Season 25 league 1

Final Standings

RubiChess and Igel advance to the premier division. RubiChess led from the start, it had two RRs with a perfect performance where it won all 6 games as white (with opening bias) and drew all 5 games in black (against opening bias). RubiChess beat all other engines at least once in a game pair, it had only two losses and won both reverse games. Several engines were in the race for 2nd place, though at the halfway point rofChade and Igel opened a gap to the rest of the field. rofChade was 2nd with a small margin, it also beat Igel in their first direct game pair. In the last RR rofChade lost a few games against lower ranked engines while Igel had its best RR with 6 wins including one against RubiChess. Igel's only loss was again to rofChade, but this time Igel managed to stay in the lead and hold on to 2nd place. 

The 4 engines that started in the entrance league did not advance further in season 25. DeepSjeng and Viridithas struggled in league 1 and both finished in the 4 bottom places destined for relegation - if there are no surprises in the next season. Caissa and Clover had better results but they couldn't keep up with the three leaders. They should start next season in league 1.

Seer crashed three times in the league, losing games on time. In one game it was losing anyway, but in two games against rofChade and Clover the position was drawn and Seer gifted wins by crashing. In the end this half point to rofChade did not change the race for 2nd place.

The two qualifiers will play in the premier division together with Stockfish, Leela, KomodoDragon, Ethereal, Stoofvlees and SlowChess, all played in the premier division of season 24. This season the premier division will be a 6DRR event, followed by a 4DRR playoff of the top 4 engines.

Interesting games

game 3, Revenge - DeepSjeng: The game reached a QRR vs QRR position, evals were mostly stable. All pieces were concentrated on the king side, DeepSjeng played inaccurately and Revenge exchanged all pieces. DeepSjeng realized it was losing the king and pawns (equal material) ending too late.

game 5, RubiChess - Clover: The center was blocked, RubiChess opened a file on the queen side and moved a rook to the 7th rank. The engines reduced to a RB vs RB position, RubiChess pinned the black bishop on the back rank and captured a pawn. Clover couldn't avoid losing more pawns and then its pieces, and finally mate.

game 6, Seer - Viridithas: By move 35 only one pair of pawns and a few minor pieces were exchanged. Seer attacked from the queen side and created connected passers in the center. Viridithas lost a bishop to stop the passers and the game reached a RB vs R position. Viridithas was 3 pawns up, Seer was careful to keep one last pawn. The game ended in a tablebase win 45 moves later.

game 11, rofChade - Revenge: The engines opened the center and exchanged pieces, the game reached a RB vs RB position with white a pawn up. Revenge thought it was quite safe until rofChade exchanged rooks. Revenge regained the pawn but its king was too far to help block a passer. rofChade won the black bishop for the passer and still had one pawn to win the game.

game 16, RubiChess - DeepSjeng: RubiChess was a pawn up, evals increased after move 30, then came back down after the game reached a QB vs QN position. DeepSjeng seemed to equalize and the engines shuffled for a while, but RubiChess' eval increased again. I'm not sure if DeepSjeng blundered or RubiChess found the right moves, RubiChess created a passer and exchanged queens. DeepSjeng lost the knight for the passer and the game ended in a tablebase win. 

game 17, Seer - Caissa: The center was blocked and there were only a few exchanges after the start. On move 49 Seer opened the h file, the black king ran to the queen side and Seer managed to capture a pawn and create an advanced passer. In a QRB vs QRN position Caissa lost its rook for the passer, the game ended in a tablebase win. 

game 18, Viridithas - Clover: The engines castled in opposite directions, Viridithas pushed pawns on the king side and created a passer in the center. The engines exchanged pieces and reduced to a RB vs RB position, Clover lost the bishop for the passer and the game ended in a tablebase win.

game 19, Igel - Clover: Most pieces stayed on the board, Clover moved its king without castling and the king side rook couldn't develop. After mover 45 the engines opened the board and exchanged pieces until only RB vs RB were left, Igel was a pawn up with an advanced passer. Clover exchanged rooks but Igel captured two more pawns, enough to win the opposite color bishops ending.

game 20, Caissa - Viridithas: The engines exchanged a few minor pieces and Caissa went a pawn up. The engines mostly shuffled for a while in a RBN vs RBN position, then the white king moved forward and Caissa created a passer. Caissa captured a second pawn and reduced to a winning N vs B ending.

game 27, RubiChess - ScorpioNN: After a series of exchanges in the center RubiChess was up a pawn with connected passers. ScorpioNN also had a passer but the white passers were stronger. RubiChess gave two minors to queen a passer, ScorpioNN gave material back to avoid mate and the end result was  QR vs QB position. ScorpioNN had a passer on the 2nd rank but its king was exposed and it was busy defending. RubiChess exchanged queens and captured the passer, then reduced to a winning king and pawns ending.

game 30, Clover - Caissa: The engines exchanged pieces until reaching a rook ending. Clover was a pawn up, it captured a second pawn to win.

game 31, Igel - Caissa: The black king remained in the center, Caissa developed its king side rook through the h file. Caissa gave the rook for a knight and attacked the white king, the engines reduced to a QB vs Q position with black 3 pawns up. Igel played patiently, it kept one pawn and forced a queen exchange. The game ended in a tablebase win after 25 moves.\

game 33, rofChade - Viridithas: Viridithas grabbed a pawn early but rofChade had a space advantage and evals increased gradually. rofChade pinned a bishop on the back rank, Viridithas gave a rook for a bishop to avoid losing a piece. The game reached a RN vs BB position, rofChade had an advanced passer and Viridithas lost a bishop to stop it. The game ended in a tablebase win.

game 34, ScorpioNN - Seer: ScorpioNN grabbed a pawn early, then created an advanced passer. Seer regained the pawn but gave a rook for a knight for the passer. Both engines created another passer, after some shuffling ScorpioNN captured the black passer on the 2nd rank. The game reached a RB vs BN position, ScorpioNN captured all the remaining black pawns, then mated after queening a pawn.

game 38, RubiChess - Revenge: The were a few exchanges after the start, evals slowly increased after move 30. RubiChess opened the queen side and gave a rook for a bishop to create an advanced passer. in a QRB vs QRR position RubiChess gave up that passer and switched to another one on the king side. Revenge lost material but couldn't stop the passer, game over.

game 41, Clover - rofChade: Queens were off early, all the rooks were on the a file with one black pawn between them. Clover moved a knight across the board to capture the pawn, with the king's help it managed to get the knight away safely. In a RBN vs RBB position Clover captured another pawn and queened a passer to win.

game 44, rofChade - Caissa: Caissa blundered when its queen moved forward to grab a pawn, it saw the next sequence of moves in its PV but thought it was safe. rofChade immediately attacked the black king, the game reached a QR vs QR position with black two pawns up but its king completely exposed. Caissa had to give its queen for a rook, the game ended in a tablebase win.

