Thursday, May 23, 2024

Season 26 superfinal games 31-40

After 40 games Stockfish leads 11-7 with 22 draws. Stockfish won two game pairs and extended its lead to 4 again. Twice Leela managed to win a game and twice Stockfish won the reverse. In both games 39-40 the losing side saw trouble before the winning side's eval reacted. Were the losing engines seeing ghosts, and proving themselves right with the wrong choice of moves?

Games 31-32 started with an 18-ply line in the Alekhine defense, four pawns attack, played in high level human games. In game 31 Stockfish gave a knight for three pawns in the center. Evals came down as the engines exchanged pieces. The game reached a RB vs R position with low evals and was adjudicated early on move 47.

In game 32 Leela captured a pawn but let Stockfish keep two pawns in the center. Stockfish's eval jumped early, it moved its queen forward on the king side and Leela moved its king without castling. Leela surrounded its king with pieces, it gave a rook for a knight, perhaps hoping that without knights it would be difficult for Stockfish to find a way to attack. However the black king side rook was trapped in the corner.

Evals continued to increase while Stockfish seemed to shuffle. On move 50 the engines exchanged queens, then the game reached a RR vs RN position and the black rook finally moved out of the corner. 

Stockfish cleared the queen side and exchanged a pair of rooks. It saw the win many moves in advance, the white king walked around the board all the way to e7. Stockfish captured pawns and created a passer, the game ended in a tablebase win. Stockfish wins the game pair, it leads 8-5.

Games 33-34 started with a line in the Modern defense played in high level human games, but not recently. In game 33 the engines played out a long PV agreement. At first Leela was up a pawn, but after several piece exchanges Stockfish regained the pawn. The game reached a QRB vs QRB position and evals started to come down. After some shuffling the engines exchanged queens and Leela captured a pawn. Leela couldn't find a way to improve and the engines shuffled, the game was adjudicated as it approached a 50 move draw. 

In game 34 Stockfish gave an early pawn, then regained it and the engines exchanged minor pieces in the center. Evals were stable around 1 until move 20m then Leela gave a rook for a bishop and pawn to expose the white king. There was a long PV agreement, Stockfish exchanged a pair of rooks and was confident its king was safe. Stockfish's eval started to increase very slowly, the game reached a QR vs QN position.

Leela didn't try to chase the white king, its eval drifted down but then started to increase as well. The white pieces without an obvious purpose, then with all pieces concentrated on the king side Stockfish pushed pawns on the queen side. Leela captured the rook for a knight while Stockfish created a doubled passer on the a file. 

Stockfish saw the win, it captured two pawns and created another passer on the king side. Leela blocked and captured one passer but couldn't prevent the queening of the other. The game ended in mate. Stockfish wins the game pair, it leads 9-5.

Games 35-36 started with a 20-ply line in the French Winawer, positional variation. In game 35 Stockfish blocked the center, Leela pushed pawns on the king side and left its king without pawn support. Stockfish opened the b file and created a passer on the queen side, Leela blocked the passer and the white king walked to the center. Regardless of the open file Leela moved its king to the queen side and exchanged a pair of rooks.

Leela opened the king side and exposed the black king. In a series of exchanges Stockfish lost its queen for pieces and the game reached a QB vs QBN position, white two pawns up with a passer on the king side. 

Stockfish captured the passer but Leela captured pawns in the center, Stockfish lost more material and the game ended in a tablebase win. 

In game 36 the engines exchanged pawns in the center, opened the queen side and exchanged queens. The black king moved forward without castling, Stockfish moved a rook forward through the queen side and exchanged a pair of rooks. The game reached a RBB vs RBN position on move 24. Stockfish moved a bishop to f8, the black knight had to stay on e8 to protect the king side pawns.

Leela captured a pawn, evals slowly increased as Stockfish pushed pawns on the king side. After the pawns stabilized Stockfish opened the king side and regained the pawn, Leela exchanged a pair of bishops.

Stockfish captured the black d pawn for its a pawn, the black knight finally moved but Stockfish let it capture a pawn and moved its king forward. The white rook moved forward and Stockfish saw the win. The engines reduced to a rook endgame, Stockfish queened a passer and mated. There were two white wins in this game pair, Stockfish leads 10-6.

Games 37-38 started with a line in the Gruenfeld defense. In game 37 there were no exchanges after the start, both kings walked to the king side without castling. On move 23 a pawn exchange opened the b file, then the engines blocked the center. The engines mostly shuffled for a while and evals came down. From move 39 the engines started to exchange pieces, Stockfish gave two pawns and moved two rooks forward on the queen side. Stockfish traded both rooks, one for a bishop, and then the game reached a QR vs QB position. Leela was a pawn up but Stockfish had enough for a draw and the game was adjudicated. In game 38 Stockfish took over the center and Leela castled its king. The white queen moved forward, in a long PV agreement the engines opened the queen side and exchanged minor pieces. Stockfish castled on move 27, an another long PV agreement the game reached a RRN vs RRB position with white a pawn up. After exchanging a pair of rooks the engines shuffled for a long time, Leela wouldn't lower its eval enough. The game was adjudicated only on move 112.

Games 39-40 started with a line in the Caro-Kann, Steinitz variation, played in high level human games. In game 39 Leela gave a knight for a pawn and forced the black king to move without castling. Evals slowly came down as the black king found safety on the king side, though the king side rook was trapped. Leela had many opportunities to capture the black rook for a knight but decided to keep the knight. In a PV agreement the engines exchanged pieces, suddenly Stockfish's eval jumped, not sure what it saw. The game reached a RR vs RRB position with white two pawns up, Leela's eval remained low.

Leela had a long think and its eval jumped over 2 as well. It captured two more pawns, Stockfish finally developed its trapped rook through the h file. The white king moved forward in the center, Leela had 4 connected passers on the queen side. Stockfish gave the bishop for one passer, the pawn chain was broken but it was not enough. 

Stockfish captured another passer but couldn't stop them all. The game ended in a tablebase win. 

In game 40 Stockfish also gave a knight for a pawn and the black king moved. Leela was surprised by Stockfish's move 12, after thinking for almost 20 minutes its eval jumped over 2. The black king remained in the center, Leela developed its king side rook through the f file and then gave it for a bishop. A knight exchange opened the center, for a while the white queen was stuck on the king side but Stockfish found a way to get it out. It moved all its major pieces to the queen side, then in a series of exchanges the engines reduced to a QB vs QBN position with white 3 pawns up. 

