Season 25 premier division, after RR4

Standings after RR4

Stockfish continues to dominate the premier division. It lost a game against Leela and won the reverse game, but it had 6 game pair wins against the other engines. Leela in 2nd place had a weak DRR with 3 game pair draws against lower ranked engines, including an unusual loss on time against SlowChess. KomodoDragon had a slightly better second DRR with 3 game pair wins, it is more secure in 3rd place. The closest race is between Ethereal and RubiChess for 4th place.

Interesting games

game 59, Stockfish - RubiChess: There were no exchanges after the start until queens were exchanged on move 23, followed by the first pawn exchange. The engines mostly shuffled though evals gradually increased, Stockfish had a space advantage and a bishop pair. On move 48 Stockfish opened the king side, RubiChess gave a rook for a bishop and reduced to a RBN vs BNN position. Stockfish created an advanced passer, RubiChess lost a knight for it. RubiChess lost more material and was mated.

game 62, RubiChess - Stoofvlees: Both engines castled long, there was some shuffling after the start and then Rubihess gave a knight for two pawns and exposed the black king. Stoofvlees surrounded its king by pieces, it missed something in a complicated position full of threats and pins and evals started to jump. In a eries of exchanges RubiChess gave a rook for a knight, the black king had less protection. This allowed RubiChess to reduce to a QB vs RR ending two pawns up. Stoofvlees couldn't protect its king, it lost pieces and was mated.

game 66, Stockfish - SlowChess: Stockfish was a pawn up from the start, evals started to increase after move 20 and Stockfish placed a strong bishop on d5. SlowChess mostly waited, after opening the b file Stockfish exchanged its bishop and placed a rook on d5, then captured another pawn and created a passer. SlowChess beame desperate, it gave two more pawns to open the king side,now it faced more passers and couldn't get rid of any of them. Stockfish attacked the black king, SlowChess lost material and was mated.

game 68, Leela - RubiChess: There were only a few exchanges after the start and evals were stable. On move 29 Leela captured a pawn and evals started to increase. RubiChess opened the queen side and tried to attack but wasn't strong enough, Leela exchanged pieces and in a QRB vs QRN position  captured a second pawn. After exchanging queens Leela created a passer, progress was slow but inevitable, it took Leela another 40 moves to queen a pawn and mate.

game 70, KomodoDragon - Leela: Most minor pieces were exchanged quickly and Leela castled long, KomodoDragon managed to create an advanced passer in the center. Leela was concerned with protecting its isolated pawns on the king side and only blocked the white passer. KomodoDragon's eval started to increase while Leela'a remained stable. KomodoDragon captured pawns on the king side, then gave its rook and attacked the black king. Leela's eval started to increase when it was 5 pawns down in a QN vs QRN position. Leela captured a few pawns back but lost its knight for a passer. After exchanging queens the N vs R ending 3 pawns up was a win, though it took KomodoDragon another 35 moves to complete.

game 73, Stockfish - Igel: Igel gave two pawns and opened the king side, Stockfish kept its king safe and evals started to increase. The game reached a RB vs RB position, Stockfish was a pawn up with connected passers. Stockfish pushed the passers forward and exchanged rooks, the bishops were same colored. Igel captured 3 pawns but couldn't stop a queening and mate.

game 75, Leela - SlowChess: There were no exchanges after the start, the engines formed long pawn lines across the board. SlowChess opened the h file, Leela walked its king to the queen side. Leela's eval was very high though SlowChess moved its queen and a rook forward. SlowChess gave a knight for two pawns and created connected passers on the king side, Leela exchanged pieces and gave back a bishop to capture the passers. Leela captured a pawn and created an advanced passer, SlowChess lost a bishop for th epasser and the game reached a RBN vs RN position. SlowChess lost more material and the game ended in a tablebase win. 

game 80, Stockfish - Stoofvlees: Stockfish castled long and pushed pawns on the king side. Evals increased, a series of exchanges opened the king side and Stockfish gave a bishop and two pawns for a rook. Stockfish used its major pieces to attack, first it sacrificed a rook and exposed the black king, the it captured a bishop. The white queen and rook chased the black king and forced mate.

