Thursday, May 30, 2019

Season 15 superfinal, games 91-100

Leela wins the TCEC season 15 superfinal. The final score is 14-7 with 79 draws. This comes as no surprise, Leela was ahead by 6 points since game 86. In the last 10 games Leela extended its lead to 7 points.

Superfinal summary
In season 14 Leela started from the lower divisions, climbed up and reached the superfinal where it lost by 1 point to Stockfish. This season Stockfish won the premier division but Leela was stronger head-to-head. In the superfinal Stockfish was still hopeful after it equalized to 1-1 in game 12. However Leela started to win minimatches, by game 26 it led 5-1. Stockfish won two more games in openings where Leela also won, Leela extended its lead to 8-3 in game 40. Stockfish tried to stay in the match with two minimatch wins and the score was 8-5 at the half. After many draws Leela crushed Stockfish's hopes with an unusual double win, extending the lead to 5 points on game 62. In the remaining games Stockfish won twice in openings that Leela also won, and Leela won two more mimatches to win the match by 7 points.

Leela improved its game compared to the previous season. It made very few blunders in the endgames, it played all types of openings well, usually better than Stockfish. It appears to have a much better understanding of long term advantages, often claiming it is much better long before Stockfish can see a win. There were a few cases where this proved to be wrong, but mostly Leela's predictions were correct.

There will be more NN engines in the next season. There were two NN engines in the premier division in season 15, will there be another one next season? Are the NN engines going to take over the chess world? When will we see a NN superfinal? Can Stockfish improve and be competitive? Will Houdini be updated? Will there be a hybrid NN-AB engine? I can't wait to find out.

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Games 91-92 were a King's Gambit variant where the white king moves. In game 91 the white king walked to the king side, trapping its rook. Stockfish's eval dropped to 0 as it regained the pawn, the engines exchanged queens on move 20. Stockfish let its rook out of the corner, then all rooks were exchanged and only BN vs BB were left on move 26. Leela's eval kept the game going, the engines reduced to a same color bishop ending and the game ended on move 103 in a 50-move draw. Game 92 started similarly, the queens stayed on the board. The white king side rook got out of the corner but the engines did not exchange rooks, evals were negative and stayed low. Both engines focused on the isolated center pawns, the game was peaceful with a few exchanges. Evals came down and the game was adjudicated with many pieces still on the board.

The engines opened the center early in game 93. Neither engine was strong enough to attack and evals came down. Leela moved its queen forward on the queen side, this led to a queen exchange and the removal of all the pawns on the queen side. The game reached a BN vs BB position on move 40, Stockfish was a pawn up but with evals close to 0 the game was adjudicated quickly.

Leela's eval started around 1 in game 94, and was over 3 already on move 12. The engines castled in opposite direction, both Leela's rooks controlled half open files, one facing the black king. Leela chose to attack on the king side, it doubled rooks on the f file and broke through. After exchanging a pair of rooks Leela had a rook on the 7th rank and a formidable bishop on d5.  


Stockfish did not want to exchange bishops and to give Leela a passer. Nevertheless, Leela captured a pawn on the king side to create one passer, then it exchanged knights and created a second passer. After exchanging bishops only QR vs QR remained, both engines had central passers but Leela's passer was much stronger. It pushed the passer forward and Stockfish stopped it on the 6th rank.


Stockfish got rid of the passer on d6 but lost another pawn on the king side. The game reduced to a rook ending with two white passers on the king side and the black king too far to help. The game was quickly adjudicated.

Both kings stayed uncastled in game 95, Leela opened the queen side and Stockfish pushed pawns on the king side. Eventually Leela castled short, Stockfish opened the king side with its pawns, then gave a bishop to get two pawns facing the black king on the 6th rank. Leela exchanged two rooks for a queen to get rid of one pawn. After a while Leela lost a bishop and captured the second pawn, the game ended in a RR vs Q tablebase draw. In game 96 Stockfish's eval was 0 from the start. Both engines castled long and the king side was open. Queens were off early and the game reached a RNN vs RBN position on move 27. The engines shuffled and stabilized the pawn lines, then reduced to a rook ending on move 52. Leela went a pawn up and the game continued until reaching a tablebase draw on move 87.

