Hi,

I'm working on a new workstation with

Dual Xeon E5-2698 v4 @ 2Ghz with 40 cores each (80 cores total).
64GB DDR4 ram

Suprisingly, when I tried to do a Mantra rendering, it only uses 40 threads, even if I selected “use all processors” in the rendering panel.

So my question is simple : is there a core limitation in houdini ? Is there a command line (in *.ini file) to fix this problem ? Because, after all, Houdini uses only 1 CPU instead of using 2 ! That's a huge loss.

I've found this thread without any answer :
https://www.sidefx.com/forum/topic/44634/ [sidefx.com]

Let me elaborate on the matter - Houdini 14, for example, can see up to 64 threads without clustering CPUs into groups. Above 64 threads, it'd divide 2 CPUs into two groups and utilizing only one - translated to the case of DUAL Intel Xeon 2698 v4 configuration, Houdini 14 sees “only” 40 threads (one group = one CPU), rendering the other CPU useless.

And when I go to Help > About Houdini > Show Details, I got :

Houdini FX Version 15.0.244.16

Platform: windows-x86_64-cl17
Operating System: Windows 10 Pro x64 (6.2.9200)
Number of Cores: 40
Physical Memory: 63.89 GB
Number of Screens: 2
Screen 0: 1920 x 1080 at -1920,0
Work Area 0: 1920 x 1080 at -1920,0
Screen 1: 1920 x 1080 at 0,0
Work Area 1: 1920 x 1040 at 0,40

OpenGL Vendor: NVIDIA Corporation
OpenGL Renderer: GeForce GTX 980/PCIe/SSE2
OpenGL Version: 4.5.0 NVIDIA 368.69
OpenGL Shading Language: 4.50 NVIDIA
Detected: NVidia Consumer
4096 MB
368.69.0.0

Environment:

HOUDINI_MAXTHREADS 40

NUMBER_OF_PROCESSORS 40

I tried to put these lines in the INI file but without success…
HOUDINI_MAXTHREADS = 80
NUMBER_OF_PROCESSORS = 80

You only have 40 real cores.

Theoretically you support 80 threads with Hyper-Threading which only yields 5 to 15% improvement in speed for all the extra threading.

But with 40 cores you will have so much overhead that I don't think it would be worth the hyper threading…