Season 23 league 1

Final standings

Ethereal and Berserk advance to the premier division. They led the league from the start, after the first two RRs they had the same score with a gap of 1.5 points ahead of Minic. Ethereal kept increasing the gap in the second half of the league, Berserk slowed down a little. In RR3 Berserk lost to Ethereal and to RubiChess, it was still leading Minic and RubiChess by 2.5 points at the end of RR3. In RR4 Berserk lost to Koivisto, RubiChess couldn't keep up but Minic closed the gap to 0.5 points. However, in their direct encounter Berserk beat Minic to keep second place. 

Koivisto performed below expectations, in season 22 it was very close to advancing to the premier division, and in the Swiss event of season 22 it finished in joint 5th place (together with Ethereal and RubiChess for example). It was suggested in the chat that the version of Koivisto submitted to season 23 had a known bug that caused it to lose strength. Hopefully it will do better next season.

Ethereal and Berserk will play 4DRR in the premier division, together with Stockfish, KomodoDragon, Leela, rofChade, Stoofvlees and SlowChess.

Interesting games

game 12, Berserk - Koivisto: Berserk had an eval advantage that slowly increased. The engines shuffled for a while in a closed position, after move 50 the position opened and Koivisto gave a rook for a bishop and two pawns. Berserk used an attack on the black king to regain the pawns and to reduce to a RR vs RB position a pawn up. It took Berserk 20 more moves to win.

game 17, ScorpioNN - Minic: The game reached a B vs pawns endgame, Minic seemed to be holding with its king guarding the black pawns. After move 100 ScorpioNN somehow managed to get its king forward, but just as it was about to win it failed to move on time and lost.

game 20, Minic - Seer: Seer tried to attack in a drawn position, it moved a rook to the 2nd rank, captured two pawns and pushed a passer forward. Minic countered on the king side where it trapped the black queen. Seer gave a knight to free its queen, the game reached a RN vs R ending and Minic used passers to win.

game 23, Berserk - Revenge: Berserk had an eval advantage, there were only a few exchanges after the start. After the engines opened the center Berserk created a passer, then added a second passer after most pieces were exchanged. In a QB vs QN position Revenge tried to delay with checks, eventually it gave a knight for one of the passers and the queen for the other, game over. 

game 27, Ethereal - Berserk: Ethereal had an eval advantage that increased from the start. Berserk had two isolated pawns, the engines exchanged pieces until only RN vs RN remained and then Ethereal captured the pawns. Berserk had to give the knight to stop two passers, the game ended in a tablebase win.

game 34, Berserk - ScorpioNN: The black king was exposed in the corner, ScorpioNN surrounded it with pieces. Berserk captured two pawns with its queen and reduced to a double rook ending. ScorpioNN regained the pawns but Berserk pushed two passers facing the black king and mated.

game 50, ScorpioNN - Revenge: ScorpioNN had an eval advantage that slowly increased from the start. The advantage was not apparent, the game reached a RRN vs RRN, the white pieces were better placed and ScorpioNN had a passer. After exchanging a pair of rooks the passer started to advance, Revenge gave a rook for a knight to capture it. The game ended in a tablebase win. 

game 52, Igel - Koivisto: All pieces were on the board when Koivisto decided to give a knight and attack the white king. Igel exchanged pieces, its king was exposed but it still managed to escape. The game reached a QN vs Q ending, Koivisto delayed with checks but eventually it was mated.

game 59, Revenge - Seer: Revenge gradually increased pressure on the king side where there was a small opening. After move 30 the engines started to exchange pieces and pawns, the game reached a QB vs BNN position. Seer tried to keep its pieces protected, it took a while but Revenge managed to break the fortress and capture a piece, leading to mate.

game 60, Ethereal - ScorpioNN: ScorpioNN gave a bishop for two pawns early, then it attacked the exposed white king. Ethereal exchanged pieces and reduced to a B vs pawns ending. Ethereal was three pawns down but it was sure of its win, however it took its time to get there. The game ended in a tablebase win on move 121. 

