Season 12 live blogging, Monday Apr 30th

We are in the final rounds of division 3, 2.5 double rounds to go. The relegation is more or less determined, Senpai and Wasp are on their way to division 4 next season. The leader ChessBrain is almost certainly promoting to division 2. The second engine to promote will be one of Pedone, Xiphos, Ethereal and Bobcat. Xiphos is leading but it still has to face ChessBrain, while the other engines have easier opponents.

The next two games are between Pedone and Xiphos, any decisive result can have a big impact on the race for promotion. We start with Pedone in white.

move 8 - The engines playing a QGD, following theory until move 6 and then playing a more rare sideline. Xiphos' eval drops to 0.

move 12 - evals continue to be low, not sure what the engines are planning. So far there are not many exchanges, kings are safe, no clear weaknesses.

move 15 - Pedone's eval is slowly increasing, it is making indirect threats on the black king. Xiphos is not impressed.

move 18 - Xiphos has a bishop pair but its LSB is still undeveloped. Pedone pushing pawns on the king side, Xiphos countering on the queen side. The game is getting interesting.

move 22 - Pedone's evals still rising, over 0.6. Pedone's PV is suggesting exchanges in teh near future. Xiphos continues tro be defensive, its queen side rook is its most advanced piece on the 5th file.

move 28 - after a few pawn exchanges the position is opening, Xiphos created a queen side passer, Pedone exposed the black king. Pedone's eval dropped, most probable outcome is now is a draw.

move 35 - Xiphos queened a pawn temporarily, a part of a series of exchanges resulting in a N vs R imbalance. Pedone with an extra pawn is behind on material but its eval is rising again. It has a king side passer now.

move 42 - the black bishop has not moved yet, and the white knight is in a great square to limit the bishop's movement. Not clear how Pedone can make progress here. Black fortress?

move 48 - liquidation! Only QB vs QR are left, Pedone gained a second pawn and evals are again close to 0.

move 56 - draw rule, game over.

I suppose a draw is good for Xiphos, and it is playing white in the next game. I'm signing off now, catch the next game later.

Season 12 live blogging, Saturday Apr 28th

Division 3 is getting close to the halfway point. Nemorino just completed two straight wins against Senpai, and this means that Wasp and Senpai are the candidates for relegation with Nemorino 2 points away. So far ChessBrain and Xiphos are leading, if Ethereal has a good result in its next two games against Pedone it may join the leaders. Pedone is also on crash alert, having crashed once in the division.

 

First game Pedone is in white.

move 10 - The engines started with a classical line of the Caro-Kann. So far Ethereal hasn't castled, with the h file open it may go the other way. Evals are close to 0, looks like Pedone has no opening advantage.

move 15 - Ethereal castled king side, and Pedone moved a rook to the h file, threatening the black king. Pedone's eval is rising, it may be planning a king side attack.

move 21 - now the white queen is on the h file and the black king is on the run. Evals over 1, Ethereal is in trouble.

move 25 - Pedone is a pawn down and Ethereal is countering on the queen side. The black king is safe in the center for now, evals are decreasing.

move 28 - Pedone can take on d4 but prefers to wait and not exchange pieces yet.

move 30 - BOOM, eval jump. Did Ethereal miss something? Pedone is driving the black queen away, the PVs show a material advantage for white.

move 33 - evals over 7, Ethereal gave a rook for a bishop, probably the black king is not safe. The game is going to end soon if Pedone doesn't crash.

move 36 - game over, Pedone is in third place, with the same score as Ethereal.

The rematch will start immediately.

move 5 - this is a different Caro-Kann, Tartakower variation. 

move 8 - still following theory, Pedone is taking its time and each move I wonder if it crashed.

move 12 - Pedone left theory on move 9, Ethereal's king moved without castling, but evals favor white. Ethereal is pushing the h pawn with an eval jump, king side attack? Is the white king safe enough for this? Pedone is not impressed.

move 15 - the black king looks in danger but the white DSB is trapped and evals dropped to 0. The white king side is still not developed, the rook is also trapped, evals get slightly negative.

move 18 - the black bishops are very active, Ethereal with a very long think and a strange a3 move. Negative evals are climbing, now over 1 for Pedone.

move 23 - Pedone appears to be on its way to a double win over Ethereal. The white DSB fights out of the trap, Pedone winning a knight for pawns.

move 28 - double BOOM, Pedone's eval jumped over 7 in two moves. Ethereal is overlooking something important.

move 30 - again king safety issues for Ethereal. it lost control of the e2 square and the king is under attack. Game is going to end in a few moves, even faster than the previous game.

move 32 - game over, quite incredible. When it is not crashing Pedone is playing very well. The race for promotion is still wide open.