The black minor pieces were static, protecting pawns and themselves. The queens move around the board and Stockfish managed to push the a pawn to a6. It saw the win in its PV, Stockfish exchanged bishops and traded the a pawn for the black c pawn, then captured the black knight for another pawn. This left a queen ending with two pawns up and the game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 11-7.  


Tuesday, May 21, 2024

Season 26 superfinal games 21-30

After 30 games Stockfish leads 7-5 with 18 draws. Stockfish won a game pair and extended its lead to +4, but then Leela won two game pairs and the gap is back to +2. There was one game pair with two white wins and one with two draws. Stockfish is in the lead but Leela is fighting back, still a long way to go. 

Games 21-22 started with a rare line in QGD with an advantage for black. In game 21 the engines castled in opposite directions, Leela pushed pawns on the king side and the black queen moved forward on the queen side. After exchanging queens the engines played out a long PV agreement, they opened the center and exchanged most pieces, (negative) evals slowly increased. On move 32 the game reached a RN vs RB position, a few moves later Stockfish captured a pawn and created a passer on the king side. 

Stockfish slowly pushed the passer to the 2nd rank, Leela captured it there but then Stockfish exchanged minors and reduced to a rook ending a pawn up. The black king moved forward, after a while Stockfish captured another pawn and the game ended in a tablebase win. 

In game 22 again the engines castled in opposite directions. Stockfish opened the c and e files, both queens moved forward but they remained on the board. Again there were long PV agreements but evals slowly came down. The engines gradually exchanged pieces and the game reached a QR vs QR position on move 42. The engines shuffled and the game was adjudicated when Leela lowered its eval. Stockfish wins the game pair, it leads 6-2.

Games 23-24 started with a 20-ply line in the Sicilian Scheveningen, Keres attack, that used to be played in high level human games 40 years ago. In game 23 both engines castled long and there were no exchanges after the start. Leela had a space advantage, Stockfish tried to avoid opening the center and traded both its bishops for knights. The h file opened and the engines exchanged a pair of rooks, then a pawn exchange opened the d file on move 47.

The engines shuffled for a long time, Stockfish played waiting moves and Leela tried to find a way into the black fortress. After move 70 evals started to increase, Leela placed a bishop on b6 and restricted the black pieces. Then the white king walked to the king side and Leela slowly arranged its pieces on the queen side. Stockfish moved a rook forward and captured a pawn, but evals were already high. 

In a series of exchanges Leela captured a knight and reduced to a RB vs R position. Leela created a passer on the king side, it was on time to stop the black a pawn and then queened its passer. The game ended in a tablebase win. 

In game 24 the engines again castled long. Stockfish didn't push pawns forward, from move 21 the engines played out a long PV agreement and evals came down. Stockfish gave a rook for two knights, then after exchanging bishops Stockfish captured a rook for a bishop. The game reached a RBN vs RB  position with black two pawns up. Evals were close to 0 despite the material imbalance, Leela created connected passers and Stockfish lost material to stop them and the game was adjudicated. Leela wins the game pair, Stockfish leads 6-3.

Games 25-26 started in the Queen Pawn's game, anti Torre variant, the black queen was out in the center. In game 25 Leela had a bishop pair advantage and queens were exchanged early. Leela had a space advantage, evals increased steadily as it blocked the center and king side. The white king walked to g5 to complete the pawn line on the king side.

Leela attacked the center, Stockfish gave a knight for two pawns and the c file opened. Stockfish moved a rook forward but alone it was weak. Leela moved a rook to the 7th rank and captured the other black rook. Stockfish lost more material and was mated.

In game 26 Stockfish had a bishop pair advantage, but the queens stayed on the board. On move 22 the engines exchanged a pair of pawns and Stockfish created a passer in the center. The engines seemed to shuffle for a while but evals increased steadily. After exchanging a pair of rooks the white queen moved forward on the queen side. Leela still refused to exchange queens, after a series of exchanges the game reached a QB vs QN position with white a pawn up.

Now Stockfish avoided exchanging queens, Leela in desperation gave the knight for two pawns and created passers on the king side, also exposing the white king. Stockfish used the bishop to keep its king safe, then captured pawns and pushed a passer forward. Leela lost its queen and the game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 7-4.

Games 27-28 started with a short 6-ply line in the French Benoni opening. In game 27 the engines opened the center and exchanged queens. The black king walked to the queen side and the white king castled long. After some more piece exchanges the game reached a RRN vs RRN position, evals were already over 2.

Material was equal but the white rooks controlled the center and restricted the black king. Leela captured a pawn on move 40, then another on move 49 to create a passer on the king side. Stockfish captured a pawn and created a passer on the queen side. On move 57 Leela captured another pawn and was two pawns up.

Leela slowly pushed passers forward and forced Stockfish to exchange pieces. The game ended in a tablebase win. 

In game 28 the engines repeated 19 plys of the reverse game, opening the center and exchanging queens. Stockfish castled long and captured a pawn, then the engines exchanged all rooks through the open center. In a BB vs BN position Stockfish thought it had a small advantage, but its extra pawn was doubled and Leela found a way to block any attempt of attack. The engines shuffled with pawn moves extending the 50-move counter, the game was adjudicated on move 141. Leela wins the game pair, Stockfish leads 7-5.

Games 29-30 started with a 20-ply line in the KID Saemich, closed variation. All pieces were on the board, the center was blocked and the c file was open. In game 29 Leela kept its king uncastled in the center, there were no exchanges until Leela captured a pawn on move 22. Evals came down, the engines exchanged queens and a pair of bishops. The white king walked to the king side and Stockfish opened the f file. In a series of exchanges the engines reduced to a RN vs RN position, evals were low and the game was adjudicated. In game 30 Stockfish captured a pawn and created a passer on the queen side, then it castled its king. The engines exchanged pieces and evals came down, Leela moved a rook forward and the engines shuffled for a while. After exchanging queens Stockfish gave back a pawn and created a passer in the center, Leela gave a bishop and captured the two white passers. The game reached a RN vs R position with black 3 pawns up and was adjudicated.


Sunday, May 19, 2024

Season 26 superfinal games 11-20

After 20 games Stockfish leads 5-2 with 13 draws. There were 2 double draws and the first game pair with two white wins. Stockfish won two game pairs and extended its lead. In both cases the win was a long and slow endgame.

