After 30 games Stockfish leads 8-6 with 16 draws. Stockfish's lead is still 2 wins after each engine won one game pair and there were three drawn pairs, one with two white wins. Leela won its first game pair of the match, adding tension to the match since it is not one-sided and the gap is still small.
Games 21-22 started with 6-ply line in the Scandinavian, Blackburne gambit. In game 21 the engines played out a long PV agreement, developing their pieces and exchanging a few minor pieces. Leela had a pawn majority on the queen side but it didn't find a way to push the pawns safely. Evals came down, the engines shuffled for a long time. After exchanging pieces the draw rule adjudicated the game on move 79. In game 22 again the engines developed their pieces mostly in PV agreement, and most minor pieces were exchanged. Evals slowly came down, the game reached a QRN vs QRB position with white a pawn up. Stockfish gave a pawn and created a passer, after some shuffling it gave another pawn. Evals were close to 0, the engines continued to exchange pieces and the game was adjudicated.
Games 23-24 started with a 19-ply line in the Sicilian, Scheveningen variation, Keres attack, played in high level human chess. In game 23 the engines castled in opposite directions, in a knight exchange Leela chose to retake with a rook and Stockfish's eval dropped. Stockfish seemed to have the initiative, it was focused on attacking the queen side while Leela blocked and interfered. Evals steadily decreased, Stockfish managed to get a knight to a3 and to open files. It gave a rook for a bishop and moved the queen forward to attack the exposed white king. The game was adjudicated in a QR vs QN position, with perpetual check in the PV.
In game 24 again the engines castled in opposite directions, in the same knight exchange Stockfish retook with a bishop. For a few moves Stockfish offered a bishop and Leela refused to take as it would expose its king to attack. In a series of exchanges the engines reduced to a RBN vs RBN position, Stockfish was a pawn up with connected passers on the queen side but evals were low.
Leela moved its rook forward and captured a pawn, Stockfish's eval started to increase. Stockfish chased the black pieces away and attacked the black king. Leela's eval reacted after 6 moves, the black king had to run forward. After exchanging bishops Stockfish captured two pawns on the king side. Leela had a passer on the king side, Stockfish was only a pawn up but now both evals were over 2.
Stockfish blocked the black passer with its rook and slowly pushed its queen side passers. Leela traded its passer with the white f pawn, and pushed its e passer forward. Stockfish captured the passer with its knight on the 2nd rank, Leela did not take back to avoid a 7-man position. This only delayed the end by a few moves after Stockfish queened a passer. Stockfish wins the game pair, it leads 7-4.
Games 25-26 started with an 18-ply line in the Sicilian Nimzowitsch variation. Both queens were out on the queen side, white was a pawn up with a passer on d6. In game 25 Leela gave a pawn and Stockfish castled long. Stockfish captured the white passer but lost a knight. The engines played out a long PV agreement where the queens were traded and the result was a BN vs R imbalance with high evals.
Stockfish formed a pawn line on the king side and tried to protect the pawns, Leela exchanged a pair of pawns and captured one, creating a passer. After exchanging a pair of rooks Leela traded a knight for the black bishop, leaving a BB vs R ending.
Both engines had a passer but the bishop pair was very strong. Leela captured the black pawns on the king side and blocked the black passer. The white passers were unstoppable, the game was adjudicated after Leela queened.
In game 26 both kings stayed in the center and the black queen retreated. Stockfish lost its passer and it gave another pawn, giving Leela a passer in the center. Evals rapidly increased, Leela captured another pawn but lost a rook by a knight fork.
Leela's compensation for the rook was the trapped knight in the corner as well as the white rook and bishop on the king side that could hardly move. Leela pushed the passer to d3 and tightened the trap. Stockfish captured the h pawn with its queen and freed its corner knight. It pushed the h pawn and opened a way out for its rook. In a series of exchanges the engines reduced to a RRB vs RB position.
Leela had connected passers on the 2nd and 3rd ranks but they were blocked, and Stockfish had an extra rook. Stockish gave a rook for a bishop and captured both passers, the game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 8-5.
Games 27-28 started with a 20-ply sideline of the French, Tarrasch closed variation. In game 27 both kings stayed in the center and there were many early exchanges. Stockfish had a passer in the center, after exchanging queens Leela created a passer on the king side. Evals steadily decreased, Stockfish castled late and blocked the white passer with its king. The game reached a RBB vs RBN position, Stockfish captured the white passer and Leela moved the rook to the 7th rank. Evals were low enough for the draw rule, Stockfish gave a rook for a bishop and the game was adjudicated. Game 28 started with a 30-ply repeat of game 27 with a transposition. Stockfish pushed pawns on the king side and created connected passers there. Leela walked its king to block together with a knight, Stockfish traded a bishop for the knight and the game reached a RRB vs RRB position. The engines shuffled for a while with evals close to 0, after exchanging a pair of rooks the game was adjudicated.
Games 29-30 started with a rare sideline of the semi Slav, accelerated Meran variation. In game 29 the engines formed a diagonal pawn wall that blocked the center and most of the queen side. The engines castled in opposite directions and evals were stable. A few pawn exchanges opened the g file, most of the black pieces moved to the king side to protect the king. All pieces were on the board, the engines shuffled for a while and then Stockfish captured the h pawn on move 38.
With two open files on the king side Stockfish slowly walked its king to the center. Leela's eval increased and it captured the a pawn, Stockfish was less convinced but it had very little time left to think. The engines exchanged all major pieces, Leela captured another pawn and Stockfish tried to hold its position but its eval increased as well. Leela created an advanced passer on the queen side, the engines reduced to a BBN vs BNN position on move 73.
Stockfish's defense collapsed, Leela's pieces moved forward and it managed to capture the black pawns on the queen side. Leela was two pawns up, the white king moved forward and Stockfish couldn't stop the passers. Leela queened and mated.
In game 30 both engines castled short, instead of a pawn wall the engines exchanged pawns and opened the board. Evals came down, the engines exchanged pieces until the game reached a queen ending. Stockfish was a pawn up but with all pawns on the king side. Evals were low enough and the game was adjudicated. Leela wins the game pair, Stockfish leads 8-6.
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