Monday, May 30, 2016

Season 9, stage 1b rounds 1-3

After waiting for about a week, finally stage 1b started. This group features Stockfish, the very popular open-source engine which tends to finish second in TCEC. Will this season be different? There are more newcomers in this group, though less than in group 1a. Andscacs and Vajolet2 may be strong, we'll have to follow their performance to see.

Important note: I will be on vacation for a few days, and will not follow TCEC closely. The next post will therefore be late and will not cover all the games in the coming rounds. I hope I don't miss anything important.

Table after 3 rounds:

Draw rate is 8/24 (33%), more draws than in the first group but still early for a real comparison. Anton (tournament director) predicted that the race for qualification will be tougher in this group, based on the testing runs he did. Looking at the current top eleven engines, of the 11 games played within this group so far 7 have been draws. Anton may have a point.
Stockfish performance is disappointing so far, starting with two draws. Naum is the only engine with a perfect score, and even this is due to Fire crashing in a winning position against Naum.

Some of the game highlights:

In Andscacs first game against Jonny white seemed to have a significant advantage after the opening, perhaps due to black not castling. However, Jonny developed a significant counterattack on the white king which equalized and even gave the advantage to black. The RB vs RB ending was drawn, but it took a while for Jonny to realize that.

Vajolet2 got a draw against Stockfish !! Stockfish fans (and me) waited to see the eval explode each time Vajolet2 moved not according to the Stockfish PV, but the evals converged to 0 very quickly. Stockfish couldn't create anything in the rook ending until a tablebase draw was reached. Vajolet2 is doing alright in the first game, but is Stockfish weaker than was expected?

Arasan-The Baron was intriguing since Arasan had a respectable first stage last season and I think its TCEC rating underestimates its strength. After a balanced start Arasan gave a knight for three pawns and attack chances on the black king. The QR vs QRN ending was very tricky and Arasan handled it very well. The white pawns became too strong in the end, forcing a white win.

Fruit-Fire reached a bishop and pawns ending with a small black advantage, but Fire's superior endgame abilities were enough to get a win. Fruit isn't playing too bad, considering its ranking.

Fire-Naum was the first crash of the stage. Naum tried a pawn attack which left its own king exposed. Fire's counter attack was deadly and soon the evals indicated a quick win, and then Fire crashed... I hope this is not going to be a problem. It would be a shame if Fire has stablity problems this season.

The Baron played a long game against Fruit, reaching a 7-man rook endgame. The position looked drawn but Fruit blundered and lost the game.

Chiron was never in trouble as black against Stockfish, the game was a very long draw with mainly shuffling moves. Stockfish avoided the 50-move rule for as long as it could, playing on increments, but there was nothing to do. Stockfish fans are getting restless...

Chiron beat Critter, and it was a bit of a surprise because Critter has a higher TCEC rating. Critter got in trouble early in the game. The material was equal but in the RRN vs RRN endgame Chiron had better pieces and pawn structure. Chiron's eval increased slowly but steadily, reaching a winning 7-man RN vs R position. At 6-men Chiron could use the tablebase, but it kept choosing moves that were not the shortest path to victory. Eventually Critter realized it was lost.

Featured game: Arasan - Stockfish
Stage 1b, round 3
Link to game on TCEC

After two draws there were questions about Stockfish's strength this season. Arasan's low rating of 2732 gave hope that Stockfish will get an easy win. It should be noted that Arasan's rating may be highly underrated, in season 8 it had a very respectable performance in stage 1a, well above its rating.

The game started very balanced, the evals staying close to 0. An hour and a half into the game the fans were getting restless, the position was getting closed and drawish. Not another draw...

Arasan made a few bad choices (according to Stockfish's PV) and got its queen into some trouble on the king side. Stockfish's response was quick and deadly. The center cleared and suddenly the white king was in danger with weak pawn and piece defenses.

Stockfish gave a rook to eliminate the knight, leaving Arasan with only the queen to defend against the attack. The evals shot up with more and more threats against the white king and queen.

In the aftermath of this attack the pieces left were RR vs RBN with two passed pawns on the king side for Stockfish. The game was adjudicated after a few more moves, with a Stockfish win. A first win this season for Stockfish !!

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