Games 11-12 started with a 24-ply line in the French, MacCutcheon, Lasker variation. The white king moved forward without castling and all pawns were on the board. In game 11 the engines blocked the center, Stockfish castled long and Leela captured a pawn on the king side. The pawns stabilized and the engines started to shuffle, with evals coming down gradually. On move 79 Leela moved a pawn to reset the 50-move counter, Stockfish captured the pawn. After a series of exchanges the game reached a QRR vs QRR position, the game ended 20 moves later in a 3-fold repetition. In game 12 Stockfish opened the center and king side, Leela kept its king in the center uncastled. Evals came down and the game reached a QRN vs QRN position. Leela captured the white pawns on the queen side, it had a passer there. Both engines gave checks with their queens, then in a series of exchanges reduced to a rook ending and the game was adjudicated.

Games 13-14 started with the unusual 1. e3 f5 Van't Kruijs opening. In game 13 the engines opened the center in a long PV agreement. The game reached a RBB vs RBN position on move 27 and evals started to come down. The engines reduced to a same color bishop ending, it took another 60 moves before Leela lowered its eval enough for the draw rule. In game 14 there were only a few exchanges after the start. Stockfish pushed pawns on the queen side and opened the b file. Leela pushed pawns on the king side and evals came down. The engines cleared most pawns on the king side and exchanged queens, Stockfish captured a pawn and had a passer in the center. The game reached a RRN vs RRN position with low evals, the game was adjudicated after a pair of rooks was exchanged.

Games 15-16 started with a Pirc, Austrian attack, played in high level human games. In game 15 Leela pushed pawns on the queen side, the engines exchanged a few minor pieces and then started to shuffle. On move 39 the engines exchanged a pair of bishops and continued to shuffle. The white king walked to the center and Stockfish opened the queen side on move 63. The white king became exposed, after the engines avoided exchanges Stockfish moved its queen forward and gave checks. Stockfish gave a rook and cleared the pawns on the queen side. The game reached a QRR vs QR position, black was two pawns up but the its king's safety was worth the material. The game was adjudicated 20 moves later after the engines exchanged queens.

In game 16 Stockfish pushed pawns in the center and its eval stared to increase early. On move 12 Leela predicted the next 18 plys and its eval stayed constant. Stockfish opened the h file and castled long while Leela captured two pawns and opened the center. Stockfish surprised Leela on move 22, after more than 10 minutes thinking Leela's eval dropped almost to 0. The engines continued with a PV agreement of 25 plys. Leela's eval jumped over 2 after another long think, Stockfish chased the black king to the center and then reduced to a RR vs RN position. Stockfish continued to chase the black king until it was trapped on the a file.

The endgame was very slow. On move 51 Leela captured the white f pawn and created connected passers, but this allowed Stockfish to move a second rook forward on the queen side. A mate threat forced Leela to exchange a pair of rooks. Stockfish created a passer on the queen side, queened and mated. Stockfish wins the game pair, it leads 3-1.

Games 17-18 started with a 20-ply line in the Nimzo-Indian defense, Kmoch variation. In game 17 Stockfish pushed pawns on the queen side, opened the a file and created connected passers. The engines exchanged a pair of rooks, Leela had a passer in the center and evals gradually increased. Leela's eval jumped over 2 despite the advancing black passers that trapped a bishop on the back rank.

Leela blocked the black passers with a knight on c3 and then exchanged queens. Leela pushed pawns on the king side and Stockfish gave a pawn to break the pawn line. After exchanging a pair of knights the game reached a RBB vs RBN position, Leela brought its king to c3 to block the black passers. The trapped white bishop was still trapped but both evals were high at this point.

Leela captured both black passers and connected a second passer in the center. The trapped bishop became free to move, Leela used it to pin the knight and then capture it. The game ended in a tablebase win.

In game 18 Stockfish immediately played a4 after book to stop any advancing pawns on the queen side. Stockfish pushed pawns on the king side and gave a pawn. Leela was not impressed but was surprised by Stockfish's move 22.

Leela expected an exchange on f5, instead Stockfish exposed the black king, Leela thought for 10 minutes and its eval jumped to 1.5. The black king moved toward the center and Stockfish opened the e file. The white major pieces threatened the black king, in a series of exchanges the engines reduced to a Q vs RN position on move 41.

Stockfish captured pawns and saw the win in its PV. The white king moved forward to support the passers, Leela lost material and the game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 4-2.

Games 19-20 started with a line in the Caro-Kann advance, Short variation, played in high level human games. In game 19 the center was blocked and the engines exchanged minor pieces. Leela pushed the h pawn forward and Stockfish castled long. Leela opened the h file and the engines exchanged a pair of rooks, Stockfish's eval dropped and the game reached a BB vs BN position. The engines started to shuffle and the game was adjudicated.

In game 20 the engines started similarly, though Stockfish kept its king side pawns back. Leela castled long and Stockfish opened the center, it thought Leela's move 21 was inaccurate and its eval jumped. In a long PV agreement the engines reduced to a Q vs RR position, Leela's eval was still close to 1.

The endgame was slow, Stockfish's eval increased steadily and Leela's eval followed more slowly. Stockfish pushed pawns on the king side and created a passer, then slowly pushed it to the 7th rank. Leela created a passer on the queen side but it was too slow. The white king moved forward, Stockfish lost the passer but captured the pawns in the center and created more passers. Leela lost one of the rooks and the game ended in a tablebase win. Stockfish wins the game pair, it leads 5-2.


Friday, May 17, 2024

Season 26 superfinal games 1-10

After 10 games Stockfish leads 2-1 with 7 draws. Stockfish won two of the first 3 game pairs, then Leela won a game pair and reduced Stockfish's lead to one. Stockfish's first win was a slow eval increase in a position that seemed to be drawn. Its second win was a long Q vs RN ending where Leela (white) thought it was safe for a while. Leela's win was the result of inaccurate moves by Stockfish at the start.

The opening book was created by Jeroen Noomen, details can be found here. Openings were taken from games of chess masters of the past, this season 18 of the openings were from Mikhail Tal's games.

