After 40 games Stockfish leads 11-7 with 22 draws. Stockfish won two game pairs and extended its lead to 4 again. Twice Leela managed to win a game and twice Stockfish won the reverse. In both games 39-40 the losing side saw trouble before the winning side's eval reacted. Were the losing engines seeing ghosts, and proving themselves right with the wrong choice of moves?
Games 31-32 started with an 18-ply line in the Alekhine defense, four pawns attack, played in high level human games. In game 31 Stockfish gave a knight for three pawns in the center. Evals came down as the engines exchanged pieces. The game reached a RB vs R position with low evals and was adjudicated early on move 47.
In game 32 Leela captured a pawn but let Stockfish keep two pawns in the center. Stockfish's eval jumped early, it moved its queen forward on the king side and Leela moved its king without castling. Leela surrounded its king with pieces, it gave a rook for a knight, perhaps hoping that without knights it would be difficult for Stockfish to find a way to attack. However the black king side rook was trapped in the corner.
Evals continued to increase while Stockfish seemed to shuffle. On move 50 the engines exchanged queens, then the game reached a RR vs RN position and the black rook finally moved out of the corner.
Stockfish cleared the queen side and exchanged a pair of rooks. It saw the win many moves in advance, the white king walked around the board all the way to e7. Stockfish captured pawns and created a passer, the game ended in a tablebase win. Stockfish wins the game pair, it leads 8-5.
Games 33-34 started with a line in the Modern defense played in high level human games, but not recently. In game 33 the engines played out a long PV agreement. At first Leela was up a pawn, but after several piece exchanges Stockfish regained the pawn. The game reached a QRB vs QRB position and evals started to come down. After some shuffling the engines exchanged queens and Leela captured a pawn. Leela couldn't find a way to improve and the engines shuffled, the game was adjudicated as it approached a 50 move draw.
In game 34 Stockfish gave an early pawn, then regained it and the engines exchanged minor pieces in the center. Evals were stable around 1 until move 20m then Leela gave a rook for a bishop and pawn to expose the white king. There was a long PV agreement, Stockfish exchanged a pair of rooks and was confident its king was safe. Stockfish's eval started to increase very slowly, the game reached a QR vs QN position.
Leela didn't try to chase the white king, its eval drifted down but then started to increase as well. The white pieces without an obvious purpose, then with all pieces concentrated on the king side Stockfish pushed pawns on the queen side. Leela captured the rook for a knight while Stockfish created a doubled passer on the a file.
Stockfish saw the win, it captured two pawns and created another passer on the king side. Leela blocked and captured one passer but couldn't prevent the queening of the other. The game ended in mate. Stockfish wins the game pair, it leads 9-5.
Games 35-36 started with a 20-ply line in the French Winawer, positional variation. In game 35 Stockfish blocked the center, Leela pushed pawns on the king side and left its king without pawn support. Stockfish opened the b file and created a passer on the queen side, Leela blocked the passer and the white king walked to the center. Regardless of the open file Leela moved its king to the queen side and exchanged a pair of rooks.
Leela opened the king side and exposed the black king. In a series of exchanges Stockfish lost its queen for pieces and the game reached a QB vs QBN position, white two pawns up with a passer on the king side.
Stockfish captured the passer but Leela captured pawns in the center, Stockfish lost more material and the game ended in a tablebase win.
In game 36 the engines exchanged pawns in the center, opened the queen side and exchanged queens. The black king moved forward without castling, Stockfish moved a rook forward through the queen side and exchanged a pair of rooks. The game reached a RBB vs RBN position on move 24. Stockfish moved a bishop to f8, the black knight had to stay on e8 to protect the king side pawns.
Leela captured a pawn, evals slowly increased as Stockfish pushed pawns on the king side. After the pawns stabilized Stockfish opened the king side and regained the pawn, Leela exchanged a pair of bishops.
Stockfish captured the black d pawn for its a pawn, the black knight finally moved but Stockfish let it capture a pawn and moved its king forward. The white rook moved forward and Stockfish saw the win. The engines reduced to a rook endgame, Stockfish queened a passer and mated. There were two white wins in this game pair, Stockfish leads 10-6.
Games 37-38 started with a line in the Gruenfeld defense. In game 37 there were no exchanges after the start, both kings walked to the king side without castling. On move 23 a pawn exchange opened the b file, then the engines blocked the center. The engines mostly shuffled for a while and evals came down. From move 39 the engines started to exchange pieces, Stockfish gave two pawns and moved two rooks forward on the queen side. Stockfish traded both rooks, one for a bishop, and then the game reached a QR vs QB position. Leela was a pawn up but Stockfish had enough for a draw and the game was adjudicated. In game 38 Stockfish took over the center and Leela castled its king. The white queen moved forward, in a long PV agreement the engines opened the queen side and exchanged minor pieces. Stockfish castled on move 27, an another long PV agreement the game reached a RRN vs RRB position with white a pawn up. After exchanging a pair of rooks the engines shuffled for a long time, Leela wouldn't lower its eval enough. The game was adjudicated only on move 112.
Games 39-40 started with a line in the Caro-Kann, Steinitz variation, played in high level human games. In game 39 Leela gave a knight for a pawn and forced the black king to move without castling. Evals slowly came down as the black king found safety on the king side, though the king side rook was trapped. Leela had many opportunities to capture the black rook for a knight but decided to keep the knight. In a PV agreement the engines exchanged pieces, suddenly Stockfish's eval jumped, not sure what it saw. The game reached a RR vs RRB position with white two pawns up, Leela's eval remained low.
Leela had a long think and its eval jumped over 2 as well. It captured two more pawns, Stockfish finally developed its trapped rook through the h file. The white king moved forward in the center, Leela had 4 connected passers on the queen side. Stockfish gave the bishop for one passer, the pawn chain was broken but it was not enough.
Stockfish captured another passer but couldn't stop them all. The game ended in a tablebase win.
In game 40 Stockfish also gave a knight for a pawn and the black king moved. Leela was surprised by Stockfish's move 12, after thinking for almost 20 minutes its eval jumped over 2. The black king remained in the center, Leela developed its king side rook through the f file and then gave it for a bishop. A knight exchange opened the center, for a while the white queen was stuck on the king side but Stockfish found a way to get it out. It moved all its major pieces to the queen side, then in a series of exchanges the engines reduced to a QB vs QBN position with white 3 pawns up.
The black minor pieces were static, protecting pawns and themselves. The queens move around the board and Stockfish managed to push the a pawn to a6. It saw the win in its PV, Stockfish exchanged bishops and traded the a pawn for the black c pawn, then captured the black knight for another pawn. This left a queen ending with two pawns up and the game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 11-7.
No comments:
Post a Comment