Games 97-98 started with a 20-ply book in the King's Indian Defense. In game 97 the engines formed long pawn lines with no exchanges, Stockfish pushed pawns on the queen side and Leela on the king side. Stockfish opened a file on the queen side on move 25, Leela gave two pawns and started a king side attack. A knight sacrifice opened the king side for the black major pieces, then in a series of exchanges most of the pieces were gone and Leela found a perpetual check draw. In game 98 there were several exchanges after the start, the engines opened the queen side. Leela's eval was over 1, Stockfish's eval stayed low. Leela refused to open the king side, after the engines exchanged a pair of rooks they started to shuffle and Leela's eval came down. The game reached a QRN vs QRN position on move 51, Stockfish opened the king side and found a perpetual check draw.

Stockfish castled long in game 99, Leela opened a file on the queen side and attacked. The white king ran to the center, Leela sacrificed a bishop and added pieces to the attack. Then most pieces were exchanged off and only RBN vs RN remained on move 29. Leela was two pawns up, all the pawns were on the king side. Stockfish's eval dropped to 0, Leela captured a pawn and thought it had small advantage. The game ended only on move 97 in a tablebase draw. In game 100 both engines castled long, though the black king did not have good pawn support on the queen side. Leela attacked with its queen and captured a pawn, Stockfish exchanged queens and regained the pawn. Stockfish had a trapped bishop, it gave a pawn to release it. This gave Leela a passer in the center and its eval jumped over 3. Stockfish blocked the passer with its pieces, the game reduced to RN vs RN position. Leela's eval peaked over 5, it couldn't find a way to improve and the engines started to shuffle from move 44. On move 104 Leela gave a pawn back and opened the queen side, its eval already below 2. The engines continued to shuffle and exchange pawns until reaching a tablebase draw on move 139.

Wednesday, May 29, 2019

Season 15 superfinal statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins


Final draw rate was 79%.


Game termination

The three most common game termination causes were:

34% - TCEC draw rule
30% - SyzygyTB
21% - TCEC win rule

Moves per game


Median= 79
Average= 89.4

The games were longer than usual, similar to what we saw in the season 14 superfinal. There were 26 games longer than 100 moves, the longest was 262 moves (game 33, draw).

Time per game (hours)


Median= 4:20
Average= 4:09

Openings

There were variable length book openings in this stage chosen by Jeroen. The first letter of the ECO codes was distributed as follows:


The book determined the opening in most cases, some of the book sequences were very short and allowed more freedom, one game pair was bookless. 86% of the game pairs repeated the same ECO code twice, and 84% repeated the same opening variant. In 3 game pairs the first ECO letter was not repeated.

Reverse pairs, wins

 
Reverse pairs, same moves 

 
Pairs of reverse games diverged very quickly, 72% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 9 plys, this happened in three game pairs (games 5-6, Dutch, two draws ; games 19-20, Sicilian Rauzer Attack, two draws ; games 79-80, Ruy Lopez modern Steinitz defence, two draws).     

Tuesday, May 28, 2019

Season 15 superfinal, games 81-90

After 90 games Leela leads 13-7 with 70 draws. There were 5 decisive games in the last 10, two double white wins and one minimatch win for Leela. Leela is 6 points ahead with 10 games to go, Stockfish still has a mathematical chance but Leela is going to win.

The engines castled in opposite directions in game 81. Stockfish's eval was around 1 after the start, it pushed pawns on the king side with support from its rooks. The king side opened and Leela hid its king behind a white pawn, then on move 26 Stockfish's eval jumped over 7 with no warning.



Leela wasn't expecting Stockfish's 28th move, white abandoned two minor pieces but the black king was in a mating net. Leela had to exchange RB for Q but it was too late. Its king was still under threat and Stockfish controlled the 7th rank. The black pawns started to fall.