Games 1-2 started with a variant of the Czech Benoni defense. In game 1 there were many exchanges after the start, the game reached a RN vs RN position on move 23. Stockfish defended a weak backward pawn and didn't allow Leela to invade with its rook. The engines shuffled and evals slowly came down until the game was adjudicated on move 80. 

In game 2 there almost no exchanges after the start, the center was blocked and the engines played behind their pawn lines. Stockfish moved its king forward instead of castling, after move 21 there were a few pawn exchanges, then in a series of exchanges the engines opened the queen side and exchanged queens. Evals were low at this stage.


The engines seemed to shuffle for a long time but evals very slowly increased. On move 68 Stockfish opened the h file and on move 80 the engines exchanged a pair of rooks. Evals were already over 2, both engines with a minute left and playing on increments.

The engines exchanged the remaining pawns on the king side and the white king moved forward. In a series of exchanges the engines reduced to a rook ending and Stockfish saw the win. Using a threat of a back rank mate Stockfish captured a pawn and created a passer. Leela lost the rook and the game ended in a tablebase win. Stockfish wins the game pair, it leads 1-0.

Games 3-4 started with a 24-ply variant of the Sicilian Sozin attack, flank variation. The center white pawns were gone, black was a pawn up but its pieces were mostly on their starting squares. In game 3 Stockfish gave a rook for a bishop and protected its exposed king in the center. Leela thought it had an advantage but its eval dropped when the black king found safety and Stockfish developed its pieces. Leela captured two pawns but after a series of exchanges the game reached an opposite color bishop ending. The engines shuffled and the game was adjudicated on move 105 when Leela lowered its eval. In game 4 Stockfish captured a rook for a bishop though not by the same line as in game 3. Evals came down quickly, the engines exchanged minor pieces and shuffled for a while. The game reached a QRR vs QRB position, Stockfish used check to capture two pawns and created passers on the queen side. Leela countered with an attack on the white king, after sacrificing a rook Leela forced a 3-fold repetition draw.

Games 5-6 started with a 25-ply variant of the King's Indian defense, Saemich variation. There was a Q vs BN imbalance but black had the advantage. In game 5 Stockfish captured two pawns quickly and created a passer in the center. Leela captured the passer and Stockfish exposed the white king with two forward knights. Stockfish also had a strong bishop controlling the dark long diagonal. Leela gave a rook for the black bishop, the game reached a QR vs RRN position with black 3 pawns up.

Leela's (negative) eval drifted down while Stockfish's slowly increased. Leela captured the black d pawn, the engines exchanged a pair of rooks, Stockfish had a pawn majority on both sides of the board. Stockfish slowly pushed pawns on the king side, it created a passer there and another on the queen side after a pawn exchange. Stockfish saw the win but when Leela captured the queen side passer its eval dropped below 1 again. 

It took Leela 8 moves to realize it was actually losing. The black king moved forward and Stockfish captured the last white pawn. The white king was trapped and the game ended in mate.

In game 6 Stockfish defended in a different way as white, it exchanged a pair of knights and kept its king safe. Leela gave a rook for a bishop and tried to attack the white king, Stockfish traded a rook for a knight and reduced to a QR vs RBB position. Stockfish placed its pieces on the back rank, the white king moved forward and used black pawns as shields. Stockfish traded its rook for a bishop, the game continued for 30 more moves with Stockfish mostly giving checks until Leela lowered its eval for the draw rule. Stockfish wins the game pair, it leads 2-0.

Games 7-8 started with a 28-ply line in the Ruy Lopez, Chigorin variation. The center was blocked and all pieces and pawns were on the board. In game 7 Stockfish exchanged pawns on the queen side and Leela thought that was a mistake. Stockfish's eval stayed around 1 while Leela's eval increased, by move 27 two files were open on the queen side and the engines exchanged a pair of rooks.

Leela avoided exchanging queens, Stockfish started to see trouble ahead. The engines exchanged the remaining rooks and then Leela captured a pawn and created a passer on the queen side. Leela captured a second pawn, then after a series of exchanges the game reached a BN vs BN position, white two pawns up with connected passers on the queen side. 

The engines traded pawns, Stockfish captured one passer and Leela created another on the king side. Stockfish couldn't prevent a queening and the game ended in a tablebase win.

In game 8 the queen side stayed closed, there was only one minor piece exchange after the start and all pawns stayed on the board. Stockfish tried to threaten the king side but nothing came out of it. The first pawn exchange was on move 32, Stockfish created a passer in the center and Leela blocked it. The engines exchanged more minor pieces and evals came down. In a series of exchanges the engines reduced to a rook ending. Stockfish's eval was 0, it took Leela another 20 moves to lower its eval for the draw rule. Leela wins the game pair, Stockfish leads 2-1.

Games 9-10 started with the old Indian defense, Janowski variation. In game 9 there were a few exchanges after the start, the engines opened the e file. The black queen moved forward on the queen side and evals came down. In a series of exchanges Leela captured two pawns and the game reached a QRB vs QRB position. Stockfish captured one pawn back and exchanged queens. The engines traded pawns and Leela regained the pawn, it was two pawns up with two passers but Stockfish managed to capture a pawn and its last pawn was also a passer. Leela pushed one passer to the 7th rank but there it was blocked. The game was adjudicated 20 moves later when Leela lowered its eval. Game 10 repeated 14 plys of game 9, the engines opened the e file. Stockfish grabbed a pawn with its queen, which then became trapped on the queen side. After a while Stockfish freed its queen, the engines exchanged a pair of rooks and then mostly shuffled for a long time. Evals slowly started to increase and were both over 1. On move 98 the game reached a BN vs BN position and then evals dropped. The engines shuffled again and the game was adjudicated. Was this a missed opportunity for Stockfish?


Wednesday, May 15, 2024

Season 26 premier division statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

Final draw rate was 59.4%. 

Game termination

The three most common game termination causes were:
51.3% - TCEC draw rule
22.3% - Mate
19.6% - SyzygyTB

There were no crashes in the stage.

Moves per game

Median= 71
Average= 79.0

There were 41 games longer than 100 moves, the longest was 251 moves (Ethereal - RubiChess, game 51, draw). 

Time per game (hours)

Median= 2:05
Average= 2:02

Openings

There were variable length book openings in this stage. 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 opening variant twice.

