Monday, July 4, 2016

Season 9, stage 2 rounds 13-15

Table after 15 rounds:

The draw rate is 70/120 (58%).
Interesting to note that the top 5 engines have so far drawn every game they played against each other. Will this trend continue for the rest of this stage as well as the next?
Houdini has lost to all the top 3 engines of this stage. Even if it qualifies for the next stage it needs an update to be a real contender. 

Some of the game highlights

Gull exchanged a rook for a bishop against Raptor, but with three extra pawns Gull had the advantage. After almost all the pieces were exchanged the B vs R four pawns up was an easy win for white. Gull gets one back after the loss on the previous game.

Jonny had an eval advantage over Hannibal from the start of the game, and was a pawn up later. After exchanging pawns on the king side Jonny had two passers, and Hannibal had to control them and defend its remaining pawns. With many pieces on the board the going was slow, but Jonny concentrated its forces, took another two pawns, enough for the win.

Fire - Komodo was an interesting battle between two top performers of this stage (even though Fire is not considered a part of the top-3 engines). The game though was not very eventful. Fire had an eval advantage in a closed position, which grew temporarily when the position opened up a bit, but then fell back down. Komodo was never in real danger.

Stockfish had an eval advantage against Naum in a closed position, and it increased when Naum opened up the queen side exchanging a few pieces. Stockfish had a better pawn structure, and when the only pieces left were N vs B the white pawns were out of the bishop's reach and one was an advanced passer, enough for a win.

Raptor - Ginkgo reached a RB vs R endgame fairly quickly, where Ginkgo had four extra pawns for the bishop. Both engines thought they had an edge, I trust Ginkgo's eval more than Raptor's. The outcome was a queening for both engines and perpetual check, so the truth was somewhere in the middle.

In the much anticipated Komodo - Stockfish game nothing really happened. Stockfish's eval reached zero very quickly and Komodo followed, and the rest of the game was just exchanging pieces and waiting for adjudication. This reminded me of the season 8 superfinal where many games were short draws. When Stockfish and Komodo see a draw coming they lock their evals at zero and let TCEC call the draw.

Chiron was glad to give a rook for a bishop against Vajolet2, ruining the black pawn structure and with more active pieces. Many exchanges later it was the advancing passer that ensured the win. This was Chiron's first win of the stage.

Hannibal - Nirvana was very strange. Hannibal had a significant eval advantage but Nirvana held a static line in a semi-closed position with many pieces. After almost 50 shuffling moves, with 2:30 minutes on the clock, Hannibal moved a pawn and suddenly the evals jumped. It looked as if Nirvana blundered a piece, and suddenly Hannibal was a rook up and winning. What was that?

Gull executed a king side attack against Rybka, with most of the black pieces stuck on the wrong side and unable to help. The game was declared a win for Gull when it was a rook down, with the black king exposed and just before Rybka started to lose material to save it.

Rybka gave a rook for a bishop against Raptor, and in return had a passer and a strong bishop pair to back it up. Raptor gave the material back to get rid of the passer, but this allowed Rybka to create another passer on the other side of the board. Again Raptor had to give material, leading to a RB vs BN ending with one pawn each. White had the advantage and Rybka found the win, though it was not obvious for me.

In retrospect Vajolet2 - Hannibal was very funny. Hannibal's eval constantly increased in a RB vs RB endgame. It queened a pawn in exchange for the other pieces, leading to a RB vs Q position. This was perhaps a bad decision since Vajolet2 seemed to be holding its position for a long time, with evals fairly constant. Hannibal's eval jumped after it exchanged RB for Q again, and both engines queened. The 6-man position was a tablebase draw, yet Hannibal was sure it was winning (eval above 11).

Fire was down a rook for a bishop against Chiron, but its bishop pair was very strong in the open position and the black king was exposed. As a result Fire was able to win material and get to a won QB vs Q ending.

Stockfish's eval started to increase after 30 moves against Protector. It took over the center winning a pawn, and hid its king behind a black pawn. When Stockfish won another pawn it was the beginning of the end for Protector. The game was adjudicated in a RRN vs RBB position, both engines saw that eventually the extra pawns were unstoppable.

Featured game: Houdini - Komodo
Stage 2, round 15
Link to game on TCEC

Could Houdini playing white be a match for Komodo? I expected at least a draw. The game started with a small eval advantage for white, but Komodo soon equalized and got a small advantage of it own, even though it was a pawn down.

Komodo advanced the d pawn as a way of opening up the position. Houdini tried to block the pawn but couldn't in the end.

As a result Houdini gave a rook for a bishop and was a little behind on material. Komodo's eval advantage grew but the way forward was not clear.

The king side pawns were taken off, leaving Komodo with only the doubled c pawns. Why is it so happy in its position? Then I saw it, both the white knight and rook are trapped !!

Adjudication came quickly though the game was far from over. The PVs show that Houdini was about to lose material in a few moves.

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