Season 15 premier division results

Final crosstable

Stockfish and Leela will play in the season 15 superfinal, a rematch of the previous superfinal. Ethereal and Fire are relegated to division 1.

The final RR did not change the engine ranking, and the top and bottom of the table were already obvious. There was one interesting result, Leela beat Stockfish in their final game of the division. This may indicate that this season Leela will be the superfinal champion.


The four engines in the middle were close during the whole division. Komodo finished ahead of the rest by a small margin, all four engines had similar strength. Of the 36 games these 4 engines played each other only 4 were decisive, including a crash by KomodoMCTS. AllieStein started this season as a newcomer NN engine in division 4, getting to the premier division and staying there is a great achievment. KomodoMCTS solved most of its stabillity issues of last season, if it continues to improve it may become better than its older relative Komodo.

The superfinal will start in about two weeks, I will be on a break until then. TCEC continues with the cup event that will start tomorrow.

A few interesting games

Houdini - Fire: Houdini had a space advantage, it pushed its king side pawns forward, leaving its king with no support and threatening the black king. Fire switched its king and rook back after castling, so the king would have an escape route. Houdini's eval increased as it played on both sides, pushing the black pieces back. Fire gave a pawn but couldn't stop Houdini's attack. Houdini won more material and the game was adjudicated with mate in the PV.

AllieStein - Houdini: AllieStein's eval increased quickly as it opened the king side and exposed the black king. Houdini hid its king behind a white pawn and the game reached a QRB vs QRB position on move 32. The engines exchanged queens and AllieStein went two pawns ahead. AllieStein's eval peaked over 6, the engines just shuffled and AllieStein couldn't find the win. The game continued to move 153 and ended in a tablebase draw.

Stockfish - KomodoMCTS: Stockfish's eval increased quickly from the start as it pushed pawns on the king side. The black pieces were stranded on the queen side, Stockfish gave a knight to open the king side on move 25 with both evals over 6. The black king had to run and KomodoMCTS lost its queen, the game was adjudicated in a QB vs RN position. 

Komodo - Fire: On move 30 most pieces were on the board, Fire had a passer on the e file and Komodo had a pawn majority and a potential passer on the c-d files. Evals increased gradually as the engines exchanged pieces, on move 44 only QRB vs QRN remained. White's passer on d6 was more advanced and more supported, the black king was exposed to attack. Fire tried to counterattack, Komodo was careful not to allow a perpetual check and the game was adjudicated in a winning QB vs Q position. Two wins for Komodo in this opening.

Leela - AllieStein: Evals were over 1 from the start, there were many early exchanges and only RRN vs RRN remained on move 17. Leela gave a rook for a knight and two pawns and created a queen side passer. Leela pushed the passer to the 7th rank with eval over 2, AllieStein countered with checks and it seemed it was holding. Then on move 60 evals jumped as AllieStein miscalculated and stopped the checks at the wrong moment. Leela lost the queen side passer but reduced to a N vs R ending with 3 connected passers in the center. AllieStein realized it was losing, and as we have seen before in this division it just gave away the rook and lost immediately.

Stockfish - Fire: Stockfish's eval climbed after the start, reaching over 1.5 with all the pieces on the board. The center was blocked and Stockfish controlled an open file on the king side. The first pieces were exchanged on move 36, Stockfish created an advanced passer on the king side and its eval jumped over 2.5. Evals increased quickly, Stockfish exchanged BN for R and Fire created a passer on the queen side. Stockfish trapped a knight and then captured it, the game was adjudicated with Fire losing more material.

Leela - Stockfish: see featured game below. Leela wins the 6th and last head-to-head game against Stockfish.

Featured game: Leela - Stockfish
Premier division, game 161
Link to game on TCEC

Leela had an eval over 1 from the start, the engines only exchanged a pair of knights, both played behind their pawn lines. The center was blocked early, and Leela's eval jumped over 2 after the blocking the king side as well.  

Stockfish's pawns on the queen side limited the movement of the black pieces. Leela shifted its pieces to the queen side and its eval increased quickly, Stockfish's also increased but more slowly. On move 35 the engines exchanged pawns for the first time, Leela was confident it was winning.

The queen side opened up and Leela's major pieces controlled the open files. Stockfish tried to challenge the white king safety but Leela closed the gap with a bishop. Evals kept jumping higher, though material was equal. Only on move 51 Leela went up a pawn, creating a potential passer on the queen side.

Leela concentrated on exchanging pieces, the game reached a RBN vs RBN position on move 60. The black central pawns became defenseless and Leela exchanged knights and went 3 pawns up.

This was an easy endgame, the game was adjudicated 15 moves later.

Season 15 premier division after RR5

Crosstable after RR5

Stockfish and Leela continue to lead, there were no significant changes at the top of the table. Stockfish had an advantage in their 5th game but it too ended a draw. Leela has a chance to win in their last head to head game in RR6.

At the bottom Ethereal had its best RR with a 3.5/7 score, including a win against Fire. Ethereal and Fire are still last but Ethereal closed the gap between them to 0.5 points.

In the middle section Komodo and AllieStein pulled ahead of Houdini and KomodoMCTS. AllieStein got a free half point when KomodoMCTS crashed in a drawn position.

For the second time in the division there were two consecutive network crashes and the GPU server had to be reset. 

A few interesting games

AllieStein - Ethereal: AllieStein had an eval over 1 from the start, and it increased quickly. AllieStein gave two pawns and then won a knight. Ethereal had three pawns as compensation but evals were very high. After exchanging queens AllieStein got one pawn back and the game reached a RRB vs RR position. The endgame took a very long time, the engines mostly shuffled. In the end AllieStein found the winning path, the game was adjudicated in a RB vs R position on move 114.