Reverse pairs, wins

Reverse pairs, same moves

Pairs of reverse games diverged less quickly than usual, 19.6% diverged immediately out of book, 48.2% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 25 plys (Stoofvlees - RubiChess, games 139 and 167, Vienna Frankenstein-Dracula variation, RubiChess won as white) 


Saturday, May 11, 2024

Season 26 premier division, final results

Final standings

Stockfish and Leela will play in the season 26 superfinal, a repeat of the last 3 superfinals. They were in the lead from the start and only increased the gap to the other engines as the rounds progressed. Stockfish won 20/24 game pairs against the other 6 engines, Leela won 17/24, both without losing a game pair. Surprisingly Stockfish drew twice against Stoofvlees, including its only game loss in the division. Leela had the only double win game pair of the division against RubiChess. Leela stayed very close to Stockfish for the first 3 DRRs, they were tied after 2 DRRs. In the last DRR Stockfish had a perfect result of 7/7 game pair wins including the only win against Leela, while Leela also drew against Berserk, giving Stockfish a small gap at the top.

Berserk and KomodoDragon were in the second group battling for third place. Berserk kept a small lead and also beat KomodoDragon twice in the first 2 DRRs. In the third RR KomodoDragon won their game pair and it closed to within 0.5 points. In the final DRR KomodoDragon was very close to Berserk, it managed to tie their score before the final round but lost to Stockfish to finish in 4th place. Berserk finished in 3rd after starting this season from the entrance league (it didn't play in season 25). KomodoDragon is officially out of the "top3" and no other engine seems to challenge the two leaders. It appears the KomodoDragon development team are more focused on the new Torch engine, which has yet to appear in TCEC.

At the bottom half of the table Ethereal, Seer and RubiChess were close from the start while Stoofvlees was clearly last. After 3 DRRs Seer and Ethereal were tied while RubiChess was 1 point behind. In the last DRR Seer lost to both Ethereal and RubiChess and Ethereal finished in 5th place, RubiChess couldn't close the gap and it finished in 7th, to be relegated to league 1.

Interesting games

game 172, KomodoDragon - Ethereal: The engines blocked the king side and KomodoDragon castled long. Ethereal gave a pawn and opened the c file, it later regained the pawn and placed a passer on a2. The white king hid behind the black passer, KomodoDragon pushed a pawn in the center to the 7th rank. Ethereal couldn't get rid of the protected passer, eventually it gave a rook for a knight to capture it. KomodoDragon created a passer on the king side and both engines saw the win, Ethereal lost material and was mated.

game 173, Stockfish - Ethereal: There were almost no exchanges after the start, long pawn lines blocked the queen side and the center. The engines exchanged a few minor pieces, all pawns were on the board until Stockfish captured one on move 32. Stockfish's eval started to increase, on move 44 the game reached a QRB vs QRB position. Ethereal regained the pawn but got its queen trapped in front of the pawns. Ethereal exchanged bishops and Stockfish captured another pawn, by the time the black queen was released Stockfish saw the win. The queens were exchanged and Stockfish captured another pawn, Ethereal lost its rook for a passer and was mated.

game 175, Berserk - Seer: The white king walked to the king side, there were only a few exchanges after the start, only one pawn exchange. Seer also moved its king without castling, the engines shuffled for a long time. On move 48 Berserk captured a pawn, the black king walked to the queen side and evals started to increase. The engines opened the queen side and Berserk attacked with its major pieces, capturing another pawn. The game reached a RRB vs RRB position, Berserk gradually captured all the black pawns. Seer lost material and was mated.

game 176, Leela - RubiChess: Leela castled long and RubiChess kept its king in the center. The engines exchanged a few minor pieces and RubiChess captured a pawn on the king side. Leela captured a pawn on the queen side and created a passer, then captured another pawn and exchanged queens. The black king walked to the queen side and eventually captured the passer, Leela captured a pawn on the king side and created another passer there. RubiChess lost a knight and captured the passer and another pawn, the game reached a RBN vs RB position. The white king moved forward and eventually helped in capturing the remaining black pawns. Leela had one pawn left and a piece advantage, the game ended in a tablebase win.

game 182, Berserk - Ethereal: There were no exchanges after the start, the engines played behind their pawn lines. By move 38 there were two minor piece exchanges, evals started to increase very slowly. The first pawn exchange was on move 52, then the engines exchanged a pair of rooks and both created a passer in the center. Berserk moved the queen to the back rank, Ethereal exchanged queens and the game reached a RN vs RN position. Ethereal captured the passer in the center, Berserk created connected passers on the king side and exchanged rooks. Berserk captured 3 pawns, queened a passer and mated.

game 183, Leela - KomodoDragon: There was one minor piece exchange after the start, on move 27 the engines exchanged queens. Evals increased, all pawns were on the board and Leela placed a pawn on b6. On move 43 the first pawns were exchanged and the engines opened the f file. KomodoDragon gave two pawns with no compensation, the game reached a RBN vs RBN position. Leela created passers on the queen side, it gained material and queened, the game ended in mate.

game 184, RubiChess - Seer: The engines blocked the queen side, then exchanged a pair of bishops. On move 23 the engines opened a file in the center, RubiChess opened the king side and attacked with major pieces. In a series of exchanges the engines reduced to a RN vs RN position with white a pawn up, RubiChess captured a second pawn and created connected passers on the queen side. Seer delayed with checks but eventually RubiChess queened a passer and mated.

game 186, KomodoDragon - RubiChess: There were no exchanges after the start, the engines formed long pawn lines. The pawns stabilized, on move 32 the engines exchanged a pair of knights and then started to shuffle. Pawn moves extended the 50 move counter, on move 145 the engines exchanged the first pawns and continued to shuffle. On move 186 there was another pawn exchange, then KomodoDragon gave a pawn. RubiChess gave a rook for a bishop, perhaps a mistake under time pressure. RubiChess had two passers but KomodoDragon blocked them while it sent its rooks to the back rank and captured a bishop. RubiChess got some of the material back but KomodoDragon captured the black passers and kept the advantage. The game ended in a tablebase win.

game 189, Stockfish - Berserk: Stockfish castled long while Berserk kept its king in the center. Berserk tried to attack on the queen side, Stockfish gave a pawn and opened the center. Stockfish gave a knight and threatened mate on the back rank, Berserk gave back the material and delayed with checks. Eventually Berserk gave a rook for a bishop to stop the back rank threat, the game reached a RR vs RB position. Stockfish pushed a passer and saw the win, it reduced to a rook ending and queened the passer. The game ended in a tablebase win.

game 194, Ethereal - Seer: There were no exchanges after the start, the engines played behind their pawn lines. On move 28 the engines exchanged a pair of bishops, the first pawn exchange was on move 31 opening the f file. Evals started to increase, a series of exchanges opened the queen side and both engines had a passer there. Ethereal captured the black passer and exchanged queens, it kept its passer defended. After a while the engines exchanged a pair of rooks and reduced to a RBN vs RBN position. The black crossed the board to help, Ethereal managed to get its rook to the king side to capture the black pawns there. Seer lost its last pawn, Ethereal was 3 pawns up and it pushed them forward. Seer lost material, Ethereal queened and mated.

