Season 17 premier division, all engines, after 150 games

Crosstable after 150 games

Leela  won 5 of its last 9 games, quite incredible. It now has the same number of wins as Stockfish, and Leela played 5 games less. Stockfish is still disappointing in games against GPU engines, so far it has one win in 12 games. AllieStein lost twice in its last 9 games, and won only one. This means it is 2 full points behind Leela and its chances of qualifying to the superfinal are much lower.

Houdini and ScorpioNN continue to accumulate losses, and are sure relegation candidates. KomodoMCTS has a -3 score, it needs a miracle to overtake two engines and survive the division. The remaining 4 engines have scores of -1 and 0, and at least one of them will also relegate.

Interesting games

Game 127, Leela - Fire: Leela had an eval around 1 after the opening. It placed a bishop on d6 and Fire gave a rook to get rid of it. Evals crawled up slowly, not a lot seemed to be happening on the board. Evals went over 2 after Leela pushed pawns on the king side and the engines reduced to a RR vs RN position. As more pawns were exchanged evals kept climbing. In the end only two pawns were left each, Leela found the right moment to exchange a rook for the knight and capture a pawn. Two advanced passers were enough for a win in the rook ending.


Game 128, Stoofvlees - Houdini: Stoofvlees gave a rook for a bishop early in the game, yet kept a small eval advantage, perhaps due to a bishop pair and better development. It pushed a pawn on the king side and created a hole in the pawns defending the black king. Houdini pushed pawns on the queen side and moved a rook forward in the center. Stoofvlees allowed the rook to take two pawns, Houdini gave the rook back for a knight while evals started to climb. Stoofvlees increased the pressure on the exposed black king, its bishop pair controlled the center. Stoofvlees captured the black knight, and after exchanging queens it also captured the black bishop. Houdini's last try was a passer on the 2nd rank, Stoofvlees lost a bishop for it but the remaining RB vs R position was a win for white.

Game 132, Ethereal - AllieStein: See featured game below.

Game 134, Leela - Ethereal: Most minor pieces were exchanged early, on move 22 each engine had its major pieces and one bishop. Leela had an eval over 1, it managed to capture a pawn and then the engines exchanged more pieces. On move 51 the game reached an opposite color bishop ending, Leela was up a pawn but usually this is not enough for a win. After a few pawn exchanges Leela created a connected pair of passers, Ethereal was able to block them and the engines shuffled for 20 moves. Surprisingly Ethereal blundered, it let the white king move closer to the pawns and they became unstoppable.

Game 139, ScorpioNN - Leela: ScorpioNN gave a rook for a knight in a closed position to create an advanced passer. Then ScorpioNN gave a second rook for a knight and pawn, evals remained low as Leela had only major pieces that couldn't penetrate the pawn wall. Leela's eval jumped over (negative) 1 when ScorpioNN captured a pawn and exchanged queens, this opened a file and both black rooks moved forward through it. Leela had to give some material back to stop the white passers, but the remaining N vs R ending was a win.

Game 143: Leela - Stoofvlees: Leela's eval jumped over 2 when Stoofvlees ignored a simple knight fork and lost a rook. Stoofvlees went all out with an attack on the white king, sacrificing its second rook. Leela defended with precision and countered with threats on the black king, it captured a knight and Stoofvlees realised it was doomed. Leela gave some material back to stop the attack completely, still with a rook advantage the game ended quickly with mate on the board.

Game 146, Komodo - AllieStein: AllieStein made a bad judgment call, it let Komodo open the center while the black king was not castled. Evals jumped high as more white pieces joined the attack, Komodo had several black pieces pinned around the black king. AllieStein could not avoid losing material, the game reached a QB vs BB position and was adjudicated on move 34.

Game 148,  AllieStein - Houdini: Houdini pushed its h pawn from the start, AllieStein allowed it to take the pawn on g2. The queen side was blocked and the engines exchanged pieces on the king side. Houdini gave a rook for a bishop and a knight and the game reached a QR vs QBN position, white two pawns up. For a long while AllieStein gave futile checks with its queen, evals increased only after it pushed its h pawn forward. When it reached h6 Houdini exchanged queens to capture it, the white rook moved forward to capture a pawn and create a passer. AllieStein traded the passer for a bishop and the R vs N ending was a win.