Houdini - AllieStein: The network crashed on move 14, the game was later resumed and resulted in a draw.

Leela - Fire: The network crashed on move 45 and the game was resumed later. Leela pushed pawns on the king side and opened a file near the black king. Queens were off early and Leela moved its king without castling, Fire captured a pawn but its LS bishop was almost trapped and Leela's eval increased to 4. The game reached a RBN vs RBB position on move 26,  the black pieces were defensive and the white knight dominated the center. After some preparation Leela created a queen side passer, Fire stopped it for a bishop when it got to the 6th rank. The endgame was slow, it took Leela almost 50 moves to capture all the black pawns. Leela pushed a passer to the 7th rank and the game was adjudicated.

Fire - Komodo: There were very few exchanges after the start, evals were close to 0 in a closed position. On move 37 Komodo opened a file on the queen side and its negative eval started to increase. The engines exchanged a pair of rooks and shuffled for a while, then exchanged Q for RB on move 58. Komodo's eval became constant, the game reached a RB vs Q ending on move 70 and it looked as though Komodo can't find a win. It took 40 moves for Komodo's eval to move again, 20 more moves for Komodo to capture a pawn. The game was adjudicated on move 137.  

Stockfish - Houdini: Stockfish had an eval advantage from the start, evals slowly increased but mostly stayed under 1. The game reached a RBB vs RBN position on move 34, Stockfish had a pawn majority on the queen side and Houdini had a passer. Stockfish's eval started to increase, it gave a pawn and used its bishops to take control of the center and trap the black knight on the h file. By the time Houdini freed its knight Stockfish's eval was over 5, the black king was surrounded and a pair of white pawns moved forward in the center. Houdini lost the knight and the game was adjudicated as it was about to lose more material.

Komodo - AllieStein: See featured game below.

AllieStein - KomodoMCTS: The game reached a RB vs RB position on move 30. AllieStein's eval peaked over 3 but it did not find a way to win. The engines exchanged rooks and the bishops were of the same color, AllieStein made no progress and the engines shuffled for a long time. Unfortunately KomodoMCTS crashed and lost.

Stockfish - Leela: Stockfish had an eval advantage under 1 from the start. On move 20 it created an advanced central passer, evals climbed over 1 and it seemed Stockfish had a real chance. Evals then dropped, Leela exchanged pieces until reaching a drawn R vs BN ending.

Ethereal - Fire: The game reached a QBN vs QBN position on move 44, with the center blocked and the king side open. Fire played passively and the white king charged forward. The black king was far on the queen side and Fire was outnumbered on the king side. Ethereal trapped the black bishop on the 8th rank and eventually captured it with the king (!!). The game was adjuducated a few moves later.

Leela - Komodo: Leela's eval climbed over 1 from the start. There were many early exchanges and only RRB vs RRN remained on move 22. Leela's eval increased as it pushed a passer on the king side, Komodo captured it but gave a rook for a bishop. It took Leela a while to capture two pawns so it had passers on both sides, when they started marching the game was adjudicated.



Featured game: Komodo - AllieStein
Premier division, game 127
Link to game on TCEC

Komodo had an eval advantage from the start of about 1. There were several early exchanges, on move 20 AllieStein captured a pawn with a bishop, but didn't see what was coming. Komodo's eval jumped near 2 after it attacked the bishop, forcing the black queen to stay on the diagonal to defend it.

Komodo attacked the black queen and controlled where it could go, there were only a few free squares available for it. After a few moves Komodo forced a rook exchange and won the black bishop, its eval over 3 in a QRB vs QR position.

After exchanging queens AllieStein saw it was losing. It preferred to give up its remaining rook than to keep fighting.

Mate was close when the game was adjudicated.

Season 15 premier division after RR4

Crosstable after RR4


Stockfish and Leela continue to lead, Fire and Ethereal are still last. I doubt this is going to change in the remaining two RRs.

Komodo and Ethereal won their first game of the division, all engines have won at least one game. Stockfish and Leela have not lost a game yet. They are the only engines in the division with a positive score. The 4 engines in the middle of the table are tied, of the 24 games they played only two were decisive, both between Houdini and AllieStein with one win each.

Stockfish completed a double win against Komodo and against Houdini. This would have been surprising and unusual only a few seasons ago, now it seems quite natural. The "big 3" are no more, Stockfish and Leela are in a league of their own.

A few interesting games

Stockfish - Komodo: Stockfish had an eval advantage from the start, there was only one pawn exchange in the first 40 moves. Stockfish's eval increased over 1.5 when it opened the center. In a series of exchanges Komodo gave a knight for pawns and the game reached a RNN vs RB position on move 55, Komodo with two queen side passers. Stockfish was better in the endgame, it used the knights to block the passers and the black rook lines. After exchanging a knight for the bishop Stockfish started to capture black pawns and the game was adjudicated. A double win for Stockfish in this opening.

Leela - KomodoMCTS: See featured game below.

AllieStein - Houdini: AllieStein had an eval over 1 from the start. On move 20 AllieStein went a pawn up, its eval was over 2.5 yet its king was exposed and uncastled in the center. Houdini tried to attack but after exchanging queens the white king was relatively safe and evals continued to increase. AllieStein played slowly, with long shuffles and a few exchanges and pawn moves. On move 93 AllieStein sacrificed a knight temporarily, the game reached a RB vs RN position and the advanced connected passers on the queen side were enough for a win for AllieStein.

Houdini - Ethereal: Houdini pushed pawns on the king side and exposed the black king early in the game. Evals increased very quickly, Ethereal gave a knight and tried to get some counterplay with an advanced passer in the center. Houdini gave the material back and reduced to a QRR vs QRR position. The black king faced the white pieces with all files open, it had nowhere to run and the game was adjudicated on move 34.

