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.

Sunday, May 19, 2019

Season 15 superfinal, games 31-40

After 40 games Leela leads 8-3 with 29 draws. Leela extends its lead to 5 points. Five of the last 10 games were decisive, including two openings with two white wins. Stockfish showed it can win games on its own without a Leela blunder, but only when it gets a big enough advantage that Leela can beat it in the reverse. The winning styles are very different, Stockfish goes for the kill when it can, Leela sees the win from afar and slowly strangles the opponent.

In games 31-32 black started a pawn up with a small avantage. In game 31 the network crashed again and the game was resumed. Evals stayed low, Stockfish's eval was 0 almost throughout the game. Stockfish gave a second pawn early, it had a strong bishop pair that prevented Leela from castling. The game reached a RB vs RN position on move 32 and Stockfish regained the material. Leela continued to play until reaching a tablebase draw on move 87. In game 32 Leela's eval was 0, Stockfish castled early and kept its pieces longer on the board. The engines gradually exchanged pieces without attacking. Stockfish captured two more pawns and gave a rook for a bishop, the game reached a QRB vs QBN position on move 37. Stockfish found a perpetual check several moves later.

In game 33 the engines opened the queen side and exchanged many pieces early with evals coming down to 0. After some shuffling the engines exchanged all rooks and the game reached a QB vs QN position on move 43. Leela thought it had a small advantage and played on, the engines gradually exchanged pawns until only one was left on move 89. Leela kept the 7-man position alive with pawn moves until finally reaching a tablebase draw on move 262. In game 34 again there were many early exchanges, Stockfish's eval came down to 0. All rooks were gone on move 27 and the game reached a QB vs QB position on move 33. This time Leela lowered its eval and finished the game with perpetual check.

Games 35-36 started with a 22-ply book in the Sicilian Najdorf variation, with the engines castling in opposite directions. In game 35 Stockfish pushed pawns on the king side, Leela gave a rook for a knight and opened a file on the queen side. Stockfish pushed a pawn to h6 and the engines started to shuffle on move 26. The black king walked to the center, away from the king side cage. Evals started to climb only on move 90 (!!), on move 100 Stockfish opened a file on the queen side with evals over 1.



The white king was exposed and moved away. Stockfish's attack on the queen side did not succeed. Evals started to jump when Leela countered and pushed the b pawn forward. After a series of exchages only QRB vs QBB were left and Stockfish had a passer.


Leela gave a few checks with its queen but had to block the passer. Stockfish found an opportunity to put its rook on the back rank, when it took the h7 pawn the game was over.

In game 36 Leela surprised Stockfish on move 19 with c4, opening a file on the queen side with the black heavy pieces facing the white king. Leela's eval jumped over 2 as it moved its knight to c6.



It took Stockfish a long while to see it was in trouble. The c6 knight was a monster and Stockfish could not force it away with pawns or heavy pieces. The only way was to use the black knight, and it took Stockfish many moves to get its knight to an attacking position. Leela was willing to exchange knights since this would create an advanced passer. When Stockfish tried instead to block a file with the knight Leela surprised it again and gave a rook for the black knight.



Leela got its passer and kept its knight. The white king moved forward for support, and after taking the black b pawn Leela had connected passers advancing on the queen side. Stockfish lost a bishop to capture one, the other reached a7. It was a matter of time before the game was adjudicated. Two white wins in this opening, with two very different games.

In game 37 the engines opened a file on the queen side and exchanged all the rooks. Evals slowly came down to 0 and the game was adjudicated by the draw rule on move 50. In game 38 the same file opened on the queen side but Leela kept its rooks. Its eval climbed over 2 as it opened a second file, Stockfish's eval was over 1 as the engines shuffled for a while. Leela surprised when it gave a rook for a knight on move 42.