game 47, Revenge - Seer: With all pieces on the board Revenge traded minors, gave a pawn and opened the g file. Some of Seer's pieces were too far to help defend the king, Seer had to trade RN for Q. The engines exchanged pieces and the game reached a Q vs BR position, Seer lost the bishop for a passer and was mated.

game 49, RubiChess - Igel: Igel didn't castle its king, RubiChess opened files on the king side and center and threatened an attack with its major pieces. Igel exchanged pieces, the game reached a rook ending with white a pawn up. RubiChess had connected passers, Igel lost its rook for one, game over.

game 50, Seer - Minic: Seer traded a knight for 3 pawns, then reduced to a RN vs RBN position and captured a 4th pawn. After exchanging knights Minic was left without pawns, eventually Minic lost the bishop for a passer and the game ended in a tablebase win. 

game 54, DeepSjeng - rofChade: DeepSjeng went a pawn up and exchanged cleared the center. The white bishop pair controlled many squares, after a long shuffle DeepSjeng captured another pawn and reduced to a RBB vs RBN position. DeepSjeng captured a third pawn and rofChade couldn't avoid a queening, it gave away its pieces and was mated.

game 58, Revenge - Clover: Both engines castled long, then Revenge opened the a file. Revenge pushed a pawn to c6 and after exchanging queens moved both rooks to the a file. Clover captured pawns but had to give material to save its king. The game reached a RB vs B position with black 4 pawns up, Revenge captured pawns and queened its last one to win.

game 60, RubiChess - Seer: Queens were off early and the black king moved without castling. RubiChess attacked through the center and created a passer. Seer walked its king to safety, after a while RubiChess started an exchange series where it gave up the passer and reduced to a BN vs R position. RubiChess created another passer, this time Seer couldn't prevent a queening and mate.

game 64, Caissa - Revenge: After move 20 the engines exchanged pieces, Caissa went a pawn up and the game reached a RB vs RB position. The white king moved forward, after exchanging rooks Caissa captured another pawn and created a passer. Revenge blocked and captured the passer while Caissa captured the remaining black pawns to win.

Standings after RR1: RubiChess +6, Igel rofChade +2, Seer +1, Revenge Minic Caissa 0, Viridithas Clover -1, ScorpioNN -2, Fritz -3, DeepSjeng -4. RubiChess leads with a 2 point margin, it has won all games with the bias in white and drew against the bias in black. The fight for 2nd place is wide open, there were many decisive games and the reverse games may be significant. The 4 newcomer engines that started from the entrance league are not so strong in this league, this is probably their final appearance this season.

game 70, Caissa - Minic: Caissa gave a pawn and opened the center, the black king did not castle and the black king side rook was trapped. In a QRN vs QRN position Minic freed its rook while Caissa captured two pawns, then exchanged queens. After a while Caissa captured a second pawn and then created a passer that Minic couldn't stop without losing a piece, game over.

game 71, Clover - RubiChess: RubiChess was a pawn up while Clover attacked the uncastled black king. The game reached a RRN vs RRN position, Clover captured two pawns and created a passer. Progress was slow, after exchanging a pair of rooks Clover pushed the passer, after 30 moves it reached the 7th rank. Clover created a second passer and RubiChess couldn't stop both, Clover queened to win.

game 74, Seer - Clover: Clover equalized though it was a down a rook for a bishop. The game was heading for a draw in a QRB vs QBB position when Seer didn't move on time and lost.

game 75, RubiChess - Caissa: RubiChess gave two pawns and attacked the black king. It sacrificed a knight as well, and then regained the material in a series of exchanges and the game reached a RB vs RN position. Caissa gave a pawn to create a passer, the engines cleared the queen side pawns and exchanged minors. RubiChess blocked the black king away from the king side and pushed its pawns there, winning a rook ending with one pawn advantage.

game 83, Caissa - Seer: The center was blocked and there were no exchanges after the start. After move 29 a few pawn exchanges created passers in the center for both engines, evals started to increase. The first piece exchange was queens on move 44 and the engines cleared the center pawns. Caissa doubled rooks on the h file, Seer gave a rook for a knight to avoid a trap for its king. In a RRB vs RBN Caissa captured pawns, then slowly improved its position. Then on move 80 Seer lost on time, though it was probably losing in any case.

game 84, Clover - Viridithas: The engines gradually exchanged minor pieces, Clover captured a pawn and the game reached a QRB vs QRN position. After some shuffling Clover captured another pawn and a series of exchanges reduced to a B vs N ending. Clover queened a passer and then mated.

game 88, RubiChess - rofChade: RubiChess threatened the black king, rofChade started a series of exchanges that resulted in a RNN vs RN position. It took a while but RubiChess managed to create a passer and promote to a queen, followed by mate.

game 94, rofChade - Seer: Almost all pawns stayed on the board and the engines shuffled for a long time. Evals were close to 0 but there were too many pieces on the board for the draw rule, then Seer lost on time again.

game 96, Caissa - Clover: There were almost no exchanges after the start and the engines mostly shuffled for a long time. Evals increased a little after move 45, Caissa pushed pawns and restricted the black pieces further. Caissa created a passer after a piece exchange, after more shuffling there were some more exchanges and only RB vs RN remained. Caissa had unstoppable passers, Clover lost material and was mated.

game 103, Igel - Minic: Igel opened the king side, captured a pawn and created a passer. Minic exchanged pieces and regained the pawn, the game reached a RBN vs RBN position. The white king moved forward to support the passer, Igel captured a second pawn and Minic lost more material. The game ended in a tablebase win. 

game 107, rofChade - Clover: All the pawns were on the board, rofChade pushed its pawns and the black pieces had to retreat. Clover gave a bishop for two pawns, the engines exchanged pieces and pawns and the game reached a RN vs R position. Clover had two passers, onr was captured and the other blocked. eventually rofChade managed to exchange rooks, then queen a passer and mate.

game 109, DeepSjeng - Igel: DeepSjeng seemed to be in control in a RB vs RR position with two advanced passers on the 6th and 7th ranks. However it didn't find the best moves and Igel managed to hold.

game 121, rofChade - Igel: rofChade was up a pawn and evals slowly increased with no exchanges. The engines started exchanging pieces after move 33 and the game reached a QRR vs QRR position. The black king was in danger and Igel gave two pawns to get all pieces involved in the defense. rofChade exchanged a pair of rooks and pushed two passers forward, eventually Igel lost a rook to stop them, game over.

game 124, Clover - Revenge: Clover controlled the open d file, it captured a pawn and created a passer on the queen side. Revenge gave a bishop for two pawns to expose the white king, but it ran out of checks after a while. Clover reduced to a RN vs R position, the game ended in a tablebase win.

game 127, Igel - Seer: There were no exchanges after the start, the first pawns were exchanged on move 20, the piece exchanged on move 29. Seer had a trapped bishop and evals increased steadily. Igel went two pawns up and reduced to a RB vs RB position, then it captured the trapped bishop. Igel queened a passer and mated.

game 129, Minic - Clover: The engines opened files in the center and evals increased. Clover gave a rook for a bishop, the white king was exposed but after Minic exchanged queens its king was safe. The engines reduced to a RN vs BN position, Minic captured more pawns and the game ended in mate.