Houdini - Stockfish: There were almost no exchanges, only a few pawns were removed after the start. Stockfish went a pawn up on move 32, its negative eval was over 1.5 but remained more or less constant for many moves. The engines mostly shuffled for 30 moves, Stockfish's eval started to increase just before the exchanges began. On move 64 the first piece was exchanged, by move 76 most pieces were gone and the engines reached a B vs R ending. The game was adjudicated a few moves later, a double win for Stockfish in this opening.

Komodo - Ethereal: The engines castled in opposite directions, Ethereal pushed pawns on the queen side and Komodo pushed pawns on the king side. By move 35 both engines opened a file near their opponent's king, Komodo was better and evals were over 1. Komodo's king side attack was strong and Ethereal scrambled back to defend. Ethereal gave a rook for a bishop to avoid mate and the game reached a QRR vs QRB position with evals over 3. The black bishop could not move, Komodo captured a pawn and created queen side passers, then reduced to a winning R vs B ending. This was the first win for Komodo in the division.

Ethereal - KomodoMCTS: KomodoMCTS played the opening badly, the black king was left without defenders and Ethereal developed a strong king side attack very early. KomodoMCTS gave a knight and tried to counter on the queen side, but it was too late. The game was adjudicated on move 32 with mate in the PV. This was Ethereal's first win in the division.

Stockfish - AllieStein: Stockfish had a small eval advantage from the start. AllieStein immediately regretted its 23rd move, Stockfish sacrificed a rook for a knight and both evals jumped over 4. AllieStein missed the combination that won Stockfish material, but it really gave up when it saw what happened. AllieStein gave all its pieces away, perhaps aiming for stalemate? Stockfish was a move away from mate when the game was adjudicated.

Fire - Ethereal: Fire created a central passer on move 24 and evals started to increase slowly. After a series of exchanges Ethereal captured the passer and the game reached a RN vs RN position on move 43 with Fire a pawn up. The endgame was slow, eventually Fire was able to create a passer and push it forward, this was enough to convert the win.

Featured game: Leela - KomodoMCTS
Premier division, game 86
Link to game on TCEC

Leela was better in the opening, its eval over 1.5 after a few moves. On move 20 Leela gave a pawn and created an central passer, then it pushed the passer to e6.

The engines exchanged pieces and Leela's eval increased quickly, it regained the pawn and its eval was over 4. KomodoMCTS had connected passers on the queen side, it used the pawns to block the center and didn't push them forward. After some shuffling Leela went a pawn up and the game reached a RBN vs RBN position on move 45.

KomodoMCTS traded its two passers to finally capture the white passer , Leela exchanged rooks and was 2 pawns up in a winning BN vs BN endgame.

The game was adjudicated 25 moves later.

Season 15 premier division after RR3

Crosstable after RR3

Stockfish and Leela are leading and it is safe to predict they will win the division. Stockfish had 4 wins in RR3 and Leela only 1, the gap between them is 2 points. However, we have seen in season 14 that the results of the premier division are not a good predictor of the superfinal outcome.

Fire and Ethereal are at the bottom and are surely going to be relegated.

Houdini and Komodo lost their first game in RR3, both lost to Stockfish. Fire won its first game off a terrible blunder by AllieStein. There is still only one decisive game that doesn't involve Stockfish, Leela, Fire or Ethereal, out of a total of 18 games.

A few interesting games

Komodo - Stockfish: See featured game below.


AllieStein - Ethereal: AllieStein had an eval over 1 from the start. Ethereal gave a rook for a bishop and pawns and evals increased quickly. By move 24 AllieStein's eval was over 4 and Ethereal had a bishop trapped in the corner. The engines shuffled for a while and then exchanged queens. Ethereal gave its trapped bishop for pawns, the game reached a RRB vs RN position with Ethereal 4 pawns up and evals over 10. AllieStein took its time, the game was adjudicated 30 moves later.

Stockfish - Ethereal: Stockfish had a small eval advantage for 30 moves, then started to increase gradually. Ethereal had two isolated pawns on the queen side, 2 weak pawns on the king side and its DS bishop was trapped. Ethereal went up a pawn but evals were over 1.5.  Stockfish continued to build pressure, eventually Ethreal's defense broke down. Stockfish opened the king side, won two pawns and created an advanced passer. Ethereal exchanged queens and lost a knight and the game was adjudicated. Back to back losses for Ethereal.

Stockfish - Houdini: Stockfish had an eval advantage that stayed around 1 for 45 moves. Houdini gave a rook for a bishop early in the game, it seemed to be holding for a long time and the engines shuffled for a while. Evals climbed a little when the engines exchanged pieces, with only RN vs BN remaining on move 62. The engines captured pawns gradually, in the end Stockfish gave the rook for a knight to get a winning endgame.

Leela - Ethereal: Leela started with an eval over 1 that increased quickly. Leela went a pawn up on move 25 after a series of exchanges, by move 40 the game reached a rook ending and Leela's eval was over 8. Leela pushed pawns forward and Ethereal couldn't stop them, the game was adjudicated with two white passers advancing.

Fire - Stockfish: Both engines had long pawn lines, the queen side and center were blocked, Stockfish had a negative eval around 1. Fire opened the queen side and exchanged queens, Stockfish's eval increased over 2. The game reached a RN vs RN position on move 47, Fire was a pawn up with passers on both sides but the white pawns were weak. Stockfish slowly captured pawns, the game was adjudicated with black 4 pawns up.