Stockfish captured the knight and was 4 pawns up when the game was adjudicated a few moves later.

In game 82 the pawns in the center and on the king side locked early. There was one open file on the queen side, all the pieces remained on the board with the first piece exchange on move 23. By then Leela's eval was over 4, though it wasn't clear why. After exchanging a pair of rooks Leela took over the open file, its eval over 6.


Stockfish had very little room to move. It refused to take the rook on c6 since this would create an advanced white passer. The engines continued to shuffle, Stockfish was almost paralyzed and Leela was patient and arranged its pieces. It put a rook on the back rank and waited for an opportunity. On move 61 Stockfish abandoned its b pawn.


A few moves later Leela captured the b pawn, and then captured a bishop. Stockfish's admitted defeat and the game was adjudicated. There were two white wins in this opening.

Games 83-84 started with a 28-ply book in the Sicilian Dragon, Yugoslav Attack variation. White castled long and black castled short. In game 83 Stockfish pushed pawns on the king side and it managed to open a file. Evals came down as the engines exchanged pieces, reaching a same color bishop ending on move 40. Leela thought it had a small advantage and the game continued for 20 more moves and reached a tablebase draw. In game 84 Leela went a pawn up, exchanges cleared the black pawns on the queen side. Leela had two connected passers on the queen side, Stockfish had a passer in the center and its eval remained low. On move 28 Leela gave a rook for a bishop, its eval over 1.5. The black king was a little exposed, Stockfish was active on the queen side and this prevented an attack on its king. On move 45 Leela gave another rook for a bishop, only QBB vs QRR remained with Leela two pawns up. The bishop pair was very strong, Leela could get some of the material back but chose to wait. After exchanging queens a white passer reached the 7th rank, Stockfish lost a rook to stop it. Both engines queened in the BB vs R ending, it cost Leela a bishop. The game reached a tablebase draw in a QB vs QR position on move 107. 

Queens were off early in game 85, evals started around 1 and slowly came down. Stockfish went up a pawn and created a queen side passer, the game reached a RRB vs RRB position on move 27. Evals came down to 0, Leela's eval went slightly negative when it regained the pawn. The engines reduced to a bishop ending on move 47, Leela went up a pawn and continued playing until reaching a tablebase draw on move 96.

In game 86 the action was on the queen side. Leela pushed pawns forward, after exchanging a pair of rooks the engines captured most of the pawns on the queen side, leaving one white passer. Leela's eval was around 1.5 as the engines continued to exchange pieces until reaching an opposite color bishop ending on move 40. Instead of being a drawish ending as usual, without warning Stockfish's eval jumped over 7 as it saw the loss coming.


The black bishop had to keep an eye on the a7 square, the black d pawn could not be protected. Leela created a passer on the king side and protected it with its bishop, now it saw the win as well. Stockfish was going to lose the bishop for one of these passers eventually and the game was adjudicated quickly.

There was one piece exchange early in game 87, all pawns remained on the board. Leela's king walked to the queen side, Stockfish castled short and then changed its mind and its king walked back to the center. Leela's eval turned negative as the engines shuffled, Stockfish pushed a pawn to a6. The first pawn was captured on move 45, Leela took the a6 pawn and went a pawn up, exposing the queen side to the white pieces. Leela's eval turned positive again and Stockfish's eval started to climb, it opened the king side and created an advanced passer in the center. When the passer reached the 7th rank Stockfish's eval was over 4, Leela was still feeling secure with an eval under 1.


The pin and attack on the a6 pawn together with the dangerous d7 pawn were too much to defend, as Leela soon realized. It gave Q for RB and its eval jumped over 8, the game was adjudicated before Stockfish won more material.

In game 88 there was one pawn exchange on move 16 and all the pieces remained on the board. Both engines castled short, Stockfish's eval was low and Leela's eval was around 1. On move 32 the engines started a series of exchanges, Leela's eval jumped when Stockfish gave a rook for a bishop. The game reached a RRN vs RNN position on move 39.


