Monday, February 18, 2019

Season 14 superfinal, games 61-70

After 70 games Leela leades 9-8 with 53 draws.
Each engine had one game pair win and Leela continues to lead by one point. Games 65-66 were the highlight. Leela had a winning 7-man position but couldn't convert in game 65. Then a network failure stopped game 66 which was then replayed twice. In the second replay Stockfish won. Leela fans were not happy...

There were many early exchanges in game 61, only RRN vs RRN were left on move 25 and evals stayed low. Leela's king was in a better position but not enough to make a difference. The engines reduced to a drawn rook ending. Evals stayed low in game 62 as well. The engines castled in opposite directions but the kings were not seriously under attack. Leela went a pawn up and its eval became negative. After a while the engines started to exchange pieces, on move 44 the game reached a rook ending. Draw was agreed more than 30 moves later.

Games 63-64 were a French Defense variation with a blocked center and a black king that moved, Leela was expected to do well. In game 63 Leela's eval was slowly increasing until move 16, then it jumped over 2.5. Stockfish was a pawn up, it seemed to disregard the danger to its exposed king and its king side rook trapped in the corner.



Stockfish quickly exchanged queens, Leela gave a pawn and its king side pawns started marching, only then Stockfish realized it was in trouble. It tried to keep the files closed so the white rooks won't come forward. Leela was 3 pawns down but its eval was close to 5.



Stockfish gave a pawn back and tried to get its trapped rook free. Leela used the time to move a rook to support the f pawn and push it forward. When it promoted Leela was a rook up and the game was over.

In game 64 both kings remained uncastled and the queens were off early. Evals slowly came down and after the pawns stabilized on move 24 the engines started to shuffle. This continued for 60 moves, with one pawn move that reset the 50-move counter. The engines then exchanged a few pieces and ended the game in a repetition. Leela wins the game pair and the lead is back to 2.

Leela started game 65 with an eval 1 and increasing. After the queens were exchanged on move 34 Leela's eval was close to 3. Material was equal but Stockfish had 3 weak pawns. Leela was patient, it took 30 moves to arrange the pieces, exchange pieces slowly and win a pawn. The game reached a 7-man position on move 73.



This was winning for white, both engines agreed. Stockfish calculated a winning line, Leela's eval remained below the win rule threshold. It seemed Leela was shuffling without a plan, the line Stockfish showed in the PV was long and slow with a pawn move many moves ahead. Leela couldn't find the right sequence of moves, its eval slowly came down. After 40 shuffling moves Stockfish realized it was too late and its eval dropped to 0. The game ended in a tablebase draw on move 143.

Game 66 looked drawish after 20 moves but then there was a network failure and the game had to be replayed. There was a long wait, the first replay was aborted as well (I don't know why, it happened while I was away from the screen. There were rumors of a Windows update). The second replay of game 66 worked. Evals were around 1 from the start, Stockfish didn't castle and kept its rook on the h file. It offered a knight but Leela wouldn't take since that would open the h file and its king would be in danger. It was clear Stockfish was better but Leela seemed to be holding. On move 37 Stockfish pushed a pawn on the king side and opened the g file. Then without warning Stockfish's eval jumped over 6.



Leela immediately saw the problem, its PV showed the game continuation. Why didn't it see it a move earlier?? Leela's king was under attack, after a series of exchanges Stockfish won a little material and the game reached a RRB vs QB position, Stockfish 3 pawns up.



The black king was in danger and Stockfish had 2 potential passers on the king side. All Leela could do was give checks with its queen, but only for a short while. Stockfish gave a rook for a bishop and created a third passer, the game was quickly over. After another unexpected save in the previous game Stockfish completes a game pair win and reduces Leela's lead to 1 again.

Games 67-68 were a variant of the King's Gambit. There were many early exchanges in game 67, by move 22 only RN vs RBN remained and Leela was 3 pawns up. Evals came down, Leela had two passers on the king side which Stockfish blocked. Leela's king moved forward on the queen side, the engines exchanged knights and Leela captured another pawn. Leela had the initiative but Stocofish made sure the white pawns didn't promote, the game ended in a draw. In game 68 the queens were off early, evals stayed below (negative) 1. The engines continued to exchange pieces until they reached a rook ending on move 34 with Leela a pawn up. Both engines had passers, one pawn advantage was not enough for more than a draw.

In games 69-70 white was a pawn up from the opening. In game 69 the engines castled in opposite directions. There were several exchanges after the start, Leela captured a rook for a bishop, all the pawns on the king side were gone except a black doubled pawn. Leela's eval was over 2 for a while but Stockfish was solid, it captured a pawn on the queen side and reduced to a QRB vs QBN position on move 30. Evals came down and Stockfish ended the game with a perpetual check draw. In game 70 both engines castled short, evals stayed around 1 and all pieces remained on the board until move 23. The engines then removed all the queen side pawns and reduced to a QR vs QB position on move 41. Stockfish wouldn't lower its eval, the engines shuffled for almost 50 moves before adjudication.

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