My Time:
CPU: Intel I7-5820K 3.30 GHz
GPU: Nvidia GTX 1080 Ti
OS: Windows 10 x64
(GPU-CUDA) 1080p @50%
Time: 46 sec (Tile Size 286x286)
Time: 46 sec (Tile Size 240x270)
Time: 47 Sec (Tile Size 300x300)
Time: 49 Sec (Tile Size 256x256)
Time: 49 Sec (Tile Size 320x320)
Time: 51 sec (Tile Size 372x372)
Time: 53 sec (Tile Size 512x512)
Time: 1m 04s (Tile Size 1024x1024)
Time: 1m 05s (Tile Size 960x540)
Time: 1m 13s (Tile Size 128x128)
Time: 2m 48s (Tile Size 64x64)
(GPU-CUDA) 2160p @50%
Time: 2m 36s (Tile Size 286x286)
Time: 2m 42s (Tile Size 256x256)
Time: 2m 42s (Tile Size 300x300)
Time: 2m 48s (Tile Size 326x326)
Time: 2m 50s (Tile Size 512x512)
Time: 3m 01s (Tile Size 200x200)
(CPU)
Time: 2m 49s (Tile Size 16x16)
Time: 2m 53s (Tile Size 32x32)
Time: 2m 53s (Tile Size 8x8)
Time: 3m 01s (Tile Size 64x64)
Time: 3m 35s (Tile Size 240x135)