Season 21 premier division, after RR2

Standings after RR2

The table is divided into two halves. Stockfish is in the lead, and 3 engines are tied for 2nd place. So far only one game pair was decisive within the top 4 engines, Stockfish beating Stoofvlees. At the bottom there are 4 engines within 0.5 points of each other. Again, only one game pair was decisive within the bottom 4 engines, ScorpioNN beat Igel. Two points separate the two halves. Top engines beat bottom engines in 10 of 16 game pairs, without loss.

AllieStein's performance has been below expectations so far (at least my expectation). In season 20 it finished 4th and was considered a part of the leading group. There are still many games to be played, it may yet climb back to the top.

There have been 4/28 game pairs with two white wins so far, 3 of which were within the top 4 engines.

Interesting games

game 1, Stockfish - AllieStein: Stockfish had an eval over 1 from the start. AllieStein moved its queen forward, Stockfish pushed it back to the king side where black pieces surrounded the black king. There were very few exchanges as evals increased, the engines concentrated forces on the king side. The engines opened the king side and both kings were left without pawn support. AllieStein exchanged minor pieces but the major pieces were the danger in the open files. Stockfish was very precise in its moves, AllieStein tried to counter against the exposed white king but Stockfish always had a way out. The engines reduced to a QN vs QN position and AllieStein gave the knight for a passer. Stockfish queened a second passer and mated.

game 4, Stoofvlees - ScorpioNN: Stoofvless had an eval advantage, the center was blocked with all pieces on the board. The engines opened a file on the queen side and one on the king side, Stoofvless went up a pawn. The first piece exchange was on move 43, the engines started to shuffle and nothing seemed to happen for a while. While shuffling evals stated to increase, the engines reduced to a QRB vs QRB position with two white passers facing the black king. ScorpioNN saw it was losing material and just gave up, it sacrificed its pieces and was mated.

game 8, Stockfish - KomodoDragon: There were a few minor piece exchanges after the start, then the engines mainly shuffled and evals stayed a little above 1. Stockfish captured a pawn on move 45, evals started to increase slowly after Stockfish created a passer on the queen side. After Stockfish created a second passer KomodoDragon tried to counter by giving two pawns and exposing the white king to attack. Stockfish kept its king and pieces safe, then reduced to a RRB vs RRB position. With a 3 pawn advantage and two advancing passers the win was a matter of time.

game 10, Leela - Stockfish: On move 26 Stockfish started a series of moves that reduced to a QB vs QB, white two pawns up and with a passer on the 7th rank. Stockfish was sure it was losing with an eval over 3, Leela's eval was less than 1. 

On move 39 Leela continued with its plan and Stockfish immediately dropped its eval to 1. Stockfish thought that Leela should have played 39. c4, and this was Leela's next move. In the game Stockfish was able to exchange queens and reduce to a drawn opposite color bishops ending.

game 13, AllieStein - Ethereal: AllieStein had an eval advantage from the start, evals did not move a lot with most pieces on the board. AllieStein castled long, Ethereal did not castle but its king walked to the king side. Evals started to increase after AllieStein gave a pawn to open the king side. Ethereal captured a second pawn but the white major pieces threatened its king. In a series of exchanges AllieStein gained a knight and the game reached a RB vs R ending with black two pawns up. After exchanging rooks AllieStein used zugzwangs to capture the black pawns, the game ended in a tablebase win.

game 15, Stockfish - Stoofvlees: Stockfish's eval increased very quickly from the start, it thought Stoofvlees was not worried enough about its king. Stockfish weakened the black king side pawns with a pawn on h6, then it attacked the back king while its eval already showed a mate score. Stockfish created a passer with a knight sacrifice, it chased the black king away and queened the passer. Stoofvlees captured a rook but with two white queens chasing the black king mate came very quickly, on move 35.

game 16, KomodoDragon - Leela: KomodoDragon gave a pawn and opened the g file. The black king was stuck in the center and unable to castle, KomodoDragon's eval started to increase. The black king ran to the queen side, Leela thought it was safe enough and its eval did not change. The engines reduced to a QRB vs QRB position, Leela started to feel the danger after KomodoDragon opened the queen side. The white queen and rook danced on the board, KomodoDragon captured a pawn and then another. Finally an attack on the king led to a QB vs RB position and mate.

game 22, Stockfish - Ethereal: Stockfish pushed a pawn to h6 and trapped the black DS bishop in the corner. Evals increased rapidly, the engines opened the queen side and each side had two passers. The black passers were connected but the white passers were more dangerous. Stockfish calculated mate when both passers were on the 6th rank. Ethereal gave its queen for a rook to capture one passer. It lost all its remaining pieces, except the trapped bishop, for the other passer. Mate followed quickly.

game 23, KomodoDragon - ScorpioNN: The engines played behind their pawn lines with very few exchanges. KomodoDragon gave a pawn to open the king side, evals increased as it attacked the black king. ScorpioNN had no pawn support for its king, it lost a piece defending and the game reached a QN vs Q position. KomodoDragon continued to attack the exposed black king, the black passers were too far to be a threat. ScorpioNN eventually lost its queen and was mated.

game 24, Leela - Stoofvlees: Leela pushed a pawn to h6 and trapped the black DS bishop in the corner. The engines opened a file on the queen side, there were very few exchanges and evals remained stable. Leela placed a rook on the 7th rank and a few moves later evals started to increase. Stoofvlees exchanged a pair of rooks and Leela went a pawn up creating a central passer. The engines reduced to a QN vs QB position, Leela soon had 3 advancing passers. The black queen captured a few pawns but couldn't stop all the white passers, it didn't take Leela long to mate.

game 25, Stoofvlees - AllieStein: The game reached a RRN vs RRB position on move 52 with evals around 1. Stoofvlees went a pawn up, after exchanging a pair of rooks evals started to increase very slowly. AllieStein gave its last pawn and causing the last two white pawns to be doubled. Stoofvlees was careful not to reduce to a drawn endgame, eventually AllieStein captured one white pawn. However it saw was about to lose and allowed a mate in 1.