AllieStein - KomodoMCTS: AllieStein seemed to be heading for a win with eval over 3, yet somehow KomodoMCTS found a perpetual check draw.

Fire - AllieStein: Evals were close to 0 from the start. AllieStein gave a rook for a bishop on move 27, yet it thought it was better with a pawn on h3 and the only remaining knight in a closed position. The game reached a QRB vs QBN position on move 39 and the engines started to shuffle. AllieStein's negative eval went over 2 and it extended the shuffle with pawn moves and exchanges. Then on move 189, it blundered badly and got its king in a mating net. Fire captured the black queen and won easily.

Featured game: Komodo - Stockfish
Premier division, game 57
Link to game on TCEC

Evals were close to 0 after the start. Stockfish's (negative) eval increased to around 1 after Komodo opened a file on the queen side. Stockfish concentrated forces on the king side but the white king was safe enough. There were a few exchanges and evals remained more or less constant.

The engines mostly shuffled with very few exchanges and pawn moves for a long time. On move 74 Stockfish's eval went over 1.5 though nothing seemed to change. A few moves later Komodo's rook moved forward, probably a mistake. Stockfish saw an opportunity and sacrificed a bishop.
 

The king side opened and all the white pieces were badly placed, not able to help the white king and blocking its escape route. Within a few moves Stockfish took over the back rank and regained the material.

Stockfish drove the white king forward, the game was adjudicated with Komodo about to lose its queen.

Season 15 premier division after RR2

Crosstable after RR2


After the reverse games of RR2 the table is getting clearer. Stockfish and Leela are leading, together they have won 7 games of the 12 decisive games so far. At the bottom we find Ethereal and Fire with 8 combined losses. The new NN engine AllieStein is strong enough for this division, so far it lost 3 games and won 2. Komodo has 14 straight draws, its younger family member KomodoMCTS has a better score with 2 wins and a loss. Houdini is still strong despite the fact that it hasn't been updated for a few seasons.

There were two consecutive network crashes, the GPU server was rebooted and the games were later resumed.

A few interesting games

Stockfish - KomodoMCTS: See featured game below.


Leela - AllieStein: Evals were over 1 from the start. The engines concentrated forces on the queen side, after opening the files many pieces were exchanged. By move 30 only QRN vs QRN were left, evals over 2.5. The black knight was pinned and AllieStein used a few moves to get it free. Leela refused offers to exchange queens, then unexpectedly KomodoMCTS blundered into a knight fork and Leela won a piece. The game continued for 35 more moves but the outcome was obvious.

Ethereal - Leela: In this game the network crashed and the game was later resumed. Leela had an negative eval under 1 in closed position with many pawns. Leela gave a pawn but Ethereal's pawn structure was weak with several isolated pawns. The engines seemed to be shuffling for a while, then Ethereal tried to take the initiative and it gave a rook for a knight and pawn. Ethreal had two connected passers on the queen side in a QRB vs QRR position, Leela thought it was safe and its eval jumped over 2. Leela opened the king side and attacked the white king. Ethereal gave a few checks but eventually Leela exchanged down to a winning B vs R endgame. 

Stockfish - Fire: Stockfish was better after the opening with an eval over 1. Evals gradually increased though material was equal, Stockfish arranged its pieces patiently until it was ready to strike. In a long series of exchanges the engines reduced to a RN vs R position. Fire was up a pawn but it was not enough to hold, the game was adjudicated with with one pawn left for each engine.

Ethereal - KomodoMCTS: Evals were low for 35 moves, then the (negative) evals started to increase to about 1. Ethereal had two weak pawns and KomodoMCTS threatened both. After reducing to a QR vs QR position KomodoMCTS captured a pawn, after exchanging queens it captured a second pawn. The rook endgame was a win for black.

AllieStein - Fire: AllieStein's eval started to jump on move 22 with all pieces on the board. The center and queen side pawns were locked, most of the black pieces were on the queen side and the black king had only pawn defenders. AllieStein pushed pawns on the king side and had a big space advantage, Fire could hardly move. Eventually AllieStein opened the king side and went a pawn up. Fire exchanged pieces to avoid mate, AllieStein captured another pawn and it had three advanced passers. The game was adjudicated 25 moves later in a double rook ending. AllieStein won this opening from both sides.

Stockfish - AllieStein: Stockfish had an eval advantage of about 1 from the start, it had more space and its pieces were more developed. AllieStein gave a pawn and opened the queen side, evals remained more or less constant. When AllieStein gave a second pawn evals climbed for a while but came back down to 1. Evals jumped over 4 as AllieStein tried to attack. Stockfish's king escaped a few checks, and then Stockfish countered with an attack on the black king. AllieStein couldn't escape without losing material and the game was adjudicated.

Featured game: Stockfish - KomodoMCTS
Premier division, game 37
Link to game on TCEC


Stockfish had a small eval advantage from the start. Its eval jumped over 1.5 after the black queen moved to the queen side early in the game. KomodoMCTS didn't think it was in danger after Stockfish opened a file on the king side.

Evals increased very slowly, Stockfish had strong central pawns and a bishop pair. The black queen side pawns were vulnerable, Stockfish had targets on both sides of the board. Its king was exposed so it had to be careful. KomodoMCTS was under a lot of pressure and was busy defending.

KomodoMCTS tried to counterattack, it gave a bishop for 3 pawns and opened the center. After a few queen checks the attack was over, evals jumped very quickly and Stockfish could see the win.

The white pieces were very strong with no pawns in the center to stop them. Stockfish had too many attacking options and it started to win material when the game was adjudicated.

Season 15 premier division after RR1

Crosstable after RR1

There were only 5 decisive games in the first RR. There are 5 different engines that won a game so there are no real leaders. Fire is the only engine that lost more than one game - it lost 3 - and it appears to be the weak engine of the division.