Standings after RR2: RubiChess +8, rofChade +6, Igel +5, Caissa +3, Clover +2, Minic +1, Seer Revenge 0, Viridithas -3, Fritz -6, ScorpioNN -7, DeepSjeng -9. RubiChess leads at the half way point, it lost its first game and drew two games with opening advantage. rofChade is in 2nd with Igel close behind, rofChade beat Igel in their direct game pair which could be important in a tiebreak situation. Caissa and Clover both improved their rank, they still have a small chance of advancing for the 3rd time this season. Seer crashed 3 times on time, it was losing against Caissa but it gifted wins in drawn positions to Clover and rofChade. I hope the qualification spots will not be decided by these crashes.

game 136, Minic - Caissa: Minic was a pawn up, the engines exchanged minors and reached a QRR vs QRR position. Minic kept its queen and exchanged rooks, in a queen ending the engines traded pawns. Minic managed to capture all the black pawns and kept two to win.

game 137, RubiChess - Clover: RubiChess was a pawn up, the engines cleared the queen side and RubiChess had a passer there. The engines gradually exchanged pieces and the game reached a B vs N ending. RubiChess pushed the passer to the 6th rank, then moved its king forward. Clover couldn't block the passer and keep the white king away, it lost its knight and the game.

game 143, rofChade - Revenge: rofChade was a pawn up, it created a passer in the center. rofChade gave a bishop and attacked through the center, Revenge gave back a knight to keep its king safe. More pieces were exchanged, Revenge captured the passer but rofChade captured pawns and the game reached a rook ending with enough advantage to win.

game 145, Fritz - Igel: Fritz had a passer on the 6th rank but wasn'r strong enough to push it forward, Igel's eval dropped to 0. When Fritz pushed another pawn Igel saw an opening to attack the exposed white king. It gave a pawn and risked facing 3 connected passers, Fritz realized its mistake too late. Igel used checks to capture the white passers and reduce to a RB vs RN position 2 pawns up. This was enough to later queen a passer and win.

game 151, Igel - Clover: The engines exchanged a few minor pieces, most pawns remained on the board. After some shuffling the engines opened files on the queen side. Igel threatened pieces with pins and forks in the center, the tension was released in a series of exchanges that left a RN vs BN position. Igel captured two pawns to win.

game 160, Seer - rofChade: The black king moved without castling, and the king side rook could only develop through the h file. Seer captured a pawn and created an advanced passer in the center. rofChade shuffled while Seer walked its king to the queen side, then a series of exchanges reduced to a RBN vs RBB position with white two pawns up. rofChade captured the passer but Seer captured all remaining black pawns and was 5 pawns up, it pushed its pawns forward to win.

game 164, DeepSjeng - Clover: There were almost no exchanges after the start, a pawn exchange opened the g file. DeepSjeng castled long and moved its pieces to the king side, then switched to the queen side when both engines created passers there. DeepSjeng captured a rook for a knight and hid its king behind a black passer. The engines exchanged queens after the black king was threatened, then DeepSjeng captured a rook for its passer, followed by mate.

game 168, Revenge - Minic: Revenge pushed a pawn to h6 and castled long. The black queen moved forward and captured two pawns but the black king was stuck in the center surrounded by open files. Revenge gave a rook and attacked with all its pieces, Minic couldn't find a safe spot for its king and it lost the queen by a fork. The game reached a QBN vs RRB position, Revenge continued to chase the black king and forced mate.

game 176, rofChade - Caissa: A series of exchanged left a QR vs QR position. rofChade had an advanced passer in the center that Caissa blocked. It took rofChade 25 moves to push the passer to the 7th rank and 10 more moves to reduce to a king and pawns ending. Caissa captured the passer, material was equal but the white king was better placed to ensure the win.

game 181, RubiChess - Igel: After the start RubiChess had a bishop pair advantage and an advanced passer in the center. In a QRB vs QRN position RubiChess pushed the passer to the 7th rank and Igel couldn't get rid of it. The engines exchanged queens, RubiChess created a second passer, Igel captured one but the other promoted to a queen. RubiChess lost the rook but had enough material to win.

game 189, Fritz - Caissa: The black king moved without castling, trapping the king side rook. The engines gradually exchanged pieces until only RBN vs RBN were left, Fritz went a pawn up and created two passers. After exchanging bishops Caissa captured one passer, it lost the knight for the other. It took Fritz another 17 moves to reach a tablebase win.

game 190, Revenge - Clover: There were many exchanges after the start and the game reached a QRN vs QRN position. Clover had two isolated pawns, after exchanging queens Revenge captured one. Revenge had a rook on the 7th rank, the white king moved forward, Clover lost material and was mated.

game 196, Caissa - Revenge: The engines opened the king side, Revenge gave a knight for a pawn to gain a development advantage. However, Caissa managed to develop its pieces and in a series of exchanges reduced to a RBN vs RB position. Revenge pushed a passer forward and Caissa gave a bishop to stop it, by then Caissa was two pawns up. The white king moved forward and captured the last black pawn, the game ended in a tablebase win. 

Standings after RR3: RubiChess +14, rofChade +9, Igel +8, Caissa +4, Revenge Seer +1, Clover -1, Minic -2, Viridithas -5, Fritz -8, ScorpioNN -9, DeepSjeng -12. RubiChess increased the lead after another RR with 6 white wins and no loss. rofChade has an advantage in the race for 2nd place over Igel, though anything can happen. Caissa is probably too far behind to have a chance to advance. Clover dropped after a poor RR with 4 losses and one win. Seer climbed a little, it had no crashes in the RR.

game 207, RubiChess - Caissa: The center was blocked and the c file was open, there were only a few exchanges after the start. Caissa walked its king to the queen side, it was without pawn support but not under attack. The game reached a RNN vs RNN position, after move 40 evals slowly increased. RubiChess captured a pawn, aftr exchanging a pair of knights RubiChess created 2 connected passers. Caissa regained the pawn and captured one of the passers, rooks were exchanged leaving a knight ending. The white king was much closer to the pawns, RubiChess captured the remaining black pawns to win.

game 209, Revenge - rofChade: Revenge was a pawn up, the engines opened the king side, rofChade castled long but Revenge castled short. rofChade tried to attack the white king, but was not strong enough after exchanging queens. Revenge captured another pawn and lost a knight temporarily, a series of exchanges reduced to a RBN vs RBN position with white a pawn up. Revenge had a passer, it avoided exchanging rooks until it captured another pawn. The white king came forward and Revenge captured the last black pawn. The game ended in a tablebase win.

