I'm referring to the French Defense (C11 ECO code) game where Alpha Zero played 30. Bxg6 ! , sacrificing a bishop for a better position. After Alpha Zero's move 30. , I couldn't find any good moves for Black. However, after the earlier move by White 28. Rc2, Houdini suggests after many hours the reply 28... Qe7 instead of 28... Kd7 which was played by Stockfish. And if 29. Ng5 , then 29... Bh6. All in all, analysis with the Houdini chess engine strongly suggests that 28... Qe7 is a much better move than 28... Kd7 for Black. Am I missing anything?
The position after 28. Rc2 is:
[StartFlipped "0"] [FEN "3kqb1r/1b3p2/1p2p1p1/pP1pP3/P2P1PQP/3BKN2/2R5/8 b - - 3 28"]
Added: Dec 18, 9am
I'm doing an infinite analysis on 4 threads using Houdini 6, with 2 Gb of hash memory. After 4 hours and a depth ~= 33, Houdini still prefers 28. ... Kd7 for Black, with an evaluation of +0.15 .
Eventually, Houdini 6 had 28. ... Ba3 as its first choice for Black. Moving the Bishop from the f8 square to the a3 square allows the Black Queen and rook to connect on the back rank. It also allows moving the Queen to the f8 or g8 squares...
Perhaps Alpha Zero's play is too deep, some of the time, to get reasonnably accurate evaluations in a few hours. Or, to simulate Alpha Zero's play could take an inordinate amount of time per move...
P.S. I upgraded to Houdini 6 today, and at 4 hours of infinite analysis with it, it's a lot less than the time spent analyzing before the upgrade.