A few interesting games

AllieStein - Ethereal: The game was stopped after a few moves due to a problem with the GPU server. When replayed, AllieStein was better in a closed position with eval over 4. It may have missed a few chances to win the game. In the end the engines exchanged down to a queen ending and Ethereal managed to hold a draw.

Stockfish - Ethereal: Stockfish had an eval advantage from the start. Stockfish gave a pawn and opened a file on the king side, Ethereal had no safe side for its king and it remained uncastled. Evals stayed around 1, Stockfish regained the pawn and the game reached a RB vs RN position on move 36. Stockfish had connected passers on the queen side and its eval started to increase. Ethereal's pieces were defensive and passive, Stockfish went a pawn up and increased the pressure. Ethereal couldn't hold, the game was adjudicated with Stockfish 2 pawns up and the queen side passers marching.


Houdini - AllieStein: See featured game below.

Leela - Fire: Leela's eval was over 1 right out of book. It applied pressure on the c file with all its major pieces. Leela gave a rook for a knight, and after Fire exchanged queens evals started to increase. The game reached a RB vs RB position and Leela's king side passers were enough for a win. Fire lost a piece and the game was adjudicated.

KomodoMCTS - Fire: Evals started low and slowly increased. KomodoMCTS controlled the center and had a space advantage. Fire did not react when KomodoMCTS pushed the h pawn and threatened to open the king side, instead Fire captured a pawn in the center, KomodoMCTS' eval jumped over 5. The king side opened and the black king was under threat and exposed. Fire exchanged down to a RB vs RN position, but its position was hopeless. The game was adjudicated with the black king trapped, white with a passer on the 6th rank and the white king moving forward.

Fire - AllieStein:The game reached a QRR vs QRB position on move 42. Evals remained low until move 75, Fire somehow allowed AllieStein to take 3 pawns and exchange queens, so only RB vs RR were left and black with 3 pawns to white's none. The endgame was very long, eventually AllieStein found a way to safely push its pawns for the win. The game lasted 160 moves.


Featured game: Houdini - AllieStein
Premier division, game 6
Link to game on TCEC

Evals stayed low for the first 40 moves with most pawns on the board. Houdini opened the queen side and evals increased, though they stayed below 1. The engines exchanged pieces and pawns gradually, and reached a RN vs RB position on move 60.

AllieStein's bishop was weak, to improve its mobility AllieStein gave up the c4 passer. The black pieces moved forward and attacked the white king and pawns. Material was equal but Houdini blocked the center and the black pieces couldn't get back, the evals jumped over 2. 

Houdini pushed the d passer forward and AlllieStein couldn't stop it in time. The game was adjudicated with Houdini close to mate.

Season 15 division 1 results

Final crosstable



KomodoMCTS and AllieStein promote to the premier division. KomodoMCTS will try to stay in the premier division, it seems to have solved the stabilllity problems that caused it to drop to division 1 last season. AllieStein started this season in division 4 and climbed all the way to the top. It is the second NN engine in the premier division after Leela.

Jonny and Chiron are relegated to division 2. Of the 4 engines that stayed in division 1 last season only Laser seems to be improving and strong enough to face the newcomers. Chiron still has stability problems, Fizbo and Jonny fought each other and in the end Fizbo survived.

The race for the top 2 places was close for a while. AllieStein had a weaker second half with only 2 wins and one loss, while Xiphos and Laser were not too far behind. In the end AllieStein held 2nd place comfortaby enough. Andscacs started weak but ended the division stronger, including two quality wins against AllieStein and Laser. The race against relegation was close. Jonny beat Fizbo in RR4 and closed the gap. A second win put Jonny ahead of Fizbo, but in the last round Jonny lost and the scores were tied in the end. Fizbo survived on a tiebreak, it had more wins than Jonny.

The engines that will play in the premier division: Stockfish, Leela, Komodo, Houdini, Fire, Ethereal, KomodoMCTS, AllieStein. The engines will play 3 DRRs with time control of 90+5.

A few interesting games

Chiron - Laser: The game reached a BN vs BN position on move 30. Evals were negative and they increased very slowly as Laser outplayed Chiron in a long endgame. After exchanging a bishop for a knight Laser's remaining knight was much stronger than the white bishop. Chiron had to defend its weak pawns and eventually couldn't stop the black king penetrating the queen side and winning the game.

Xiphos - Fizbo: There were many early exchanges, only RB vs NN remained on move 27 with Fizbo two pawns up. Xiphos opened a file on the king side and moved the rook behind the black pawns. Fizbo couldn't prevent the creation of a king side passer that won the game for Xiphos.

KomodoMCTS - AllieStein: A 20 move miniature that ended in a repetition draw.

Chiron - Xiphos: Xiphos gave a knight for pawns and forced the white king to move uncastled early in the game. Xiphos had a queen side passer and Chiron's king side rook was trapped in the corner. Chiron lost a piece when it tried to free its rook. The game reached a rook ending with Xiphos 3 pawns up, a straightforward win.

KomodoMCTS - Fizbo: Fizbo gave a pawn at the start, evals increased very slowly as the engines exchanged pieces. On move 46 only QNN vs QBN were left and evals were over 1.5. Ten moves later the engines reduced to a N vs B ending. KomodoMCTS used the extra pawn to create a queen side passer. Fizbo lost the bishop to stop the passer and the game was over.

Chiron - KomodoMCTS: The game reached a RR vs RNN position on move 25 with Chiron 2 pawns up and evals close to 0. There were many pawns on the board and the black knights were more effective than the rooks. KomodoMCTS outplayed Chiron, it captured a pawn and created a pawn majority on the king side. The threat of a passer was enough to force Chiron to give a rook for a knight and the game was adjudicated.