Game 149, Leela - Komodo: Leela kept its king in the center, with open files on both sides of the board. Queens were exchanged early and Leela had an eval around 1. For 25 moves the engines mostly shuffled, Komodo was clearly waiting for Leela to try something. On move 51 Leela finally pushed a pawn and opened the queen side, evals started to increase. Komodo's bishop couldn't get out of the king side, so Leela had an advantage on the queen side. After exchanging most pieces Leela had a queen side passer in a RN vs RB position. By the time Komodo freed its bishop the passer was advancing with the support of the white king. Komodo lost its rook to stop the passer, the game was over when Leela's eval became high enough.


Featured game: Ethereal - AllieStein
Premier division, game 132
Link to game on TCEC

Ethereal had an eval advantage from the opening, it was better developed and had a space advantage. AllieStein managed to castle its king and develop its pieces, evals remained stable for a while. 

Ethereal started to press on the queen side and evals increased gradually, then Ethereal gave a knight for a pawn. This created a passer on the 6th rank and evals were over 2. AllieStein had pieces busy defending a pawn on the queen side, and its DS bishop was almost trapped.

AllieStein lost the DS bishop, gave a rook for one of the white bishops and removed the passer. Ethereal then gave the material back, created a queen side passer and placed a rook on the 7th rank.

The added threat of mate was too much to handle, enough for a win a few moves later.

Season 17 premier division, all engines, after 120 games

Crosstable after 120 games

There are three engines without loss and a positive score, Stockfish with 7/28 wins, AllieStein with 4/18 and Leela with 2/18. At this rate we will see a replay of last season's superfinal between Stockfish and AllieStein. Leela's win rate is disappointing, it drew all 12 games against CPU engines so far. Stockfish's result agains GPU engines isn't great as well, so far one win in 8 games. AllieStein has a good chance of winning the premier division.

ScorpioNN is likely to finish last, it has a score of -4 after 18 games, compared to Houdini with -4 in 28 games. KomodoMCTS will probably be the 3rd engine to relegate. One of the 4 engines with scores close to even - Komodo, Fire, Ethereal, Stoofvlees will be the 4th to relegate.

There were 10 decisive games in the 30 reverse games, compared to 3 in the first 30 GPU games. 


Interesting games

Game 92, Stoofvlees - Komodo: There were no exchanges after the opening except one pair of pawns. Stoofvlees had a space advantage, its eval was around 1 and it started to increase after move 25, though the engines seemed to be shuffling. Gradually the black pieces were pushed back and struggled to find moves. After exchanging knights Stoofvlees put its remaining knight on c6, its eval over 3. After the king side was locked Komodo gave a rook to get rid of the white knight, Stoofvlees slowly prepared its queen side attack. When it was ready Stoofvlees opened files on the queen side and exchanged down to a RB vs BN position. Stoofvlees captured a pawn and the game was adjudicated before it captured more.

Game 94, AllieStein - Fire: See featured game below.

Game 95, Ethereal - ScorpioNN: Ethereal had a small eval advantage after the opening, its eval jumped over 2 after a ScorpioNN blunder. A series of exchanges led to a QBN vs QR position, the exposed black king gave Ethereal a significant advantage. Ethereal sacrificed its bishop but had the black king in a mating net. ScorpioNN soon lost its queen and then was mated.

Game 96, KomodoMCTS - AllieStein: KomodoMCTS forced a stalemate draw with a queen sacrifice. AllieStein's eval went crazy for a few moves before the end.

Game 99, ScorpioNN - Komodo: Another ScorpioNN blunder. This time it thought it could capture a pawn, noticing a move later that Komodo loses its queen temporarily but can immediately trap the white queen. This led to a R vs BN imbalance, the black bishops and knights were very strong. Eventually Komodo captured a knight and the game was over not long after with another mate.

