Quick CPU vs GPU speed comparison (Archviz interior scene)

[Karol.Osinski]

Hey all, this morning I've found 5 minutes to run a quick test on one of our more complex archviz scenes and compare CPU and GPU performance.
The scene takes 20GB of RAM.

I run a progressive render with following settings.

msr: 24
max subdivs: 70
noise treshold set to 0.009 (probably too low but I don't it matters in this case)
max render time of 4 minutes.
Ray bundle size: 128 on CPU and 192 / 16 on GPU - I left those at default.

V-RAY CPU: 2 x i9 7900X
V-RAY GPU RTX: 2 x 2060 SUPER + 3970X (I am not sure if it was utilized in RTX mode)

I started renders simultaneously and as expected CPU started frame faster, although only maybe 20 seconds faster then GPU. Light cache calculation was about 20% faster on CPU but this I think it is related to i9 7900X handling it better than 3970X (please correct me if I am wrong).
As you can see from the images the GPU is significantly cleaner.

On LITTLE thing...on the second frame of animation GPU stopped with an Optix error...


I also uploaded the second frame to give you an idea of what kind of Archviz environment it is.

[Karol.Osinski]

P.S CPU did around 100 passes while GPU 1000+... is this expected ??

[nikoleta.garkova]

Hi Karol.Osinski

The error you've received could be caused by a lot of things. Would it be possible to update your GPU drivers, run another test and see if you still get it? If so, please do forward the scene to support@chaosgroup.com for further investigation, thanks!

[Micha]

I would disable the CPU for GPU rendering, since it could cause a slowdown, since some CPU spend to much time for emulating GPU rendering and forget to feed the GPU. Or you test it before and if the CPU helps, you could keep them.

[glorybound]

I don't think I had a GPU job that didn't fail with one of those errors. It might take a while, but it'll happen eventually.

[squintnic]

weird settings
this is not a great comparison - do you have render and load times ?
how much vram used? what GPU settings?

[Karol.Osinski]

Hey squintnic, thanks for your comment. I am sorry, I kinda ruched this test and I am aware it is not really comprehensive comparison..What do you mean by weird settings?
High MSR (I always use it higher numbers instead of 6 for progressive renders).
I almost always find 100 of max subdvis an overkill for most of the scenes.
Low treshold of 0.009 I think in this case it does not change anything as with such low max render time (4 minutes) the sampler wasn't be able to reach that treshhold anywhere in the image in order to stop there.
Ray bundle size I left at defaults.

The load times I provided in percentage but if I remember well the scene load on CPU was 1 min. while on GPU 1:25 sec. - very similar results with LC calculations (in both cases at 2500).

[Karol.Osinski]

p.s I gotta check the VRam usage and how 20gb of RAM usage with CPU translates to it.

[squintnic]

maybe i missed the render time for each?

[oglu]

There is much more noise in the CPU render.

[Micha]

For the last two questions - so far I understood, the render time is fixed to 4min and we see the quality difference.

[Karol.Osinski]

There is much more noise in the CPU render.

It showed me that 2x i9 7900x did around 100+ passes while 2x 2060 SUPER did 1000+... it looks a bit unrealistic to me and I wonder if the CPU / GPU passes are really equalivent to each other.

[Karol.Osinski]

Hi Karol.Osinski

The error you've received could be caused by a lot of things. Would it be possible to update your GPU drivers, run another test and see if you still get it? If so, please do forward the scene to support@chaosgroup.com for further investigation, thanks!

HI nikoleta.garkova , thank you. I am happy to say that running GPU in bucket mode did not give me any error and even managed to render all 8 frames of animation (Archviz stills).

I am looking forward to post some better testings results using bucket mode for much better comparison...as soon I find some spare time.