Season 27 league 1

Final Standings

Obsidian and Caissa advance to the premier league. From the start there were three engines leading: Obsidian, Caissa and Ceres. After the first two RRs Obsidian led with 8 game pair wins and one loss to Ceres, Caissa was second with 6 game pair wins (including against Ceres) and no loss, and Ceres was 3rd with 6 game pair wins and one loss. In RR3 Obsidian increased its lead while Caissa and Ceres were tied. It appeared that Ceres had a better chance of qualifying because Caissa drew 3 games as white against lower ranked engines. However, RR4 was a disaster for Ceres. It lost 3 games (one to Obsidian) and only managed one win, drawing 4 times against lower ranked engines. Caissa also missed chances in RR4, with one loss and only two wins, but this was enough to ensure 2nd place before the last round.

Ceres started this season in the qualifying league, first time playing in TCEC. It easily reached league 1 and was considered a strong candidate to play in the premier division, perhaps even close in strength to Leela and Stockfish. As it turns out its journey ended in league 1 this season, it will get another chance next season. League 1 is a tough league with 12 strong engines and only 2 advancing. Recall that last season Obsidian and Caissa were tied with Seer in 2nd place, and Seer advanced only on a tiebreak. This season Obsidian and Caissa will test their strength against the strongest TCEC engines.

Obsidian and Caissa will play in the premier division together with Stockfish, Leela, Berserk, KomodoDragon, Ethereal and Seer.

Interesting games

game 8, rofChade - Caissa: The center was blocked, the engines exchanged a pair of knights and rofChade captured a pawn, creating a passer on the queen side. The engines exchanged a few pawns and pieces, then mostly shuffled for a long time. After a series of exchanges the game reached a rook ending with rofChade two pawns up. The engines traded pawns and the game ended in a tablebase win.

game 12, Obsidian - PlentyChess: Obsidian captured a rook for a knight and pawn early, the engines reduced to a RRB vs RBB position. After some shuffling PlentyChess captured a pawn but one of its bishops became trapped. Obsidian captured two pawns before the black bishop was freed, the engines exchanged rooks and the game ended in a tablebase win.

game 17, Caissa - RubiChess: RubiChess gave a rook for a bishop and pawn, it created a passer that Caissa captured. RubiChess avoided exchanging queens, after a while Caissa captured a pawn. The game reached a QRR vs QRB position, RubiChess delayed by attacking the exposed white king. Caissa exchanged a pair of rooks and captured a pawn. After finally exchanging queens the game ended in a tablebase win. 

game 23, Obsidian - Devre: After a series of exchanges there was a material imbalance of R vs BB with white two pawns up. Obsidian moved two rooks forward, then captured a rook for a knight leading to a RR vs BBN position. The engines traded pawns, Obsidian had a passer on both sides and its rooks threatened the black king. Devre lost material and the game ended in a tablebase win.

game 26, Devre - PlentyChess: The engines exchanged all bishops, after some shuffling they exchanged a pair of knights. Devre moved a rook forward, captured a pawn and then moved the second rook forward. The game reached a RRN vs RRN position and Devre captured a second pawn. PlentyChess captured one pawn back but its knight was trapped and captured. Devre exchanged all rooks, queened a pawn and mated.

game 27, Ceres - Obsidian: The engines started to exchange pieces on move 25. Ceres went a pawn up and then the game reached an opposite color bishop ending and Ceres captured a second pawn. Ceres pushed a passer to the 7th rank, the black king had to block while the white king was free to move forward. Obsidian couldn't cover all squares with its bishop, Ceres captured another pawn and promoted a passer (to a knight?) to win.

game 38, Ceres - Uralochka: All pieces were on the board until move 40, except for one minor piece exchange. Ceres created a passer on the queen side and evals started to increase. Uralochka captured the passer, Ceres created another and pushed it to the 7th rank. In a series of exchanges Uralochka captured the passer and lost some material, the game reached a RB vs R position. Uralochka was two pawns up with a passer but the extra bishop was stronger. Ceres exchanged rooks and the game ended in a tablebase win. 

game 39, Caissa - PlentyChess: The engines castled in opposite directions, evals increased steadily though there were only a few exchanges. Caissa placed its major pieces behind the e pawn, PlentyChess gave a knight for a pawn to block the e file. In desperation PlentyChess gave a rook for a knight and created an advanced passer. Caissa captured the passer and exchanged queens, PlentyChess lost more material and was mated.

game 50, Caissa - Devre: The engines exchanges pieces and pawns, first Devre was up a pawn, then Caissa equalized and the game reached a QRB vs QRB position. Devre had connected passers in the center, Caissa captured both and went a pawn up. After exchanging bishops Caissa used the exposed black king to reduce to a queen ending two pawns up. Caissa pushed a passer forward to win.

game 63, rofChade - Devre: The game started with a black bias and a Q vs BN imbalance. Devre was two pawns up with a passer in the center. After the pawns stabilized the engines shuffled for a long time, after move 75 evals increased as the engines reduced to a Q vs RB position. Devre created a second passer, rofChade captured one but Devre gave its pieces to queen the other. The queen ending was long, eventually Devre reduced to a winning king and pawn ending.