Jonny - Xiphos: Jonny was a pawn up with two connected passers on the queen side, yet evals turned negative due to Xiphos controlling the light squares and a hole in the white king's defense. Xiphos' eval jumped when it pushed pawns on the king side. Jonny exchanged pieces and gave a bishop but couldn't get out of trouble, the game was adjudicated before Xiphos won more material.

AllieStein - Xiphos: The engines castled in opposite directions, AllieStein pushed a pawn to h6 and its eval started to increase. The game reached a QRB vs QRN position on move 22, AllieStein's eval jumped over 2 after it created a queen side passer. After exchanging queens AllieStein pushed the passer to a6, Xiphos had to block it with its knight. Eventually the white king penetrated the king side and captured two pawns, winning the game.

Andscacs - Jonny: The game reached a QR vs QB position on move 26. Jonny protected its center pawns with the bishop, but its defense crumbled after Andscacs opened the king side. After exchanging queens Jonny couldn't stop the white pawns on both sides.

KomodoMCTS - Laser: Evals were low for the first 50 moves, the position was closed except for a file on the queen side that KomodoMCTS controlled with its rooks. Laser exchanged bishops and allowed KomodoMCTS to take over the back rank in a QRR vs QRR position, evals started to jump quickly. The engines reduced to a queen ending, KomodoMCTS was a pawn up and that was enough for a win.

Fizbo - Chiron: Chiron captured a rook for a bishop and Fizbo's eval jumped over 1. Chiron had a rook and bishop trapped on the queen side, the white pieces were very active and they had many targets. Fizbo managed to get the material back and after several exchanges the game reached a QN vs RRB position. By the time Chiron freed its trapped rook Fizbo gained more material, it was a pawn up in a Q vs RB won ending.

Chiron - AllieStein: The network crashed, the game was later resumed and ended in a draw.

Laser - Fizbo: Laser had an eval advantage under 1 from the start. It pushed a pawn on the king side and punched a hole in the black king's defense. The engines exchanged down to a QRR vs QRR position and the black king walked to the queen side. Evals started to jump after Laser opened the queen side, it went a pawn up and exposed the black king and the game was adjudicated.

Xiphos - Andscacs: The center was locked and Xiphos attacked the queen side. It went a pawn up and created a passer in the center. The passer reached the 7th rank and evals were over 4. Andscacs captured the passer but lost a piece, the game was adjudicated soon after that in a QRB vs QR position.

After RR3: KomodoMCTS +6, AllieStein +5, Xiphos and Laser +2, Andscacs +0, Fizbo -2, Jonny -5, Chiron -8. Both the top 2 and the bottom 2 have a gap of 1.5 points to the closest engine. There are 7 games per engine left to play.

AllieStein - Andscacs: See featured game below. This was AllieStein's first loss in the division.

Jonny - Fizbo: Jonny was a pawn up, the game reached a QRR vs QRR position with two passers each for both engines. Fizbo pushed a passer to the 2nd rank, then pushed the second and Jonny's eval jumped over 5. The black king was exposed to attack while black passers shielded the white king. Jonny chased the black king, capturing pawns in the process. The result was a double rook ending with Jonny two pawns up and a win. Jonny's first win in the division.

Laser - Chiron: The engines exchanged pieces until only BN vs BN were left on move 29. Laser captured a pawn and exchanged a knight for a bishop, evals increased over 2.5. Then Laser captured a second pawn and created connected passers on the queen side, enough for a win. Two wins for Laser in this opening.

Five rounds to go: KomodoMCTS +6, AllieStein +4, Laser +3, Xiphos +2, Andscacs +1, Fizbo -3, Jonny -4, Chiron -9. Two critical wins for Jonny and Laser, together with a loss for AllieStein, and the gaps at the top and bottom of the table are down to 0.5 points.

AllieStein - KomodoMCTS: AllieStein had an eval advantage from the start, it pushed pawns on the queen side and had more space. On move 26 AllieStein sacrificed a knight and its eval jumped over 2.5, KomodoMCTS saw the sacrifice coming but thought it could hold. Suddenly AllieStein had connected pawns in the center on ranks 6 and 7, KomodoMCTS saw the problem but too late. It gave material to stop the pawns and the game reached a RR vs RN position. The game went on for 30 more moves, eventually AllieStein went up 2 pawns and the game was adjudicated.

Xiphos - Chiron: Xiphos played better in a closed position, it patiently increased the pressure on the weak black pawns until Chiron's defense crumbled. Evals were over 4 when Xiphos captured a pawn, Chiron started to lose material and the game was over quickly. Xiphos won this opening from both sides.

Fizbo - KomodoMCTS: The engines castled in opposite directions, Fizbo pushed pawns on the king side but it did not have enough strength for an attack on the black king. Meanwhile KomodoMCTS' bishops both targeted the white king, and negative evals started to jump when the center opened. KomodoMCTS increased the pressure with its queen and rook on a open file, Fizbo could not defend and the game was adjudicated within a few moves. KomodoMCTS won this opening from both sides.


Three rounds to go: KomodoMCTS +6, AllieStein +5, Laser and Xiphos +3, Andscacs +1, Fizbo and Jonny -4, Chiron -10. Still nothing decided. AllieStein increased the gap to 1 point at the top. Fizbo and Jonny are tied, Fizbo has more wins and has a tiebreak advantage.

Andscacs - Laser: The game reached a RBN vs RBB position on move 32, Andscacs had an eval advantage under 1 with equal material. Laser exchanged pieces and reduced to a bishop ending, but it chose to take the wrong bishop and ended with same color bishops, evals jumped over 2.5. Laser couldn't defend its pawns and Andscacs created a passer to win.

