Friday, June 10, 2016

Season 9, stage 1b, rounds 10-12

Table after 12 rounds:

The draw rate is  29/96 (30/2%) which is almost the same as stage 1a.
Nine engines fighting for the eight qualifying places for stage 2. Combining the points and the remaining games I would say that Fire, Vajolet2, Andscacs and Critter are are the most likely candidates for finishing in 9th place. The Fire-Vajolet2 game in round 13 and the Critter-Andscacs game in round 15 are therefore critical. Any decisive result here can have a large effect on the final ranking.
At the top Stockfish has weaker opponents than the others, I think it will finish first. However Jonny and Nirvana still have a shot, both haven't lost a game yet and are playing well. Relevant games are Naum-Jonny (round 13), Naum-Nirvana (round 14) and Nirvana-Jonny (round 15). Chiron will probably also move up in the ranks, but I don't think it has a shot at number 1.

Some of the game highlights:

Jonny - Gaviota reached a RBN vs RBB endgame by move 20. The position looked drawn but Jonny soon outplayed Gaviota, despite the bishop pair. One bishop became almost useless and the other exchanged for a knight, and from there Jonny won comfortably.

Critter beat Fire quite easily, a bit surprising for me. Critter was ahead on eval right from the start, so it may be a biased opening or Fire misplaying the opening. Fire had a bishop pair for Critter's knight pair, but with most pawns on the board the knights were much better. Fire is still fighting for qualification and it needs better results.

Chiron beat Naum without too much difficulty, again somewhat surprising (although Naum has an extra point due to the Fire crash). After applying pressure on the queen side Chiron was able to get two connected passers in the center with only RRB vs RRB remaining. From there the win was just a question of technique (way over my head but still straightforward).

Naum - Arasan was a long game where Naum held a significant eval advantage but was not able to penetrate Arasan's defense. The game almost ended by the 50 move rule twice, but somehow Naum found the path to victory (by random shuffling and luck?).

Delphil and Firefly drew the battle for last place, making sure that both get points in this stage. Both will probably not get any more points... And we still don't know which should be last.

The Baron managed to get a draw against Critter. Pieces were exchanged quickly and the pawn structure was symmetric enough that neither engine could develop any significant threats. For a short while the Baron had a pawn advantage and hopes that it can make something out of it, but there was not enough material left on the board.

Jonny - Stockfish was a battle for first place. The game was interesting, including a queening as well as a knight sacrifice towards the end. However both evals fell to zero after 26 moves so the draw was inevitable.

In Critter - Gaviota there was a long struggle in the center, the evals stayed relatively low for over 50 moves. Gaviota had an isolated advanced pawn which it tried to defend, but in the end Critter found a way to take the pawn, gain control of the center and win the game.

Arasan was a pawn down against Nirvana and the evals were in Nirvana's favor. However in the N vs B endgame Nirvana couldn't convert its advantage and the game ended in a draw.

Fruit tried a bishop for three pawns exchange against Naum, but this backfired in the end. Naum played the QR vs QRN ending better taking the white pawns one by one until the game was adjudicated.

Featured game: Gaviota - Stockfish
Stage 1b, round11
Link to game on TCEC

Gaviota was supposed to be one of the weaker opponents of Stockfish, so I expected a quick demonstration of power and next game please. Things didn't turn out quite as smoothly. Gaviota held its own for a long while, all evals close to zero and material being reduced. After 35 moves there were only RN vs RB left, with no significant weakness for either side.

This was surely a draw, but you can never let your guard down against Stockfish. After a few innocent moves (errors by Gaviota?) Stockfish saw an opportunity to force a rook exchange.

Suddenly the black bishop has targets and white's pieces are too weak to defend all of them. A few moves later it was all over.

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