The engines that will play in the season 28 entrance league are:
relegated from season 27 league 1: PlentyChess
relegated from season 27 league 2: BlackMarlin, Arasan, Minic, DeepSjeng
played in season 27 entrance league: Renegade, Altair, Booot, Patricia, Tucano
new to TCEC (played in Swiss tournament): Integral, Starzix, sirius
returning to TCEC: Clover (season 26 league 1), ScorpioNN (season 26 league 2), Stash (season 26 entrance league)
Final standings
Integral, PlentyChess, Booot, Starzix and Arasan advance to league 2. There was a tie in 5th place, Arasan and Clover played a tiebreak match and in the 5th game pair Arasan won.
Integral won 13/15 game pairs without loss, it lost only one game against Booot. PlentyChess won 12/15 game pairs and lost only to Integral. Arasan was in 2nd place after RR1 with 7 wins and one loss, in RR2 it played as black against stronger engines and it drifted down in the table. Booot finished in third without a game pair loss and only one game loss to Integral. Starzix had 3 game pair losses but 10 wins, it finished in 4th place. With only two rounds remaining Clover was able to tie the score with Arasan, their final results were almost identical. A tiebreak match was played and Arasan won. Interestingly both Arasan and Clover lost a game to Patricia, for Patricia the win against Clover was its only game pair win in the league.
A tiebreak was played between DeepSjeng and ScorpioNN, not sure why it was needed. DeepSjeng won the 2-game match and is officially in 11th place, ScorpioNN is in 12th.
The 5 qualifiers will play in league 2 together with:
played in season 27 league 1: Igel, Uralochka
played in season 27 league 2: Velvet, Ginkgo, Stormphrax
new in TCEC: Reckless, Horsie (I'm not sure why these are starting in league 2, perhaps based on their results in the Swiss tournament)
Interesting games
game 4, Integral - Starzix: Starzix pushed the f pawn and its king was vulnerable. Integral pushed a pawn to g6 and threatened a king side attack. The engines reduced to a double rook ending and Integral went a pawn up. Integral used a passer on the 7th rank to reach a winning rook ending.
game 8, Patricia - Clover: Patricia controlled an open file on the queen side. After a very long shuffle the king side opened, the white queen moved forward and drove the black king to the center. Patricia had a passer on the 7th rank and active knights, Clover lost material and was eventually mated.
game 12, Stash - Minic: Minic sacrificed a knight to open the king side, it tried to attack the white king. Stash protected its king, gave the piece back and reduced to a RB vs RB ending with a pawn up. Minic lost the bishop for a passer, the game ended in mate.
game 18, Arasan - Altair: Arasan had a space advantage, it gave pawns to open both sides and placed both rooks on the 6th rank. Arasan moved a pawn to g7 and threatened the black king, Altair exchanged pieces but lost material. Arasan converted a RB vs R ending.
game 26, PlentyChess - Clover: PlentyChess opened the queen side, captured a pawn and created a passer. Clover countered with a knight sacrifice to create connected passers on the king side. Clover gave a bishop to capture all remaining white pawns, in BBN vs N position PlentyChess captured all black pawns and mated.
game 29, BlackMarlin - Minic: BlackMarlin doubled queen and rook on the open h file, Minic countered on the queen side and won a rook for a passer. However, BlackMarlin used the exposed black king to gain material and win a QN vs Q ending.
game 34, Integral - Booot: Booot opened the queen side but its king was stuck in the center. Integral had an active rook on the queen side and it pushed pawns on the king side. Booot kept the king side closed, Integral placed a pawn on the 7th rank. Booot lost material and was mated.
game 50, sirius - Arasan: The game reached a R vs B ending, Arasan was a pawn up with connected passers and one on the 2nd rank. sirius captured one passer and blocked the other, but it couldn't find the winning moves. The game was adjudicated after a very long shuffle on move 282.
game 53, Patricia - Renegade: Patricia went a pawn up in a closed position, after a long shuffle it captured a second pawn. The engines reduced to a double bishop ending, Patricia used a passer to win.
game 69, Clover - Altair: Altair kept the king side closed, Clover captured a pawn and opened the queen side. In a series of exchanges Altair lost two knights for a rook. Clover used a passer to gain more material followed by mate.
game 70, ScorpioNN - Renegade: ScorpioNN gave a rook for a knight and captured black pawns. The game reached a RB vs RR position with 3 white pawns and all black pawns gone. ScorpioNN pushed connected passers and seemed to be winning, but it let Renegade capture a pawn and block the connected passers to hold a draw.
game 78, Arasan - Patricia: In a RR vs RB position Patricia, with no tablebase support, blundered and exchanged rooks. The result was a 7-man win for Arasan, 80 moves long.
game 88, Starzix - BlackMarlin: In a closed position Starzix opened the center and its two bishops threatened the black king and pieces. After a series of exchanges the game reached a R vs B ending which Starzix won.
