topic Re: Prioritize GPU, but fallback to CPU if not available in Arnold GPU Forum

Prioritize GPU, but fallback to CPU if not available

am_wilkins — Tue, 10 Sep 2024 15:15:14 GMT

Hi,

I was wondering if there was a way or plans to implement a "pseudo-XPU" system for Arnold GPU.

My thoughts were that you can choose to prioritize rendering on a GPU if available, however if there isn't a GPU then Arnold will fall-back to the CPU.

This way a job can be submitted to a CPU and GPU based render farm and succeed rendering on either systems.

All the best,

amwilkins

Re: Prioritize GPU, but fallback to CPU if not available

Stephen.Blair — Tue, 10 Sep 2024 16:14:57 GMT

On the Device tab

Re: Prioritize GPU, but fallback to CPU if not available

am_wilkins — Wed, 11 Sep 2024 07:05:47 GMT

Hi Stephen,

Oh wow... I had completely missed that for some reason, that's what I get for posting before double-checking.

Thanks very much, we'll try it out. 👍

amwilkins

Re: Prioritize GPU, but fallback to CPU if not available

am_wilkins — Tue, 15 Apr 2025 12:28:26 GMT

Hi,

Finally managed to get around to testing this, however it doesn't appear to work.

Setting the Fallback Device to CPU, and submitted a render job to CPU only nodes gets me these errors:

Node #1 example:

ERROR | [gpu] no compatible NVIDIA GPUs found (GPU-rendering) WARNING | [kick] render aborted due to earlier errors

Node #2 example: (yes, drivers are out of date)

ERROR | [gpu] NVIDIA driver 512.15 is too old, version 537.13 or higher required (GPU-rendering) WARNING | [kick] render aborted due to earlier errors

In any event, Arnold doesn't flip over to CPU and starting rendering.

Any reason why this wouldn't be working?

I tried various device expressions using just "*" or trying to specify certains cards (btw documents aren't well updated for this except the C4D ones.)

all the best,
amwilkins

Houdini Core Version 20.5.410
Arnold Core: 7.3.6.0

HotA: 6.3.6.0

CPU: AMD Ryzen TR 3990x / 3970x

RAM: 128GB
GPU: NVIDIA RTX 4090 / RTX A4000
OS: Windows/Linux

Re: Prioritize GPU, but fallback to CPU if not available

DeclanRussell — Tue, 29 Apr 2025 09:52:13 GMT

Hi am_wilkins,

It seems currently that Arnold is assuming that you have a GPU compatible system before doing the checks for the fallback. Its currently working more like this: If I have a GPU compatible system, but no GPU matches the search criteria of the gpu_default_names regex or gpu_default_min_memory_MB threshold, then apply the fallback rules. I've made ARNOLD-16277 to add the case where you may not have a GPU compatible system to follow the fallback rules.

Re: Prioritize GPU, but fallback to CPU if not available

am_wilkins — Mon, 05 May 2025 07:25:58 GMT

Okay thanks, yes that would be ideal.

Usually in a farm setup with a mix of cpu and gpu, the cpu machines would generally either have old or on-board GPU, etc.

Re: Prioritize GPU, but fallback to CPU if not available

thiago.ize — Fri, 25 Jul 2025 23:59:55 GMT

Hi, this was fixed in the just released arnold core 7.4.3.0:

CPU fallback when no supported GPU found: Arnold falls back to CPU rendering according to the value of the render_device_fallback option when there are no supported GPUs. (ARNOLD-16277)

Re: Prioritize GPU, but fallback to CPU if not available

am_wilkins — Mon, 28 Jul 2025 07:34:20 GMT

Good day,

Okay awesome, will get us updated to this latest release and try test this again.

Thank you.