game 81, Stoofvlees - Igel: Evals were stable until move 39, Igel missed something and evals jumped. Stoofvlees opened the d file, then in a series of exchanges the engines reduced to a B vs R ending. Stoofvlees was only one pawn up but it pushed a passer to the 7th rank. It used a second passer to open the way for the white king to move forward. Stoofvless captured a pawn and created another passer, Igel lost its rook to stop it. Stoofvlees had one last pawn to win. 

game 82, Leela - Stockfish: Queens were off early, evals were stable, Stockfish created a passer in teh center and the white king moved to block it. Stockfish placed a knight on c3 that interfered with the white piece movement, but was also trapped there. Leela moved its attention to the king side and evals increased. Leela managed to capture a pawn and create a passer, then it used exchanges to create two more. Stockfish couldn't stop all the passers and it lost a rook, the game ended in a tablebase win.

game 83, RubiChess - Ethereal: Both kings remained in the center uncastled, Ethereal had difficulties to develop its king side pieces but eventually the h file opened and the engines exchanged a pair of rooks. RubiChess moved its queen forward on the king side, Ethereal was busy defending and couldn't attack the exposed white king. The engines reduced to a RB vs RB position, RubiChess captured a pawn and created a passer. Ethereal delayed but couldn't stop the passer, it lost a rook and the game ended in a tablebase win.

game 84, KomodoDragon - SlowChess: KomodoDragon pushed a pawn to h6, it moved its king without castling. A series of exchanges opened files on the queen side and evals started to increase. The engines shuffled for a while, KomodoDragon placed its major pieces o the open files, then it gave a rook for a bishop and attacked. The game reached a RB vs RR position with the black king in the corner and a white rook on g7. The white king moved forward and the engines traded pawns, SlowChess lost a rook for a passer and the game ended in a tablebase win.

Standings after RR3: Stockfish +10, Leela +6, KomodoDragon +3, RubiChess -1, Ethereal  -2, Stoofvlees -3, Igel -5, SlowChess -8. Stockfish lost the game in black against Leela, it continues to be perfect in white. Leela won its 3 white games, including against Stockfish, but lost in black against KomodoDragon. KomodoDragon had a good RR3 with a +2 score, compared to a -1 score in RR1.

game 85, Igel - SlowChess: Igel pushed pawns on the king side with evals increasing steadily. After opening the g file the white queen moved forward through the center, in a series of exchanges Igel captured a bishop and reduced to a RN vs R position. Igel had enough pawns, the game ended in a tablebase win.

game 89, Leela - Igel: The engines castled in opposite directions and Leela pushed pawns on the king side. The engines exchanged minor pieces in the center, Leela captured a pawn and created a passer. Igel captured the passer and in a series of exchanges the game reached a QRR vs QRR position. Leela again had a passer that it slowly pushed forward. After reducing to a rook ending Leela captured a pawn and had 2 passers on the 7th rank, it forced a queening and won.

game 91, Stockfish - KomodoDragon: see featured game below

game 92, Ethereal - SlowChess: The king side was open and both engines castled long. Evals increased steadily though SlowChess moved a rook forward and captured a pawn. Queens were exchanged and Ethereal regained the pawn, then it exchanged pieces and captured two more pawns. The game reached a RB vs RB position, Ethereal slowly pushed a passer forward and SlowChess lost the bishop to stop it. The game ended in a tablebase win.

game 95, KomodoDragon - Stoofvlees: The engines opened the h file and exchanged a pair of rooks early. Both engines castled long and the game reached a QRB vs QRN position. KomodoDragon captured a pawn and created a passer on the king side. Stoofvlees thought it was safe for a few moves after exchanging the minor pieces, it even captured two pawns. However when it stopped to think it realized it was losing. KomodoDragon pushed the passer to the 7th rank, then pinned the black rook. Stoofvlees couldn't get out of the pin, a white pawn moved forward and captured the rook, mate followed.

game 98, Leela - KomodoDragon: KomodoDragon castled long, Leela moved a bishop forward and captured a pawn. KomodoDragon moved its major pieces to the king side but was not strong enough to attack, Leela exchanged pieces when it could and evals increased. Leela gave two pawns and opened the queen side, then traded RN for Q. In a QB vs RBN position Leela captured pawns and went two pawns up. It pushed a passer, gave its queen for a bishop and queened the passer. KomodoDragon lost material and was mated. There were two white wins in this game pair.