Standings after RR1: Berserk Ethereal +5, Minic +4, RubiChess +1, ScorpioNN Revenge 0, Koivisto Seer -1, Arasan Fritz -2, Igel -3, Nemorino -6. Berserk, Ethereal and Minic are leading with a small margin. There are only two promotion spots, so far Ethereal has a small advantage since it beat Berserk. Minic benefited from a crash by ScorpioNN. Still too early for predictions.

game 75, Ethereal - Minic: The engines exchanged pieces, Ethereal had an eval advantage but evals did not change for a while. After move 30 the game reached a QRN vs QRN position, Ethereal had a pawn majority on the queen side and evals started to increase. Minic gave a rook for a knight and got rid of the queen side pawns, it took Ethereal more than 30 moves to get to a tablebase win.

game 82, Arasan - Ethereal: The game reached a BN vs BB position, Arasan had a passer on the king side and a pawn majority on the queen side. After some shuffling Arasan created a passer on the queen side. Ethereal tried to block but eventually Arasan found a way to drive a blocking bishop away. Ethereal captured the passers but gave a bishop, the game ended in a tablebase win. There were two white wins in this opening. 

game 86, Seer - Minic: Seer had an eval advantage which slowly increased from the start, the engines exchanged pieces and pawns and the advantage was not clear to me. On move 38 Seer went a pawn up and created an advanced passer, then traded it and another pawn became a passer. Minic held for 30 moves, the advantage was small but enough for Seer to convert. There were two white wins in this opening. 

game 90, RubiChess - Koivisto: RubiChess managed to place a rook on the 7th rank early in the game. Koivisto blocked the rook and RubiChess gave it for a bishop, and then moved a passer to the 7th rank. Koivisto tried to block the passer, but the engines exchanged pieces and eventually RubiChess gained material and forced a queening to win.

game 102, Revenge - RubiChess: The engines shuffled for a while, after move 40 Revenge's eval started to increase. Revenge gave a pawn and created a passer in the center. In a RNN vs RBN position the black pawns were weak and Revenge captured them one by one. The game reached a knight ending and Revenge had enough pawns to win. 

game 112, Seer - Koivisto: Seer was up a pawn in a QRB vs QRN position, it had a doubled pawn but its pieces were better placed. Seer dominated the center, Koivisto had to protect its king and this allowed Seer to reduce to a winning rook ending two pawns up. 

game 113, ScorpioNN - RubiChess: ScorpioNN appeared to be winning in a RB vs R ending, but it exchanged rooks and reduced to a tablebase draw. Probably some bug.

game 119, Berserk - Minic: Berserk had an eval advantage that slowly increased, material was equal but Minic had a bishop that was almost trapped. The game reached a RRB vs RRB position and Berserk went a pawn up, Minic gave another pawn to free its bishop. Minic regained the pawns but lost its rook to stop a passer, game over. 

game 123, Minic - Koivisto: Minic had an eval advantage that increased in a closed position. When the engines opened the position with exchanges Minic was up a rook for a bishop and pawn. The game reached a RN vs BN position, Koivisto held on to an advanced passer but lost its other pawns. Minic blocked the passer, it had two pawns left and that was enough to win. 

game 124, Igel - RubiChess: RubiChess decided to give a knight and attack the white king. It looked scary with black pawns facing the white king, but Igel found safe squares for its king and kept the material advantage. The engines reduced to a BBN vs R position, Igel captured the black passers and then used passers of its own to win. 

game 128, Ethereal - Seer: Ethereal had a central passer early in the game. Seer created a central passer as well but it was not supported and Ethereal captured it and went a pawn up. The engines gradually exchanged pieces until only BNN vs BNN were left, then Ethereal captured a second pawn. The material advantage was sufficient for a win, it took Ethereal another 30 moves.