Standings after RR7: Stockfish +17, Leela +16, Berserk +3, KomodoDragon +2, Ethereal -6,  Seer -7, RubiChess -8, Stoofvlees -17. No change in the lead after both Stockfish and Leela won their games as white against lower ranking engines. Similarly there is no change in the race for 3rd place between Berserk and KomodoDragon. Ethereal beat Seer and is now ahead in 5th place, RubiChess also beat Seer but it is still in 7th place facing relegation with Stoofvlees.

game 197, Stockfish - Leela: See featured game below. 

game 198, Berserk - RubiChess: The engines started a series of early exchanges, in the aftermath RubiChess was down a knight for two pawns and the white king was exposed in the center. Berserk was confident it had an advantage, it continued to exchange pieces until only RRN vs RR remained. RubiChess placed both rooks on the 2nd rank, Berserk was down to its last pawn and it exchanged a pair of rooks. Slowly Berserk pushed its pawn forward until it became a passer. RubiChess lost its rook and the game ended in a tablebase win.

game 199, Stoofvlees - Seer: The engines exchanged a few minor pieces and blocked the king side. On move 27 the a file opened, gradually Stoofvlees exchanged all rooks and reduced to a QBN vs QBB position. Almost all pawns were on the board and the bishops were blocked. Stoofvlees captured a pawn and opened the d file, then gave a bishop for two pawns and created a passer on the king side. After a series of exchanges the game reached a pawns vs bishop ending, Seer couldn't prevent a queening and was mated. There were two white wins in this game pair. 

game 203, Seer - Berserk: The engines blocked the center and castled in opposite directions. After exchanging queens Berserk doubled rooks on the c file, then traded a rook for a bishop and the game reached a RRN vs RBN position with black two pawns up. The engines cleared the pawns on the king side and Berserk created a passer in the center. The engines shuffled for a while, Berserk went wrong somewhere and Seer managed to force a piece exchange that left a R vs B ending. The white pieces were stronger, Seer slowly captured pawns and the game ended in a tablebase win. There were two white wins in this game pair.

game 205, Stockfish - RubiChess: The engines castled in opposite directions, opened the f file and blocked the center. Stockfish thought RubiChess played inaccurately evals started to increase. Stockfish declined a bishop for rook exchange and kept the center blocked. The engines exchanged more pieces, then RubiChess gave a pawn and gave Stockfish an advanced passer. Stockfish saw the win, it won a rook for the passer and the game reached a RBB vs BN position. RubiChess lost more material and was mated.

game 206, Leela - Seer: The engines blocked the center and played mostly behind their pawn lines. After exchanging a few minor pieces the engines exchanged queens, then stabilized the pawns. Seer had a pawn line across the board, confident in its defense its eval was below 1. Leela was confident it was winning with a high eval. For a long time the engines shuffled, on move 55 Seer probably blundered, Leela gave a pawn and started to attack the queen side. It captured a pawn and created a passer, Seer captured the passer but Leela created another and the game reached a RRB vs RRB position. Seer lost a bishop for the passer, both engines created more passers but Seer wasn't fast enough. Leela gave a rook, queened and mated.

Standings with 3 rounds to go: Stockfish +19, Leela +16, Berserk +3, KomodoDragon +2, Ethereal -6,  Seer -8, RubiChess -10, Stoofvlees -16. After beating Leela for the first and only time in the division Stockfish is almost certain to finish first, it is 1.5 points ahead of Leela with 3 games left. Berserk still has a small advantage over KomodoDragon. They drew their final game against each other, Berserk lost to Seer and KomodoDragon only drew against Stoofvlees. Ethereal has a 1 point advantage over Seer, which has a 1 point advantage against RubiChess, it is likely that the order will stay like this and the RubiChess will relegate.

game 213, Stockfish - Seer: The center was blocked and there were no exchanges after the start. Stockfish had more space, on move 31 the engines exchanged minor pieces and Stockfish captured a rook for a bishop. The first pawn exchange was on move 39, evals started to increase only after queens were exchanged on move 48. Seer sent a knight forward to capture a pawn, it created a passer but the knight was trapped. In a series of exchanges Stockfish traded a rook for two minors and the game reached a RBN vs RN position. Stockfish captured the black passer and exchanged rooks, Seer trie to protect its pawns but its king got trapped in the corner and mate followed.

game 215, Leela - Ethereal: The engines exchanged minor pieces and Leela captured an early pawn on the queen side. Leela's eval increased in a closed position, it slowly pushed its a pawn until it became a passer. On the king side Ethereal pushed pawns and exposed the white king, it captured two pawns and created connected passers. Leela was confident it can deal with this threat, and Ethereal's eval also started to increase. All pieces moved to the king side, Leela kept its king safe and then exchanged queens and reduced to a RRN vs RRB position. Leela added a second passer on the queen side, Ethereal lost a rook for one passer. It pushed its passers but Leela was ready for them, Leela captured both passers and also captured the second black rook for its second passer. The game ended in a tablebase win.

There is no change in the gaps between engines except that Seer is only 0.5 points ahead of RubiChess. Berserk only drew as white against Stoofvlees, keeping KomodoDragon's chances of catching up to third place.

game 219, Ethereal - RubiChess: Ethereal castled long and RubiChess kept its king in the center. RubiChess tried to attack the queen side and it captured a pawn in the center to create a passer. Ethereal regained the pawn and opened the center, with doubled rook on the d file threatening mate on the back rank. In a series of exchanges the engines reduced to a QBB vs QBN position, RubiChess was a pawn up and the white king was completely exposed but evals were in white's favor. Ethereal chased the black king and regained the pawn to create a passer on the king side. RubiChess gave its bishop for pawns to get rid of the passer. The white pieces attacked the black king, Ethereal forced a queen exchange and the game ended in a tablebase win.

game 220, KomodoDragon - Seer: The engines castled in opposite directions, KomodoDragon pushed pawns on the king side and managed to open the f file. After a series of exchanges the game reached a RRB vs RRN position with white a pawn up. KomodoDragon had a passer in the center, after exchanging a pair of rooks Seer regained the pawn, then it captured the white passer but lost its knight. Seer lost more material, it allowed a queening and was mated.