Evals continued to increase as Leela moved its pieces patiently. It took 10 moves for Leela to exchange knights and another 10 moves to capture a pawn. Leela's eval was over 10 by then.


The rook on h4 was trapped but not for long. The white king moved to the center, Stockfish had to move its pieces and the white rook could get out safely. Stockfish avoided exchanging rooks and it defended as long as it could. Eventually Leela moves a rook behind the black pawns and used the other rook to keep black king far on the other side. The game was adjudicated on move 99. Two white wins in this opening.

Games 89-90 started with a 19-ply book in the Benoni Defense. Evals were around 1 at the start of game 89. The first piece exchange was on move 24, in a series of exchanges all the queen side pawns were gone, Leela gave a rook for a bishop and the game reduced to a RRN vs RBN position on move 34. The knights were exchanged, evals came down and the engines started to shuffle. Leela's eval turned negative, all pawns were gone except for two black pawns. Leela continued playing, the game was finally adjudicated on move 180 with the 50-move draw counter almost at 0. In game 90 there were again only a few exchanges from the start. Leela controlled an open file on the queen side, Stockfish gave a rook for a bishop and pawn and Leela's eval jumped over 3. After exchanging queens the game reduced to a RRB vs RBN position on move 40. The white rooks were strong but the bishop was trapped on the king side. Leela went a pawn up and its eval close to 10 but it couldn't find a way to close the game. The engines shuffled, then exchanged rooks, Stockfish got a pawn back and the engines shuffled some more. The white bishop stayed trapped and Leela's eval slowly came down. On move 155 Leela finally gave its bishop up for a pawn and the game reached a drawn 7-man R vs BN position. The game was adjudicated on move 211. Was that a narrow escape for Stockfish? Or was it a bad evaluation by Leela?

Sunday, May 26, 2019

Season 15 superfinal, games 71-80

After 80 games Leela leads 10-5 with 65 draws. The last 10 games were all draws, including the bookless pair of games. Only 20 games are left, Leela is going to win almost surely.

In games 71-72 black started a pawn up in the Vienna Gambit. Stockfish's eval was 0 almost throughout game 71. Leela had an advanced passer on the king side, after a series of exchanges the white king side pawns were gone and Leela had a second passer. Stockfish's king walked to the queen side to get out of trouble. Leela gave a piece in a series of exchanges, its two passers reached the 6th and 7th ranks in a QRB vs QR position on move 29. Stockfish gave checks and then blocked the passers, Leela's eval came down and the game was adjudicated. In game 72 Stockfish had the same passer on the king side but its eval came down to 0 very quickly. Leela castled long and gave a rook for a bishop to remove the black passer. Most of the king side pawns were gone and Stockfish moved its king to the queen side. The engines shuffled for a while, then Stockfish gave two pawns and opened the queen side. Leela's king was under attack, after a series of exchanges the game reduced to a drawn queen ending. Leela continued playing until adjudication on move 81. 

Games 73-74 started with white a pawn up and with a queen side passer in the Benko Gambit. In game 73 evals started over 1. Stockfish had to move its king early, it walked to the king side. The white passer got to the 5th rank and Leela blocked it with pieces. Evals came down slowly, the engines exchanged most of the minor pieces. After a while the center and king side were blocked and the pawns on the queen side couldn't advance. The engines shuffled and the game was adjudicated early on move 38. In game 74 both engines castled short, Leela kept its queen side pawns back and its eval remained over 1.5. After a series of exchanges only QN vs QB remained on move 30, Leela's eval jumped over 2 while Stockfish's eval dropped to 0. Leela went up 3 pawns but could only give checks, or stop and allow Stockfish to give checks. Leela's eval slowly came down, it lost its knight and then the engines exchanged queens. The game ended in a tablebase draw.

