That page says:
"OpenCl is used for export as well as when calculating RAW display when the zoom level is above 75%. This is true only if our benchmark has determined that OpenCL performance is superior to CPU processing."
OpenCL (Open Computing Language) can sometimes do calculations faster than the main processor (CPU) by involving more processors available via the OpenCL framework. For example involving a hefty GPU (graphical processing unit) sitting on a graphics board with lots of memory and otherwise idle processor cycles to burn.
Applications may feed a test-calculation via OpenCL to benchmark it to see if it actually performs better than just using the central processing unit in a straight forward manner. Capture One has a setting where the user may set OpenCL usage always off, always on or auto. Capture One will use all GPUs (think multiple graphic cards on one computer) to boost speed.
DxO will apparently use OpenCL for export (calulations) and when calculating RAW display when the zoom level is above 75%. if OpenCL proved to be faster when bechmarked, that is.
You may perhaps like this web page:
http://everything.explained.today/OpenCL/
Beware of the "framework battle" as indicated by Apple's move explained here:
https://www.imore.com/opengl-and-ope...d-macos-mojave
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Odd S.