I Don’t quite often render with CPU+GPU.
Most of the time I use GPU only.
But a whole ago I noticed that for some reason CPU+GPU wasn’t fast enough. Also when I use CPU+GPU for rendering, In the last tile it takes Forever to render when samples are 1000+
So I did a test on my old piano project
And here are the result
1080P with 100samples
16* 16=? (Didn’t bother rendering)
32* 32= 3min 07sec
128* 128 = 48sec
256* 256 = 42sec
512* 512 = 40sec
CPU + GPU
16* 16= 2min 3sec
32* 32= 1min 22sec
128* 128= 38sec
256* 256= 38sec (???)
512* 512= 1min 12sec (???)
I was trying to find a sweet spot for CPU+GPU rendering, 128* 128 and 256* 256 tiles gave me same render time, And only 2-8sec less only GPU rendering.
And yes 512* 512 tiles took more time because last tile took so much time, same as 256* 256 tiles. Even though with 256* 256 tiles it was a bit faster than 128128 tile, but because of that last tile we got the same result.
So for me 128 128/256* 256 tiles looks like a sweet spot, but not really worth it.
I also heard that for some people 1616/ 3232 is a sweet spot for CPU+GPU rendering,
So i’m guessing it depends on each hardware.
My CPU is not very powerful for rendering, But people who’re using Ryzen CPU may find more interesting rendering time with CPU+GPU.
i5 6400 (Boost up to 3.3GHZ)
16GB DDr3 Ram (2Slot)
Rx 590 OC Edition 8GB Graphics card
Here is the .Blend file
I hope some people find this test useful