Game 102, AllieStein - Ethereal: AllieStein's eval increased after the opening, reaching about 2.5. All pawns were on the board, there were several exchanges of minor pieces and the engines shuffled for a while. Ethereal captured a hanging pawn while AllieStein pushed pawns forward on the king side and created an advanced passer. Evals started to increase again after the position opened a little and only major pieces remained. AllieStein attacked the black king, Ethereal exchanged queens to stop the attack. The white king came forward, Ethereal had to keep an eye on the white passer and this let AllieStein capture more pawns. The game was adjudicated in a double rook ending with white two pawns up.

Game 107, Stoofvlees - Ethereal: Stoofvlees gave two pawns early, the black pawn line had holes on both sides and the black king stayed in the center without castling. After a series of exchanges Ethereal was down a knight and up 3 pawns, the game reached a RBN vs RB position with evals over 2. Stoofvlees captured a pawn and created a king side passer. After exchanging knight for bishop the black rook moved forward and captured another pawn, the game was adjudicated a few moves later.

Game 109, Leela - ScorpioNN: Both engines did not castle kings, and moved their pieces behind the pawn lines. Leela's eval was around 1.5 for a long time as the engines shuffled, evals came down as the 50-move draw approached. Just before the draw ScorpioNN grabbed a pawn, the engines reduced to a RN vs RB position and evals went up again. Leela had two advancing passers and ScorpioNN gave the bishop to stop them. After exchanging rooks the white knight was on time to stop the black pawns and the white king captured a pawn to create a winning passer.

Game 110, AllieStein - Stoofvlees: AlllieStein started the game with an eval over 1, and its eval increased very fast to over 10 by move 23. It developed its pieces rapidly, after opening the king side the black king was in danger. The engines reduced to a QR vs QR position, material was equal but the exposed black king was a big advantage for AllieStein. Stoofvlees escaped being mated but it lost the rook and the game was adjudicated.

Game 117, ScorpioNN - KomodoMCTS: ScorpioNN had a space advantage after the opening, its eval increased quickly. The engines opened the queen side and exchanged queens, then started to shuffle. ScorpioNN waited for the right moment to open the king side and capture a rook for a bishop. The engines shuffled again in a RRB vs RBN position, ScorpioNN had an advanced passer that KomodoMCTS blocked with its bishop. The engines exchanged rooks, it seemed that ScorpioNN was not in a hurry to win but eventually the material advantage was enough. The game was adjudicated when KomodoMCTS had no pawns and ScorpioNN had two advanced passers. There were two white wins in this opening, too biased perhaps.

Game 120, Stockfish - Stoofvlees: Stockfish gave a pawn early and created a gap in the pawn lines on the queen side. All pieces were on the board until move 23, and evals were close to 0. Stoofvlees pushed a pawn on the king side all the way to f3, then offered a rook and threatened to expose the white king. Stockfish waited until it thought it was safe to take the rook, evals stayed low even though the black queen was facing the white king. Then Stockfish's eval jumped over 4 suddenly, Stoofvlees thought it had at least a perpetual check draw for 4 additional moves before it realised Stockfish can escape. The black attack was over after a few piece exchanges and the material advantage became decisive. The game was adjudicated with mate a few moves away.

Featured game: AllieStein - Fire
Premier division, game 94
Link to game on TCEC

There were many exchanges after the opening, clearing the center. Fire went a pawn up yet AllieStein's eval was over 1. Fire's queen side was not developed, its bishop almost trapped. The black king was vulnerable especially on the dark squares.

AllieStein gave a second pawn to put a bishop on the long diagonal threatening the black king, its eval jumped high. Fire's eval slowly reacted, it gave a rook to remove the bishop and the game reached a R vs N position, black a pawn up. AllieStein's eval was already way over 10.

AllieStein pushed its pawns forward, but then it started to shuffle without purpose. After 30 moves it finally captured a pawn and created a passer on the king side.

The game was adjudicated a few moves later.

 

Season 17 premier division, all engines, after 90 games

Crosstable after 90 games

There were only 3 decisive games in the first 30 games involving GPU engines, and only one of these was a CPU-GPU match. As a result the CPU engine standings did not change. In the GPU part of the table Leela and AllieStein have one win each, a better win rate than Fire which is currently in 2nd place. Still very early to make predictions.