In game 75 both engines castled long, most pieces and pawns were on the board and evals slowly came down. Stockfish pushed a pawn on the queen side and threatened the black king with its queen. The attack was not strong enough, evals were close to 0 and Stockfish ended the game with a perpetual check. In game 76 Stockfish pushed pawns on the queen side, Leela opened a file on the king side and exchanged rooks. The black king remained in the center, the white king castled long, both were vulnerable to attack. The engines exchanged most pieces and only QB vs QB remained on move 39. Stockfish's eval was at 0, Leela played on. On move 64 the queens were exchanged to reach an opposite color bishop ending. The game ended in a tablebase draw only on move 142.

Games 77-78 were bookless. Stockfish started game 77 with e4, and it turned into an Italian opening. All pawns remained on the board and evals stayed low. Leela concentrated its major pieces on the king side while Stockfish opened the queen side. After a series of exchanges the game reached a RNN vs RBN position on move 28. Stockfish could have finished the game with a repetition but continued and the engines reduced to a rook ending. The game ended in a tablebase draw. Leela started with d4 in game 78 and the game continued in a closed Catalan opening. On move 16 Leela's eval started climbing though it was a pawn down. It was over 1.5 for a few moves and then came down slowly. Stockfish remained calm, it gave the pawn back and exchanged pieces. The game reached a QN vs QB position on move 37 and Stockfish's eval was 0. Leela avoided exchanging queens until move 69, its eval came down and the game was adjudicated not long afterwards.

In game 79 the engines played behind the pawn lines, there was one piece exchange and one pawn exchange in the first 25 moves. On move 32 Leela's eval turned negative over 1, the king side pawns locked in a pawn line with a black pawn on g3 and the h file open. The engines started to shuffle, Leela trying to break in and Stockfish defending the entrances from within. The engines exchanged a pair of rooks on move 63, Leela's eval started to climb. The remaining rooks were gone on move 82 and the shuffle continued. Stockfish's eval suddenly jumped over (negative) 1.5 on move 111, evals climbed over 2. Then on move 125 Stockfish's eval dropped to 0, did Leela miss something? The engines started exchanging pawns and pieces and the game reduced to a queen ending, Stockfish found a perpetual check draw. In game 80 again there were few exchanges in the opening. Stockfish's eval stayed low, the engines opened a file on the queen side and Stockfish controlled it. A pair of rooks was exchanged on move 40, after some shuffling Leela's eval came down. The game reached a RB vs RB position and was adjudicated a few moves later.

Friday, May 24, 2019

Season 15 superfinal, games 61-70

After 70 games Leela leads 10-5 with 55 draws. Leela added two wins, winning a game pair from both sides. This is quite unusual for top level engines, Stockfish made a serious error of judgment in the opening as white. WIth 30 games left it is likely that Leela is going to win this match.

In game 61 evals were around 1 at the start. Leela thought Stockfish's 18th move was a blunder and its eval jumped over 1 (negative) while Stockfish's eval remained positive. Two moves later Leela had a protected passer on the king side.



The engines continue to shuffle with all pieces still on the board. Stockfish did not see any danger until move 33, by then Leela's eval was over 4. On move 37 the first pieces were exchanged and Leela added a second passer on the king side.


Leela opened a file on the queen side and threatened the white king. Stockfish was careful not to exchange pieces that would weaken its defense. After some shuffling Leela gave a rook for a knight, exchanged queens, captured a pawn and created a third passer in a RRB vs RRN position.


The black pawns started to move and Stockfish couldn't stop them and its counter attack was weak. Stockfish gave a rook and bishop to capture all three passers, the game was adjudicated in a R vs RNN position.

In game 62 the engines opened the center and the black king was forced to move early. Leela's eval climbed over 2 while stockfish's eval remained low. Stockfish moved its king to the queen side in a slow long castling, then the engines locked the queen side pawns. After opening a file on the king side Stockfish's major pieces faced the white king but were not strong enough to attack. Leela's eval jumped over 3, after exchanging queens it went a pawn up and created a king side passer.