game 218, Viridithas - Caissa: Viridithas pushed pawns and opened the king side. The white king walked to the queen side without castling, Viridithas doubled its rooks on the h file. The game reached a QRR vs QRR position and Viridithas attacked the back rank. Caissa tried to protect its king, it lost first one pawns then another and Viridithas reduced to a winning king and pawns ending.

game 223, Igel - Revenge: Most of the action after the start was on the queen side, both engines created a passer there. Igel gave two pawns, letting Revenge have 3 passers but exposing the black king to attack. Igel captured pawns and the game reached a RRB vs RRN position with white a pawn up. Revenge lost a piece for a white passer, Igel had enough advantage that it gave its bishop to reduce to a winning 7-man rook ending. It took another 35 moves to adjudicate the game.

game 231, Viridithas - rofChade: Both engines didn't castle their king, there were only a few exchanges after the start and the engines mostly played behind their pawn lines. After opening the king side and exchanging a pair of rooks Viridithas gave 2 pawns and captured a bishop. In a RBN vs RN position Viridithas captured 3 pawns and pushed passers forward. rofChade couldn't avoid a queening, game over.

Standings with 5 round to go: RubiChess +16, Igel +11, rofChade +9, Seer +4, Caissa +3, Revenge +1, Clover 0, Minic -1, Viridithas -4, Fritz ScorpioNN -12, DeepSjeng -15. Drama in the fight for 2nd place. Igel won 3 games in white against lower ranked engines, and rofChade lost twice in black. Igel is leading rofChade by a point with 5 games to play, it still has to play black against rofChade and rofChade has a tiebreak advantage.

game 235, Igel - Minic: Minic was a pawn up and Igel had a bishop pair advantage. The engines cleared the queen side pawns and shuffled for a while, evals were mostly stable until move 45. Igel regained the pawn and reduced to a RBB vs RBN position. Minic may have held longer but it was inaccurate in time pressure, Igel threatened mate and Minic had to give a rook for a bishop. The game ended in a tablebase win.

game 247, Igel - RubiChess: RubiChess pushed the g pawn and Igel moved a bishop to h6, disrupting the black king's castling. The engines opened the king side, RubiChess captured two pawns and the white king was exposed. RubiChess gave a rook for a bishop and blocked the g file, then it castled long and the game reached a QRR vs QRN position. Igel moved its pieces forward, RubiChess delayed with checks but eventually Igel reduced to a R vs N ending. Igel captured pawns, then queened a passer and mated.

game 250, Fritz - Clover: Fritz was a pawn up with eval advantage but Clover seemed to equalize. Clover gave a bishop for two pawns and exposed the white king. On move 42 Fritz blundered twice, it saw Clover's response in its PV but realized the mistake only after Clover moved. Clover used an attack on the white king to capture the white queen and reduce to a QN vs RRB position with black two pawns up. Fritz couldn't defend against the rushing passers and the attacks on its king, it lost pieces and the game ended in a tablebase win.

Standings with 2 rounds to go: RubiChess +16, Igel +13, rofChade +10, Seer +4, Caissa Clover +2, Revenge +1, Minic Viridithas -3, ScorpioNN -12, Fritz -14, DeepSjeng -16. Igel increased the gap to rofChade to 1.5 points. rofChade only drew as white against Clover while Igel beat RubiChess as white. With two games to play this is a substantial advantage for Igel, though it still has to face rofChade as black.

game 253, rofChade - Igel: rofChade castled long and pushed pawns on the king side, placing a pawn on h6. Evals started to increase after the center was opened, Igel pushed pawns on the queen side, rofChade went a pawn up and created connected passers. rofChade gave back the pawn to bring a passer to the 7th rank. In a RB vs RB position rofChade pushed a second pawn forward, Igel lost material and was mated.

With this win rofChade is only 0.5 points behind Igel in 2nd place. In the last round rofChade plays as black and Igel as white so Igel still has an advantage. In case of a tie rofChade will advance.

The Igel - Seer game 259 didn't start properly and had to be restarted. As a result the game was played last, after the ScorpioNN -  rofChade which was supposed to be last according to the schedule.

rofChade held a draw against ScorpioNN as black. Igel needs a draw to finish in 2nd place.

game 259, Igel - Seer: Igel captured the h pawn and exposed the black king to attack. The white d pawn became a passer, the game reached a QRN vs QRN position. After exchanging queens Igel captured all the black pawns and was 5 pawns up. Seer tried to avoid a 7-man tablebase loss but it couldn't avoid a queening and mate.

Igel secures 2nd place with this win, rofChade finished 3rd.

Season 25 league 2 statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

Final draw rate was 63.2%. 

Game termination

The three most common game termination causes were:
49.2% - TCEC draw rule
23.1% - SyzygyTB
17.4% - Mate

There were no crashes in the stage.

Moves per game

Median= 63
Average= 69.7

There were 32 games longer than 100 moves, the longest was 175 moves (Velvet - Caissa, game 9, draw). 

Time per game (hours)

Median= 1:01
Average= 1:00

Openings

There were variable length book openings in this stage. The first letter of the ECO codes was distributed as follows: 

The engines had little freedom to choose the opening variant, 94.7% of the game pairs repeated the same ECO code and 90.1% repeated the opening variant twice. Only in 1.5% of the game pairs the first letter of the ECO code was not repeated.

Reverse pairs, wins

Reverse pairs, same moves

 

Pairs of reverse games diverged less quickly than usual, 14.4% diverged immediately out of book, 51.5% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 44 (!) plys (DeepSjeng - Caissa, games 62 and 128, Sicilian Najdorf, Polugayevsky variation, two draws) 

Season 25 league 2

Final standings

Clover, Caissa, Viridithas and DeepSjeng advance to league 1. The 4 qualifiers from the entrance league continue their journey in season 25, all advance for a second time. These engines led the league from the start, together with Arasan. At the half way point Arasan was in 4th place and DeepSjeng trailing by a point. In RR3 Clover, Caissa and Viridithas extended their lead while DeepSjeng and Arasan continued to battle for 4th place. Two rounds to go DeepSjeng and Arasan were tied, but then DeepSjeng beat Arasan in their only decisive game and this was enough to secure the qualification spot.

When the league started Arasan lost a few games in the first rounds against engines that were supposed to be weaker. It turned out that Arasan was run using wrong settings, this was fixed and its first few games were rerun.