game 94, Integral - Clover: Integral opened the center and created a passer, Clover gave a rook for a knight and tried to counter on the queen side. After exchanging pieces Integral gave back the material, it captured the black pawns on the queen side while Clover captured the center passer. In a RB vs RN position Integral pushed a queen side passer, Clover stopped it but lost its pawns on the king side. Integral pushed passers on the king side to win.
game 101, PlentyChess - Arasan: The engines exchanged pieces in a closed position, PlentyChess created a passer on the queen side and only QB vs QN were left. After exchanging queens PlentyChess created a second passer on the king side to win.
game 106, Altair - BlackMarlin: Altair captured a pawn and reduced to a QRN vs QRN position. After a long preparation Altair captured a second pawn and then converted a knight ending.
game 107, Booot - Starzix: Booot was two pawns up early in a closed position. The engines exchanged pieces until only BBN vs BBN were left, Starzix gave two pieces for the remaining white pawns. Booot captured the black pawns and mated.
game 109, Integral - PlentyChess: Integral created a queen side passer, then captured a pawn and pushed another passer to the 7th rank in the center. PlentyChess blocked the passer, regained the pawn and created a king side passer. It tried to avoid exchanging queens, eventually Integral reduced to an opposite color bishop ending. Integral lost the advanced passer but captured all black pawns, PlentyChess couldn't avoid a queening and mate.
Standings after RR1: Integral +7, Arasan +6, PlentyChess +5, Booot +3, Starzix Clover +2, BlackMarlin Renegade 0, Altair DeepSjeng -1, Tucano -2, Patricia -3, sirius ScorpioNN -4, Minic Stash -5. Integral leads with no loss and one draw with white. Arasan and PlentyChess are close behind, each with one loss and one draw with white. Booot, Starzix and Clover are in the race for the first 5 places which qualify for league 2.
game 123, BlackMarlin - Arasan: Arasan captured a rook for a knight while BlakMarlin created advanced connected passers in the center. Arasan tried to block, BlackMarlin exchanged pieces and gave a bishop to push a passer to the 7th rank in a Q vs QR position. Arasan could not stop the queenings, it lost material and was mated.
game 134, Integral - BlackMarlin: Evals increased from the start in a closed position, on move 37 Integral went a pawn up and created a passer in the center. Gradually Integral captured all the remaning black pawns, then queened a pawn to win.
game 149, Minic - BlackMarlin: In a closed position Minic managed to create connected passers in the center. BlackMarlin gave a bishop to capture both passers and the game reached a RBN vs RN position. BlackMarlin lost a knight for another passer, Minic won in a KBN vs K ending.
game 154, Booot - Integral: Booot threatened the black king side, Integral moved its queen forward on the queen side and Booot blocked its path back. Integral gave a rook for a knight to open the block. In a QRR vs QRN position Booot captured two pawns, then reduced to a winning R vs N ending.
game 168, Integral - Arasan: Integral gave a pawn open a file on the queen side, then gave another pawn and hid its king behind a black pawn. Integral regained one pawn, it kept pressure on the queen side until Arasan gave a knight for a pawn, but Arasan's counter was weak. Integral created a passer on the queen side and exchanged pieces, it queened and mated.
game 178, PlentyChess - Starzix: PlentyChess attacked on the king side, it gave two minor pieces to expose the black king. In a series of exchanges the engines reduced to a RB vs RN position. PlentyChess was two pawns up, Starzix lost material to stop a queening and was mated.
game 198, Patricia - Arasan: Patricia gave two pawns and attacked the king side. Arasan gave a knight and exchanged pieces, the game reached a QRN vs QR position with black two pawns up. Patricia used the extra piece to capture pawns, it pushed a passer to win.
Standings with 5 rounds to go: PlentyChess +11, Integral +10, Booot Starzix +6, Arasan +5, Clover +4, Renegade BlackMarlin Altair 0, DeepSjeng Tucano ScorpioNN Patricia -5, Minic sirius -7, Stash -8. PlentyChess and Integral have a significant lead and will probably finish in the first two places. There are 4 engines in the race for the other 3 qualification spots, and anything can happen.
Standings with 2 rounds to go: Integral +12, PlentyChess +11, Booot +8, Starzix +7, Arasan +5, Clover +4, Renegade 0, BlackMarlin Altair -1, Tucano -4, Minic DeepSjeng -6, ScorpioNN sirius Patricia -7, Stash -8. Booot and Starzix will probably qualify in places 3-4. Clover still has a chance of qualifying instead of Arasan, it has a game against Minic as white while Arasan will face Starzix as white.
Clover beat Minic, and there is a tie with Arasan with one round to go.
Arasan only drew against Starzix, there is a tie for 5th place between Arasan and Clover.