Stockfish exchanged a bishop for a knight and got the pawn back. Both engines applied pressure on their opponents' weak pawns, in the end it was Leela who had the upper hand. After exchanging a pair of rooks it won the f5 pawn and connected a second passer on the king side in a RBN vs RNN position.



Stockfish captured the c4 pawn as well, material was equal but Leela had a winning advantage. It could block the black passer while pushing its own, Stockfish had to give a knight to stop it. The game was adjudicated when the second white passer pushed forward. An unexpected double win for Leela in this opening.

Evals were low throughout game 63. There were many early pawn exchanges and open files. The two kings were vulnerable to attack. In the end Stockfish gave two rooks for minor pieces and finished with a repetitive check draw. In game 64 Stockfish's eval was 0 right from the start. The center was blocked, Leela exposed the black king with a knight sacrifice, and got the material back a few moves later. Only QB vs QB remained on move 36, both kings were exposed and the queens gave checks. Leela gave a bishop to get a pawn to b7, Stockfish continued to give checks until the game was adjudicated on move 138.

In games 65-66 the engines castled in opposite directions. Leela was active on the queen side in game 65, it sacrificed a knight to clear the white pawns and exposed the white king. Evals stayed low as Stockfish moved its king to the center and Leela created a queen side passer. In a series of exchanges Stockfish gave two minors for a rook and only RR vs RB remained on move 46. All the remaining pawns were passers but the engines couldn't force a queening. The game reached a tablebase draw on move 74. In game 66 Leela was active on the king side but could not break the black defense. Evals stayed low, when Leela sent all its major pieces forward Stockfish atacked the white king with its queen and found a perpetual check draw.

In games 67-68 again the engines castled in opposite directions. In game 67 Stockfish pushed pawns on the king side, after a long series of exchanges only RRB vs RRN remained on move 27. Leela was a pawn up, Stockfish moved both its rooks to the 7th rank and forced a perpetual check draw. In game 68 Leela pushed pawns on the king side and again there were early exchanges, this time the engines kept the queens on the board. Stockfish's eval came down to 0, Leela's eval stayed around 1. Stockfish went a pawn up on move 34, Leela pressed the king side but did not find a way in. The engines exchanged a pair of rooks and Leela avoided exchanging another pair. Stockfish ended the game with a rook sacrifice and perpetual check.

Games 69-70 started with a 24-ply book in the Semi-Slav Defense, with black two pawns up and a development advantage for white. There were many early exchanges in game 69, Stockfish forced the black king side rook to move and Leela kept its king in the center. Evals came down as queens were exchanged, the game reached a RB vs RN position on move 29. Stockfish equalized material, both engines had a passer they pushed forward. Once the pawns stopped moving the game was adjudicated. In game 70 Leela's eval jumped over 1 after a few moves and started climbing. The black king stayed in the center and the queens did not come off. The game reached a QRB vs QRN position on move 38 with equal material, Leela's eval was over 2. After exchanging the rooks Stockfish's dropped to 0. Leela had a queen side passer, Stockfish threatened mate and Leela gave checks until it could make a pawn move safely. The passer stopped on the 7th rank and Leela continued with checks. It could queen the pawn but the resulting QB vs Q ending would be a draw. This only delayed the inevitable, the game finally reached a tablebase draw on move 202.

Wednesday, May 22, 2019

Season 15 superfinal, games 51-60

After 60 games Leela leads 8-5 with 47 draws. Last 10 games were all draws, no change in the score.

Games 51-52 started with black a pawn up. In game 51 Stockfish exchanged pieces and its eval remained low. The white major pieces were active in the center and Leela had to defend the back rank. Stockfish put a rook on the 7th rank and the engines started to shuffle. On move 64 the engines started to exchange pieces and the game reached a queen ending. Leela played on and didn't lower its eval for a long time, the game ended in a tablebase draw on move 143. In game 52 the engines locked the queen side and didn't push the remaining pawns. They exchanged pieces gradually until reaching a rook ending on move 42. Stockfish went a pawn up and its eval was around 1, but the ending was a draw. The game was adjudicated only on move 144. 

