!UnknownFunction (0x000007fec7043b16) + 0 bytes [UnknownFile:0]
UnrealLightmass-Core.dll!UnknownFunction (0x000007fec703800d) + 0 bytes [UnknownFile:0]
kernel32.dll!UnknownFunction (0x0000000076ae59ed) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x0000000076d1c541) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x0000000076d1c541) + 0 bytes [UnknownFile:0]
Oh and a windows out of ram message pops up for UnrealLightmass(I have 8 gigs of ram and an ssd + hdd installed)