Table after 24 rounds:
The draw rate is 111/192 (58%). There have been 72 openings played from both sides so far, and in only 4 both engines won - potentially a biased opening. One of these was due to a crash. Another feather in Cato's cap.
Komodo increased its lead to a full point. It had two quality wins against Gull and Andscacs. In the race for 8th place the only thing that changed is that Rybka has made a small step forward. Hannibal's crash is also important since it will now lose all tiebreaks automatically. Now only half a point separates the 4 engines in the race, we may not know the qualifier until the last round.
Some of the game highlights
Raptor - Chiron was a draw after 217 moves, a close second to the record for this stage, 219 moves.
Protector and Hannibal started the game ok, but in the 15th move Hannibal had a very long think. After more than 80 minutes, when all fans were sure that it was locked in an infinite loop, Hannibal finally moved, and immediately crashed. A serious setback for Hannibal's qualification chances.
Stockfish had an eval advantage from the start against Nirvana, and it grew steadily. Nirvana did not castle and had a weak bishop in a QRN vs QRB position, with only a threat of an attack on the white king. Stockfish hid its king behind a black pawn and then it had better placed pieces and a dangerous passer. Nirvana gave two pawns to force a queen exchange but the game was already lost.
Fire - Vajolet2 started with many early exchanges and evals close to zero. At some point Fire's eval started to grow to about 1, and the game reached a queen ending which can be very tricky. Fire's advantage was tablebase support, which Vajolet2 lacked. In one move Fire's eval jumped to over 9, it won a pawn and threatened to queen another. As a result Fire got a two pawn advantage and the game reached a won 6-man position. Funnily, Fire kept playing non-optimal moves while Vajolet2's eval kept resetting the win rule, and the game continued for another 20 moves until a pawn was taken.
Fire couldn't beat Raptor with white, Stockfish couldn't beat Vajolet2 with black, a disappointment to both. Nirvana tried hard to beat Houdini, but only got a rook ending with f+h pawns, a known 6-man tablebase draw.
Jonny had a very effective king side attack against Ginkgo. Ginkgo tried to exchange pieces to get out of trouble but ended up a bishop down in a RB vs R ending. This was an easy win for Jonny, continuing its good performance this stage.
Gull - Komodo was another masterpiece by Komodo (see featured game). Gull opened a file in front of its king allowing Komodo to apply pressure. When Gull blocked with pieces it also supported these with its king, creating pin opportunities for Komodo which ultimately led to Gull losing a bishop. The game continued for more than 20 moves with evals slowly increasing and Komodo targeting the white pawns until adjudication. Impressive that Komodo beat Gull from both sides of this opening.
Andscacs' pieces were much more active than Protector's, and this was reflected in the eval. When the position opened up a little Andscacs also had a serious threat against the black king. Most pieces were exchanged leaving a BN vs R ending, but black couldn't defend its pawns. It was two pawns down when the game was stopped.
Tired of crashes Hannibal and Chiron played a 14 move miniature with a repetition draw.
Andscacs had more space in a closed position playing black against Chiron. There were long stretches of shuffling moves in the game. The first breakthrough came when Andscacs trapped a white rook, and then brought a knight from the other side of the board for an exchange. The second breakthrough was 40 moves later when the black queen found a way behind the white pawn line. Andscacs was declared the winner a few moves later, a double win against Chiron.
Naum held its position against Jonny for over 40 moves. Naum had a pawn advantage but Jonny's pieces were much more active while Naum's pieces could hardly move. After a few exchanges Jonny had advanced passers in a RN vs RN position, and after the rooks were exchanged the game was over. A first double win for Jonny.
Ginkgo - Nirvana was important in the race for 8th place. Ginkgo had an eval advantage of over 1.5 at some point, and the game reached a QN vs QB ending two pawns up for white. However Nirvana was able to draw with perpetual check.
In Houdini - Vajolet2 the black queen wandered far from its lines and was a bit caught up in the center. Houdini saw a blunder and immediately its eval jumped over 3. The impressive thing was how Houdini planned almost all the remaining moves in advance. For over 25 moves it stopped to think twice, and other than that played blitz with under 5 seconds per move. After exchanging almost all pieces the game reached a won 6-man position. A first double win for Houdini.
Featured game: Komodo - Andscacs
Stage 2, round 22
Link to game on TCEC
Andscacs' performance this stage has been quite strong, and its qualification for stage 3 is almost certain. Could it withstand Komodo's power with the black pieces?
The game started with a small eval advantage for Komodo, Andscacs defended well for about 25 moves before starting to play small inaccuracies that allowed Komodo to improve its position and increase the evals. Komodo had a dangerous passer in the center, and Andscacs had to block with pieces and was feeling the stress. The black king tried to help with the defense of a knight, but was that a good idea?
By moving to g7 the king self-pinned the knight, and when the rook on d6 was eliminated the king too couldn't move so as not to lose the knight. Andscacs was getting under more and more pressure, after rooks were exchanged the passer became too big a threat.
With the black knight pinned and the black queen in the corner too far to assist, Andscacs had no choice but to lose a piece to get rid of the passer. The evals were over 2 and rising, but with only QBN vs QN did Komodo have enough material for a win?
The pieces danced on the board with slowly increasing evals but it was difficult to see what was the improvement. After 12 moves a first breakthrough for Komodo, it was able to force a knight exchange.
And the evals jumped to 250 ! A sure win for Komodo, though how it was going to do it was still a mystery. The experts in the chat indicated that all that is needed is a queen exchange to finish the game, the bishop and king were enough to get rid of black's pawns. But the PVs did not explain how Komodo was going to do this. The pieces continued to dance for more than 30 moves, Andscacs stayed cool and refused to exchange, and the 50-move rule was getting closer and closer. And then, finally, Komodo found the right series of moves.
Andscacs could not avoid the queen exchange and the game was finally over. Beautiful game, great display of Komodo's strength.