Thursday, October 26, 2023

Season 25 superfinal games 61-70

After 70 games Stockfish leads 20-13 with 37 draws. Stockfish's lead is 7 wins after each engine won a game pair. There were 3 drawn game pairs, two had two white wins. Leela game pair win came after 17 game pairs which were either drawn or Stockfish wins. Leela almost won a second game pair, but an inaccuracy late in game 70 gave Stockfish the win and the game pair was drawn.

Games 61-62 started with a sideline of the QGD, Semi Slav defense, with the black king uncastled and the black queen on h6. In game 61 evals increased quickly after the start, Stockfish kept its king in the center and Leela forced it to move. Leela moved a knight forward and traded it for a rook.

Leela pushed pawns on the queen side, after some shuffling Leela captured a pawn on the king side and created a passer. The white queen moved forward on the queen side and captured two pawns, creating a passer there as well. Leela gave a pawn and add two more connected passers on the queen side.

Stockfish lost a bishop for two of the passers, Leela gained more material and mated.

In game 62 Stockfish pushed pawns in the center, it traded a rook and a pawn for two minor pieces. The black queen captured a knight and walked into a trap, Stockfish captured the queen for a rook. The game reached a QBN vs RRB position on move 25.

Leela was two pawns up, it doubled rooks on the open e file and its eval drifted down. Stockfish's eval steadily increased, it pushed pawns on the queen side and on move 41 exchanged a pair of pawns. Leela's eval started to increase as well, by move 56 the white queen captured two pawns and opened the queen side.

Leela pushed its passer to the 2nd rank, Stockfish traded its queen for the two black rooks and stopped the passer. The game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 18-11.

Games 63-64 started with a 20-ply sideline in the QGD, Albin counter-gambit, white was a pawn up and black had a passer in the center. In game 63 there was a long PV agreement after the start, the engines exchanged minor pieces and Leela captured the black passer. Evals came down, after exchanging queens the game reached a RRB vs RRB position. Stockfish slowly captured the pawns back, the engines reduced to a rook ending. Leela had a passer but it couldn't push it beyond the 6th rank. The game was adjudicated when Leela lowered its eval for the draw rule. 

In game 64 Stockfish pushed pawns on the queen side and captured the black passer. On move 20 Leela played h6, this weakened the black king and Stockfish's eval jumped. Stockfish attacked the king side with its queen and a knight, Leela gave a rook for the knight, Stockfish sacrificed another knight to expose the black king. Leela was forced to trade its queen for a rook to save its king from mate. On move 29 there was an imbalance of Q vs BBN on the board with high evals.

Stockfish ignored the black passer and continued to attack with its queen and rook. After exchanging rooks Stockfish captured the black passer. Stockfish pushed a passer on the king side, Leela lost a bishop for it. The white king moved forward and Stockfish mated. Stockfish wins the game pair, it leads 19-11.

Games 65-66 started with a 22-ply sideline in the Sicilian Taimanov, Szen variation, that appeared in a Fischer-Taimanov game. Both kings were uncastled, black had a strong knight on d4 as well as an eval advantage. In game 65 Stockfish grabbed the g pawn with a rook, this gave Leela time to improve its piece arrangement. Leela drove the black knight on d4 away, both kings moved forward and evals came down. The engines exchanged all rooks through the open g file and reduced to a QB vs QN position, evals were low and the game was adjudicated early on move 36.

In game 66 Leela also grabbed the g pawn as in game 65. The pieces stayed on the board longer, Stockfish moved a knight to d5, it drove the black knight from d4 and Leela moved it to c5. Stockfish castled long and (negative) evals started to increase. Leela managed to exchange the knights in the center, after queens were exchanged the game reached a RBN vs RBB position on move 40.

The engines blocked the queen side, Stockfish walked its king to the king side and pushed the h pawn forward. Leela exchanged pawns and got rid of the white e pawn, suddenly it was 3 pawns against 1 on the king side. Leela hid its king behind the white passer and shifted the rook to the queen side. The black rook moved to the 2nd rank and trapped the white king.

Leela captured the white h pawn, then gave a pawn to get the white f pawn out of the way. Leela pushed pawns on the king side and Stockfish lost pieces trying to avoid mate. Stockfish raced to queen a passer but was mated on the other side. Leela wins the game pair, Stockfish leads 19-12.

Games 67-68 started with a rare sideline of the KID, four pawns attack. In game 67 the engines opened the d file, a black knight made an unusual journey of 5 moves and was traded for a bishop. In a series of exchanges the engines reduced to a RRB vs RRB position and evals came down. Leela doubled rooks on the d file, after a few pawn exchanges the engines started to shuffle. After 40 moves Leela exchanged a pair of rooks and the game was adjudicated. In game 68 the engines opened the d file and also the b file, Stockfish moved its king forward without castling. The white queen moved forward, in a long PV agreement there were many exchanges and Stockfish gave a rook for a bishop. For a few moves Stockfish's eval jumped, then unexpectedly dropped back even though it anticipated Leela's move. Stockfish regained a rook for a bishop, after exchanging queens the game reached a rook ending. Stockfish was up a pawn with a passer, Leela gave a pawn and as a result all the white pawns were isolated and a pair was doubled. Leela held the draw, though it wouldn't lower its eval for a long time

Games 69-70 started with a rare sideline of the Pirc defense, Austrian attack. In game 69 Leela attacked the king side, the engines exchanged minor pieces and Stockfish was a pawn up but the black king was vulnerable. After a few pawn moves and some shuffling Stockfish moved its queen to a3, perhaps to attack the unguarded b3 pawn.

Leela thought this was a mistake and its eval jumped, Stockfish's eval reacted only 3 moves later. Leela attacked the black king and Stockfish quickly moved its queen back to help. Leela regained the pawn, after exchanging queens it created a passer on the queen side. Then it captured two more pawns and reduced to a RN vs RB position.

While Stockfish focused on the white a passer Leela managed to capture the last black pawn and create passers on the king side. Leela pushed passers forward, Stockfish stopped one before the game ended in a tablebase win.

In game 70 there were early exchanges, the engines opened the f file and exchanged a pair of rooks. The game reached a QRB vs QRN position on move 20, there were a few pawn moves and the engines started to shuffle. On move 74 the engines opened the a file and shuffling resumed, evals drifted down and the game seemed to be heading for a draw.

Stockfish thought Leela's move 89 was an inaccuracy and its eval started to increase, Leela's eval increased as well. Both engines were low on time and played in blitz mode. Stockfish managed to double rook and queen on the a file, then moved its rook forward and exchanged rooks. The white queen moved forward and used a mate threat to capture a pawn and create a passer. Stockfish blocked Leela's attempt to counter attack, then it captured a second pawn.

Stockfish exchanged queens, Leela managed to regain the two pawns including the passer on the queen side. However, the black king was too far to defend the isolated pawns on the king side, Stockfish captured two pawns, queened and mated. There were two white wins in this game pair, Stockfish leads 20-13.


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