Season 12 live blogging, Thursday Apr 26th

Division 3 is running, Ethereal and Xiphos are joined by 6 more engines, all trying to promote to the next division and to avoid relegation. The second double round has just ended - in the new games schedule reverse games are played consecutively. We join game 17 ChessBrain vs Pedone, the engines currently in the lead with two wins and two draws each.

move 10 - the engines are playing a Queen's Indian Petrosian line, move order was a bit unusual but it transposed back on move 8, and then diverged from opening databases.

move 13 - Pedone pushed the c pawn and forced white to move a bishop. ChessBrain's eval was climbing for a bit but dropped back. Pedone is harassing the white LSB, while both its own bishops are quite restricted.

move 16 - Pedone expected to exchange bishops, ChessBrain chose to move its bishop away and threaten the black king. ChessBrain's eval is rising again, Pedone's going to 0.

move 18 - Pedone's queen side rook looks miserable, blocked by its own pieces. The king side looks ready for a white attack. However, even ChessBrain thinks Pedone is still solid enough. Now Pedone's eval is slightly negative? Its PV shows many exchanges and a pawn advantage.

move 21 - Evals back to positive. ChessBrain's PV shows a different story, a pawn advantage for white. The queen side looks blocked now, expect action on the king side. Pedone freed its queen side rook and both evals close to 0.

move 25 - engines are pushing pawns on both sides, the position is opening up. ChessBrain's eval is higher again, it's fluctuating a lot. Pedone is seeing many exchanges, will ChessBrain simplify this time? It appeared to sacrifice a knight but Pedone left it alone - probably too dangerous.

move 30 - ChessBrain has a bishop pair, probably contributing to the eval. Now Pedone has a pawn advantage on the queen side, the king side attack is not picking up and the white king is also exposed. Will ChessBrain's eval hold over 0.5?

move 35 - more simplifications, now queens are off and rooks may be next. Time is running short and the engines will start to blitz moves.

move 41 - ChessBrain gave a rook for a bishop and pawn, hoping its bishop pair is strong enough in a RBB vs RRN position. Pedone gave another pawn, evals dropping. Pedone is planning to get rid of a white bishop, and here is the simplification. The B vs R endgame is going to be a draw unless an engine blunders.

That's it for me for this session. The draw rule is in effect, probably a draw soon.

Season 12 division 4 final results

Division 4 final crosstable



Ethereal and Xiphos are promoted to division 3. Ethereal did not lose a game in the division and led from the start. In the early rounds Rodent was close to the top of the table, but with 4 losses to Xiphos it finished 3rd.

Scorpio crashed 7 times, mostly on the very first move after book. This is disappointing since its performance was better than it was in season 11 in the games it did finish. According to the 3-strike rule all its games are removed and it is automatically relegated (though there is no relegation in division 4). The formal crosstable taking this into account does not change the standings significantly.

Leela's games (LCZero) attracted a lot of attention, as it is a community effort and a different approach to the search and score algorithms in other engines. The project is trying to use the same learning approach of Google's Alpha zero, using normal hardware and public resources for training the neural nets. In division 4 it had several interesting games but it lost almost all of them (its single win was a Scorpio crash...), usually blundering in the middle and endgame even if it had an advantage. The project is rapidly evolving and there is a good chance it will perform much better in the next season.

Division 3 is about to start, with the engines Bobcat, Wasp, Nemorino, Pedone, ChessBrain and Senpai joining Ethereal and Xiphos. The format will be identical to division 4, 4RR with 30+10 time control. I expect division 3 to be a more exciting event than division 4, with a higher draw rate and closer scores. According to the CCRL rating list the engines are quite close. Ethereal's author appears regularly on the chat and thinks its engine should promote again, in season 11 it finished last in division 3 so that would be a significant improvement.

Season 12 division 4 statistics

Draw rate, wins



Final draw rate was 25.9%. This is unusually low, and in part due to the fact that Leela lost almost all of its games


Game termination

The three most common game termination causes were:
63.4% - TCEC win rule
11.6% - TCEC draw rule
9.8% - TB position

There were 2 games that ended in mate on the board, Leela games in both cases, extreme examples of Leela blunders. There were 7 crashes, all by Scorpio. 