Standings after RR1: Obsidian +4, Ceres Caissa +3, RubiChess +1, rofChade Uralochka PlentyChess Devre 0, Revenge Viridithas -2, Igel -3, Stoofvlees -4. Obsidian, Ceres and Caissa are at the top. Ceres is without loss, yet Obsidian leads despite losing to Ceres. There are 5 engines which can still close the gap with a good reverse RR. 

game 70, RubiChess - Devre: RubiChess had a pawn majority on the queen side, and the black king was vulnerable on the king side. The engines exchanged pieces until only RN vs RB were left, RubiChess gave two pawns for the bishop. There was only one white pawn left, RubiChess captured all remaining black pawns to win.

game 74, Caissa - rofChade: The engines opened the queen side and after a series of exchanges the game reached a QRR vs QRB position with black two pawns up. Caissa exchanged a pair of rooks and captured a pawn, rofChade still had a passer in the center. Caissa pinned the bishop and captured the passer, then the engines shuffled for a long time. Eventually Caissa found a way to capture a pawn, rofChade lost more material and the game ended in a tablebase win.

game 80, Obsidian - Uralochka: The engines exchanged a few minor pieces, when the c file opened Obsidian moved a rook forward and Uralochka gave its queen for two rooks. The game reached a QN vs RRN position, Obsidian captured a pawn and Uralochka gave a rook for a knight. The white king moved forward and Uralochka lost more material, leading to a tablebase win.

game 83, RubiChess - Caissa: The engines exchanged pieces until only QRB vs QRB remained. RubiChess captured a pawn, Caissa decided to not equalize pawns but exchange rooks instead. RubiChess reduced to a queen ending with a pawn up and connected passers. The game ended in a tablebase win.

game 90, Uralochka - PlentyChess: There were a few exchanges after the start, the engines castled in opposite directions, Uralochka gave a pawn but managed to push a pawn to h6. PlentyChess gave a rook for a bishop and captured the h6 pawn and the game reached a QRB vs QBN position. The black king was vulnerable and PlentyChess exchanged queens but lost the knight, the game ended in a tablebase win.

game 101, Ceres - PlentyChess: Ceres kept its king in the center and opened the king side. PlentyChess gave a trapped bishop for 3 pawns and the engines reduced to a RN vs R position. Ceres captured black pawns and kept one white pawn to secure the win.

game 108, Revenge - RubiChess: The engines opened the queen side, in a series of exchanges Revenge traded Q for RB, then RubiChess gave a knight for two pawns. Revenge moved both its rooks to the 7th rank and RubiChess traded its queen for the rook pair, resulting in a BBN vs RB position. Revenge pushed a passer to the 7th rank and RubiChess lost its rook for it, game over. 

game 113, Caissa - Uralochka: Caissa went a pawn up, then Uralochka gave a rook for a knight and pawns and exposed the white king. The game reached a RRB vs RBB position, Caissa captured pawns and was a pawn up. Caissa pushed a passer and Uralochka gave a bishop to stop it. Caissa gained more material and the game ended in a tablebase win.

game 119, Obsidian - RubiChess: The engines opened the queen side, RubiChess moved its queen forward to capture a pawn. Obsidian trapped the queen and traded RB for it. RubiChess was two pawns up, after some time the game reached a QR vs RRB position. Obsidian created an advanced passer and started to gain material, first the black bishop and then a rook to win.

game 126, Caissa - Ceres: The engines exchanged many pieces and pawns, leading to a R vs BN imbalance with white two pawns up. Caissa captured another pawn and all its 4 pawns were passers. The game reached a RR vs RBN position, Ceres captured one pawn back and reduced to a rook ending. Ceres avoided captured to delay but the game ended in a tablebase win.

game 130, Uralochka - RubiChess: The game started with a Q vs BN imbalance and a black bias. RubiChess was two pawns up, there were many early exchanges and the game reached a Q vs RB ending. The engines traded pawns and evals were low, but Uralochka was inaccurate and evals jumped. RubiChess pushed a passer to the 2nd rank, then found a safe square for its king and Uralochka had to give its queen for a rook to avoid a queening. The black king moved forward and Uralochka couldn't prevent a queening and mate.

Standings after RR2: Obsidian +7, Caissa +6, Ceres +5, RubiChess +2, forChade 0, Viridithas Igel Stoofvlees -2, PlentyChess Uralochka Revenge -3, Devre -5. The 3 leaders haven't changed, and there are only two qualifying spots in this league. Obsidian leads, Caissa is in 2nd place ahead of Ceres. There are no engines without loss, Ceres has one game pair loss to Caissa, Obsidian has one game pair loss to Ceres. Caissa has no game pair losses. RubiChess is not too far behind, it has only one game pair loss but not enough wins to join the leaders. PlentyChess, Uralochka and Devre dropped after a weak RR2.

game 137, Ceres - rofChade: Ceres gave a pawn but rofChade had weak pawns on the queen side including isolated doubled pawns. The engines exchanged pieces, Ceres had a strong bishop pair and rofChade gave a rook for one of the bishops, with RBN vs BBN remaining. The engines slowly traded pawns until each engine had only one left. After exchanging knights it took Ceres a long time to force a bishop exchange and a tablebase win. 

game 177, Obsidian - rofChade: After a series of exchanges Obsidian was a pawn up and only minor pieces remained. Obsidian captured another pawn and had doubled passers in the center. rofChade tried to blockade and all pieces were in the center, eventually Obsidian managed to reduce to a BN vs NN position. rofChade lost a knight for one passer, Obsidian queened the other and mated.