The pawn structure looked ugly, but Leela's knight was an advantage and the black bishop could not attack the isolated white pawns. Leela captured the d6 pawn and its eval climbed over 4. The game reached a QBN vs QRB position and evals continued to climb. Stockfish gave the material back and Leela went two pawns up in a QB vs QB ending.


The ending was not trivial, Stockfish's last hope was to reach a drawn opposite color bishop ending. Leela was willing to trade queens if its queen was on c6 since this would create connected passers. In the end Leela managed to capture the b6 pawn and then exchange queens. Three pawns were enough for the win.

In game 39 the center was blocked, Leela opened a file on the queen side and moved its heavy pieces there. The engines exchanged a pair of rooks and Stockfish's eval jumped over 2. It saw an opportunity for a king side attack with the black queen too far to retreat. Leela saw the danger 3 moves too late.


Stockfish sacrificed a bishop and a pawn, opening the king side and threatening mate. It then followed with a rook sacrifice that forced Leela to lose a queen. The game reached a QB vs RBN position on move 31.

Stockfish gave the bishop but captured the black knight a few moves later. Leela had no defense against the white queen, after capturing a few pawns the f pawn became a passer and the game was adjudicated with mate in the PV.
A spectacular win for Stockfish.

Leela's eval jumped over 2 early in game 40. Leela pushed a pawn to h6, then in a series of exchanges the queens were off. Leela had a bishop pair and the black bishop was almost trapped, yet material was equal and Stockfish was calm.


Evals increased slowly, Leela pushed pawns on the king side and moved its king forward. Stockfish would not exchange its knight for a bishop while its own bishop was trapped. Leela opened a file on the queen side and forced a bishop for knight exchange. After exchanging a pair of rooks Leela went a pawn up.


The remaining bishops were of opposite color so Leela had to be careful to keep its rook. It managed to push the black king back and then moved the white king forward. Leela started capturing black pawns, it was 3 pawns up when the game was adjudicated. Again two white wins in this opening in two different styles.

Friday, May 17, 2019

Season 15 superfinal, games 21-30

After 30 games Leela leads 5-1 with 24 draws. Leela gets two more wins, so far the only way Leela loses is by blundering in an endgame. We have not seen a weak opening for Leela until now.

Stockfish had a small eval advantage from the start of game 21. The engines opened the king side and Leela was able to get a pawn to f3, its eval turned slightly negative. The white king walked to the center, Leela shifted to the queen side and opened a file. Stockfish attacked the back rank with a rook, after a series of exchanges only RR vs RB remained. Leela was two pawns up with a queen side passer, Stockfish closed the game with perpetual check. In game 22 Stockfish's eval was 0 from the start and remained almost constant the entire game. There were only a few exchanges after the start, the engines developed behind pawn lines. A series of exchanges that started on move 28 opened the position, both engines had passers on the queen side. Leela pushed a passer to a6 and there it was blocked. After a while the engines reduced to a QRN vs QRB position and captured all the queen side pawns. Leela continued to play and the game ended in a tablebase draw on move 97.

Games 23-24 started with a 24-ply book in a closed Ruy Lopez. In game 23 evals started around 1 and slowly came down. Stockfish was strong in the center and Leela pushed pawns on the queen side. A series of exchanges cleared most of the pawns on the queen side by move 34, by move 47 only QRN vs QRB remained. Stockfish went a pawn up and reduced to a rook ending, 3 vs 2 pawns on the king side. It took almost 50 moves for Stockfish to lower its eval for the draw rule.

In game 24 Leela's eval started at 1 and slowly increased. There were almost no exchanges until move 28, Stockfish's eval stayed under 1. A series of exchanges opened the position, material was equal yet Leela's eval was over 2, Stockfish was still not convinced.


The engines exchanged a few pawns and evals continued to increase. The game reached a BN vs BN position on move 53 and Leela went a pawn up for the first time after taking the h4 pawn. Stockfish had connected passers in the center but Leela's passers on the two flanks were more dangerous. 