Moves per game

 

Median= 59.8
Average= 66.3

Includes 5 games where Scorpio crashed almost immedately out of book, and one of the longest games in TCEC history with 353 moves (Fruit - Scorpio, round 6, draw).

Time per game (hours)
  

Median= 1:11
Average= 1:12

Openings

There were 2-move book openings in this stage chosen by Cato. The first letter of the ECO codes was distributed as follows:


For each round all four games had the same book sequence, and again in the reverse round. There were 14 book sequences, each repeated 8 times. For some sequences all the openings had similar codes (e.g. Sicillian or French). In others the engines had more freedom to choose.

If we use the opening 'family name' (using format FAMILY_NAME: VARIANT....) the top 3 are:
Sicillian - 24 times
QGD - 20 times
English - 13 times

The engines had a lot of freedom to choose the opening variant. Only 25% of the game pairs repeated the same ECO code twice, and only 5.4% repeated the same opening variant. In 19.6% of the game pairs the ECO first letter was not repeated twice.

Reverse pairs, wins

 

Reverse pairs, same moves 

 

Pairs of reverse games diverged very quickly, 82.1% of the pairs diverged at most after 1 move. One game pair repeated 7 moves after book (Tucano - Xiphos, rounds 25 and 22, Grünfeld: Modern Exchange).

 

Season 12 live blogging, Friday Apr 20th

Season 12 has started with division 4, a 4RR with eight engines, the top two will qualify for division 3. The games are about an hour long each and we are about half way through the second RR. Ethereal is leading, with Rodent and Xiphos close behind, it is likely that 2 of these three engines will promote.

A lot of interest in this division is the new NN engine Leela chess zero (LCZero). It entrered the competition at the last moment and has a lot of fans, many people are donating their computing resources to help train Leela. So far it is not doing well, usually it blunders in teh middle or end game. However it is always interesting to watch. There is a good chance that next TCEC season it will do much better.

The Leela - Tucano game is just starting.

move 6 - evals are close to 0, Tocano's just turned slightly negative. This is not a very popular line for QGD, but there are some GM games with this line, so it is playable.

move 10 - Leela is pushing pawns on the queen side, its king is still in the center. The bishop on b2 has control of the long diagonal. Tucano is ahead on developement.

move 14 - Leela opened the queen side, it should get its king to safety soon.Tucano's eval is increasing gradually.

move 21 - Tucano is a pawn up after a series of exchanges, eval over 1. Leela is finally ready to castle, but it will have to defend to hold the game. Will the black pawn majority on the queen side be enough for a win? Will Leela blunder?

move 24 - The engines exchanged a pair of rooks and only QRB vs QRN remain. Leela usually blunders the endgame, and this game is heading to a B vs N endgame with black a pawn up.

move 27 - Tucano has a rook on the 2nd rank, its eval is over 1.5. It's too bad it has no PV and we can't see what it is planning.

move 31 - Tucano's eval continues to increase, over 2 now. The remaining rooks are off the board and Leela may lose another pawn soon.

move 35 - I don't see how Leela can stop the queen side pawns in the long run. It's trying to counter on the king side but the queen alone cannot do a lot.

move 38 - there is a black pawn on d3, it will cost Leela the bishop. Can it do something with its queen and pawns on the king side? Leela's eval is still below 1.5.

move 44 - Leela is still optimistic but Tucano's eval is over 6 and it is winning the Q vs QN ending.

move 55 - soon Leela will run out of checks, it is a knight and pawn down and it's just a matter of time now.

I don't think Leela blundered badly in the game, perhaps it gave away a pawn too easily. Once it lost the second pawn and Tucano started to march on the d file Leela lost a piece and the game.

A final look at season 11

Season 11 is over, Stockfish is the winner. Season 12 is about to start, there is almost no pause between seasons now, and I want to have a last look at season 11 as a whole.

Season 11 changed the competition format and introduced a division system. Engines were split to 4 divisions based on season 10 results, and a fifth division was used for candidate engines that did not participate in season 10. In general I think the new format was a success. The engines' results depended on their performance against other engines of similar strength. In the previous format in early stages there were many games where the result was almost known in advance due to the huge difference in engine rating.

