We have seen in other threads that the comparision was not fair. While Stockfish used 64 cores and no opening book and no endgame tablebases, Alpa Zero used something equivalent to 400 to 2000 cores and something equivalent to an opening book. Also, they didnt use the latest development version of Stockfish but an older Version.
Some said even Fritz could beat Stockfish under such circumstances and further that Alpha Zero is probably equally strong.
Some said that this just proves how optimized modern chess engines are, as Alpha Zero beated the engines in the other games much clearer.
Still it is cool that an Algorithm can learn how to play chess like this in just four hours, even if they used Power comparable to 500.000 to 1.250.000 cores to train Alpha Zero (im quoting a dude here who said they used 5000 TPUs and one TPU is said to be comparable to 100 - 250 modern cores, depending on how you count, correct me if i am wrong here).
For comparison, my laptop has four (outdated) cores.
Sources:
groups.google.com/forum/?fromgroups=#!topic/fishcooking/pcFRIurN_l4