The 4 qualifiers will play in league 1 together with:
played in season 24 league 1 - Igel, Revenge, RubiChess, rofChade, ScorpioNN, Seer, Minic, Fritz 

Interesting games

game 1, Viridithas - BlackMarlin: The game reached a RB vs RB position with white a pawn up and each engine with one passer. The engines shuffled for a long time, then BlackMarlin played inaccurately and evals increased. Viridithas captured the black passer, BlackMarlin lost its rook for the white passer, game over. 

game 3, Clover - Halogen: Clover had a pawn majority on the queen side that later became a passer. Clover created a second passer with a piece exchange. In a QRB vs QRN position Clover created a third passer and pushed all three to the 7th rank. Halogen lost two pieces for the passers, and the game ended in a tablebase win. 

game 4, Arasan - Velvet: Velvet had a passive bishop stuck on the king side, the engines opened the queen side and evals increased steadily. Arasan captured a pawn and created a passer in a QBN vs QBN position. Arasan threatened the black king, it gave the knight and captured 3 more pawns. Velvet lost its bishop and couldn't stop all the passers, Arasan queened and mated.

game 5, Caissa - Marvin: The queen side was blocked, Caissa gave a pawn and created a passer in the center. The white king walked to the queen side and Caissa attacked on the king side. The engines exchanged pieces and the game reached a double rook ending with white a pawn up. Caissa had connected passers, Marvin lost material to stop them and was mated.

game 12, Viridithas - Uralochka: Viridithas castled long and opened the king side. Uralochka attacked on the queen side and gave two minors for a rook, in a series of exchanges the engines reduced to a QRN vs QR position with black 4 pawns up. Viridithas captured 3 pawns back and pushed a passer to win. 

game 15, Arasan - Tucano: Arasan gave a knight for 3 pawns and created connected passers. Tucano captured a rook for a bishop and tried to block the passers, Arasan captured another pawn and created another passer. Tucano captured one passer but lost material and eventually was mated.

game 19, BlackMarlin - Marvin: Marvin was up a pawn but its king moved without castling. The game reached a QR vs QR position and the black rook was stuck on the queen side. By the time Marvin freed its rook BlackMarlin captured pawns and reduced to a rook ending with connected passers. Marvin tried to block the passers with its king and was mated.

game 23, Viridithas - Arasan: Arasan was a pawn up but its king moved without castling. Queens were off and Viridithas captured a rook for a bishop, leading to a RRB vs RBN position. After exchanging a pair of rooks the engines captured pawns until there was only one left per engine. Arasan tried to block the white passer but lost its bishop, Viridithas queened and won.

game 25, Clover - BlackMarlin: The king side opened and Clover castled long. BlackMarlin protected its king and the engines exchanged pieces until only QRN vs QRB remained. Clover was a pawn up with a passer, the game ended in a tablebase win.

game 26, Arasan - Uralochka: Uralochka was a pawn up early, the engines gradually exchanged pieces until only RB vs RN remained. Arasan used a pin on the back rank to capture pawns, then queened a passer to win.

game 27, Caissa - Viridithas: Queens were off early, after a while Caissa captured a pawn. The engines shuffled a long time in a closed position, then exchanged pieces until reaching a rook ending. Caissa captured more pawns and queened a passer to win.

game 29, DeepSjeng - Halogen: The engines shuffled in a QRN vs QRN position, then DeepSjeng captured a pawn. Halogen exchanged queens and pushed a passer but DeepSjeng captured it. Halogen lost the bishop to avoid mate, it took DeepSjeng 35 more moves to convert the win.

game 36, Clover - Arasan: Arasan gave a rook and two pawns for a bishop early, putting a knight on d3 and forcing the white king to move. However this did not compensate for the material after Clover moved its king to safety. Clover gave back a rook for a bishop and reduced to a RB vs RN position with 3 pawns up. Arasan couldn't stop the white passers, game over. 

game 38, Caissa - Clover: Clover was up a pawn from the opening. The queen side was blocked and Clover created a passer in the center. There was a lot of shuffling, Clover moved its major pieces to the king side and threatened the black king. Clover moved its king to the center, then used a mate threat to capture all the black pawns on the queen side. It was 5 pawns up, it exchanged pieces and gained more material, the game ended in mate.

game 40, DeepSjeng - Viridithas: Evals started to increase after move 30. DeepSjeng attacked the king side and in a series of exchanges reduced to a RBB vs RB position with black two pawns up. The white bishop pair was strong, Viridithas gave up material and was mated quickly.

game 51, DeepSjeng - Clover: DeepSjeng captured a passer on the queen side, then gave it back to create an advanced passer in the center. Clover gave a rook for a knight to get rid of the passer, the game reached a RBB vs BNN position with black two pawns up. The black pawns were isolated and DeepSjeng captured all of them. Clover tried to stop the last white pawn, it lost material and the game ended in a tablebase win.

Standings after RR1: Clover +5, DeepSjeng +3, Viridithas +2, Caissa Arasan +1, BlackMarlin Halogen Tucano -1, Marvin Uralochka Velvet -2, Wasp -3. There are 5 engines competing for the the 4 qualifying spots. These are the 4 newcomers that advanced from the entrance league, and Arasan that is trying to take one spot from them. The current standings may be biased by the openings, the picture will be clearer after RR2 and the reverse games.

game 70, Velvet - Arasan: The engines opened a few files and exchanged all rooks. The black queen moved forward and was almost trapped, Arasan gave a knight pawns to help the queen escape. In a QBN vs QN position Velvet gave a third pawn and created a passer. After exchanging queens Arasan couldn't prevent a queening, game over.

game 71, Marvin - Caissa: Marvin had an advantage from the opening, there were no exchanges and evals came down. Marvin gave a rook for a knight and pawn to open the king side and attack. Caissa defended its king and evals turned negative. Marvin gave a rook and tried to keep the attack alive, Caissa gave a rook for a bishop while Marvin captured pawns. The game reached a RB vs B with white 3 pawns up, the white passers were not strong enough and Caissa mated.

game 89, Arasan - Viridithas: Viridithas was up a pawn but its king moved without castling. The game reached a RRB vs RRB position, Arasan regained the pawn and created a passer. Arasan then gave a rook for a bishop and pawn and reduced to a B vs R ending. The white passer was fast, Viridithas moved its king to block it while Arasan connected a second passer. Viridithas managed to stop the passers but the king and pawns position left was a win for Arasan.

game 91, BlackMarlin - Clover: BlackMarlin had an advantage from the opening and was a pawn up. After a long shuffle the center opened, BlackMarlin gave a rook and knight to queen a passer. In an unusual imbalance with 3 queens on the board BlackMarlin was not accurate enough, its king and queens were targets for Clover. BlackMarlin tried to push pawns, Clover captured them and went 2 pawns up. The white pieces were pushed back around the king and eventually Clover captured a queen for a rook. Clover captured another piece and then chased the white king and mated.

game 102, Arasan - Clover: Clover was a pawn up but its king moved without castling. Clover managed to develop its king side rook, most pieces moved to the queen side. Arasan had a strong bishop pair, while the two black knights were more passive. Arasan captured two pawns and the game reached a RBB vs RNN position. Arasan slowly pushed a passer forward, Clover lost its rook to stop it. The game ended in a tablebase win.

game 106, Viridithas - DeepSjeng: Viridithas pushed a pawn to f6 and trapped a black bishop in the corner. After some preparation Viridithas gave a pawn and opened the king side, DeepSjeng freed its bishop but the black king was in danger. DeepSjeng traded its queen for a rook and a bishop, reducing to a QR vs RRB position. Viridithas increased the pressure, gained material and won.

game 114, Caissa - Arasan: There were many early exchanges and the game reached a RB vs RB position with white a pawn up. After exchanging bishops it took Caissa 20 moves to capture another pawn. It slowly pushed a passer forward to win.

