Not sure what changed on my PC, but b1/b2 Visualize is not utilizing the GPU any more.  I know b1 was working because i rendered a 1080p 100pass 180frame video using the denoiser in 30min!  Wowza!  Today however, i cannot get it (b1 or b2) to utilize the GPU no matter what i do.  Tried lowering the preview resolution, closing/reopening the project, closing/reopening Visualize, restarting the PC.  GPU is GTX 1080.