GPU rendering slower than CPU rendering

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TAO
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GPU rendering slower than CPU rendering

Post by TAO » Tue May 12, 2020 1:37 pm

I'm not completely sure but on my PCs here PathCPU runs faster than PathGPU. And I have good performance GPUs.
It's same in LuxCoreUI and LuxCoreRender in 3ds max.
I try the same scene on other machines and the result was the same whit Nvidia 2080, much better with AMD GPU but somehow the same.
Perhaps I missed something.

PathCPU - Intel 9900K
PathCPU.jpg
PathOCL - GPU NVIDIA 1080 8G
PathOCL-GPU.jpg
PathOCL - GPU+CPU
PathOCL-CPU+GPU.jpg
It's almost the same for MaxToLux that use LuxCore.
Also if I restart the scene a couple of times in LuxcoreUI and switch between GPU and CPU render will slow down more.

One more thing if I use point light (infinite) even in a close environment like a room, render will take much more time to compile, and render getting slower than before.
Omid Ghotbi (TAO)
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kintuX
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Re: v2.3 Vs v2.4 performance

Post by kintuX » Tue May 12, 2020 1:48 pm

Same here, I'm starting to observe the same.
Considering compilation time, especially with 2 (or more GPUs) make light to mid-weight scenes not worth it.
And then, for heavy weight scenes, there's the RAM limit.

epilectrolytics
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Re: v2.3 Vs v2.4 performance

Post by epilectrolytics » Tue May 12, 2020 4:14 pm

TAO wrote: โ†‘
Tue May 12, 2020 1:37 pm
I'm not completely sure but on my PCs here PathCPU runs faster than PathGPU. And I have good performance GPUs.
This looks strange indeed, I can't confirm this on my system, everything works as expected here.
Screenshot.jpg
From your screenshots I see you're using LuxCoreUI v2.2.
Maybe something is wrong with your scene?
Can you share in text form (.cfg) so that we can take a look and run a test?
Also the first image (Intel CPU) with the highest speed looks noisier than the others despite similar sample count which should not be the case.

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Re: v2.3 Vs v2.4 performance

Post by juangea » Wed May 13, 2020 9:00 am

I would say it makes no use to post this with LuxCore 2.2, check the situation with 2.3 or 2.4. :)

epilectrolytics
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Re: v2.3 Vs v2.4 performance

Post by epilectrolytics » Wed May 13, 2020 9:41 am

juangea wrote: โ†‘
Wed May 13, 2020 9:00 am
check the situation with 2.3 or 2.4. :)
Agreed, and I did check with 2.4 too, same result (GPU faster than CPU with Cornell scene, though smaller difference).
But I'm curious what kind of setup could possibly slow down GPUs so much, no matter which Lux version ?

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Re: v2.3 Vs v2.4 performance

Post by TAO » Wed May 13, 2020 11:07 am

That's a good point let me check with v2.4
But I'm curious what kind of setup could possibly slow down GPUs so much, no matter which Lux version ?
That's my whole point. GPU should be faster in any circumstances with such a simple scene with only two objects and one light and just a gamma correction.
Last edited by TAO on Wed May 13, 2020 11:18 am, edited 1 time in total.
Omid Ghotbi (TAO)
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lacilaci
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Re: v2.3 Vs v2.4 performance

Post by lacilaci » Wed May 13, 2020 11:15 am

Maybe some luxcore gui bug? A 2.4 build from 2 days ago runs definitely faster on gpu than on cpu.
In an production scene example I got 20sec/100 samples rendering on 2070 and 50sec/100 samples on amd 2700(Blendluxcore).
Which is more or less as I always remember the difference between this cpu and gpu config in luxcore.

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Re: v2.3 Vs v2.4 performance

Post by TAO » Wed May 13, 2020 11:33 am

It tried v2.3 and it's slightly faster on PathCPU but the bad news isูˆ its ganna crush any time I change the renderer to OpenCL or getting too slow on many scenes.
Annotation 2020-05-13 155044.jpg
Here a screen capture from what happened.
LuxCore UI v2.3 2020-05-13 15-50-24.mp4
(2.01 MiB) Downloaded 15 times
I'm Not sure but I don't think the issue is about the scene, I can render this exact scene in v2.2

And the scene. the super light scene, no texture.
t3.zip
(83.01 KiB) Downloaded 17 times
Omid Ghotbi (TAO)
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viewtopic.php?f=5&t=1010&start=160#p22925

epilectrolytics
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Re: v2.3 Vs v2.4 performance

Post by epilectrolytics » Wed May 13, 2020 2:20 pm

Apparently the scene is ok, it works with v2.2, v2.3 and v2.4alpha on my PC.
GPU is always faster but on v2.3 less than on v2.2 and v2.4 :?
Screenshot.jpg
Something I noticed:

Code: Select all

opencl.cpu.use = "1"
opencl.gpu.use = "1"
opencl.devices.select = "11"
You have your Intel CPU activated as an OCL device and it should be contributing in OCL mode.
Can you confirm that with pressing "J" during rendering which should show the statistics of all working devices?

My Ryzen has no OCL driver and will only work natively, so I cannot test the original configuration of the file.

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Re: v2.3 Vs v2.4 performance

Post by TAO » Wed May 13, 2020 3:01 pm

Definitely there is an issue with v2.3 and 2.4 if I disable CPU manually by editing the scene config file, it will load successfully and render but still slower or at the best case with the same performance as GPU.
But if I try to enable GPU and CPU OpenCL in render engine menu Luxcoreui will crush.
Screen.jpg
If you look closely nothing wrong with the scene file.
I need to set the CPU device to 0 manually to even load the scene when I want to use OpenCL.
Omid Ghotbi (TAO)
Download link to last MaxToLux build.๐Ÿ‘‡๐Ÿ‘‡
viewtopic.php?f=5&t=1010&start=160#p22925

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