macOS High Sierra (v10.13.6)
AMD Radeon Pro 580
Intel i7-7700K @ 4.20 GHz
GPU (2.79b, 2018-3-22):
128x128
Time: 4 min 27 seconds
256x256
Time: 3 min 58 seconds
512x512
Time: 4 min 40 seconds
CPU:
8x8
Time: 2 min 28 seconds
32x32
Time: 2 min 34 seconds
64x64
Time: 2 min 47 seconds
128x128
Time: 2 min 56 seconds
256x256
Time: 3 min 12 seconds
Using the latest build, I got even quicker times:
CPU (v2.79 2018-10-17):
8x8
Time: 1 min 50 sec
32x32
Time: 1 min 51 sec
64x64
Time: 1 min 52 sec
128x128
Time: 1 min 59 sec
256x256
Time: 2 min 6 sec
GPU:
128x128
Time: 2 min 19 sec
256x256
Time: 2 min 8 sec