Standings after RR2: Ethereal Berserk +7, Minic +4, RubiChess Seer ScorpioNN +2,  Revenge +1, Igel -2, Koivisto -3, Arasan -4, Fritz -5, Nemorino -11. Ethereal and Berserk lead at the half way point, beating almost all of their opponents in game pairs. They have only one game pair loss between them, and that is Ethereal beating Berserk. Minic lost to both leaders in RR2 and the gap starts to look significant. ScorpioNN and Seer had good results in RR2, they join RubiChess in joint 4th place, with a small chance of promoting.

game 146, RubiChess - Berserk: RubiChess used the half open g file to threaten the black king. Exchanges opened the g file, RubiChess managed to place pawns on f6 and h6, still Berserk thought it was holding. Berserk's eval suddenly jumped, it gave a rook for a bishop and tried to delay with checks. Eventually the black king had no escape in a QR vs QN position and RubiChess mated.

game 155, Berserk - Revenge: Evals increased very slowly, there were a few pawn exchanges but all pieces were on the board until move 41. A series of exchanges left a QRB vs QRB position with Berserk a pawn up. Berserk was very patient, eventually it captured the bishop and reduced to a tablebase win.

game 156, Koivisto - RubiChess: Koivisto captured a knight early in the game, the white king was exposed in the center but not in any danger, RubiChess realized it had no compensation for the piece. The game reached a RBN vs RB position, Koivisto used the extra piece to capture black pawns, then promoted a passer and mated.

game 159, Ethereal - Berserk: Berserk traded a rook for a knight and two pawns, the game reached a QRR vs QRB position. Ethereal regained the pawns and placed both rooks on the 7th rank. Berserk had 3 connected passers but they were not strong enough, Ethereal captured two passers and reduced to a winning R vs B ending.

game 170, Ethereal - RubiChess: Ethereal had an eval advantage that increased slowly from the start. Material was equal but Ethereal used a strong bishop pair to capture a pawn and then reduce to a RB vs RB position. RubiChess tried to hold, it lost another pawn and exchanged rooks. However, the remaining opposite color bishops ending was a win for white.

game 179, RubiChess - ScorpioNN: RubiChess was a pawn up but evals did not change a lot until ScorpioNN decided to give 2 more pawns and attack. ScorpioNN realized too late that was a mistake, RubiChess stayed calm and reduced to a Q vs RB position. ScorpioNN had a passer on the 7th rank but there were too many white pawns to deal with, RubiChess captured the passer and the game ended in a tablebase win. 

game 189, Koivisto - Minic: Minic couldn't find safety for its king, it was forced to move without castling and it had little pawn support. Koivisto took advantage of the situation, it captured two pawns and reduced to a RN vs RN position. Minic got one pawn back, both engines pushed a passer forward. Koivisto was faster though and Minic had to give its rook to stop the white passer, game over. 

game 192, Ethereal - ScorpioNN: The engines traded R and two pawns for BN early in the game. Evals increased as the engines exchanged pieces until only QBB vs QR remained. ScorpioNN had more pawns but its king was in danger, and it was Ethereal that managed to push a passer to the 7th rank. After exchanging queens Ethereal shuffled for a while, it took almost 40 moves to get to a tablebase win.

game 195, Igel - Revenge: The engines mainly shuffled, the pawns were blocked across the board except for the h file. Piece exchanges extended the game beyond move 100 and evals started to increase. Igel opened the position by sacrificing a knight for two pawns, then a series of exchanges led to a knight ending with white a pawn up. The white passers gave Igel the win. 

Standings after RR3: Ethereal +11, Berserk +9, Minic RubiChess +4, Seer +3, Revenge ScorpioNN +2, Koivisto -1, Igel -3, Arasan -6, Fritz -9, Nemorino -16. Ethereal and Berserk have a significant lead, it would be quite a surprise if either of them fails to promote. RubiChess had a good result in RR3, including a win against Berserk.

game 207, Ethereal - Minic: Ethereal captured a pawn and then reduced to a RRN vs RRN position. Ethereal had an advanced passer, Minic captured it but had to give a rook for a knight. The game ended in a tablebase win.

game 210, Koivisto - Berserk: Only a pair of knights was exchanged after the start, evals increased slowly. After move 26 Koivisto opened the position and went a pawn up. Then a series of exchanges reduced to a BN vs BN position, Koivisto had doubled passers. Berserk tried to block but eventually it lost both pieces to stop the passers, the game ended in a tablebase win. 