The kings went to the king side and the pieces to the queen side. Stockfish was too busy defending that it could not push its passers. Leela exchanged bishops and captured another pawn, the resulting knight ending was a win for white.

Games 25-26 started with a 21-ply book in the Queen's Indian defense, Fianchetto variation. In game 25 the engines opened the queen side early and Leela was up a pawn. Evals slowly came down, the engines mainly shuffled for a while. On move 30 the exchanges resumed and Stockfish equalized material. On move 43 the game reached a QBN vs QBN position and the game was adjudicated a few moves later.

The network crashed in game 26 and it was later resumed. It started identically to the reverse game up to move 17. Stockfish was a pawn up and had a queen side passer, Leela had the bishop pair advantage and more space. The engines started to shuffle on move 20 with a few pawn moves in between. On move 38 Leela gave a second pawn, and this led to a series of exchanges and a QRB vs QNN position.


For a while evals did not change. The engines exchanged pawns and queens, all remaining pawns were on the king side except for one isolated black pawn on the king side. The black knights were too far away and busy defending their king. Leela captured the a pawn, its eval jumping over 6.5.


The white pieces were stronger than the black knights. The game was adjudicated after Leela moved its king forward.

There were many early exchanges in game 27, by move 21 only RRB vs RRN remained. Stockfish was up a pawn while Leela pushed a pawn to h3 and had a rook on the 2nd rank. Stockfish captured a second pawn but evals were close to 0, the white king was in danger and Leela's control of the 2nd rank compensated for the material. The engines reduced to a rook ending and continued to play, the game ended in a tablebase draw on move 87. In game 28 both engines captured a rook in the corner early. The white king had to move but Leela's eval was over 1.5 and increasing. The white king walked to the queen side, Leela's eval peaked over 4 and the game reached a QRB vs QRN position on move 32. Stockfish gave a pawn and created an advanced passer, its eval dropped to 0 while Leela's eval remained around 3. Leela could not improve its position, it won a second pawn but eventually lowered its eval as Stockfish found a perpetual check draw.

In game 29 the engines opened the queen side early, both kings castled short and were not involved in the game. Evals started around 1 but came down as the engines fought for control of the open files. The rooks were first to go, then the queens and the game reached a drawn BBN vs BBN position. The network crashed again in game 30 and the game was later resumed. Stockfish's eval was close to 0 throughout the game. There were many early exchanges that opened the position and led to a R vs BB imbalance. Leela was two pawns up and it thought it had an advantage, Stockfish held the position without a problem. The game reached a R vs BB ending on move 45, Leela kept playing untile reaching a tablebase draw on move 166.

Wednesday, May 15, 2019

Season 15 superfinal, games 11-20

After 20 games Leela leads 3-1 with 16 draws. Stockfish equalized after a Leela blunder in an endgame. Leela responded with two wins. So far only Leela has shown it can turn an advantage to a win. It is still early in the match but Stockfish does not appear to be strong enough to win.

Games 11-12 started with a 17-ply book in the French Tarrasch closed variation. Evals fell to 0 very quickly in game 11, the engines gradually exchanged pieces and Leela's eval turned slightly negative. On move 30 Stockfish gave a rook for a knight and pawn, Leela refused to exchange queens and the game reached a QRB vs QRR position. The engines captured pawns, then in a series of exchages reduced to a B vs R drawn ending.

In game 12 Stockfish's eval fell to 0 very quickly, Leela kept a small eval that stayed under 1. On move 32 Leela captured a rook for a knight, Stockfish had a passer it pushed to the 3rd rank. The game reached a QRB vs QBN position, the engines shuffled and Leela's eval slowly came down. On move 62 the queens were exchanged and Stockfish created a second advanced passer. The game was heading for a draw when suddenly Stockfish's eval jumped over 4.


Leela should have blocked the d pawn with its rook. Instead Leela had to block with the king, it couldn't take the pawn because it would lose the rook in a fork. It took Leela 6 moves to realize it was losing. The two passers were too strong and Leela couldn't stop both without losing material.