Standings after RR1: Stockfish +4, KomodoDragon +1, Stoofvlees Leela Igel 0, AllieStein -1, ScorpioNN Ethereal -2. Stockfish has a promising lead, still very early in the league. Igel drew all its games so far.

game 34, Stoofvlees - Ethereal: Stoofvlees had an eval advantage that increased from the start. The queen side was blocked and the black pieces had little room. Ethereal opened a file in the center and gave a rook for a knight and two pawns. Stoofvlees reduced to a RB vs BN position, then created an advanced passer on the queen side. Ethereal had a passer on the king side but the white king was on time to block it. Ethereal had to deal with more white passers and couldn't prevent a queening and a win for Stoofvlees.

game 35, Leela - Igel: The game reached a R vs N ending on move 40, Igel was a pawn up and evals were around 1 and stable. On move 41 Igel blundered and Leela's eval jumped over 5. Igel saw the problem a few moves later, Leela started to capture pawns, then won with its passers.

game 36, KomodoDragon - Stockfish: Stockfish's develpment was slow, its queen grabbed a pawn and moved forward, then it castled long without full pawn support. KomodoDragon regained the pawn, then traded a knight and two pawns for a rook. KomodoDragon's pieces were strong in the open board, it targeted the black queen and then started to chase the black king to the center. In a series of exchanges KomodoDragon won a piece and reduced to a BB vs N position. The last white pawn secured the win. There were two white wins in this opening.

game 41, Ethereal - AllieStein: The black king remained in the center unable to castle. After AllieStein moved its king to the king side and some shuffling the engines opened a file in the center and Ethereal went a pawn up. Ethereal had a pawn majority on the queen side, after exchanging bishops it created an unstoppable passer. AllieStein gave as many checks as it could, but Ethereal had two queens and it mated once there were no more checks. There were two white wins in this opening.

game 42, ScorpioNN - Igel: Evals were over 1 and there were only a few exchanges after the start. The black king was left without pawn support, evals increased as the engines reduced to a QRB vs QRB position with white a pawn up. After exchanging queens ScorpioNN captured a second pawn. Igel gave its bishop to stop a passer, the last white pawn gave ScorpioNN the win.

game 44, Leela - KomodoDragon: KomodoDragon gave a rook for a knight and pawn, evals started to increase as Leela exchanged pieces. The game reached a RB vs BN position, Leela created an unstoppable passer to win. There were two white wins in this opening.

game 52, Stoofvlees - Leela: See featured game below.

game 54, Leela - ScorpioNN: The game reached a RN vs RB position with evals under 1. ScorpioNN had 2 passers on the queen side and Leela had 2 passers on the king side. Leela thought ScorpioNN's decision to move its king towards the center was a mistake, it allowed the white rook to block the black king away from the white pawns. Leela's eval jumped after another ScorpioNN blunder, this time it did not push a passer. This gave Leela the advantage in the passer's race for promotion, it won a rook for a knight as a result. The R vs B ending was a win for white.

game 55, KomodoDragon - Ethereal: Evals were over 1 from the start, the black queen grabbed an early pawn and retreated to the king side. Evals jumped after Ethereal missed KomodoDragon's move 21, in a series of exchanges KomodoDragon reduced to a QRN vs QRN position with an advanced white passer in the center. Eventually Ethereal lost a piece for the passer, and the game reached a winning knight vs pawns ending. 

game 56, Stockfish - Igel: The center was blocked and evals were under 1 for a long time. Evals increased a little after Igel gave a pawn and opened the queen side. Stockfish had a passer, after reducing to a QBN vs QNN position Stockfish pushed the passer forward one square. The engines exchanged queens and this created a second white passer. Stockfish gave a pawn and pushed its first passer to the 6th rank, Igel used its knights to keep the white passers away from promotion. Stockfish exchanged a pair of knights, Igel captured the white passer in the center but by then Stockfish had passers on both sides of the board. The black king couldn't cover them all, Stockfish queened a pawn and won. 

Featured game: Stoofvlees - Leela
Premier division, game 52
Link to game on TCEC

Evals slowly came down after the start. The engines castled in opposite directions, Leela opened the king side and then gave a rook for a knight and pawn to created a passer. The engines exchanged pieces and opened the position. Leela captured a second pawn and created another passer. On move 44 Leela thought for over 9 minutes and its eval jumped close to 2, quite unexpected.

Stoofvlees expected this move in its PV, and it continued as it planned exchanging the rooks. According to Leela's PV a different continuation could have been better for Stoofvlees. Evals came down again and the game continued. In a QR vs QN position Stoofvlees used the exposed black king to clear the black pawns on the queen side and create connected passers. This time both evals increased, after exchanging queens only R vs N remained.

Stoofvlees pushed its passers forward. Leela moved its king forward and captured the rook for a passer. The remaining pawns raced forward and both engines promoted a passer simultaneously. Stoofvlees captured the knight, Leela saw it was losing and underpromoted to a rook. The game ended in a tablebase win a few moves later. There were two white wins in this opening, though the games were not similar.