In the lower divisions one of the interesting engines was Laser. In season 10 it finished last and it started season 11 on division 3. Between seasons the engine was upgraded and it was known that it was much stronger, it was not a big surprise that it promoted to division 2. In division 2 Laser still played well and managed to promote again to division 1. The division 1 engines were stronger than Laser, yet it finished the division above the relegation threshold and will start season 12 in division 1. I would like to see other engines improve between seasons, this is the sort of thing that makes TCEC interesting.
 
In the premier division it was expected that the top-3 engines - Stockfish, Houdini and Komodo - would fight for a place in the superfinal. In season 10 the race was very close, and Stockfish lost by half a point. This season Komodo was able to keep up until the halfway point of the premier division, but then lost sight of the leaders. It finished third despite beating Stockfish once, the only Stockfish defeat in the division. Stockfish finished first, with much better results against lower ranked engines than Houdini.

Based on the 12 games Houdini and Stockfish played in the premier division I assumed the superfinal would be close with many draws. Instead, the superfinal was extremely one-sided, Houdini struggled in many openings and lost 20-2. Stockfish was upgraded between divisions on top of the upgrade between seasons, and Houdini was the same as season 10, and it showed.

Leela to play in season 12

Towards the end of season 10 Google published its Alpha Zero chess project, where it used specialized hardware and its infinite resources to train a neural net based engine using only the rules of chess and self-play. The claim was that this engine could beat Stockfish.There was a lot of controversy surrounding this claim, and Google hasn't responded to any of the arguments, probably it only used chess as a proof of concept and it has bigger plans for the technology. The chess community, on the other hand, did not ignore the claim and a new chess engine was born - Leela Chess Zero. This project tries to imitate Google's ideas using standard hardware, where everyone can participate in the ongoing training procedure. At the end of season 11 Leela got to a level where it could compete (and lose) against the weakest engines in TCEC. It played exhibition matches against Scorpio and against a weak Stockfish, losing both but not without winning a few games. Its rating was estimated to be around 2750. Just before season 12 started Anton announced that Leela will play in division 4 after an engine dropped out. There have been last minute bugfixes and improvements, this is going to be exciting to watch.


site stats
This is a graph of the all time monthly hits for this blog: 



During the season the statistics reports were promoted on the chat and used in chessdom. The last 6 months have seen at least 1000 hits each month, peaking towards the higher divisions. The total number of hits is over 22,000.

Thanks to all the readers, I hope to continue being informative as well as interesting in the next season.

Go TCEC!!

Season 11 superfinal, games 91-100

The superfinal of season 11 is over, Stockfish beat Houdini 20-2 with 78 draws. This was one of the most one-sided superfinal matches in TCEC history.

There were a few exchanges at the start of game 91, Houdini gave an early pawn, the center was blocked and there was one open file on the queen side when the engines started to shuffle on move 29. After 70 moves the engines opened up the position, after exchanging queens the evals came down to 0. The game ended in a repetition with only pawns on the board. Evals were close to 0 in game 92. The position was more open and the engines gradually exchanged pieces until reaching a tablebase draw.

Game 93 started with Stockfish a pawn up and eval close to 1. After an early series of exchanges only RRB vs RRB remained on move 23, Stockfish had passers on the king side and Houdini had passers in the center. Both engines queened pawns and the game reached a tablebase draw. In game 94 Stockfish got the pawn back and evals were at 0 from move 20. Stockfish sacrificed a bishop and exposed the white king, Houdini traded down to a drawn rook ending.

Game 95 was a King's Gambit, a second variant of this opening in the superfinal. The white king was moving forward facing a black queen and two pawns. Houdini was a pawn up and had a small eval advantage. It chose to give back the pawn and exchange queens. Stockfish's king was awkward on the 3rd rank, yet it stayed safe. Stockfish exchanged all rooks leaving only BB vs BB, evals came down to 0. The game continued 40 more moves before draw adjudication.
In game 96 Stockfish didn't press on the king side, it patiently developed its pieces instead. Houdini regained the pawn by capturing on b7 with its queen, opening a file for a black rook. Both kings remained in the center, Stockfish's king side pawns looked intimidating.



Evals started to increase, first Houdini traded a rook for a knight and pawns, then Stockfish won a bishop for two more pawns. After exchanging queens only RN vs RRB remained, Houdini was 4 pawns up but playing a rook down against Stockfish is not a great idea...



The white king found safety behind its pawns, but it couldn't come out to help with the defense. Stockfish had an extra piece and it started to capture the white pawns. Its last pawn became a passer and started to march, ensuring a win for Stockfish.

