Using darktable with a 1440p display, amd rx560 with opencl enabled, and kabylake i7 CPU. Ubuntu 18.10. AMD ROCM opencl driver.
OpenCL provides a massive speedup for image Export (around 500%) but I am not seeing a any increase in performance with openCL during interactive editing.
Measuring performance metrics I can see a decrease in pixelpipe processing times with opencl enabled being reported on the terminal (-perf option) however I don’t ‘feel’ darktable any more snappy when e.g. zooming in when all my fave modules are activated . It takes 3-4 seconds for darktable to finish “Working…” before the zoomed-in or out image image is displayed, with or without openCL enabled.
I did notice that if I reduce the size of the darktable window (I call it viewport) then zooming in and out becomes a lot snappier / responsive.
I followed the opencl optimization guidelines here: https://www.darktable.org/usermanual/en/darktable_and_opencl_optimization.html
but still I don’t see any perceptible difference in snappiness for interactive use with opencl activated vs. de-activated.
Wondering - any recommended setting/s that people are using in order to leverage more OpenCL for interative image editing?
I noticed some ppl lower the screen resolution when working with DT but I’d rather avoid that approach
 profiled denoise, local-contrast/laplacian, sharpen, velvia, shadows&highlights, and occassionally a few more. e.g. Lens correction, exposure tweaks, color balance &c.