Standings after RR2: Clover +7, Caissa +6, Viridithas +5, Arasan +4, DeepSjeng +2, BlackMarlin -1, Velvet Uralochka -2, Wasp Tucano -4, Marvin -5, Halogen -6. Caissa had an excellent RR2 with 5 wins, it jumped to 2nd place. The 4 leaders each has one game pair loss, DeepSjeng in 5th has none but it only has one game pair win against the lower ranked engines.

game 146, Clover - Viridithas: The engines mostly shuffled for a long time with all pawns on the board. The first pawn exchange was on move 79, on move 98 the engines opened the center and the game reached a QR vs QN position with black a pawn up. After exchanging queens Clover moved its king forward, it captured most of the black pawns and the game ended in a tablebase win.

game 155, Viridithas - Arasan: The black king was stuck in the center and under attack, Arasan gave a rook for a bishop to stay alive. Arasan tried to counter, it gave a knight for two pawns and attacked but Viridithas moved its king to safety. In a RRN vs RB position Viridithas kept one pawn and captured black ones gradually, the game ended in a tablebase win.

game 168, Clover - Arasan: Clover was a minor piece up but its queen side pieces were not developed. Arasan played inaccurately, it gave pawns and tried to attack through the center but Clover kept its king safe and developed its pieces. The engines exchanged pieces until only RBN vs RB remained, Arasan gave up material and was mated.

game 194, DeepSjeng - Caissa: Caissa had an eval advantage from the opening, material was equal and the engines gradually exchanged pieces, the game reached a double knight ending with black a pawn up. After sone shuffling the engines exchanged a pair of knights, then DeepSjeng allowed the remaining knights to be exchanged and regained the pawn. This was a bad idea since Caissa had a passer, the white king could not defend both sides of the board and the game ended in a tablebase win.

Standings after RR3: Clover +11, Caissa Viridithas +10, DeepSjeng +5, Arasan +3, BlackMarlin 0, Uralochka Velvet -3, Wasp -5, Marvin -7, Tucano -9, Halogen -12. The 3 leaders are going to qualify, the final order is not decided yet. The 4th qualification spot is still a race between DeepSjeng and Arasan. DeepSjeng had a good RR3 with 4 wins against lower ranked engines, Arasan had only 1 and it has to be better in RR4 to have a chance.

game 199, BlackMarlin - Viridithas: Evals increased from the start in a closed position with equal material. BlackMarlin opened the queen side and threatened the black king, then moved a rook forward on the king side. After some shuffling Viridithas exchanged queens to get its king to the center, the game reached a BN vs BN position with white two pawns up. Viridithas lost a bishop but couldn't stop a white passer, BlackMarlin queened and mated.

game 201, Halogen - Clover: Halogen started with an eval advantage but Clover managed to equalize. Halogen was not careful, itlet Clover open the queen side and reduce to a RRN vs RRB position. Material was equal but Clover had connected passers it pushed forward and Halogen couldn't stop. Clover gave some material and queened one passer, then slowly converted the QB vs RR ending. 

game 221, Arasan - Viridithas: Arasan had an eval advantage and more space, the engines exchanged most minor pieces. Arasan opened a file on the king side and gave a pawn while it threatened the black king. In a QRR vs QRR position Arasan moved its queen to the center and the black king had to leave the corner. After exchanging a pair of rooks Arasan moved its rook to the 7th rank, Viridithas gave its queen to get rid of it. Arasan queened a passer to win.

game 234, Arasan - Clover: Arasan had an eval advantage from the start, the engines gradually exchanged pieces and the game reached a RN vs RN position. Arasan restricted the black king to the h file, it gave a pawn and moved its king forward through the center. Clover couldn't protect its pawns, Arasan captured all of them and was left with two white pawns. The endgame was slow, Arasan gave one pawn away but the 7-man position was still a win. 

Standings with 5 rounds to go: Caissa +13, Clover +12, Viridithas +8, DeepSjeng +6, Arasan +5, BlackMarlin +1, Uralochka Velvet -4, Wasp -6, Marvin -7, Tucano -11, Halogen -13. Clover and Caissa are battling for 1st place, Viridithas lost twice and will probably finish 3rd. Arasan still has hope, it won twice against the leaders and reduced the gap to DeepSjeng to 0.5 points. The DeepSjeng-Arasan game 257 may determine the 4th place.

game 236, Clover - Caissa: There were almost no exchanges after the start, by move 35 only one pair of pawns and one pair of bishops were exchanged. Clover gave a pawn and opened the king side, Caissa surrounded its king with minor pieces for protection. Caissa gave a rook for a bishop and pawn, there was a period of shuffling and then Clover managed to move a rook  to the 7th rank. Clover captured a bishop and Caissa's defense collapsed. Clover gained more material and mated.

Standings with 2 rounds to go: Clover +14, Caissa +12, Viridithas +9, DeepSjeng Arasan +6, BlackMarlin +2, Uralochka -3, Velvet -6, Marvin -8, Wasp -9, Tucano -10, Halogen -13. Clover is back in the lead after it beat Caissa. Arasan managed to close the gap to DeepSjeng in 4th after DeepSjeng held a draw against Clover and Viridithas, while Arasan only managed a draw against Caissa playing black with an eval advantage. 

game 257, DeepSjeng - Arasan: Arasan blocked its own knight and lost it for a pawn early in the game. There was no compensation for the lost piece, the engines gradually exchanged pieces until only RN vs R remained. DeepSjeng was patient, it went a pawn up and created a passer, the game ended in a tablebase win.

DeepSjeng secures the 4th promotion spot with this win, it is a point ahead and has a tiebreak advantage over Arasan before the last round.

Season 25 entrance league statistics

A summary statistics table of previous stages and seasons.  

Draw rate, wins

Final draw rate was 52.9%. 

Game termination

The three most common game termination causes were:
36.5% - SyzygyTB
35.8% - TCEC draw rule
19.6% - mate

There were 3 crashes in the stage, Caissa lost on time twice (once in a winning position), and MrBob crashed once (in a losing position).