Games 13-14 started with a 22-ply book, a popular Symmetrical English variation. In game 13 Stockfish had an eval of around 1. It opened the king side but did not develop an attack on the black king. Leela opened a file on the queen side, the engines exchanged a pair of rooks and evals came down. The engines exchanged pieces until the game was adjudicated in a QBN vs QBN position. In game 14 Leela pushed pawns on the king side, Stockfish gave a bishop and cleared the white king side pawns, exposing the white king. The engines continued to exchange pieces and pawns and evals came down. On move 43 only RN vs R were left, Leela continued to play another 30 moves but Stockfish held the draw.

Game 15 started with a network crash and was restarted. Stockfish had an eval over 1 from the start, it kept its king in the center even though the engines cleared the center pawns. The black queen was very active, Leela went a pawn up. By the time Stockfish moved its king to safety evals came down. Stockfish regained the pawn, after queens were exchanged the position became very drawish with pawns only on the king side. The game ended in a tablebase draw.

Leela started game 16 with an eval over 1 that increased slowly. All the pawns remained on the board, the engines mostly played behind the pawn lines. On move 21 Stockfish remained without a knight, a disadvantage in a closed position. Stockfish's eval was under 1, only when Leela's eval reached over 3 did Stockfish start to think it was in trouble.


The black king side rook was trapped, and the c6 pawn was a long term weakness which Leela could attack with multiple pieces. The engines shuffled for a while, then Leela found a plan to improve its position. The doubled pawns on the d file had to be protected, Leela moved its king to the center so it could take the role of defender.


Leela could attack more freely with its pieces, it captured the h4 pawn, the first pawn to be taken in the game. A few moves later the queens were exchanged leaving only RRN vs RRB, Leela's eval was winning, Stockfish still wasn't convinced. Indeed, there was a very long shuffle, only on move 120 Leela went two pawns up. Stockfish finally agreed it was losing, the game was adjudicated on move 143.

Games 17-18 started with a 22-ply book in the King's Indian defense, Bayonet attack. Evals were over 1 from the start of game 17, the center was blocked and Stockfish had a significant space advantage on the queen side. Stockfish gave a pawn and opened the queen side, then moved its knights forward. Leela had two connected passers on the queen side while Stockfish put a protected knight on e6. Leela gave a rook to get rid of the white knight, simplifying the position. After some shuffling Stockfish gave the material back and captured the black passers. The engines reduced to a BB vs BN position, Stockifsh was a pawn up but could only shuffle. The game was adjudicated on move 111 with the 50-move draw getting close.

In game 18 Stockfish pushed pawns on the king side and opened a file, while Leela pushed pawns on the queen side all the way to a6. Leela's eval was over 2 after it opened a file on the queen side and exchanged several pieces. Stockfish's eval also increased slowly, it had less space and its pieces surrounded the black king defensively, trying to hold the position.


Leela applied pressure and tried to find a way to break black's position. After exchanging the LS bishops Leela gave a pawn temporarily and forced a queen exchange. Evals jumped over 5 as Stockfish's defense collapsed.


All the black pawns were on dark squares, targets for Leela's bishop. Stocksih couldn't protect them all and Leela went two pawns up. Then it was just a matter of pushing pawns forward to get the win.

In game 19 Stockfish castled long while Leela kept its king uncastled and pushed pawns on the queen side. Evals came down to 0 by move 20 and stayed there for the rest of the game. Leela pushed a pawn to a3 but could do no more on the queen side. Stockfish opened the king side but did not attack the black king. The engines continued to exchange pieces, Stockfish ended the game with perpetual check. In the reverse game 20 both engines castled long. There were many early exchanges, with RN vs RB remaining on move 25. The game reached a N vs B ending which continued for more than 50 moves before reaching a tablebase draw.