Laser drops 1.5 points behind AllieStein and with 2 games to go it is almost surely out of the promotion race. Jonny and Fizbo are still tied.

Jonny - Andscacs: Jonny's eval was over 1 after it created a pawn majority on the queen side. Andscacs had a central passer and it felt relatively safe. Jonny pushed its pawns and its eval slowly increased, Andscacs miscalculated and thought it could counter with an attack on the white king and get a draw. It soon realized its mistake but Jonny was two pawns up in a won QR vs QR ending. Two white wins in this opening.

Xiphos drew its game against AllieStein and lost its chance to close the gap. It is 1 point behind, AllieStein has the head-to-head tiebreak advantage as well so Xiphos is out. Jonny's win puts it 0.5 points ahead of Fizbo before the last round. Fizbo has the tiebreak advantage (more wins), it needs to score better that Jonny in the last round.

KomodoMCTS - Jonny: The engines castled in opposite directions. Jonny pushed pawns on the queen side, it was not fast enough and KomodoMCTS took the initiative. KomodoMCTS pushed pawns on the king side and opened a file facing the black king. It increased the pressure and the evals increased , after a long series of exchanges KomodoMCTS won a piece and reduced to a winning BN vs B ending.

Jonny needed a draw to survive following Fizbo's draw against Laser. With this loss Jonny finishes 7th on a tiebreak and is relegated.


Featured game: AllieStein - Andscacs
Division 1, game 85
Link to game on TCEC

AllieStein had an eval advantage from the start. The engines castled in opposite directions, AllieStein pushed pawns on the king side while Andscacs opened a file on the queen side near the white king. Andscacs attacked with its queen and forced the white king to the center, both evals turned negative quite unexpectedly, AllieStein appears to have missed something.

Andscacs attacked through the center and opened files, while it gave a rook for a bishop. Evals were negative over 1.5, the engines exchanged down to a QRR vs QRN position with the white king completely exposed in the center and surrounded without the ability to move.

AllieStein had to give material to escape a mating net, the game reached a RR vs Q ending, Andscacs two pawns up. Evals were over 2 without change for a while. Could AllieStein hold this after all?

Andscacs chose to ignore its queen side pawns and it created a passer on the king side. AllieStein thought it had a chance when it captured both the black pawns on the queen side. This was a mistake and Andscacs' eval jumped over 7,  now AllieStein lost control of the black passer on the king side.

Andscacs pushed the h pawn and AllieStein could not stop it without losing a rook. The game was adjudicated with the passer about to promote.

Season 15 division 1 statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

 
Final draw rate was 65.2%.


Game termination

The three most common game termination causes were:
32.1% - TCEC win rule

31.3% - TCEC draw rule
17.0% - SyzygyTB, 3-Fold repetition

Chiron crashed once in the division.

Moves per game

 
Median= 56
Average= 66.6

There were 14 games longer than 100 moves, the longest was 180 moves (Game 13, AllieStein - Jonny, draw).

Time per game (hours)

 
Median= 1:53
Average= 1:49

Openings

There were 12-ply book openings in this stage chosen by Cato. The first letter of the ECO codes was distributed as follows:


The engines had almost no freedom to choose the opening variant. 83.9% of the game pairs repeated the same ECO code twice, and 75.0% repeated the same opening variant. Only in 1.8% of the game pairs (one game pair) the ECO first letter was not repeated twice.

Reverse pairs, wins

 
Reverse pairs, same moves 



Pairs of reverse games diverged very quickly, 42.9% diverged immediately out of book, 76.8% of the pairs diverged at most after 1 move. There were many long sequences of repeated moves, the longest was 20 plys (Laser - Jonny, games 68 and 96, QGD semi-Slav Meran variation, two draws).

Season 15 division 1 after RR2

Crosstable after RR2

The table is getting clearer with half of the division complete. AllieStein and KomodoMCTS are leading, they are the only engines that are consistently winning games while almost not losing. AllieStein is close to completing the journey from division 4 to the premier division in one season, I haven't seen it make serious blunders in this division. Jonny and Chiron are at the bottom with the opposite picture. Chiron crashed once against AllieStein, it has been reduced to 32 threads and is stable since then. Laser is the only other engine with a positive score, it has one win and 13 draws. I thought Andscacs should perform better, it was in the premier division for a few seasons. The engines still have to play 14 games each, so anything can happen and we may see surprises yet. 

A few interesting games

KomodoMCTS - Xiphos: KomodoMCTS had an early eval advantage and a passer in the center. The engines exchanged most pieces and opened the position with only RBB vs RR remaining on move 39. The white bishops were strong and KomodoMCTS won the endgame.


Fizbo - Jonny: Fizbo attacked the king side and sacrificed material to expose the black king. Jonny survived the attack but evals were high, eventually Fizbo won two pawns and reduced to a winning BN vs BN endgame.

Xiphos - Fizbo: Xiphos had an advantage from the start, Fizbo's pieces were pushed back. Xiphos opened the king side and evals jumped up quickly. Fizbo countered and exposed the white king. Xiphos was a piece up, it reduced to a QN vs Q endgame and the game was adjudicated a few moves later.

Andscacs - KomodoMCTS: KomodoMCTS took over after Andscacs traded Q for RR on move 19. The game reached a RRB vs QN position on move 32. KomodoMCTS slowly improved its position and Andscacs was busy defending its pieces. The breakthrough came when KomodoMCTS pushed its king side pawns and opened files near the white king. The added mate threat allowed KomodoMCTS to create a passer on the queen side and later win a piece. The game ended in a tablebase R vs Q win.

