20-Way NVIDIA/AMD GPU Darktable OpenCL Photography Performance

With the holiday season in full swing, whether you are just a casual photographer or professional, Darktable is easily one of the best photography workflow applications and it's free software! Darktable has offered OpenCL acceleration for providing faster performance on GPUs and with the imminent Darktable 2.2 release there is even better OpenCL results. For those curious about the OpenCL performance of Darktable, I've done some Darktable 2.2-RC1 benchmarks on a variety of NVIDIA GeForce and AMD Radeon graphics cards under Ubuntu Linux.