Wednesday, September 9, 2015

Season 8 group 1b after 9 rounds

The crosstable of group 1b after 9 rounds is:

With two rounds left qualification is almost fixed. Stockfish, Houdini and Hannibal have qualified while for Nirvana and Equinox there is only a slim theoretical chance they will not qualify. The sixth qualifier will probably be Chiron. Nightmare and Scorpio have a game against Stockfish, I don't believe they have a chance. Junior has a real chance, only if it beats Chiron in the last round.

Pedone - Houdini was nearly a huge surprise. Houdini reached the endgame with an advantage of R to BP, and for many moves it seemed that both engines are shuffling pieces with no plan. According to the chat Houdini missed several opportunities to win, and made an important pawn advance only when the 50 move draw was near. In the end Houdini saw the light (perhaps Pedone blundered, it was very low on time for most of the endgame) and managed to win, but it was very close.

Hannibal - Nightmare was also a very long game. Nightmare played a rare gambit which gave Hannibal an early pawn advantage. The endgame however was very drawish and long, Hannibal made pawn moves only when close to the 50 move draw. Apparently Nightmare blundered when only opposite colored bishops remained on the board, allowing Hannibal to sacrifice the bishop for two pawns and find a win.

Nightmare played the same gambit again as black against Nirvana and lost again, perhaps not a good choice?

Crafty managed a draw against Scorpio, its first score not counting the game where Pedone crashed.

Equinox crashed twice, against Nirvana and Stockfish. It's really a shame since it is a strong engine. In the game against Stockfish the two engines were shuffling for 30 moves, and the game could have been a draw if Equinox didn't crash. Stockfish's record remains perfect.

Notable game
Houdini - Stockfish, round 8
Game on TCEC archive

This was the main attraction of group 1b, the epic battle between giants. Of course it had little effect on the qualification, and there will be many more games between these opponents in later rounds. In the context of stage 1 this was a highlight.

The game was played at a level way above my ability to describe. For the first 35 moves the evaluation scores were close to 0 for both engines. When pieces started coming off the board Stockfish started showing signs it had a small advantage, and indeed by move 49 it was up a pawn:

Was one pawn enough for this endgame?  The game progressed without changing the evaluations significantly, knights were exchanged and black added a second passed pawn on the a file.

A few moves later a pair of rooks was exchanged, as well as the passers on the d and h files, and only 7 pieces were left on the board.

Those with access to 7-man tablebases announced a draw. Houdini and Stockfish played on though, and the evaluations remained stable until around move 80 when Stockfish's evaluations started to jump. On move 84 the 7-man people announced that Houdini made a mistake and now the game was a win for black. The game continued on for another 20 moves and was adjudicated at this position:

The same 7 pieces are still on the board, but now both engines see the black win. For me it is difficult to see the difference, and the mate is still over 30 moves away. Stockfish was able to see it with 5-man tablebases, Houdini could not handle the difficult ending.

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