Moves per game

Median= 66.5
Average= 72.6

There were 25 games longer than 100 moves, the longest was 198 moves (MrBob - Caissa, game 86, Caissa won). 

Time per game (hours)

Median= 1:01
Average= 1:00

Openings

There were variable length book openings in this stage. The first letter of the ECO codes was distributed as follows: 

The engines had almost no freedom to choose the opening variant, all of the game pairs but one repeated the ECO code and the opening variant twice. In all of the game pairs the first letter of the ECO code was repeated.

Reverse pairs, wins

Reverse pairs, same moves

Pairs of reverse games diverged quickly, 27.5% diverged immediately out of book, 63.3% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 11 plys (Clover - Winter, games 51 and 171, Alekhine's defence, four pawns attack, fianchetto variation, Clover won as white) 

Season 25 entrance league

In season 25 TCEC introduced a new entrance league, but it is just a new name for the qualification league. The Swiss format was abandoned and the entrance league will be a double RR. The 16 engines playing were chosen using the results of the Swiss event that was played earlier.

The engines that will play in the entrance league are:

relegated from season 24 league 2 - Booot, Expositor
played in Swiss season 24 - Smallbrain, Mantissa, MrBob, StockDory, Stash, Weiss, Winter, Equisetum, ChessFighter
new to TCEC - Clover, Caissa, DeepSjeng, Viridithas, BlackCore

Final standings

Viridithas, Clover, DeepSjeng and Caissa advance to league 2. They led the league from the start together with Booot and SmallBrain. Caissa lost twice on time and in the final rounds Booot and SmallBrain came close to it, however a win in the last round secured 4th place for Caissa.

All 4 promoting engines are new to the TCEC leagues. They played in the Swiss event that started the season, their results in the league were better than in the Swiss event which also includes a luck factor.

The 4 advancing engines will play in league 2 together with:
played in season 25 league 1 - BlackMarlin Marvin
played in season 25 league 2 - Uralochka Arasan Wasp Halogen Velvet Tucano

Interesting games

game 1, Caissa - Booot : Caissa used the weak black pawn structure on the queen side, first it went a pawn up and then it captured a second pawn and created two passers. Caissa gave a rook for a bishop to connect the passers, Booot started to lose material but could only capture one passer, Caissa forced mate. 

game 2, Winter - Mantissa: Winter went a pawn up, then gradually reduced to a RBN vs RBN position. Mantissa gave another pawn to free its bishop, after exchanging bishops Winter pushed pawns to win.

game 11, MrBob - Viridithas: The game reached a RRB vs RRB position, the black king was trapped in the corner and it seemed MrBob had the advantage. However, MrBob blundered and allowed Viridithas to exchange the remaining queen side pawns. MrBob was a pawn up but the endgame was a draw.

game 21, Clover - Weiss: After an early series of exchanges lover was up a pawn with connected passers on the queen side. Clover pushed the passers slowly, Weiss managed to separate them but both reached the 7th rank eventually. Weiss lost  a bishop for one passer, Clover queened the other and mated.

game 27, DeepSjeng - Equisetum: After 35 moves the engines opened the center and DeepSjeng went a pawn up. DeepSjeng used threats on the black king to gain an exchange and reduce to a RR vs RN position. The game ended in a tablebase win.

game 32, Winter - Stash: The center was blocked, evals gradually increased while Winter doubled rooks on the open c file. Winter moved a rook forward and traded it for two minors, then opened the king side and attacked the black king. Stash lost material and was mated.

game 33, Stash - Booot: The game reached a RRB vs RBN position with black two pawns up. Booot slowly pushed connected passers forward, Stash pushed a passer to the 7th rank where it was blocked. It took Booot 25 moves to captured the white passer and queen a pawn safely, the game ended in a tablebase win.

game 36, Clover - Mantissa: After the engines opened the position with exchanges the game reached a QRN vs QRB position, pawns were equal but Clover had a passer. Mantissa managed to stop the passer but Clover reduced to a won king and pawns ending.

game 47, Winter - BlackCore: BlackCore captured a pawn but its king was exposed. Winter created a passer and BlackCore lost a bishop to stop it. In a QRN vs QR position Winter attacked the black king, captured the queen and mated.

game 51, Clover - Winter: Winter traded a knight for a rook, but Clover had a passer on the wueen side and the black queen was far on the king side. After exchanging queens Clover gained the material back and the white king moved to support the passer. Winter lost a bishop for the passer, in a bishop vs pawns ending Clover used zugzwang to win.

game 52, Viridithas - Caissa: The game reached a RB vs RB position and was heading for a draw when Caissa blundered and exchange rooks. The bishops were of opposite colors and Viridithas was only one pawn up, but the black king was trapped and the white king was free to support a passer. Caissa couldn't stop a queening, game over.

game 53, Equisetum - Mantissa: Most pieces were on the queen side, Equisetum shifted to attack the black king on the other side. Mantissa gave a pawn and hid its king behind a white passer, Equisetum captured a second pawn and reduced to a QR vs QR position. Mantissa lost more material and was mated.

game 57, Booot - DeepSjeng: The game reached a RN vs RB position with white a pawn up. DeepSjeng could have held perhaps, but it didn't play accurately enough. Booot gave back the pawn, opened the king side and moved its king forward. Eventually it captured a pawn and reduced to a 7-man win.

game 61, Caissa - Equisetum: Equisetum gave a rook for a knight and pawn, Caissa patiently exchanged pieces until only QRN vs QBB remained. Caissa had a passer, after queens were exchanged Equisetum was forced to lose a bishop to stop the passer. The game ended in a tablebase win.

game 68, Equisetum - Winter: Both kings were exposed and under attack, Equisetum had more pieces involved and was more dangerous. After most pieces were exchanged the game reached a Q vs RN position, Equisetum chased the black king away and queened a passer to win. 

game 72, DeepSjeng - Weiss: Weiss gave a knight for two pawns to try to free some space for its pieces. DeepSjeng mostly shuffled for a while, Weiss tried to protect its king and eventually lost a few pawns. DeepSjeng gained more material and queened a passer to win.

game 81, Clover - Booot: Evals gradually increased as the engines exchanged pawns and pieces though material was equal. Booot had two isolated pawns to protect and its pieces were passive. Eventually Clover created a passer and Booot gave a rook for a bishop. Booot couldn't stop the passer without losing more material, game over.

game 87, DeepSjeng - Mantissa: Mantissa was up a pawn but the king side was open and the black king was in danger. The engines shuffled for a long time, when the black king tried to run to the center DeepSjeng moved its pieces forward to attack. Mantissa lost material and was mated.

game 91, Caissa - DeepSjeng: In a drawn opposite color bishops ending Caissa failed to move and lost on time.

game 97, Viridithas - Booot: When the position opened the black king was more exposed and vulnerable. Viridithas used this to capture a pawn and to create connected passers. In a RRB vs RRB position Booot could stop the passers, Viridithas queened to win. 