All knights were off early in game 53, evals started at 1 and slowly came down. The engines kept all the pawns until move 25. The king side was blocked, the engines opened a file on the queen side and Stockfish's major pieces controlled it. After exchanging queens only RRB vs RRB remained on move 32. Leela went a pawn up and Stockfish ended the game with perpetual check. In game 54 the engines opened the queen side and center. On move 25 Leela exposed the black king, yet Stockfish's eval went down to 0 and stayed there. After exchanging queens only RBB vs RBB were left on move 34, Leela's eval came down as well. The engines reduced to a same color bishop ending, Leela kept playing until it lowered the eval for the draw rule on move 116.

Stockfish started game 55 with an eval over 1. Leela's eval clilmbed over 2 as the engines exchanged queens and Stockfish captured a rook for a knight early in the game. There were only a few piece exchanges as the engines' pawns advanced, evals came slowly down and were under 1 when the game reached a RRB vs RBB position on move 38. Leela created connected passers in the center that compensated for the material, evals dropped to 0. Pawn moves kept the game going, Stockfish gave a rook to get rid of one black passer and create two pairs of white passers on both sides. Leela gave a bishop to get rid of the pair on the king side. The game reduced to a 7-man RB vs RB position and ended by the 50-move rule on move 186. In the reverse game 56 Leela's eval remained over 1 for a long time. There were many early exchanges and the game reached a RRB vs RRB position on move 22. The engines shuffled with a few pawn moves, Stockfish's eval remained low. A series of exchanges reduced to a B vs R ending on move 85, Leela with a pawn on the 7th rank. Leela's eval came down and the game ended in a tablebase draw.

Games 57-58 started with a 22-ply book in the Benoni defense. Evals started over 1 in game 57. The engines cleared the queen side pawns in a series of exchanges, Stockfish's eval dropped to 0. The engines continued to exchange pieces and only RN vs RN were left on move 34. Stockfish was a pawn up but Leela's eval also came down. The game reached a drawn rook ending and was adjudicated. In game 58 Leela's eval jumped over 2 when Stockfish sacrificed a bishop and knight for 4 pawns. All the king side white pawns were gone and the white king was exposed and under attack. It ran to the center, Stockfish opened the queen side and threatened to add rooks to the attack. A series of exchanges stopped the attack and left a QRB vs QB position on move 35, Stockfish was 4 pawns up and Leela had only one pawn left. Stockfish's eval was 0, it gave checks and attacked the white pieces with the queen. On move 71 Leela gave material back and the game reduced to a bishop vs pawns ending, the game reached a tablebase draw.

Games 59-60 started with black two pawns up in a Danish Gambit. There were many early exchanges in game 59, only RRN vs RRB remained on move 24, Stockfish one pawn down. Stockfish pushed a pawn to h6 and placed a rook on the 7th rank, its eval dropped to 0. On move 45 the game reached a double rook ending with equal material, Leela played on and the game ended in a tablebase draw on move 90. In game 60 there were again many early exchanges and the game reached a RB vs RN position on move 23, Stockfish a pawn up and evals close to 0. Leela equalized material, the engines continued to capture pawns and the game ended in a tablebase draw on move 44.

Tuesday, May 21, 2019

Season 15 superfinal, games 41-50

After 50 games Leela leads 8-5 with 37 draws. Stockfish won two minimatches and Leela's lead is down to 3 points. In both wins the game was heading for a draw and the change in evals came very late when Leela was short on time. 

There were no exchanges for the first 24 moves in game 41, Leela's eval came down and Stockfish's eval stayed around 1. The engines opened a file on the queen side, then Leela gave a pawn on the king side. Stockfish had a passer but all the white pawns were blocked. The engines shuffled for a while, Leela gave a second pawn but Stockfish couldn't break the black defense. After a series of exchanges Leela regained the material and the position opened. Stockfish ended the game with perpeteual check. In the reverse game 42 there were many early exchanges and only RBN vs RNN were left on move 24. Leela's eval was around 1.5 for a while, after some shuffling the engines reduced to a rook ending. Leela's eval came down and the game ended in a tablebase draw.