game 215, Minic - ScorpioNN: ScorpioNN captured a pawn early in the game, however its king couldn't castle and Minic developed better. Minic regained the pawns and reduced to a BB vs BN position, it used the bishop pair to control the black pawns. Eventually Minic went a pawn up, ScorpioNN reduced to an opposite color bishops ending but Minic used an unstoppable passer to win.

game 218, Seer - Minic: The game reached a QRR vs QRR position, with a white passer on the 7th rank. Seer chose to trade RR for Q and lost the passer. It was two pawns up and with better play it may have won, but it couldn't find a way to push its pawns safely and instead it gave checks. The game ended by the 50 move draw rule on move 203.

game 222, RubiChess - Koivisto: RubiChess was a pawn up with an eval advantage, but it allowed Koivisto reduce to an opposite color bishops ending that was a draw.

game 225, Berserk - Ethereal: The game reached a queen ending, Berserk was up a pawn but it couldn't find a way to win and Ethereal held a draw. 

game 232, ScorpioNN - Berserk:  ScorpioNN had two passers in a RB vs RB position, but it chose the wrong moment to exchange rooks and was left with a drawn opposite color bishops ending.

game 234, Revenge - RubiChess: Revenge created a passer on the queen side early in the game, the engines exchanged pieces until only NN vs NN were left. The white knights were better coordinated and the white passer forced RubiChess to block with one knight. Revenge captured all the black pawns, it lost the queen side passer but forced a promotion on the king side to win.

Standings with 5 rounds to go: Ethereal +14, Berserk +8, Minic +6, RubiChess Seer +4, Revenge +3, ScorpioNN +2, Koivisto -1, Igel -2, Arasan -9, Fritz -10, Nemorino -19. Berserk is still in second place but after a loss it is only 1 point ahead of Minic in third place. Minic won 3 games as white against lower ranked engines, and lost once as black against Ethereal. Rubichess is further away together with Seer, 2 points from second place.

game 245, ScorpioNN - RubiChess: There were no exchanges until move 25, then evals started to increase. The engines reduced to a BB vs BB position, both engines had a passer but the white passer was more advanced and better supported. ScorpioNN captured a bishop for the passer, it was two pawns down but it used the bishop pair to capture black pawns. The last white pawn ensured the win. There were two white wins in this opening.

game 249, RubiChess - Seer: Seer gave a pawn on the queen side and then regretted it. RubiChess pushed a passer to the 7th rank on the queen side while it made threats on the black king on the king side. For many moves Seer could capture a rook but didn't want to lose a crucial bishop. Seer defended its king and eventually made the R vs B exchange, but RubiChess used its passer to capture a rook. In a RBB vs RN position an unstoppable passer gave RubiChess the win.

game 251, Berserk - Minic: The engines seemed to be shuffling but evals slowly increased. When the king side opened Minic was up a pawn with a central passer but its king was exposed. Berserk captured black pawns until it was 3 pawns up, then reduced to a RB vs RB position. Minic couldn't hold its passer and the game ended in a tablebase win.

Standings with 2 rounds to go: Ethereal +15, Berserk +9, Minic +6, RubiChess Seer +4, Revenge +3, ScorpioNN +1, Koivisto 0, Igel -3, Arasan -Fritz -10, Nemorino -19. Minic got as close as 0.5 points to Berserk in second place, but then lost to Berserk as black. RubiChess and Seer are out of the race, Minic only has a theoretical chance. Berserk needs 0.5 points in two games to ensure a place in the premier division. 

Berserk held against Arasan, Minic beat Koivisto. One round to go Berserk is 1 point ahead of Minic, it has a tiebreak advantage so it is sure of second place.

game 262, RubiChess - Minic: RubiChess created a passer on the queen side early in the game, evals slowly increased as the engines seemed to be shuffling. A series of exchanges reduced to a QRB vs QRN with RubiChess a pawn up, RubiChess then pushed its passer to the 7th rank. Minic captured the passer but lost its queen, RubiChess mated not long afterwards.