Execution is slower with OpenCL


(masmys) #1

This is my first post to this wonderful forum. I mostly lurk here picking up things :slight_smile:

I regularly use darktable on my debian system. Today I ran the phoronix benchmark on darktable with just cpu and then opencl. The results are surprising (to me). Darktable takes twice the time to complete the test with OpenCL as compared to just cpu. The results are here:

CPU Only

With OpenCL

I just want to understand whether this is the expected behavior? If not, how to address the problem?


#2

You don’t have a particularly strong graphics card.


(masmys) #3

I had an inkling of that. Still, should it not improve the speed rather than slow it down completely?


#4

The GT610 only can do up to 155 gigaflop with all single precision FMA instructions, which is terribly optimistic. Realistically it’s half of that at the very best, and only in ideal conditions.

Your CPU is somewhere around 40 gigaflop. I suspect it’s closer to being fully utilized than the GPU.


(masmys) #5

Thanks for the helpful explanation. Which card would be better for darktable/rawtherapee which is also not very expensive?


#6

What’s your budget?


(masmys) #7

I can spare up to INR 7000 (i.e., ~$100) :slight_smile:


#8

You may find an Nvidia GTX 950 or 1050 for $100. They’re approximately ten times more powerful than your current GPU.


(masmys) #9

Thanks. Hopefully that should give me a big in processing speeds :slight_smile: