Friday, January 22, 2021

Season 20 superfinal games 21-30

After 30 games the score is tied 1-1 with 28 draws. The last 10 games were all draws again, the draw streak is now 24 games. We are still waiting for the book bias to be high enough for decisive games.

Games 21-22 started with the Wing gambit in the Sicilian Defense and a small bias for black. In game 21 Leela opened the center, it had a queen side passer that stayed behind while all pieces were still on the board. Stockfish gave a second pawn and opened files in the center, activating its major pieces. The black king was more exposed and this compensated Stockfish for the pawns, evals were close to 0. Leela traded its queen for the two white rooks, it pushed a passer forward and Stockfish used its queen to force a perpetual check draw. In game 22 Stockfish captured a second pawn early with its queen. Leela placed a knight on c7 and forced the black king to move, trapping the king side rook. Leela moved pieces forward on the queen side, Stockfish developed its rook through the h file and threatened the white king side. When Leela broke through the queen side Stockfish ended the game in perpetual check again.

Games 23-24 started with a 26-ply book in the King's Indian defense, orthodox variaton. In game 23 the center was blocked and all pieces and pawns were on the board. Stockfish pushed pawns on the queen side, the engines traded the first pair of pawns on move 19. Leela pushed pawns on the king side, after a few exchanges in the center the engines opened a file on the king side. The queens were exchanged and evals were close to 0, both engines thought the position was balanced. With no pawn moves the game was adjudicated on move 37, still many pieces on the board. In game 24 Leela pushed pawns on the queen side, several pawn and piece exchanges opened a file there. Evals came down to 0 and both engines preferred to keep the king side closed. The game was adjudicated on move 35, it seems both engines didn't see potential in this opening, resulting in two quick draws..

In game 25 Leela forced the white king to move early. There were many early exchanges that left only RB vs RB on move 28. Stockfish was a pawn up, the engines exchanged rooks and were left with an opposite color bishop ending. Stockfish would not lower its eval, the game was adjudicated after more than 30 shuffling moves. In game 26 both kings stayed uncastled in the center, with open files on both sides. The engines exchanged pieces until only QRB vs QRN were left on move 25. After exchanging rooks the engines avoided pawn moves, evals were low enough for an early draw rule.

In games 27-28 the black king moved right after the start, trapping the black king side rook. In game 27 the white king stayed in the center and most of the action took place on the queen side. There were many exchanges and only RRB vs RRB were left on move 27. Stockfish was a pawn up with two passers on the queen side, but evals were close to 0. Leela captured one of the passers, Stockfish finally castled on move 32. Other than that the exchanges continued and the game ended in a tablebase draw. In game 28 Leela gave a pawn and castled long. It managed to get a passer on d6, though not well supported. It took a while for Stockfish to capture the passer, by then all minor pieces were exchanged and Stockfish was still a pawn up. Leela regained the pawn and the game reached a QR vs QR position. Leela's eval was too high for the draw rule, the engines shuffled, exchanged queens, then reduced to a tablebase draw.

In game 29 the engines opened the queen side. A series of exchanges cleared the queen side pawns and left a BBN vs BBN position on move 30. Both evals were 0, the engines continued to play until reaching a tablebase draw. In game 30 the queen side remained closed, there were only a few exchanges and the engines played behind their pawn lines. Stockfish traded both its bishops for white knights, the engines started to shuffle on move 34. After 35 moves Stockfish captured a pawn, this opened a diagonal and Leela's eval increased a little. However shuffling resumed, after almost 50 moves Leela moved a pawn and lowered its eval, the game was adjudicated a few moves later.


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