In game 97 Stockfish started with an eval of around 1. The engines locked the center and shuffled for a while. Gradually the position opened up, first Houdini made a hole in the pawn line on the king side and then Stockfish opened two files on the queen side. After another shuffling period Stockfish gave a rook for a bishop and pawns and the engines traded down to a BB vs RB position. Stockfish's eval was above 1, it got a pawn to the 7th rank but Houdini gave the material back to get a drawn opposite color bishops ending. In game 98 Houdini kept a passer on the queen side, the center was locked and Stockfish concentrated forces on the king side. The engines were essentially shuffling from move 30, after 30 moves the engines exchanged a pair of rooks and continued shuffling. After avoiding the 50-move draw the engines traded down to a bishop ending and the game reached a tablebase draw.

Stockfish had an eval advantage starting game 99. The engines castled in opposite positions but did not push pawns forward. On move 31 Stockfish exchanged queens and created an advanced passer in the center, giving Houdini a similar passer though less advanced. Only RRN vs RRB remained and evals stayed under 1, the game seemed to be heading for a draw.



Stockfish had a pawn advantage on the queen side and it created another passer there. Houdini supported its passer with all pieces available, matching the white attacking pieces. Then Houdini allowed the white d pawn to reach d7 forcing a rook to move, Stockfish saw a winning line and its eval jumped over 3.



The win was not clear at first, the engines eliminated the passers in the center and exchanged minor pieces. Stockfish then took over the 7th rank with its rooks, captured a pawn and exposed the black king to attacks. Houdini had to be careful not to get into a mating net, Stockfish captured a second pawn and its queen pawns were free to march. The game was soon over.
Houdini started an attack on the black king with a knight sacrifice in game 100. Stockfish exchanged any piece it could, Houdini got the piece back and only RB vs RB remained with Houdini a pawn up on move 29. Evals were over 0.5, but after exchanging rooks the game reached an opposite color bishops ending, and the extra pawn was not enough. The engines continued to play for a hundred more moves before lowering evals enough for a draw. This was the last game of the season and the engines wanted to stay as long as they could.

Season 11, superfinal stats

Draw rate, wins



Final draw rate was 78%, very close to the draw rate of the last superfinal and slightly better than the target rate 80%.

Game termination

The three most common game termination causes were:
32% - TCEC draw rule
28% - TB position
22% - TCEC win rule


Moves per game

 

Median=62
Average=73.2

The distribution has a long right tail. There were 17 100+ move games, three of these were decisive, all black wins.
 
Time per game (hours)
  
Median= 4:12
Average=4:09

The short increment made sure the game duration would not far exceed 4 hours.

Openings

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


If we use the opening 'family name' (using format FAMILY_NAME: VARIANT....) the top 3 are:

Sicillian - 14 times
King's Indian - 10 times
Caro-Kann - 8 times
Spanish -  8 times

This is very similar to the distribution in season 10.

Almost all of the book lines had the same ECO codes in reverse games, except for one paired game - games 11-12, one was A08 Reti: KIA, French Variation and the other was C00 French: KIA. There were 6 game pairs with different opening variants.

Reverse pairs, wins

 
There was only one biased openings with two white wins. On the other hand there was one opening where Stockfish won both games, a rare event in superfinals.


Reverse pairs, same moves  


Reverse games diverged very quickly, 36% diverged immediately after book, 68% diverged at most after two plys.

Season 11 superfinal, games 81-90

After 90 games Stockfish leads 18-2 with 70 draws. It is now official: Stockfish is the winner of the superfinal of season 11. Houdini can not close the gap in the remaining ten games.

Stockfish had an eval close to 1 at the start of game 81. It gave a pawn and opened the king side, took over the long diagonal looking at the black king and threatened mate on the h file. Stockfish's eval was over 2 very quickly.



Houdini exchanged pieces to get its king out of immediate danger. It was still a pawn up and had passers on both the king and the queen side, while Stockfish had a bishop pair, a central passer, and the black king was still exposed. Stockfish's eval was already above 3.



After exchanging a few pawns Stockfish put a rook on the 7th rank, and together with the bishop pair they confined Houdini's king and two pieces to the back rank.



The black pawns could not be defended and Stockfish created a second passer on the king side. With the two passers advancing the game was soon over. Houdini forced the black king to move without castling in game 82. Houdini's eval was around 0.8 for a while, but it came down as the engines opened files and exchanged pieces. The game reached a RB vs RB position and ended in a tablebase draw.