We have seen the characteristic properties of GPU engines: longer games, mate on the board, the inability to convert won endgames. The increase in draw rate was unexpected but it may still improve.

There were two network crashes in CPU-GPU games.

Interesting games

Game 64, Fire - AllieStein: AllieStein was sure it was better in a BN vs RN position with white 3 pawns up. It gave the knight for pawns and pushed a passer to the 2nd rank, its eval over (negative) 10 for a few moves. Fire was willing to trade its bishop for the passer in case it tried to promote, and AllieStein knew this would lead to a draw. Instead the engines shuffled for almost 50 moves, and only then AllieStein made the trade, its eval coming down to around 1.5. Still AllieStein wouldn't give up and the game ended in a 50-move draw on move 161.


Game 69, Komodo - ScorpioNN: ScorpioNN was a pawn up and its (negative) eval kept increasing. ScorpioNN's eval peaked over 4, Komodo also thought it was behind with an eval of 2. It seemed ScorpioNN could attack on the king side, but it just kept shuffling as evals slowly came down. The engines started to exchange everything, the game ended in a tablebase draw on move 150.

Game 73, ScorpioNN - AllieStein: AllieStein captured a pawn with its queen and then retreated, there was no eval change so the pawn was not poisoned. On the contrary, its (negative) eval started to increase. ScorpioNN tried to press on the queen side, AllieStein gave a rook for a knight and broke through the center. After some shuffling AllieStein captured another pawn, the game reached a QR vs QB position with black 3 pawns up. The black pawns moved forward and ScorpioNN couldn't stop one from promoting, the game ended with mate on the board. First decisive game for a GPU engine.

Game 83, Leela - Stoofvlees: Stoofvlees gave a lot of material early in the game, it was down a full rook on move 25. The white king was on the run from the black queen and bishops, Leela slowly untangled its pieces and then the material advantage became evident. Stoofvlees tried to push a passer and lost it in the end, it tried giving checks with its queen but Leela found safety for its king. The game ended with mate on the board.

Game 84, ScorpioNN - Stoofvlees: See featured game below.

Game 87, KomodoMCTS - ScorpioNN: There were no exchanges in the first 25 moves. The center was blocked and the engines opened files in the flanks. KomodoMCTS was active on the queen side and evals started to increase, ScorpioNN was weak there with a blocked pawn on c7 and an almost trapped bishop on c8. KomodoMCTS broke through the queen side, ScorpioNN countered on the king side and there was a massive exchange. The game reached a queen ending, KomodoMCTS was a pawn up and its pawns were more advanced. The game ended in mate.


Featured game: ScorpioNN - Stoofvlees
Premier division, game 84
Link to game on TCEC

ScorpioNN had a space advantage, it pushed its pawns forward and the black pieces had to move back. Stoofvlees gave material to open the board and to counter with an attack on the exposed white king. Evals went over 2, Stoofvlees was a rook down and both engines didn't believe the king side attack compensated for the material loss.

ScorpioNN avoided threats of a perpetual check, Stoofvlees chased the white king but it escaped to the queen side where it had the protection of its pieces. Along the way Stoofvlees captured a few pawns. ScorpioNN forced a queen exchange that stopped the threats on the white king. The game reached a RBN vs BN position with black 4 pawns up.

All evals were very high, ScorpioNN just had to get rid of a few pawns and exchanged pieces, it seemed an easy win. ScorpioNN went after the black bishop first, it exchanged its knight for it, losing its last pawn in the process. Both engines seemed less sure about the outcome, their evals drifted down.

Stoofvlees kept three pawns on the king side, and together with the knight it built a fortress that ScorpioNN couldn't break. The white king stood in the way of the pawns without moving, and the white pieces could not mate the black king without its help. The engines just shuffled for 50 moves, and ScorpioNN ended the game by giving the bishop for a pawn. The draw was quite unbelievable.

Season 17 premier division, CPU only full results

Final crosstable for CPU only games

Stockfish continues to dominate the CPU part of the division. It added 3 more wins in white, KomodoMCTS is the only engine it hasn't beaten. Fire is still in 2nd place, the only other engine with a positive score, though it lost once to Stockfish. Houdini continues to be weak, both it and KomodoMCTS have a good chance of relegating this season.