game 99, Stoofvlees - SlowChess: Stoofvlees castled long, SlowChess pushed pawns on the queen side and its king remained in the center. Stoofvlees tried to open the king side but SlowChess avoided exchanges until its king walked to the queen side. After opening the king side the engines traded pawns and Stoofvlees went a pawn up. The engines exchanged a pair of rooks and Stoofvlees moved a rook to the 7th rank. In a series of exchanges the engines reduced to a Q vs RN position, SlowChess lost the roo for a passer and the game ended in a tablebase win.

game 100, Stockfish - Ethereal: The engines exchanged all knights, the queen side was open and Stockfish captured a pawn on the king side. Ethereal gave a rook for a bishop and pushed pawns in the center, after exchanging queens evals started to increase in a RRB vs RBB position. Ethereal stopped a white passer and regained the pawn, after exchanging a pair of bishops Ethereal had a passer in the center and Stockfish had two on the king side. Stockfish gave one passer but trapped the black king on the open h file. It used the threat of mate to gain material and win.

game 102, Ethereal - Stoofvlees: The engines exchanged pawns on the queen side, Ethereal's eval jumped when it gave a knight and created a passer. Stoofvlees thought it was fine for a few moves, then its eval jumped as well. Ethereal regained the piece and the game reached a RRN vs RRN position. Ethereal gave a rook for a knight and pawn, then the white king moved forward on the king side. Stoofvlees captured the passer on the queen side but could not defend the king side. After a pairof rooks was exchanged Ethereal queened a passer and mated.

game 103, SlowChess - Leela: The engines started to shuffle on move 30, with piece exchanges resetting the 50-move counter. Leela was out of time and playing on the 6 second increments, on move 152 Leela moved too late and lost on time.

game 105, KomodoDragon - Igel: Both engines did not castle their kings, there were almost no pawn exchanges after the start and both engines played behind their pawn lines. Igel placed both knights on the 4th rank and tried to hold a pawn line across the board. KomodoDragon exchanged a bishop for one of the black knights, then moved pieces to the queen side where the black king was located. The engines opened the queen side with exchanges, KomodoDragon captured two pawns and then moved it major pieces forward on the king side. The game reached a QR vs QR position with the black king on the run and a white 3 pawns up. Igel lost its queen for a rook, KomodoDragon queened a passer and mated.

game 106, RubiChess - SlowChess: Both engines castled long, evals started to increase on move 20 after SlowChess created an advanced passer in the center while RubiChess had a pawn majority on the king side. RubiChess moved a rook forward on the king side and exchanged queens, then reduced to a RBN vs RBN position. RubiChess captured the black passer and was 3 pawns up, it gained material and the game ended in a tablebase win.

game 110, Stockfish - Leela: Evals were stable for a long time, the engines exchanged pawns and a few minor pieces. On move 32 the engines opened the queen side and evals started to increase slowly. Stockfish doubled rooks on the open c file, then created an advanced passer after an exchange. After some shuffling Stockfish gave a rook for a knight and the game reached a QRB vs QRR position. Leela couldn't get rid of the white passer, Stockfish captured two pawns and the queens were exchanged. Leela tried to delay but Stockfish was patient, eventually Leela couldn't stop the white passer, Stockfish queened and mated. There were two white wins in this game pair.

Featured game: Stockfish - KomodoDragon
game 91

Stockfish pushed pawns on the king side and castled long. it gave a pawn and opened the king side. The black king remained in the center and evals slowly increased. KomodoDragon had a rook on the open h file, Stockfish regained the pawn, then the engines exchanged a pair of rooks and queens. On move 40 Stockfish went a pawn up, its first material advantage of the game. 

Stockfish had one passer, still on its initial square. Progress was slow in a difficult middlegame, the black bishop pair was strong in an open board. KomodoDragon wanted to separate the white pawns on the queen side, on move 54 it gave a rook for a knight and captured the b pawn. In a RBN vs BBN position KomodoDragon blocked the white passer and Stockfish captured a pawn. 

Progress was again slow, pushing the passer required a lot of preparation. On move 72 Stockfish pushed the passer the the 5th rank, on move 78 Stockfish gave back the rook for a bishop but then its passer was unstoppable. Stockfish queened the passer and mated.