Fizbo - Andscacs: Andscacs concentrated forces on the king side and Fizbo used this to attack on the queen side. Fizbo opened files for its major pieces and Andscacs was caught without sufficient defenders. Andscacs gave two pieces and tried to counter with an attack on the white king, Fizbo exchanged down to a winning tablebase position.

Andscacs - Chiron: Evals were close to 0 in the first 30 moves. The engines opened the queen side and Chiron created a passer, Andscacs pressed on the king side. Chiron was not careful enough and it lost a rook for a knight to defend its king side. Andscacs reduced to a RR vs RN position, removed the black passer and went a pawn up. The game was adjudicated after Andscacs pushed a pawn in the center with support of its king.

AllieStein - Xiphos: AllieStein had a eval advantage from the start, the engines followed a Benoni defense line with a BN vs R imbalance. By move 32 only RB vs R remained, black 3 pawns up. AllieStein stopped the black pawns and created a queen side passer, enough for a win.

KomodoMCTS - Laser: KomodoMCTS was up a knight for a pawn and evals were over 2 for a while, but Laser compensated with a passer on the 2nd rank and KomodoMCTS settled for a perpetual check draw.

Chiron - AllieStein: Chiron crashed without making a move, it was reduced to 32 threads.

Xiphos - KomodoMCTS: Most pawns remained on the board and after several exchanges the engines started to shuffle from move 38. Xiphos opened the queen side and took conrol of a file 40 moves later, KomodoMCTS had a passer as compensation and the engines continued to shuffle. Xiphos captured the black passer and attacked the back ranks, it was able to reduce to a RB vs RN position, a pawn up with an advanced passer in the center. KomodoMCTS could not protect its pawns and the game was adjudicated with white 3 pawns up. This opening had two white wins.

Chiron - Jonny: Chiron gave a pawn but had an eval advantage after the start. Chiron pushed pawns on the king side and evals jumped over 2, both kings became exposed but the black king was under attack. Jonny gave the pawn back and exchanged queens, Chiron went up a pawn and had two passers facing the black king. Jonny couldn't hold and the game was adjudicated with Chiron a piece up.

Fizbo - Xiphos: Xiphos chose a line with a Q vs RN imbalance, Fizbo's eval was over 1. Fizbo had a passer on the queen side and a pawn on h6, threatening the black king on the dark squares. Xiphos gave a rook for the passer and the white DS bishop.Fizbo opened the king side and the black king walked to the center, surrounded by pieces. Fizbo reduced to a QB vs RBB position and created a queen side passer, the game was adjudicated when the passer reached the 6th rank. Two white wins in this opening.

KomodoMCTS - Andscacs:  See featured game below. KomodoMCTS won this opening from both sides.

Andscacs - Fizbo: Evals started to increase after move 25, Andscacs' rooks controlled the central files and its LS bishop had a open diagonal near the black king. Andscacs used the threat on the king side to capture three pawns on the queen side, and that was enough for a win. Two white wins in this opening.

Jonny - Laser: Jonny gave a knight for pawns early in the game, it was 4 pawns up and evals were low. After 40 moves evals turned negative and slowly increased. The engines reduced to a R vs RB position, Laser started capturing the white pawns while keeping one black pawn safe. Jonny was down to 2 pawns, Laser separated the white king from the pawns and the game was adjudicated.

Chiron - Andscacs: Evals were low and negative, slowly increasing. The engines were active on the queen side, on move 34 each engines had one pawn left there. Chiron pushed its pawn to the 7th rank before Andscacs captured it, and the game reached a NN vs BN position with Andscacs a pawn up on move 51. The engines exchanged a pair of knights and the black king came forward. Andscacs captured a second pawn and that was good for a win. Andscacs won this opening from both sides.

AllieStein - Fizbo: Fizbo played the opening badly, it lost a knight for a pawn a few moves after book and AllieStein's eval jumped over 4. Fizbo captured a pawn and the engines exchanged down to a QRN vs QR position on move 29. AllieStein took a long time to convert the win, the game was adjudicated on move 101.

KomodoMCTS - Chiron: KomodoMCTS gave a pawn and attacked through the center. The engines exchanged most pieces and reached an opposite color bishop ending with KomodoMCTS a pawn up. The engines shuffled for alomst 100 moves and then Chiron blundered and lost the game, though the winning line was not clear to me when the game was adjudicated.

Xiphos - Jonny: a 15-move miniature that ended in a repetition draw.

AllieStein - Chiron: The engines castled in opposite directions and AllieStein pushed pawns on the king side. It gave a pawn but its eval was over 2 after the king side opened and a white pawn reached h6. Material was equal but AllieStein's king was safer and its pawn structure was better. AllieStein went a pawn up and created passers on the queen side, it again took its time but the win was certain. The game was adjudicated in a winning rook ending. AllieStein won this opening from both sides, though the first win was a Chiron crash.

Featured game: KomodoMCTS - Andscacs
Division 1, game 36
Link to game on TCEC

Evals were low for the first 35 moves. Andscacs pushed its king side pawns forward, leaving its king exposed. Yet KomodoMCTS concentrated on the center and queen side and did not try to attack the black king.


KomodoMCTS pushed the c pawn and attacked the center, its eval jumped over 1. Andscacs took the pawn and this was probably a mistake. This allowed KomodoMCTS to open the center and clear the long diagonal of pawns, evals jumped high very quickly. KomodoMCTS put a queen and a bishop on the long diagonal, with a direct line to the black king and with only pieces in the way.



Andscacs couldn't handle all the threats and its defense crumbled. It started losing material, giving a queen for a rook.



Andscacs' position was hopeless, the game was adjudicated.