The GPU engines will start playing in the division in the next phase. I'm looking forward to these games, the CPU-GPU matchup of this season. I will continue to report every 30 games, each time a full RR is completed. This is as close to a balanced table as we're going to get this season.


Interesting games

Game 31, Stockfish - Ethereal: The first pair of pawns was exchanged on move 27. Ethereal used minor pieces to close gaps in its pawn line, evals were over 1 but the position looked stable. The engines shuffled for 30 moves, then Stockfish exchanged a few pieces and opened a file on the queen side, its eval jumping over 2. After some more shuffling Stockfish went two pawns up and reduced to a RB vs RN ending. The game continued for 20 more moves, Stockfish pushed pawns forward until adjudication.

Game 39, Fire - KomodoMCTS: KomodoMCTS sacrificed a bishop for pawns, the white king remained in the center facing two black central pawns. Fire gave the piece back to remove the pawns, the engines exchanged most pieces and Fire reduced to a rook ending with one pawn advantage. KomodoMCTS thought it was safe, with evals at 0 even when Fire was seeing mate in the future. However it was Fire that was right and the game was over quickly.

Game 40, Ethereal - KomodoMCTS: Pawn lines were mostly stable from move 22, Ethereal gave a pawn but it had an eval advantage. The engines shuffled for a long time, with a few pawn moves and exchanges that reset the 50-move counter. On move 80 Ethereal's eval jumped as it gave a second pawn and opened the king side. Ethereal sacrificed a knight, its attack on the black king was strong and KomodoMCTS gave its queen for a rook to stop it. The game reached a Q vs RB ending, the queen was much stronger and Ethereal soon captured enough material to win.

Game 41, Stockfish - Fire: See featured game below.

Game 53, Stockfish - Houdini: After 35 moves evals were close to 0, Houdini was a pawn up and Stockfish had strong major pieces in the center. Stockfish's eval jumped over 1 when the black knight got into trouble. After a series of threats and pins Houdini gave a rook for a bishop and reduced to a RR vs RN position, black two pawns up. The white rooks were very active, Houdini had a passer it pushed to the 2nd rank. Stockfish was very patient, it blocked the passer with its king and captured two pawns. Houdini avoided exchanging rooks, in the end it had to give up the passer and the game was finally adjudicated on move 87.

Game 58, Ethereal - Houdini: All pieces were on the board, the engines exchanged a pair of pawns and opened the h file. Houdini took over the file and evals increased to about 1 (negative). Ethereal gave a pawn on the queen side, all pieces were still on the board as the engines shuffled for a while. Evals turned positive gradually, a series of exchanges opened the position and only QRB vs QRB remained. Houdini was a pawn up but Ethereal had a dangerous queen side passer. After exchanging queens Ethereal started to capture black pawns. Houdini tried to push passers but could not protect them, the game was adjudicated with white 3 pawns up.

Featured game: Stockfish - Fire
Premier division, game 41
Link to game on TCEC


Fire moved its queen forward early in the game, Stockfish avoided exchanging queens, its eval was around 1. The white king looked exposed but it was safe from attack. The black king was more vulnerable.

Stockfish pushed the black queen to the queen side and then attacked the black king. Fire refused to take a sacrificed knight to keep the king side pawns, Stockfish gave a rook to take out a defending knight. Fire's eval was still close to 0, it didn't see what was coming.

Fire gave the material back and the game reached a QR vs QR position, the black king was still under threat. Both engines raced to promote a pawn, Stockfish went up a pawn and exchanged rooks.

In the end both sides promoted a pawn and lost one queen, in the queen ending the white pawns were better placed and Fire could not avoid another white promotion, the game was adjudicated quickly.

Season 17 premier division, CPU only, after RR2

The organizers have decided to order the premier division games so that the GPU hardware usage is optimized. The CPU only games will be played first without a need for a GPU machine. Then all the CPU-GPU and GPU-GPU games will be played. Eventually all games will be played (a 2xDRR tournament), but it will be very difficult to understand the relative standings of the engines until the very end.