The engines castled in opposite directions in game 83. Stockfish pushed a pawn on the king side, weakening the black king position. Houdini pushed pawns on the queen side, Stockfish gave a rook for a bishop to eliminate one pawn. Stockfish captured another pawn in the center, creating a queen side passer, evals started to increase. Stockfish's eval peaked around 1.5, it had 4 queen side passers in a QBN vs QRB position. Houdini's pieces were very active and could attack the white king, Houdini gave back the material and got rid of two of the passers. Evals dropped to 0, it took the engines another 30 moves to reach a tablebase draw. In game 84 the engines again castled in opposite directions and pushed pawns in a similar manner. The files remained closed on both sides of the board, and after a few exchanges the engines started to shuffle on move 27. Evals came down to 0 and 55 moves later the engines opened the queen side and the game ended in a perpetual check draw.

Evals were close to 0 throughout game 85. The engines exchanged pieces gradually until reaching a rook ending. Stockfish lost its rook to stop a black pawn queening. Then Stockfish promoted a pawn, and Houdini was forced to close the game with perpetual check. There were many early exchanges in game 86, and only QRR vs QRR remained on move 21. The engines shuffled for a while and then reduced to a drawn rook endgame.

Houdini was a pawn up in game 87 with a queen side passer. Stockfish was ahead in development and it quickly equalized. Evals were close to 0 as Stockfish concentrated forces against the weak black king side and opened it by pushing pawns. Stockfish let Houdini capture a bishop on the queen side for a dangerous attack on the black king, which was strong enough to force a perpetual check draw. In game 88 Stockfish pushed the queen side pawns forward, ignoring the lack of development on the king side and keeping the king in the center. Houdini placed its rooks on the queen side and prevented the black passer from advancing. Evals dropped to 0 after a series of exchanges, Houdini eliminated the black passer and only RN vs RN remained. The game continued until reaching a tablebase draw.

Stockfish started game 89 with an eval advantage that increased gradually and was over 1 on move 20. Houdini had a pawn advantage on the queen side and it pushed its pawns forward. After a series of exchanges Stockfish won a pawn and QRB vs QRN remained. On move 44 after 12 minutes of thought Stockfish's eval jumped to almost 3. Houdini thought for 10 minutes and its eval also jumped. Both engines did not provide a PV that showed what they planned, however in the following move the evals dropped back, very strange. The engines traded pieces and the game reached a drawn B vs N ending.  Houdini had an eval advantage in game 90, an early series of exchanges left QRB vs QRN on move 22. Stockfish was up a pawn but its king was vulnerable. After exchanging queens the evals came down, the game reached a tablebase draw.

Season 11 superfinal, games 71-80

After 80 games Stockfish leads 17-2 with 61 draws. Houdini finally got its 2nd win, this time drawing the reverse game. Stockfish still has a 15 win advantage, and with 20 more games to play it only needs a few more draws to be declared the winner of the superfinal.

Stockfish had an eval close to 1 at the start of game 71. Both engines attacked the opposite kings and after several exchanges the net outcome was that Stockfish was up a rook for a knight and pawn on move 23. Houdini's king was exposed and evals started to increase in a QRB vs QBB position. After exchanging queens Houdini had passers in the center and Stockfish had a doubled passer on the king side. Houdini managed to get a pawn to the 2nd rank protected by a bishop. It couldn't promote but Stockfish had to keep its rook guarding the file. Stockfish's evals was over 2 for a while but it soon realised Houdini was holding. After many moves Stockfish released the black pawn to promote to a queen, and the game ended in a RB vs Q draw. Another narrow escape for Houdini, seems this is the best it can do to show its strength. In game 72 Stockfish equalized quickly and Houdini's eval dropped on move 24. The engines were mostly shuffling with most pawns on the board. Houdini broke through the center, leading to many exchanges and a drawn rook ending.

Many early exchanges in game 73 left RRB vs RRB on move 32 and evals close to 0. The engines continued to exchange pawns and pieces until reaching a tablebase draw. In game 74 evals were negative for a while but Houdini was never in any danger. After exchanging queens the game reached a RB vs RB position. Both engines had advanced passers, Stockfish gave a rook to stop the black passer, Houdini forced a perpetual check draw ro avoid the queening of a white passer.

