Many readers will have already heard about GPU processing and the fact that darktable can make use of OpenCL to improve performance. As we still lack a detailed documentation of that topic, please find here a few explanations and howtos. The Background Processing high resolution images belongs to the more demanding tasks in modern computing. Both, in terms of memory requirements and in terms of CPU power, getting the best out of a typical 15, 20 or 25 Megapixel image can quickly bring your computer to its limits.