For me this is a little disappointing, I think that the most interesting part of this division is the CPU-GPU clash and now it will be postponed and the crosstables will not be balanced for most of the division. It will be very surprising to me if Stockfish does not dominate the CPU part of the division. I would like to see whether Leela can put up a fight this season, whether AllieStein is as strong as last season, and whether Stoofvlees can beat AllieStein or Leela.

Despite these reservations, the chess is going to be of the highest level as it always is in TCEC !!

Crosstable after RR2

As expected Stockfish is in the lead with 3 wins, all when playing white. Fire is in second place with a win and no loss, quite surprising for Fire, though it may be temporary and there are many games to be played yet.
Houdini is last with 2 losses, Houdini is using only 64 threads of a possible 176 and this may affect its strength relative to the other engines.

Interesting games

Game 1, Stockfish - Ethereal: The game reached a RB vs RB position on move 33, both evals were close to 1 and Stockfish quickly went up a pawn and created a passer. Ethereal had to block the passer and Stockfish used this to capture a second pawn. Ethereal tried to counter by pushing a passer to the 2nd rank, Stockfish forced a rook exchange and the game was adjudicated.

Game 6, Stockfish - Komodo: Stockfish had a small eval advantage after the opening, which started to increase after 25 moves to over 1. By move 40 Stockfish was a pawn up with a pawn majority on the king side. After exchanging most pieces the game reached a QB vs QB position, Stockfish's eval climbed rapidly while Komodo's eval stayed around 2. The endgame was long and subtle, Komodo got the pawn back and tried to create a fortress. The white king assisted in blocking a black pawn and finally Komodo acknowledged that it was losing. The game was adjudicated with Stockfish 2 pawns up in a queen ending.

Game 9, Fire - KomodoMCTS: see featured game below.

Game 12, Komodo - Houdini: Komodo gave a pawn and opened a file on the king side, after exchanging queens it had a passer on the 6th rank facing the black king. A strong bishop on the long diagonal added pressure on the black king and evals increased over 2. Houdini had to give a rook for a knight, the engines exchanged down to a RR vs RB position. The black rook had to block the passer, Komodo started to pick up pawns and the game was adjudicated.

Game 23, Stockfish - Houdini: Houdini captured a pawn with its queen and opened a file for Stockfish facing the black king. Stockfish then gave a rook for a knight while threatening mate. Evals jumped as Stockfish increased the pressure, Houdini exchanged queens and saved its king, but Stockfish captured a rook and was a piece up. Houdini tried to defend for another 15 moves before giving up.

Featured game: Fire - KomodoMCTS
Premier division, game 9
Link to game on TCEC

KomodoMCTS opened the queen side early, its queen went forward and Fire used its pawns to push it back. Evals climbed to around 1 after Fire captured a rook for a bishop and pawn, and then placed its knight on c5.

KomodoMCTS exchanged knights on c5, at the cost of a white passer. Fire pushed the passer to the 7th rank while evals increased slowly.

KomodoMCTS tried to counter on the king side, it pushed its e passer forward and attacked with its queen. Fire kept its king safe, it exchanged pieces and traded its c passer for another on the a file.

KomodoMCTS had to abandon its passer to block the white a pawn, then lost its bishop to capture it. Fire was a rook up and the game was adjudicated a few moves later.

Season 17 league 1 playoff statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

 
Final draw rate was 66.7%.


Game termination

The three most common game termination causes were:

38.3% - SyzygyTB
23.3% - TCEC draw rule
13.3% - TCEC win rule

There was 1 crash in the stage, but that was due to a wrong parameter setting for ScorpioNN. The game was resumed after the parameter was fixed. There were 8 games with mate on the board, mostly ChessFighterNN losses.

Moves per game


Median= 72.5
Average= 74.8

These are NN-related numbers, significantly higher than in AB engine games.
There were 9 games longer than 100 moves, the longest was 148 moves (ScorpioNN - Fire, game 27, draw).

Time per game (hours)

 
Median= 2:01
Average= 1:56

Openings

There were 8-move 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, all of the game pairs repeated the same ECO code and the same opening variant twice.

