OpenCL not working - hardware acceleration

[Bucic]

Recently I went ahead and confirmed whether OpenCL is actually working on my GIMP installation. It seems it doesn't. I've tested it on the non-legacy Photocopy filter as well as with Exposure adjustment, same as this bloke https://www.youtube.com/watch?v=zVLjBa6Lqbk There is absolutely no perceivable difference in the performance with OpenCL disabled or enabled.
I've got fresh nVidia drivers, Geforce 660 Ti by MSI, AMD FX6300 (6-core 3.5 GHz), Windows 7 x64. So not having OpenCL in working condition is a huge waste.

What can I do to troubleshoot it? Now I realized OpenCL has was never working on my GIMP installs, even though I tried enabling it since early GIMP 2.9 times.

[Bucic]

Anyone? :/

[Ofnuts]

Hard to tell for me also. A bug report mentions a --gegl-disable-opencl option (which would mean that the old "GEGL_ENABLE_OPENCL" variable is obsolete). I assume you have already set the Enable OpenCL in the preferences.

An old benchmark on Tom's Hardware explains that the effects aren't always visible. They used a motion blur on a large picture to see something.

[Bucic]

(02-11-2019, 07:57 AM)Ofnuts Wrote: Hard to tell for me also. A bug report mentions a --gegl-disable-opencl option (which would mean that the old "GEGL_ENABLE_OPENCL" variable is obsolete). I assume you have already set the Enable OpenCL in the preferences.

An old benchmark on Tom's Hardware explains that the effects aren't always visible. They used  a motion blur on a large picture to see something.

Yes, I have "Use OpenCL" enabled in the preferences.
Which bug are you referring to specifically?

Today I found two new resources with people claiming OpenCL may not be that noticeably beneficial right now.
https://gitlab.gnome.org/GNOME/gnome-pho...bc59f9c39a

Quote:until there's
OpenCL coverage for all the operations that are used it's not going to
have the expected performance boost due to memory transfers between
the CPU and GPU. In fact, today, for many cases using the GPU is
measurably, sometimes significantly so, slower than the CPU.

and
https://discuss.pixls.us/t/gimp-speed-up...pu/8004/11

Quote:The wiki is back up and running. I tested the Alien Map function on my 6000x4000 16-bit image, since according to the wiki, Alien Map uses open CL.
Again, it was slower with Open CL enabled. (10.2 seconds with Open CL enabled, 9.3 seconds with it disabled). I have 16 GB of RAM, by the way, and not using any swap space, if that matters.
Note that I’m not actually applying the changes, just previewing them, then removing the preview to time it to go back to normal.

EDIT:
Based on
https://wiki.gimp.org/wiki/Hacking:Porti..._to_OpenCL
I used Stretch Contrast to test this. The result is: OpenCL is slower by ~20% on a 21 MP image, 8-bit precision.

Related
https://www.tomshardware.com/reviews/pho...08-10.html

[Bucic]

I'd like to share a comment I found on Youtube:

Quote:LILA
2 hours ago
Yes, OpenCL has not really impressed us so far, in particular compared to common multi-threading implementation (i.e. CPU only). In some cases, it even makes issues as various driver implementations were buggy (this is unfortunate as apparently OpenCL has not been a priority for some hardware vendors). This is the reason why this is not enabled by default in GIMP and we even added a big fat warning under the option: "OpenCL drivers and support are experimental, expect slowdowns and possible crashes (please report)."
Anyway feel free to try but for now, this is not considered as the recommended way to run GIMP.

Quote:LILA
5 hours ago
Indeed I just checked in the dev log, this is a very new warning, added just a few weeks ago. So it's not in any released version yet (the warning will be in 2.10.10). You are right.

As for the hype, not to say we don't sometimes put some on specific features (don't blame us, we can get excited by what we do! ), but for OpenCL specifically, I think we have been quite timid (since at the opposite, we were not so excited by results here! Of course, I guess some may have been a bit excited at the very start of the OpenCL integration, which is normal). Looking at 2.10.0 release notes (probably the only release news we talked about OpenCL?), we cite it twice (in a huuuuge note), always together with some remark to cool down the hype such as "available for systems with stable OpenCL drivers" or "if OpenCL drivers work well for you". Doesn't sound very hype to me. :-)

Or maybe you mean third party articles, but then we don't control these! 

https://www.youtube.com/watch?v=uaZRcZf6lg0