Standings after RR3: Obsidian +12, Caissa Ceres +9, RubiChess +3, Stoofvlees Igel Viridithas -2,  rofChade -3, Revenge PlentyChess -5, Uralochka -6, Devre -8. Obsidian increased its lead after winning all 5 games with white against non-top3 engines. Ceres and Caissa are tied in 2nd place and only one will qualify, Ceres won all 4 games with white against non-top3 engines while Caissa drew 3 of 6 such games it played. This gives Ceres a better chance of qualifying. On the other hand Ceres has to play as black against both Caissa and Obsidian. 

game 203, rofChade - Ceres: rofChade created doubled passers in the center, one was gone in a minor piece trade, but the other was protected and Ceres had to block it. rofChade gave a rook for a bishop, the game reached a QB vs QR position with white two pawns up. Ceres blocked the passer with its queen, the engines mostly shuffled for a while. Eventually the white queen moved forward to prevent a second passer on the king side. After a few pawn trades the queens were exchanged, Ceres captured the passer in the center and rofChade created more passers on the sides. rofChade pushed a slowly pushed a passer to the 7th rank, the game ended in a tablebase win.

game 206, Caissa - rofChade: Caissa gave a pawn but opened the king side and exposed the black king. rofChade gave the pawn back and countered with an attack on the white king that wasn't effective. The engines reduced to a RBN vs RBN position with white a pawn up. Caissa captured a second pawn and created connected passers on the queen side. One passer slowly advanced and rofChade lost the rook to stop it. The game ended in a tablebase win.

game 214, Revenge - Ceres: Early exchanges opened the queen side and Revenge was up a pawn with a passer. After another series of exchanges only RBN vs RBB were left and Revenge captured a second pawn. Ceres captured one pawn back and the game reached a rook ending. After trading pawns it was a 7-man position which Revenge converted. 

game 215, RubiChess - Caissa: There were many early exchanges, the game reached a RRB vs RRN position and evals were stable. Evals started to increase after RubiChess exchanged a pair of rooks and moved a rook forward. RubiChess captured a pawn, Caissa did the same but its knight couldn't retreat to safety. Instead Caissa gave the knight for more pawns, it was two pawns up and there was only one white pawn left. RubiChess pushed its pawn forward, it gave its pieces and queened. In the Q vs R ending the black pawns were too slow to promote and too far from the black king, the game ended in a tablebase win.

game 225, Obsidian - Ceres: There were many early exchanges and the game reached a RN vs RB position, Ceres was a pawn up while the white rook and king were more active. Evals suggested a draw but Ceres made the wrong move, allowing Obsidian to reduce to a king and pawns ending. Obsidian quickly equalized material, and using its active king it forced the black king back and captured another pawn to win.

Standings with 5 rounds to go: Obsidian +13, Caissa +9, Ceres +6, RubiChess +4, Stoofvlees rofChade -1, Viridithas -2, Igel -3, Revenge PlentyChess -5, Uralochka -7, Devre -8. Obsidian continues to lead, it is very likely to finish first in the league. Ceres had a terrible RR4 so far with 3 losses and no wins, including 3 games it only drew as white against weaker engines. Caissa lost one game as well, but it also won a game and drew as white only once against weaker engines. As a result Caissa has a 3 win gap in 2nd place and Ceres needs a miracle to close this gap in 5 rounds. One of the remaining games is Caissa as white against Ceres. 

game 251, Obsidian - RubiChess: Obsidian gave two pawns and attacked the king side, RubiChess gave a rook for a bishop to protect its king. The game reached a QRR vs QRB position and Obsidian moved a rook to the 7th rank. After a while the white queen moved forward as well, Qbsidian captured a pawn and created an advanced passer. RubiChess gave the bishop so its queen could check the white king, but Obsidian eventually found safety for its king. RubiChess lost more material and was mated.

Standings with 2 rounds to go: Obsidian +15, Caissa +10, Ceres +6, RubiChess +4. The 3 leaders drew their games as black. Obsidian won twice as white and ensured first place. Caissa increased its 2nd place lead to 4 wins after it won its game as white and Ceres only drew. Caissa will finish 2nd almost surely. 

game 254, Revenge - Obsidian: Revenge captured a pawn and the engines exchanged queens, they continued to exchanged pawns and pieces until the queen side was cleared and only BBN vs BBN were left. Revenge created a passer in the center and slowly pushed it forward. Obsidian captured a pawn but had to give a bishop for the passer. Obsidian lost more material, Revenge queened and mated.

Ceres held a draw against Caissa, with this result Caissa ensured 2nd place.