Season 20 premier division, final results

Final standings

Leela and Stockfish will play in the season 20 superfinal. This was the expected result, Leela and Stockfish led the league from the start, gradually increasing the gap. In the last DRR Leela won 5 game pairs while Stockfish won only 4. The final score is a tie, their head-to-head score is a tie as well. As a result r-mobility was used to decide that Leela is the winner of the premier division. It is interesting to note that of 28 games in white Leela won 24 and Stockfish won 22.

rofChade and Ethereal are relegated to league 1. rofChade was the weakest engine of the division, it failed to win a single game pair and lost 25/28 of its games in black. Ethereal and ScorpioNN fought to survive and were only 1 point apart when the last DRR started. Ethereal's loss in white was a final blow from which it couldn't recover. Overall Ethereal and ScorpioNN had similar results: both suffered a double loss in a game pair, both lost most of their games against the top 5 engines. Ethereal beat rofChade in two game pairs and ScorpioNN in only one. However ScorpioNN beat Ethereal in their first game pair, and essentually Ethereal didn't close the gap since.

After several seasons of slow decline Komodo was updated to KomodoDragon this season and it jumped back to 3rd place above AllieStein and Stoofvlees. Recall that Komodo was close to relegation in season 19. 

There was a clear divide between the top 5 engines and the bottom 3 engines. Of the 60 game pairs played between these groups the top 5 engines won 50 and drew only 10. Three of the game pair wins were double wins.

Interesting games

Game 174, Stockfish - KomodoDragon: KomodoDragon gave a pawn and opened the queen side. Stockfish's eval increased as it shifted to the king side and opened the h file. KomodoDragon felt threatened after a white pawn reached g6, and the black king walked to the center. The black king side collapsed and Stockfish captured two more pawns. Stockfish had two passers on the king side, it traded a rook for a knight and pushed both passers to the 7th rank in a RBN vs RRB position. KomodoDragon could not avoid losing material and the game.

Game 178, Ethereal - Stoofvlees: There were many early exchanges and the game reached a queen ending on move 29. Ethereal was a pawn up and it created a passer on the queen side. Stoofvlees gave checks with its queen and Ethereal was careful to avoid a perpetual check draw. The king moved all the way forward to support a queening, and with two queens Ethereal mated quickly.

Game 183, Stoofvlees - KomodoDragon: The engines shuffled for a long while, both had very little time left. On move 71 KomodoDragon grabbed a pawn and allowed Stoofvlees to open a file on the king side and exchange pieces. The engines reduced to a BN vs BN position, Stoofvlees created a queen side passer. After a second passer moved forward KomodoDragon could not prevent a queening, Stoovflees gave a bishop but with a queen the game was over quickly.

Game 190, Stoofvlees - Stockfish: The queen side was blocked, Stockfish had a knight on the 5th rank but it was trapped. The engines exchanged all rooks through an open file in the center while evals increased steadily. Evals were over 4 when the queens were exchanged and only BBN vs BNN remained. The black pieces could hardly move, Stockfish gave its trapped knight for pawns on the queen side in desperation. Stoofvlees created a passer on the king side, Stockfish stopped it but lost its remaining pieces, game over.

Game 191, ScorpioNN - rofChade: ScorpioNN created a passer on the queen side and doubled its rooks in an open file there. rofChade gave a rook for a bishop to capture the passer and the engines reduced to a RR vs RN position. The white rooks dominated the board, ScorpioNN slowly captured pawns until it had passers on both sides of the board. rofChade blocked a passer on the queen side with its king, ScorpioNN pushed passers on the king side and managed to promote them to two queens, with mate a few moves later.

Game 192, Ethereal - KomodoDragon: The center was blocked, there was an open file on the queen side and KomodoDragon had a passer there as well, while Ethereal had a bishop pair advantage. The engines shuffled for a while, evals came down after KomodoDragon opened the king side. KomodoDragon created a passer on the king side and evals became negative. After exchanging a pair of rooks and another shuffle period evals increased and KomodoDragon pushed its passers forward. Ethereal captured the passer on the king side, opening a file for the black pieces to enter. Ethereal captured the queen side passer as well, but with a black queen and rook on the 2nd rank KomodoDragon started to capture pieces and forced a win. A rare win for black in the division.

Game 194, rofChade - Ethereal: There were no exchanges after the start, the engines shuffled with evals around 0.5. Starting from move 39 the engines traded pawns and evals increased. rofChade created an advanced passer in the center, then a series of exchanges led to a BN vs R position. Ethereal captured the white passer, for a long while it seemed that Ethereal was holding. It blocked the white king from moving forward and rofChade didn't find a way to threaten any black pawn safely. However evals kept increasing, first rofChade captured a pawn, then finally on move 108 it pushed a pawn on the king side and created a passer. Ethereal had to give its rook for a knight to stop the passer, there were enough white pawns left to win.