Stockfish's eval climbed above 1 at the start of game 75. The engines castled in opposite directions, there were many early exchanges and queens were off as well. Houdini didn't seem to be worse on the board, material was equal and the pawns structures were similar.



Stockfish used its bishop to block the king side and apply pressure on the black king, together with a rook on the 7th rank. The evals slowly increased, then suddenly jumped above 2.5. Houdini moved a rook on the back rank to d8 and not g8 as Stockfish recommended, Stockfish played the same response it planned and doubled rooks on the e file.



Houdini gave a rook to take out the white bishop, and the evals jumped higher very quickly. The game reached a RR vs RN position, the white pawns on the queen side started to march and Houdini saw it couldn't stop them in the long run.
In game 76 both engines castled long, evals stayed close to 0. After exchanging most pieces only RB vs RB were left on move 31 and the game ended in a tablebase draw not long afterwards.

Stockfish had an eval advantage of about 1 in game 77. The engines castled in opposite directions, both engines pushed pawns towards the opposing king and opened files. Stockfish's eval peaked close to 2, it attacked on the king side and exposed the black king. However the eval had a sudden drop, Houdini's counter on the queen side exposed the white king and was enough for a perpetual check draw.
Houdini had an eval advantage in game 78. Stockfish delayed castling its king until after queens were exchanged. On move 30 only RRB vs RRB remained with equal material. Evals hadn't moved a lot since the opening, probably a draw.



Houdini captured a pawn and the engines exchanged a pair of rooks. It was not clear how Houdini can improve its position, and the bishops of opposite color made the position look drawish. Yet the evals slowly crept up. Houdini managed to capture a second pawn and create a passer on the king side. Could this be Houdini's day?



Houdini secured its passer and then moved its rook forward where it could attack the black king and threaten the queen side pawns. Stockfish was forced to exchange rooks and then it saw a win for Houdini. Houdini took a few more moves to realise that despite the opposite color bishops ending it had a winning position.



With two passers and the king on its way to the queen side Houdini was too strong and Stockfish agreed it was a win for white. Finally an opening where Houdini wins a game and does not lose on the reverse.

Game 79 had a wild start. The king side remained undeveloped and both engines kept their kings in the center uncastled. Stockfish pushed two pawns on the queen side and one got to the 7th rank. Houdini arranged its pieces for an attack on the white king, with the pawn on a3 blocking the escape route. Stockfish's eval was over 1 but changed very little.



Both queens attacked simultaneously, and both kings looked very vulnerable. Stockfish queened its pawn and for a while played with two queens. Houdini's mate threat kept it alive, forcing white to lose one of the queens. After a series of exchanges the remaining queens were gone and the attacks were over, Stockfish had a material advantage with RRN vs RBB remaining.



The engines exchanged a pair of rooks and the evals increased slowly. It is possible that Houdini could have held, but Stockfish found a way to improve and its evals started to jump. As usual Houdini realised it was in trouble a few moves later. The black bishop pair was harassed by the white rook, allowing Stockfish to arrange its pieces and keep the black king away. 



The white pawn started to march and the game was soon over. Houdini couldn't stop it without losing material. What a game!
 In game 80 both kings remained uncastled, but both engines kept their pieces behind the pawn lines and did not attack. The engines started to shuffle with almost all pieces on the board. On move 32 the pawn lines locked across the board, with only the f pawns able to move. Nothing happened for the next 75 moves, except a few f pawn moves and a few piece exchanges. To finish the game the engines opened up the king side and exchanged all pieces but a pair of knights.

Season 11 superfinal, games 61-70

After 70 games Stockfish leads 15-1 with 54 draws. Stockfish added one win in white and one in black, Houdini had a narrow escape in another game. With 30 games remaining Stockfish will undoubtedly win the match, can Houdini get a win in the remaining games?

Stockfish started game 61 with an eval under 1. On the board Stockfish had a space advantage on the queen side and a bishop pair. Houdini had a queen side passer, facing all the white pieces the passer was not going anywhere.



Stockfish's eval continued to increase. Houdini gave the passer to open a file on the queen side, and tried to counter attack. Stockfish's pieces were all aimed at the black king from a distance, looking very dangerous. Houdini tried to block the center, according to the evals Stockfish was much better though it was not clear on the board.



Stockfish broke through the queen side. Houdini gave a rook for one of the bishops, and Stockfish created an advanced queen side passer. The combination of the passer with a mating threat on the king side was enough for a win.
In game 62 Houdini did not keep its bishop pair, preferring to capture an early pawn. Stockfish exchanged queens and got the pawn back, evals decreasing toward 0. The game reached a RB vs RB position on move 28. In the end only pawns remained, both engines queened one pawn but the result was still a draw.