Monday, May 13, 2019

Season 15 superfinal, games 1-10

The season 15 TCEC cup is over, Leela is the winner, keeping its title from last season. In the semifinals Leela beat Houdini with two wins in 7 games, and Stockfish beat KomodoMCTS with the same score. It is interesting to note that KomodoMCTS beat its elder brother Komodo in the quarter-final by a single win in the last game of eight played. In the final Leela won the third game and Stockfish won the 8th game to even the score. Then Leela won the next game and held the draw in the reverse, winning the first tiebreak minimatch and the cup.

In the premier division Stockfish was in front, it had a better score than Leela against the lower ranked engines. However in their head to head games Leela managed to beat Stockfish once out of 6 games. Recall that last season in the superfinal Stockfish won but by the smallest of margins. It is very hard to predict the result of this superfinal and I hope we have another close and competitive match.

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After 10 games Leela leads 1-0 with 9 draws. The first 9 games were drawn, including one pair of King's Gambit games where Stockfish is considered to have an advantage.

Stockfish started game 1 with an eval close to 1. The center was blocked, the engines castled in opposite directions but the position remained closed with only one pair of pawns exchanged. Leela's eval became negative, the queen side was blocked and the engines shuffled from move 23. On move 49 Leela gave a rook for a bishop and created a king side passer, its eval jumping over 1. It pushed the king side pawns a little and after a few more piece exchanges its eval peaked over 2.5. However, Leela could only continue shufflling, in the end Stockfish gave back the material and found a perpetual check draw. In the reverse game Leela's eval was over 1, the engines exchanged pieces and the position was more open. Stockfish's eval dropped to 0 as Leela captured pawns. After exchanging all rooks Stockfish was down 3 pawns, its counterattack on the white king was strong enough to win a bishop. Leela captured all the black pawns and Stockfish forced a perpetuak check draw.

Games 3-4 started with a 30-ply book sequence in the Sicilian Scheveningen variation. In game 3 Stockfish started with a small eval advantage that fell to 0 after the engines opened the queen side. Stockfish had a queen side passer, the engines exchanged pieces until reaching an opposite color bishop ending and a draw. In game 4 Leela's eval went over 1 after it created a passer on the king side. Stockfish hid its king behind the passer and was relatively safe. The engines exchanged pieces and shuffled for a while, evals came down after Stockfish opened the center. The exposed white king gave Stockfish enough compensation, the game was adjudicated a draw in a QRN vs QRB position.

Queens were off early in game 5, Stockfish was a pawn up. The game reached a RRB vs RRB position on move 28 and the engines shuffled until adjudication close to the 50-move rule. In game 6 Leela had an eval around 1 from the start. Stockfish kept its king in the center, Leela attacked on the queen side and forced the black king to move. The game reached a R for BN imbalance on move 24, Leela attacked the exposed black king with its queen and rook. Stockfish's eval remained at 0 despite what appeared to be a scary situation. On move 40 the engines traded Q for RB and the game reached a RRB vs QBN position, Leela's eval dropped. The rest of the game was mostly shuffling, Leela managed to capture all the black pawns but not more. In the end Stockfish found a way to force stalemate on move 144.

Games 7-8 were a KGA variant. In game 7 queens were off early and Stockfish's eval was 0. There were many early exchanges, on move 32 Stockfish gave a rook for a knight and only RBN vs RRN were left, Stockfish two pawns up. Then Stockfish gave a knight for a pawn, Leela was down to one pawn and Stockfish had 4 passers on the queen side. The white passers compensated for Leela's material advantage, Leela captured two passers but could only stop the other two. After a long shuffle the engines exchanged down to a tablebase draw. In game 8 Stockfish had 2 connected passers facing the white king on move 11. Both evals were negative over 1 when the engines played out a PV agreement that started with Leela giving a rook and pawns for a bishop. Stockfish's eval dropped despite the material advantage, Leela gave another rook for a knight and attacked the black king. Stockfish gave up its passers and an exchange to get out of trouble. Leela's eval dropped and Stockfish ended the game with perpetual checks.

