Update user manual section concerning OpenCL

[elstoc]

Copied from https://github.com/darktable-org/darktable/issues/2271

Is your feature request related to a problem? Please describe. Contrary to information in user manual, OpenCL generally doesn't work on AMD cards.

Describe the solution you'd like The information given in https://www.darktable.org/usermanual/en/darktable_and_opencl_amd.html reads:

While NVIDIA devices and most modern AMD/ATI devices will most often run out of the box, there is more to do for older AMD/ATI graphics cards, namely those prior to the HD7xxx series.

That doesn't reflect current situation now, as most AMD cards now use open drivers which do not support OpenCL well enough to work in darktable (missing image operations: https://dri.freedesktop.org/wiki/GalliumCompute/, https://bugs.freedesktop.org/show_bug.cgi?id=87738). There are two alternatives, namely amdgpu-pro or ROCm. They usually don't work out of the box and require manual setup. Moreover quite often they don't work at all. In my particular use case, amdgpu-pro gives corrupted images and crashes the system, while ROCm doesn't work due to lack of PCIe atomics. See also the discussion below the article https://www.darktable.org/2012/03/darktable-and-opencl/

Thus I believe the information in user manual is quite obsolete and misleading and should be partially rewritten.

• section 10.2.1 should note that AMD cards may cause problems (also ATI should be changed at least to ATI/AMD)
• section 10.2.5 should mention the case of [opencl_init] discarding device 0 XXX due to missing image support.
• section 10.2.6 is generally completely obsolete as it deals with really old cards running with long unsupported fglrx driver. It should be updated to describe a current situation and the existing text should clearly reflect that it deals with a legacy situation.
• possibly even the article https://www.darktable.org/2012/03/darktable-and-opencl/ should get another update concerning this situation.

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This issue has not had any activity in the past 60 days and will be closed in 365 days if not updated.

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This issue has not had any activity in the past year and has therefore been closed.