Superfinal summary
In season 14 Leela started from the lower divisions, climbed up and reached the superfinal where it lost by 1 point to Stockfish. This season Stockfish won the premier division but Leela was stronger head-to-head. In the superfinal Stockfish was still hopeful after it equalized to 1-1 in game 12. However Leela started to win minimatches, by game 26 it led 5-1. Stockfish won two more games in openings where Leela also won, Leela extended its lead to 8-3 in game 40. Stockfish tried to stay in the match with two minimatch wins and the score was 8-5 at the half. After many draws Leela crushed Stockfish's hopes with an unusual double win, extending the lead to 5 points on game 62. In the remaining games Stockfish won twice in openings that Leela also won, and Leela won two more mimatches to win the match by 7 points.
Leela improved its game compared to the previous season. It made very few blunders in the endgames, it played all types of openings well, usually better than Stockfish. It appears to have a much better understanding of long term advantages, often claiming it is much better long before Stockfish can see a win. There were a few cases where this proved to be wrong, but mostly Leela's predictions were correct.
There will be more NN engines in the next season. There were two NN engines in the premier division in season 15, will there be another one next season? Are the NN engines going to take over the chess world? When will we see a NN superfinal? Can Stockfish improve and be competitive? Will Houdini be updated? Will there be a hybrid NN-AB engine? I can't wait to find out.
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Games 91-92 were a King's Gambit variant where the white king moves. In game 91 the white king walked to the king side, trapping its rook. Stockfish's eval dropped to 0 as it regained the pawn, the engines exchanged queens on move 20. Stockfish let its rook out of the corner, then all rooks were exchanged and only BN vs BB were left on move 26. Leela's eval kept the game going, the engines reduced to a same color bishop ending and the game ended on move 103 in a 50-move draw. Game 92 started similarly, the queens stayed on the board. The white king side rook got out of the corner but the engines did not exchange rooks, evals were negative and stayed low. Both engines focused on the isolated center pawns, the game was peaceful with a few exchanges. Evals came down and the game was adjudicated with many pieces still on the board.
The engines opened the center early in game 93. Neither engine was strong enough to attack and evals came down. Leela moved its queen forward on the queen side, this led to a queen exchange and the removal of all the pawns on the queen side. The game reached a BN vs BB position on move 40, Stockfish was a pawn up but with evals close to 0 the game was adjudicated quickly.
Leela's eval started around 1 in game 94, and was over 3 already on move 12. The engines castled in opposite direction, both Leela's rooks controlled half open files, one facing the black king. Leela chose to attack on the king side, it doubled rooks on the f file and broke through. After exchanging a pair of rooks Leela had a rook on the 7th rank and a formidable bishop on d5.
Stockfish did not want to exchange bishops and to give Leela a passer. Nevertheless, Leela captured a pawn on the king side to create one passer, then it exchanged knights and created a second passer. After exchanging bishops only QR vs QR remained, both engines had central passers but Leela's passer was much stronger. It pushed the passer forward and Stockfish stopped it on the 6th rank.
Stockfish got rid of the passer on d6 but lost another pawn on the king side. The game reduced to a rook ending with two white passers on the king side and the black king too far to help. The game was quickly adjudicated.
Both kings stayed uncastled in game 95, Leela opened the queen side and Stockfish pushed pawns on the king side. Eventually Leela castled short, Stockfish opened the king side with its pawns, then gave a bishop to get two pawns facing the black king on the 6th rank. Leela exchanged two rooks for a queen to get rid of one pawn. After a while Leela lost a bishop and captured the second pawn, the game ended in a RR vs Q tablebase draw. In game 96 Stockfish's eval was 0 from the start. Both engines castled long and the king side was open. Queens were off early and the game reached a RNN vs RBN position on move 27. The engines shuffled and stabilized the pawn lines, then reduced to a rook ending on move 52. Leela went a pawn up and the game continued until reaching a tablebase draw on move 87.
Games 97-98 started with a 20-ply book in the King's Indian Defense. In game 97 the engines formed long pawn lines with no exchanges, Stockfish pushed pawns on the queen side and Leela on the king side. Stockfish opened a file on the queen side on move 25, Leela gave two pawns and started a king side attack. A knight sacrifice opened the king side for the black major pieces, then in a series of exchanges most of the pieces were gone and Leela found a perpetual check draw. In game 98 there were several exchanges after the start, the engines opened the queen side. Leela's eval was over 1, Stockfish's eval stayed low. Leela refused to open the king side, after the engines exchanged a pair of rooks they started to shuffle and Leela's eval came down. The game reached a QRN vs QRN position on move 51, Stockfish opened the king side and found a perpetual check draw.
Stockfish castled long in game 99, Leela opened a file on the queen side and attacked. The white king ran to the center, Leela sacrificed a bishop and added pieces to the attack. Then most pieces were exchanged off and only RBN vs RN remained on move 29. Leela was two pawns up, all the pawns were on the king side. Stockfish's eval dropped to 0, Leela captured a pawn and thought it had small advantage. The game ended only on move 97 in a tablebase draw. In game 100 both engines castled long, though the black king did not have good pawn support on the queen side. Leela attacked with its queen and captured a pawn, Stockfish exchanged queens and regained the pawn. Stockfish had a trapped bishop, it gave a pawn to release it. This gave Leela a passer in the center and its eval jumped over 3. Stockfish blocked the passer with its pieces, the game reduced to RN vs RN position. Leela's eval peaked over 5, it couldn't find a way to improve and the engines started to shuffle from move 44. On move 104 Leela gave a pawn back and opened the queen side, its eval already below 2. The engines continued to shuffle and exchange pawns until reaching a tablebase draw on move 139.
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