KomodoDragon is tied with Berserk in 3rd place, though Berserk has a head to head tiebreak advantage. Ethereal is safe in 5th place, Seer is still 0.5 points ahead of RubiChess before the last round.

game 221, Stockfish - KomodoDragon: Stockfish created an early passer on the queen side through an exchange. KomodoDragon captured the passer and Stockfish created a pawn majority on the king side. KomodoDragon gave a rook for a knight to capture one pawn but Stockfish still created an advanced passer facing the black king. Stockfish cleared the black pawns on the queen side and created another passer there, the game reached a QRB vs QBN position. After exchanging queens Stockfish saw the mate, KomodoDragon lost more material and after queening Stockfish mated.

Berserk secured 3rd place after KomodoDragon lost its last game, then is held a draw against Leela and didn't need the tiebreak. RubiChess only drew against Stoofvlees and finished 7th.

Featured game: Stockfish - Leela 
game 197

Stockfish pushed pawns on the king side and kept its king uncastled in the center. Stockfish captured a pawn in the center, then another on the king side, it was prepared for Leela forking king and rook with a knight. Stockfish lost the rook and didn't try to recapture, instead it attacked the black king though it was down a rook for a while. The black king was exposed and Leela surrounded it with pieces.


Leela gave material back and in a series of exchanges the engines reduced to a queen ending. Leela's eval was much lower than Stockfish's and it drifted down for a long time. After trading pawns Stockfish was a pawn up with a passer. Stockfish saw a win from a mile away while Leela's eval was below 1. 

The white king moved forward and after a while so did the passer. On move 75 Stockfish forced a queen exchange, then it queened the passer and the game ended in a tablebase win.


Sunday, May 5, 2024

Season 26 premier division, after RR6

Standings after RR6

Stockfish is leading in front of Leela, it won 5 game pairs in the third DRR and Leela only 4. Surprisingly Stockfish drew against Stoofvlees for the second time. KomodoDragon got close to Berserk after beating it in their direct match for the first time. Berserk won the previous two matches. Both Berserk and KomodoDragon had a weak DRR with only 1 game pair win against other lower ranking engines. 

Interesting games

game 116, KomodoDragon - Ethereal: The engines castled in opposite directions, KomodoDragon pushed pawns on the king side and placed a pawn on h6. Ethereal tried to attack on the queen side, the engines traded a rook for two minors and then exchanged queens. Ethereal had 3 connected passers on the king side, in a series of exchanges the engines reduced to a BN vs R position and KomodoDragon created connected passers on the queen side. KomodoDragon managed to block the black passers, the engines traded one pair of passers but Ethereal couldn't stop the remaining white pawns. KomodoDragon queened and mated.

game 117, Stockfish - Ethereal: The center was blocked, Ethereal pushed pawns on the king side and Stockfish thought that was a bad idea. Stockfish gave a pawn and a rook for a bishop, then used threats on the black king and queen to equalize and reduce to a RBN vs RBN position. Stockfish's pieces were better, it captured a pawn and the exchanged down to a knight ending. Stockfish captued more pawns and created passers, then queened and mated.

game 118, Stoofvlees - KomodoDragon: The center was blocked, there were a few exchanges after the start and both kings walked to the king side without castling. Stoofvlees created a passer on the king side, the pawns stablized and the engines shuffled for a long time. On move 57 KomodoDragon let Stoofvlees push the passer, after a minor piece exchange Stoofvlees pushed it to h7. After another long shuffle Stoofvlees attacked from the king side. It lost its passer and the game reached a RB vs RN position but its pieces and pawns were much netter. Stoofvlees captured a pawn and trapped the black knight, KomodoDragon lost more material and the game ended in a tablebase win.

game 120, Leela - RubiChess: There were a few pawn and minor piece exchanges after the start, both engines castled long. Leela's eval was high although the engines seemed to shuffle for a while. RubiChess pushed the h pawn, it became a passer but then Leela captured it and exchanged a pair of rooks. The white king walked to the king side, then Leela gave a knight for 3 pawns and reduced to a RB vs RBN position. Leela pushed a passer forward, RubiChess exchanged pieces but couldn't stop the passer. Leela queened and mated.

game 123, KomodoDragon - Berserk: The engines castled in opposite directions, all pieces were on the board and the d file was open. KomodoDragon pushed pawns on the king side, after move 22 the engines exchanged a few pieces. Berserk captured a pawn and exchanged queens, giving KomodoDragon a passer on the queen side in a RBN vs RNN position. KomodoDragon managed to get the pawn back, Berserk captured the passer but KomodoDragon created another. The game reached a rook ending, KomodoDragon pushed the passer with its king supporting. Berserk couldn't prevent a queening, the game ended in a tablebase win. 

game 130, KomodoDragon - RubiChess: KomodoDragon was up a pawn from the start with a passer on g7. RubiChess equalized material and captured the passer, KomodoDragon created another and pushed it to h7. RubiChess attacked the white king and for a while thought that was enough as a counter. KomodoDragon kept its exposed king safe and captured a knight for a pawn. RubiChess captured the white passer, KomodoDragon captured more pawns and created another passer on the king side. The game reached a RN vs R position, KomodoDragon protected its last pawn and reduced to a tablebase win.

game 132, Stoofvlees - Berserk: The center was blocked and the engines opened the c file, Stoofvlees went a pawn up and created a passer on the queen side. Without any exchanges Stoofvlees slowly moved all its pieces to the king side, then started to exchange pawns and pieces from move 39. Berserk captured the passer on the queen side, Stoofvlees gave a knight for pawns to expose the black king and create passers on the king side. Stoofvlees captured back a knight and was two pawns up in a RRB vs RRB position. It pushed passers on the king side, Berserk lost material and the game ended in a tablebase win. 

game 133, Stockfish - Berserk: The engines castled in opposite directions and gradually exchanged pieces. The game reached a QRB vs QRB position, Berserk had a passer in the center but the black king was exposed. Stockfish used checks to capture a pawn and create a passer on the king side. Stockfish used a queen exchange to create another passer, Berserk captured one but the other was on the 7th rank. Berserk lost material and the game reached a tablebase win.

game 137, KomodoDragon - Stockfish: See featured game below.