The black king moved early in game 43, it was exposed on the king side but Stockfish didn't try to attack. Leela was surprised by Stockfish's move 19 and its eval jumped over 2.5, in a long series of exchanges the engines reduced to a QB vs QB position with Stockfish a pawn up.


There were a few pawns moves and exchanges, and then a long shuffle. It appeared that the game was heading for a draw, evals remained constant or slowly decreasing. Leela was getting short on time and perhaps this caused the blunder, it let Stockfish exchange queens on move 79. Leela's eval jumped over 2.5, but Stockfish saw mate after a few moves.


Leela realized it was losing much too late. There was no way to prevent Stockfish from taking the a pawn, and Leela couldn't stop both white pawns.

In game 44 the black king side was open and Stockfish castled long. Leela's eval was around 2, queens were off early and there were several exchanges until move 23. The engines started to shuffle with pawn moves resetting the 50-move counter. On move 120 the engines exchanged a pair of rooks and only RBB vs RBN remained. The next exchange was on move 163, the engines slowly reduced to a B vs N ending. The network crashed on move 201, and since it was a drawn 7-man position the game was not resumed but manually adjudicated a draw.

There were a few exchanges early in game 45, but none from move 8. The engines formed pawn lines and stayed behind them, Leela pushed a pawn to a3, Stockfish pushed its king side pawns. Evals stayed under 1, from move 40 the pawn moves stopped and the engines started to shuffle. Stockfish's eval started to increased on move 77, Leela was short on time and its moves may have been less than perfect. On move 84 pawn moves ended the shuffle,  Stockfish had a passer in the center and a knight on g6, evals were over 3.


A series of exchanges opened the position, when it was over Stockfish was up two pawns with two advanced passers.


Leela tried to counter attack with its queen and rook through the queen side. This left the black king vulnerable, Stockfish protected its king and attacked the king side. The game was adjudicated with mate in the PV. 

In game 46 Leela moved its king without castling, it pushed its king side pawns and had a space advantage. There were no pawn exchanges until move 25, Leela's eval was over 3 when Stockfish gave a pawn and the engines opened two files on the queen side. The engines shuffled for a while, on move 52 the queens were exchanged and Leela's eval was over 4.5. All the pawns were blocked, Leela gave a rook for a bishop and two pawns to create a queen side passer in a RB vs RR position. Stockfish's eval dropped, it allowed Leela to capture a pawn and found a perpetual check draw.

Evals came down quickly in game 47 and they remained low throughout the game. The engines gradually exchanged pieces and the game reached a RB vs RN position on move 35. The game was soon adjudicated. In game 48 the black king side rook moved early and Stockfish kept its king uncastled. Leela's eval kept climbing, peaking over 2. The engines exchanged several pieces and played mostly behind the pawn lines. On move 39 the pawns stopped moving, Leela couldn't find a way to improve and its eval slowly came down. The game ended with the 50-move draw.

Evals were around 1 at the start of game 49. There were no pawn exchanges for the first 23 moves, then the engines exchanged pawns and opened the queen side. By move 34 all the pawns on the queen side were gone and evals came down. The game reached a RBN vs RBN position and ended in a tablebase draw. In game 50 again the engines waited before exchanging pawns. After a long series of exchanges that ended on move 29 Stockfish was a pawn up, there were open files on both sides of the board controlled by Leela's rooks. Stockfish's eval came down to 0 as the engines shuffled for almost 50 moves. The engines exchanged the remaining pieces and reached a rook ending. Both had passers, first Stockfish gave a rook queened and then Leela did the same. Leela's eval was over 2 but the queen ending was a draw, the game was adjudicated on move 158.