game 102, DeepSjeng - Winter: DeepSjeng captured a rook for a knight and pawn early in the game, then a series of exchanges reduced to a RN vs R position with black two pawns up. Winter traded pawns but DeepSjeng held on to one last pawn to ensure the win.

game 105, Booot - Mantissa: Mantissa moved its king without castling, blocking its king side rook. Booot sacrificed a knight for two pawns and exposed the black king, Mantissa gave back the piece and the game reached a rook ending with white a pawn up. Booot captured another pawn and queened a passer to win.

game 111, Clover - SmallBrain: The engines gradually exchanged pieces and pawns while evals increased. The game reached a RB vs RN position, SmallBrain could not defend its pawns and Clover captured them all. The two white pawns left were enough to win.

game 112, Viridithas - Equisetum: Evals were stable until move 40 though white was a pawn up. Equisetum gave a rook for a knight, the game reached a QR vs QN position and Viridithas went a pawn up. Equisetum lost its queen for a passer, game over.

Standings after RR1: Viridithas +7, Clover DeepSjeng +6, Booot Caissa +4, SmallBrain +3, Winter +1, Mantissa Weiss 0, Equisetum -1, BlackCore -2, Expositor -4, Stash MrBob -5, StockDory -6,  ChessFighter -8. The newcomers are leading at the half, there are 4 of them in the top 6 engines that are fighting for 4 qualification spots. Winter also started well but then fell back from the leaders.

game 129, SmallBrain - Booot: Evals were stable and the engines mostly shuffled, then on move 44 Booot gave a rook for a bishop. After a few exchanges and more shuffling SmallBrain gave a rook for two knights and opened the position. In a QRN vs QR position Booot was 3 pawns up, SmallBrain captured pawns and reduced to a winning king and pawns ending.

game 137, Booot - Winter: Booot was a pawn up from the start, the engines exchanged pieces and pawns and the game reached a rook ending. Winter could have held perhaps, but in the end the game reached a tablebase win.

game 148, Viridithas - Weiss: Weiss castled long and Viridithas slowly increased the pressure on the queen side. Viridithas pushed pawns and opened the queen side, then used an attack on the black king to capture pawns. The engines reduced to a rook ending with white 3 pawns up, enough for a win.

game 152, Stash - Winter: Stash was a pawn up but evals were stable and the engines shuffled. After move 60 Winter played inaccurately, it let Stash open files and its king was in danger. By the time Winter realized it was in trouble Stash captured a rook for a bishop. The game reached a R vs N ending, Stash queened a passer to win.

game 165, Viridithas - Mantissa: Viridithas gave pawns to open files and attack the uncastled black king. Mantissa was 4 pawns up when Viridithas captured a rook, in a QRB vs QRB position Viridithas chased the black king. Mantissa lost material and the game ended in a tablebase win.

game 167, BlackCore - Winter: BlackCore prepared an attack on the king side, most black pieces waited with only a little room to move. BlackCore opened the king side and a series of exchanges reduced to a QN vs RRN position. Winter gave the knight for a passer, all the pawns were captured and the game ended in a tablebase win.

Standings with 8 rounds to go: Viridithas +10, DeepSjeng +8, Clover +7, Booot Caissa +6, SmallBrain +5, Equisetum +2, Weiss +1, Winter Mantissa -1, BlackCore -4, Stash -5, Expositor -6, MrBob StockDory -9, ChessFighter -10. The top 6 engines are still in the race for qualification. Booot lost to SmallBrain but it used wins against weaker engines to stay in joint 4th place. Equisetum won 3 games and climbed in the table, though it will probably not close the gap to the leaders.

game 180, SmallBrain - Mantissa: After shuffling for a while the engines exchanged pieces and reduced to a RN vs RN position. SmallBrain had a passer on the king side, it captured a pawn and created a second passer on the queen side. SmallBrain exchanged rooks, queened a passer and mated.

game 188, Winter - Equisetum: Winter was up a rook for a bishop and seemed to have an advantage. Then it let Equisetum reduce to a RN vs BN position with the white rook trapped. Evals dropped to 0 and the game was adjudicated a draw. 

game 189, Caissa - SmallBrain: Caissa opened the king side and threatened the black king. SmallBrain was a pawn up but its pieces were on the queen side and struggled to help. Caissa forked the black queen and rook with its knight, SmallBrain escaped but lost two pawns. The pressure on the black king increased, Caissa gained material and the game ended in a tablebase win. 

game 193, Weiss - Booot: Evals increased gradually from the start, material was equal but Weiss had a space advantage. The engines opened files and reduced to a RRN vs RRN position, Weiss created a passer and went a pawn up. After exchanging a pair of rooks Weiss captured two more pawns, Booot gave a knight for one passer and the rook for another, game over.

Standings with 3 rounds to go: Viridithas +12, DeepSjeng Clover +9, Caissa +8, Booot  SmallBrain +6, Equisetum Weiss +3, Winter -1, Mantissa -2, BlackCore -5, Stash -6, Expositor -7, MrBob ChessFighter -11, StockDory -13. The 4 qualification spots are almost decided. Caissa beat SmallBrain and it is holding on to 4th place. Booot also moved a step further away from qualification after its loss to Weiss.  

game 218, Clover - Equisetum: Clover gave a pawn and a bishop to attack the black king. Equisetum gave the material back and the game reached a RN vs RB position. The white rook was on the 7th rank, Clover moved its king forward and captured pawns. Equisetum lost its pieces for passers, game over.

game 223, Caissa - Weiss: Evals increased with most pieces and pawns still on the board. Caissa gave a rook for a bishop to create an advanced passer, then captured a pawn and connected a second passer. However, after some shuffling without a clear plan Caissa failed to move and lost on time. This is its second crash in the league.

Booot and SmallBrain drew their games in round 28, with 2 rounds to go they are now only 0.5 points behind Caissa in 4th place.

Caissa, Booot and SmallBrain all drew their games in round 29, the 4th place will be decided in the last round. Caissa has a head to head tiebreak advantage against both Booot and SmallBrain.

game 233, Booot - Equisetum: Evals increased while the engines exchanged pieces, the game reached a RRN vs RRB position with the black bishop stuck behind pawns. Booot captured a pawn and reduced to a king and pawns ending. The one pawn advantage was enough to win.

Booot still has a chance to finish in 4th place, it needs Caissa to lose (or crash). SmallBrain drew its game and it is out of the race.

game 240, Caissa - Mantissa: Caissa placed a protected knight on e6, Mantissa moved its king without castling. Caissa opened the h file and the black king was in danger, Mantissa exchanged pieces and the game reached a RN vs BN position with white a pawn up. Caissa had connected passers, it gave the rook for a knight and used 7-man tablebases to win.

With this win Caissa finishes 4th ahead of Booot.