[sorenbouma]

I might be wrong, but I think this cost calculation is way off:

Their running cost estimate of a single TPU in a machine with 4 "TPUs" is based off the price of a cloud TPU v2-8, but a v2-8 is actually 4 ASICS on 1 board.

Also, because of the date of publication being around the time v2s were announced, and the fact that the TPU is only used for inference and GPU is used for training, I think self play was likely done on TPU v1s, which use 5x less power per ASIC and so are likely much cheaper

I also think the way they calculated the number of TPUs required is wrong, it looks like they assume 1 machine with 4 TPUs makes 1 move in 0.4 seconds, but since making 1 move only requires a forwards pass through a moderately sized CNN with 19x19(tiny) input, 1 TPU should be able to make thousands of moves in parallel per second.

[brilee]

Making one move requires 1600 MCTS playouts to explore the game tree, so it's a 1600-1 correspondence of "forward pass" and "move played".