Reverse pairs, wins

 
Reverse pairs, same moves

 
Pairs of reverse games diverged very quickly, 43.3% diverged immediately out of book, 83.3% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 10 plys (Ethereal - Fire games 36 and 51, Nimzo-Indian classical variation, two draws).  

Season 17 league 1 playoff, final results

Final crosstable

Fire, KomodoMCTS, ScorpioNN and Ethereal will play in the premier division, together with Stockfish, Leela, AllieStein, Komodo, Houdini and Stoofvlees.

rofChade was in the race for 4th place until the very last game of the league. It was better than Ethereal in their head to head matches, it lost the race due to its many losses to higher ranked engines.

Notable games
Game 32, Fire - rofChade: The black king was uncastled in the center, Fire gave a knight for two pawns to open the center and attack. rofChade couldn't find safety for its king and it gave a rook for a bishop to stop the attack. This led to a RR vs RBN position, Fire was 4 pawns up and that was enough to win.
Game 33, ScorpioNN - KomodoMCTS: ScorpioNN had an eval advantage from the opening, its eval climbed over 3 very quickly and then stayed there. The center was blocked and the black pieces were on the queen side, leaving the black king vulnerable. The engines mostly shuffled for a while, ScorpioNN moved its focus to the queen side. KomodoMCTS felt safe and evals slowly decreased, the engines opened a file on the queen side and exchanged a pair of rooks. Then scorpioNN broke through the center with a knight for pawns sacrifice and evals jumped back. The pressure on the black king increased until KomodoMCTS exchanged pieces and gave a bishop. ScorpioNN was up 3 pawns in a knight ending, a straightforward win.
Game 39, KomodoMCTS - rofChade: There were only a few exchanges after the opening, KomodoMCTS had a small eval advantage, evals stayed under 1 until move 35. The engines opened files on the queen side and evals jumped over 2, they continued to increase while the engines exchanged pieces. Eventually KomodoMCTS went up a bishop and the game was adjudicated.
Game 40, ChessFighterNN - rofChade: ChessFighterNN's eval increased quickly after the opening and went over 5. rofChade's eval was over 2 which was more believable. The visible advantage was two white passers and only one black passer. Despite the clear eval advantage ChessFighter did not play the right moves and rofChade was able to remove one passer and to reduce to a drawn bishop ending.

Scores after RR3: Fire +6, KomodoMCTS +4, ScorpioNN +2, Ethereal -1, rofChade -3, ChessFighterNN -8.
The most interesting race is for 3rd and 4th place. ScorpioNN is in 3rd after it adds two wins in RR3 and creates a small gap to the two engines below. rofChade loses twice in RR3 and is moving away from the premier division. Ethereal with 5 draws is in 4th place, 1 point above rofChade. There are 5 rounds left. 

Game 48, KomodoMCTS - ScorpioNN: KomodoMCTS had a small eval advantage after the opening, Evals jumped after KomodoMCTS sacrificed a knight and exposed the black king. ScorpioNN was not prepared for the deadly attack, it gave a rook to try to save its king. KomodoMCTS started to capture black pieces and ScorpioNN resigned. There were two white wins in this opening, a possible opening bias.

Scores after round 18: Fire +6, KomodoMCTS +5, ScorpioNN +1, Ethereal -1, rofChade -3, ChessFighterNN -8.
ScorpioNN lost a game but with only two rounds to go it is almost certainly going to be in the top 4. The last game in the playoff is between Ethereal and rofChade, rofChade has a tiebreak advantage so it can still overtake Ethereal with a win.  

In round 19 rofChade beat ChessFighterNN, Ethereal drew against KomodoMCTS and ScorpioNN drew against Fire. The 4th place will be determined in the last game, rofChade needs a win, any other result is good for Ethereal. There will not be a tiebreak in any case.

Game 59, Fire - KomodoMCTS: The game reached an opposite color bishop ending and appeared to be an easy draw. However, KomodoMCTS blundered and let the white king approach a pawn in a way that prevented the black bishop from defending. Fire had two advanced passers, and the game was over when one promoted to a queen.

In the last game rofChade needed a win but it was Ethereal that had an eval advantage, and the game ended in a draw.