Wednesday, June 22, 2016

Season 9, stage 2, rounds 4-6

Table after 6 rounds:

The draw rate is 33/48 (69%), much better than what we had in the first two rounds.
Komodo is dominating the start of this stage, other than that the differences between the engines are quite small. If this trend continues the qualification race may be very close, still a very long way to go.

Some of the game highlights

Vajolet2 - Jonny reached a drawn 6-man rook ending, with two white pawns on the g and h files. Vajolet2 did not have tablebase support so it thought it was winning for about 15 moves before it realised that there was no way to win.

Fire had a rook for a knight in the game against Rybka, and had an eval advantage of about 1. In the end it had to give the exchange back and the RB vs RN endgame was drawn.

Stockfish was a pawn up against Gull, and ahead on eval. However, after most pieces were exchanged one pawn was not enough in the rook endgame, with 4-3 pawns on the king side. It took quite a while for both engines to lower their evals for adjudication.

Houdini started the game against Andscacs with an eval advantage. It was able to convert threats on the black king and control over the dark squares into a winning BN vs BN endgame with an advanced passer. Andscacs had to give a piece to avoid queening, and Houdini won comfortably.

Ginkgo - Hannibal reached a blocked BB vs BN position, where black had a passed pawn but there was no way to break the pawn line. Hannibal's eval kept climbing to over 5, with nothing to back it up, going back down reluctantly for the 50-move draw. Someone should look at that eval function.

Komodo exchanged RPP for BN against Protector. The position became blocked with a black pawn line (Protector had all pawns on the board), Komodo had a space and eval advantage. When Komodo challenged the pawns on the queen side Protector chose to lock pawns completely. This allowed Komodo to focus only on the king side, and it found a way to force black to move a pawn and weaken the line. This was enough for Komodo to convert the space advantage to material and a winning position, the game ended just before the wall broke down.

Protector was a pawn up early in the game against Raptor, with two passers on the queen side. After exchanging most pieces the position was a rook endgame with a passer for Protector, it was a bit tricky but Protector found the way to win.

Andscacs sacrificed a knight in the opening against Ginkgo, to get a strong attack against the king and to win 3 pawns. Later in the game with less pieces on the board the advancing pawns were much stronger than the knight leading to an easy win. Will Ginkgo be able to return the favor in the rematch?

Nirvana had an eval advantage in the opening against Vajolet2. After a while the engines started exchanging pieces, reaching a queen ending with white a pawn up. The advancing passer with queen support was enough for a win.

Fire was up a pawn out of the opening against Nirvana, offset by 3 pawns in one file. In the middlegame Fire outplayed Nirvana and won a rook for a bishop. In the RB vs BN endgame Nirvana had connected advanced passers but with no support from the king, Fire had a dangerous passer as well. Both engines gave pieces to get rid of the passers but this left a winning R vs B position for Fire.

Stockfish held an eval advantage over Jonny for a while, but after a rook exchange the evals came down. Stockfish couldn't find a win in the RBN vs RBN position, Jonny gave the knight to get rid of the white pawns and the game ended in a repetition draw.

Ginkgo kept a small eval advantage against Gull, material being equal. Evals started going up near the endgame where Ginkgo had a passer in a B vs N position. Both engines played without tablebases, and when they reached a winning 7-man position it was not clear Ginkgo could find the win. There were no serious blunders though, and the win became clear for both engines after a while.

Andscacs blockaded effectively playing black against Naum. After more than 70 moves Naum started to open up the position (out of frustration?), and even got a passer. However, it turned out that the central pawns Andscacs had in the center were more effective with less pieces on the board. The RN vs RB ending with connected passers was a win for black.

Featured game: Komodo - Hannibal
Stage 2, round 6
Link to game on TCEC

The opening looked quiet, Komodo with a small advantage. The kings castled in opposite directions and Komodo immediately started a pawn attack on the king side. Hannibal was happy to get a two pawn advantage but this opened up files and the queen was the only defender left.

Suddenly Komodo's eval jumped to almost 4, BOOM. Hannibal didn't see it because of the rook sacrifice that was coming.

After the rook sacrifice Hannibal had a long think and realised it had a problem. The black king was in a mating net, with no pawns and the rooks too far to help. Hannibal had to lose the queen to avoid an immediate loss.

The position was lost anyway. Komodo forced a knight for rook exchange to reach a won Q vs R ending. What an attack for Komodo, beautiful.

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