In game 9 the network crashed on move 20 and the game was later resumed. Stockfish had an eval advantage of around 1 from the start. Stockfish won a pawn with doubled rooks on the f file, Leela forced a queen exchange. The queen side was blocked, Leela used the open file to exchange all rooks and the game reached a same color bishop ending on move 34. Evals dropped to 0 and the game was adjudicated.

Leela had an eval over 1.5 after the opening in game 10. It opened the a file and pushed a rook to a7, Stockfish countered by pushing pawns on the queen side and creating an advanced passer. Leela won a piece, Stockfish's eval was around 1 as it thought the passer was worth the material. Then Leela offered a rook exchange on move 24:


Stocfish exchanged on c6, allowing Leela to create a passer. Leela thought this was a mistake and its eval jumped over 3, it anticipated an exchange on c8.  As expected Leela gave a knight to remove the black passer. It was up a pawn with two passers on the queen side, yet Stockfish thought it was relatively safe. It anticipated to get rid of the c6 passer through a queen exchange, and failed to see Leela's move 29:


Stockfish's eval jumped after this move. Leela gave back a pawn but kept its passers, only then the queens were exchanged. Several moves later Stockfish had to give a knight to get rid of the passers, leading to a RBN vs RB position.


The ending was far from trivial, with all the pawns on the king side. However Leela did not blunder, perhaps taking longer than was necessary. Eventually it forced a bishop exchange and Stockfish agreed the RN vs R position was a win.

Wednesday, May 1, 2019

Season 15 premier division statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins


Final draw rate was 75%.


Game termination

The three most common game termination causes were:
38.7% - TCEC draw rule
24.4% - TCEC win rule
20.2% - SyzygyTB

KomodoMCTS crashed once in the division.

Moves per game


Median= 69.8
Average= 80.8

There were 38 games longer than 100 moves, the longest was 217 moves (Game 112, Komodo - Leela, draw).

Time per game (hours)


Median= 2:59
Average= 2:51

Openings

There were 16-ply book openings in this stage chosen by Cato. The first letter of the ECO codes was distributed as follows:


The engines had almost no freedom to choose the opening variant. Indeed, all of the game pairs repeated the same ECO code twice, and repeated the same opening variant.

Reverse pairs, wins


Reverse pairs, same moves   


Pairs of reverse games diverged very quickly, 40.5% diverged immediately out of book, 75% of the pairs diverged at most after 1 move. The longest repeated sequence was 11 plys (Komodo - Houdini, games 134 and 162, Sicilian Kan variation, two draws).

Sunday, April 28, 2019

Season 15 premier division results

Final crosstable


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

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


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

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

A few interesting games

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

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

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

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

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

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

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

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

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


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


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


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


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

Thursday, April 25, 2019

Season 15 premier division after RR5

Crosstable after RR5


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

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

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

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

A few interesting games

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


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

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

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

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

Komodo - AllieStein: See featured game below.

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

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

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

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



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

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


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


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


Mate was close when the game was adjudicated.

Monday, April 22, 2019

Season 15 premier division after RR4

Crosstable after RR4


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

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

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

A few interesting games

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

Leela - KomodoMCTS: See featured game below.

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

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

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

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

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

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

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

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

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


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



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



The game was adjudicated 25 moves later.

Saturday, April 20, 2019

Season 15 premier division after RR3

Crosstable after RR3


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

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

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

A few interesting games

Komodo - Stockfish: See featured game below.


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

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

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

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

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

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

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

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

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



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

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


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

Tuesday, April 16, 2019

Season 15 premier division after RR2

Crosstable after RR2


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

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

A few interesting games

Stockfish - KomodoMCTS: See featured game below.


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

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

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

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

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

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

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


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


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


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


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