Standings after RR5: Stockfish +12, Leela +11, KomodoDragon +1, Berserk 0, Seer -3, Ethereal -5, RubiChess -7, Stoofvlees -9. Stockfish has a small lead at top, it only drew as white against Stoofvlees  and won as black (with bias) against KomodoDragon. Leela drew as black (with bias) against Berserk and drew as white against KomodoDragon. KomodoDragon is in third place after gaining 2 full points on Berserk in RR5, including a direct win in their game. Both KomodoDragon and Berserk lost against Stoofvlees this RR. 

game 142, Berserk - RubiChess: There were only a few exchanges after the start, the engines exchanged a pair of bishops and then traded a pair of pawns, Berserk created a passer on the queen side. Berserk pushed the passer to the 5th rank, RubiChess captured a pawn and exchanged queens. Berserk regained the pawn and reduced to a RNN vs RR position, RubiChess captured the white passer but Berserk had another on the king side. Berserk slowly pushed the passer to the 7th rank, RubiChess lost a rook for the passer and the game ended in a tablebase win.

game 143, Stoofvlees - Seer: Stoofvlees gave a knight for 3 pawns and cleared the queen side black pawns. Stoofvlees captured another pawn but then evals turned negative as the engines reduced to a R vs RB ending with 4 white pawns and 1 black. Stoovlees chose the wrong king move and Seer pushed its pawn forward faster than the white pawns. Stoofvlees lost its rook for the pawn and the black pieces were on time to stop the white pawns. The game ended in a tablebase win. 

game 144, Ethereal - KomodoDragon: The engines castled in opposite directions, Ethereal pushed pawns on the king side, gave a pawn and opened the h file. The white queen moved forward and attacked the black king, in a series of exchanges the queens were exchanged and Ethereal captured a rook for a knight. KomodoDragon captured a pawn and created a doubled passer on the king side ,the engines shuffled and traded pawns for a while. After move 53 Ethereal created connected passers on the queen side, then it managed to trap and capture a knight. The game reached a RRB vs RB position, KomodoDragon lost more material and was mated. There were two white wins in this game pair.

game 149, Stockfish - RubiChess: The engines castled in opposite directions, after exchanging all rooks Stockfish pushed pawns on the king side and opened the h file. The engines exchanged queens and the game reached a BNN vs BNN position with white a pawn up. Both kings moved to the center and the bishops were exchanged, on move 47 Stockfish created a passer on the king side. RubiChess blocked the passer and the white king for a while, after exchanging a pair of knights Stockfish saw the win. RubiChess lost a knight for the passer, Stockfish created another and queened to mate.

game 150, Leela - Seer: There were a few pawn and minor piece exchanges after the start, on move 28 the engines opened the f file. Seer captured a pawn and Leela attacked on the king side. Leela managed to place a protected bishop on d6, Seer gave a rook to capture it and another pawn. The game reached a  RR vs RN position, Seer was two pawns up with a passer in the center. The white pieces were more effective, Leela kept the black king confined on the king side. Leela captured the black passer, then captured two more pawns on the queen side and created a passer. Seer lost its knight, the black king was trapped and the game ended in mate.

game 157, Stockfish - Seer: Seer was up a pawn with a passer on the queen side but its king moved without castling and blocked the king side rook. Seer tried to develop the rook through the h file but it was still restricted and not effective. After some shuffling Seer captured another pawn and connected a passer, while Stockfish placed a rook on the 7th rank. Seer pushed its passers and gave a rook for a knight, after more exchanges the game reached a RR vs R position with black 4 pawns up. Stockfish captured pawns and saw the win, it managed to control the black pawns, eventually it queened and mated.

game 158, RubiChess - KomodoDragon: RubiChess was up a pawn with a passer on g7 from the start. KomodoDragon captured the passer and RubiChess created another on the h file. After exchanging queens the engines traded pawns on the queen side, the game reached a RRN vs RRN position with white two pawns up and with passers on both sides of the board. KomodoDragon captured the passer on the king side but couldn't stop the passer on the queen side. RubiChess queened and mated. There were two white wins in this game pair. 

game 159, Leela - Ethereal: There was one minor piece exchange after the start, all pawns were on the board and both kings remained uncastled. Leela developed its king side rook through the h file, pawn lines blocked the center and queen side with a small hole on the g file. Leela's eval was high though the engines seemed to shuffle. On move 48 Leela opened the g file and exchanged a pair of rooks, after exchanging the remaining rooks Leela created connected passers in the center on move 66. Ethereal lost material for one passer, the game reached a Q vs BB position. Leela gained more material and mated.

game 164, KomodoDragon - Seer: KomodoDragon castled long despite the weak pawn cover there. It then pushed pawns on the king side, giving two pawns and opening the g file. KomodoDragon doubled rooks on the h file, Seer exchanged queens to avoid mate. KomodoDragon captured pawns and moved a its rooks to the 7th rank, Seer exchanged a pair of rooks and the game reached a RN vs RN position with white two pawns up. KomodoDragon slowly pushed connected passers on the queen side, then trapped the black king and mated.

Featured game: KomodoDragon - Stockfish
game 137

The game started with a black bias, Stockfish was a pawn up and the white king moved without castling. KomodoDragon regained the pawn, its king walked to the queen side and trapped the rook there. Stockfish captured a pawn and opened the a file for the white rook the . KomodoDragon tried to create some pressure on the king side with major pieces, Stockfish exchanged a pair of rooks and the game reached a QRB vs QRB position. 


The white king moved to free the rook. The engines shuffled for a while, KomodoDragon's eval remained low but Stockfish's eval increased steadily. On move 54 the engines exchanged rooks, KomodoDragon started to see the problem. Stockfish exchanged pawns on the king side and created a passer. 

The engines traded pawns and Stockfish connected a second passer, KomodoDragon created passers on the queen side but they weren't fast enough. KomodoDragon lost the bishop for one passer and the game ended in a tablebase win.