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.