Friday, May 13, 2016

Season 9, stage 1a, rounds 7-9

Table after 9 rounds

The draw rate is now 20/72 (28%).

Nothing is clear in the middle section of the table. Hannibal has improved its position while Bobcat and DisasterArea are over 1.5 points back with only six games left. It looks like a race between Fizbo, Hannibal, Raptor and Texel for the last two qualifying places.Of these Raptor has the easiest games left, and it may be the surprise qualifier of the round.

Some of the game highlights: 

Hannibal struggled a little against weaker Myrrdin, but managed to get a win with better endgame skills.

Rybka held off Komodo in a closed position, but when files started to open Komodo's king side attack was deadly. 

Texel had illusions of winning against Raptor but could only reach a drawn queen endgame with a pawn advantage.

Houdini beat Gull decisively in black. In season 8 Gull performed better than Houdini, and was slightly better in their head-to head games (1 win and 7 draws). I don't think they changed since then, so it was a bit of a surprise to see Gull lose in this way.

Raptor gained a valuable half point drawing against Ginkgo. Ginkgo had the advantage of a bishop pair in an BN vs BB endgame, but Raptor was able to exchange down so that black was left with only a bishop, leading to a tablebase draw.

Hannibal demolished Laser after a classic case of taking a poisoned pawn. Hannibal is improving its chances of qualification to stage 2.

Ginkgo-Komodo was a great battle. Komodo sacrificed two pawns and Ginkgo thought it had an advantage, even though the position was closed and the extra pawns were both doubled. When the position opened Komodo had the advantage and Ginkgo had to defend its king. With the eval increasing Ginkgo held on for 30 more moves, exchanging pieces and pawns when it could. In the end the position reached a 6-man rook ending which was won for black. Komodo showing its strength against a worthy opponent.

Raptor survived another tough match, this time playing black against Gull. Gull had an eval advantage for a while but could not find a weakness in a QBBN vs QBBN position.

Fizbo thought it had an advantage over DisasterArea when DA sacrificed a knight for pawns. Fizbo's eval climbed to over 5 in the resulting QRN vs QR position, but this was just lack of endgame knowledge and no tablebases. The game ended in a 5-man tablebase draw, with Fizbo a knight up.

Hakkapeliitta surprised Bobcat (and everyone else) with a rook sacrifice leading to a pawn on the 7th row. This led to a deadly attack on the king and a material imbalance of QN vs RRB. The PVs of both engines showed a won Q vs R endgame. This was a blow to Bobcat's qualification hopes.

Featured game: DisasterArea - Gull
Stage 1a, round 8
Link to game on TCEC

DisasterArea reached a balanced RRN vs RRB and pawns endgame against Gull by move 36, could it hold the position despite the big ELO gap between the engines?

The pawns started to be exchanged and Gull's rooks became more active. Gull's eval gradually increased reaching over 1. At some point DA chose to exchange a rook for a bishop, hoping to reach a drawn ending.

After a while Gull was able to get a pawn back while exchanging rooks, leading to an 8-man NPP vs RPP position.

Playing without tablebases Gull managed to convert a win. The startegy was to force the white king to protect g4, bring the black king around to the first row, and force a knight sacrifice to avoid mate. Tricky and slow, but Gull nailed it.

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