Game 196, Leela - Stoofvlees: There were many early exchanges and the game reached a RRN vs RRN position with evals under 1. Leela had a passer in the center that Stoofvlees blocked with its king. Stoofvlees blundered and gave a pawn so it could move a rook to the 2nd rank. This allowed Leela to push its passer to the 7th rank, only then Stoofvlees realized it was losing, 6 moves too late. Stoofvlees captured the passer but got mated by two rooks on the back ranks.

Scores after RR7: Leela +18, Stockfish +17, KomodoDragon +9, AllieStein +4, Stoofvlees -2, ScorpioNN -12, Ethereal -14, rofChade -20. Leela still leads by 0.5 points, 4 of its remaining games are with white. Stockfish has only 3 white games left, unlikely that it can catch up. Ethereal is still only 1 point behind ScorpioNN, its losses to rofChade and to KomodoDragon playing white were hard blows. It also has only 3 white games left, its best hope is to win the one against ScorpioNN.

Game 197, AllieStein - Stoofvlees: The game reached a RB vs RN position, AllieStein saw something that Stoofvlees missed and its eval jumped over 4. It took 13 moves for AllieStein to go a pawn up with the queen side pawns gone except one white passer. AllieStein moved its rook to the 7th rank while its king came forward. The black king could not move out of the back rank, the black pieces were too far to help and AllieStein captured all the black pawns on the king side. AllieStein was 3 pawns up and clearly winning, but it was in no hurry and the game continued for more than 50 moves before reaching a tablebase win.

Game 205, AllieStein - ScorpioNN: AllieStein had a passer in the center with the queen side clear and a Q vs RN imbalance. The engines reduced to a Q vs RB position and ScorpioNN gave its bishop to capture the white passer. The resulting 7-man position was a tablebase win for white, but slow with long term planning necessary. AllieStein wasn't able to find the correct move sequence in time and the game ended just before the 50-move draw.

Game 207, Leela - KomodoDragon: see featured game below.

Scores with 3 rounds remaining: Leela +20, Stockfish +19, KomodoDragon +8, AllieStein +5, Stoofvlees -2, ScorpioNN -13, Ethereal -16, rofChade -21. Leela still leads Stockfish by 0.5 points. Ethereal only managed a draw against ScorpioNN, it is now 1.5 points behind and is very likely to be relegated.

Two rounds to go. Ethereal lost to AllieStein and ScorpioNN held against KomodoDragon, Ethereal cannot survive even theoretically since ScorpioNN has a tiebreak advantage. Leela and Stockfish drew their head to head game, their final head-to-head score is a tie with one game pair win each.

Game 218, Stockfish - Stoofvlees: Stockfish pushed pawns on the king side, its eval jumped over 3 after Stoofvlees gave a rook for a bishop. The king side opened and both kings were exposed to attack. Stockfish pieces were better placed and its attack was quicker. Stockfish captured a knight and the black king was caught in a mating net. Two white wins in this opening.

Leela drew against AllieStein, going into the last round Stockfish and Leela are tied for 1st place.

Leela and Stockfish drew their last games. The r-mobility tiebreak was used to decide that Leela won the premier division.  

Featured game: Leela - KomodoDragon
Premier division, game 207
Link to game on TCEC

Leela was up a rook for a bishop and pawn early in the game. Leela controlled an open file in the center, KomodoDragon had advanced pawns on the queen side and its pieces were active there. Evals were around 1 when KomodoDragon moved its queen forward to capture a pawn. Leela used the fact that the black queen was far to attack the back rank. After move 24 it thought for 7 minutes though KomodoDragon's last move was expected in both PVs.

Leela's eval jumped over 3, it changed its PV move to a knight sacrifice on g6. The black king was exposed and after exchanging a pair of rooks Leela's remaining major pieces moved forward. KomodoDragon reduced to a R vs BN position to avoid a back rank mate.

The white rook kept the KomodoDragon's king away from the pawns. The black pieces protected the queen side pawns and Leela went after the pawns on the king side. The engines traded a few pawns and KomodoDragon lost the pawns on the king side, Leela went two pawns up with two passers.

KomodoDragon kept its bishop on the diagonal protecting a7, its king came forward to block the white king. Leela then pushed the h pawn and sacrificed its rook to promote it to a queen. The game was over not long after that.