In game 63 Stockfish had an eval advantage under 1. The queens were exchanged early, the engines continued to trade pieces until reaching a rook ending with evals at 0. The game ended in a tablebase draw. Game 64 was similar, Stockfish's eval was 0 from move 18. The engines exchanged all their pieces to get a king and pawns ending, both engines queened a pawn and another draw.

Stockfish had an eval advantage in game 65 despite keeping ints king uncastled in the center. The engines exchanged queens early, by move 32 only RBB vs RBN remained and evals were close to 0. The game ended 40 moves later in a B vs N ending.
Houdini was ahead on eval starting game 66, Stockfish quickly equalized. After a few exchanges the center opened up. Houdini had a pawn majority on the queen side, material was balanced and evals were close to 0.



Houdini seemed more dominant in the central files. and yet the evals turned negative. Possibly the white king was more vulnerable to attack with no pawns on the 2nd rank. After exchanging bishops Stockfish controlled the long a8-h1 diagonal with its queen. Houdini gave a rook to take out the central black knight and then exchanged queens to get a RB vs RR ending. Evals were still below 1.



Houdini allowed the black rooks to take over the 2nd rank, and the evals jumped over 1. After several futile checks Stockfish found a way to improve. It used its rooks to guide the white king slowly to the queen side, with the h5 pawn blocking the path to the king side.



With its king unable to help Houdini's defense soon collapsed. Stockfish brought its king forward and pushed pawns on the king side. Houdini had to move its pawns and they became targets for the black rooks. The PV at the end of the game showed how black can capture all the white pawns. 

Stockfish's eval was close to 1 in game 67, Houdini's king was uncastled in the center with almost all pieces on the board. Houdini trapped a white bishop on the king side yet the evals increased over 1. Stockfish gave two pawns and got a rook on the 7th rank, threatening the black king. It then freed its trapped bishop and got the pawns back, evals approaching 2. Houdini exchanged queens but evals continued to increase, white had passers on the king side and Houdini gave a rook for a bishop to stop them. The engines reached a RB vs BN ending and the evals stayed high but constant. Unexpectedly Houdini held the position to a draw. In game 68 Houdini mainained an eval of about 0.5 for over 40 moves. Stockfish castled its king, the engines opened the queen side and exchanged pieces. It again seemed that the black king was under threat when Houdini's rook moved to the 7th rank, though it didn't stay there for very long. In a QRB vs QRB position Houdini captured a pawn, Stockfish countered by trading down to a drawn rook ending.

Evals stayed low in game 69. The engines exchanged pieces in an open position, when all minor pieces were gone the two kings were exposed to attacks. The engines chose to draw by reducing to a tablebase draw, though there were possible perpetual check draws available. In game 70 Stockfish gave a rook to get a perpetual check draw after only 31 moves.

Season 11 superfinal, games 51-60

After 60 games Stockfish leads 13-1 with 46 draws. The last 10 games have all been draws, Stockfish may be taking a break since it is almost surely going to win the match.

Houdini was a pawn up after the start of game 51. All pieces remained on the board as the engines started to shuffle on move 19. After 35 moves Houdini gave a rook for a bishop, and the position opened up. After a series of exchanges only RR vs BNN remained, Houdini with 3 extra pawns. Evals were close to 0 despite the unusual material imbalance, a white passer cost Houdini a knight, the engines then traded pieces until reaching a tablebase draw. In game 52 the engines kept the pieces on the board for the first 35 moves. Stockfish was a pawn up with a queen side passer and eval above 1. After a few exchanges the evals dropped and the engines started to shuffle. At move 112 the engines started to open the position, after clearing the queen side the game was adjudicated.

Stockfish started game 53 with an eval advantage with all pieces on the board. The engines were close to a 3-fold repetition on move 17, instead the pawns locked the queen side and the engines exchanged a few pieces and pawns. The position opened a little and the engines exchanged most pieces, Houdini gave a knight for pawns to break the white pawn line on the king side. The game reached a bishop vs pawns ending, Houdini was 3 pawns up. The result was a draw though it took 65 shuffling moves to get there. In game 54 the engines were essentially shuffling from move 19. Evals turned negative but stayed constant. The pawns stopped moving on move 49 as the shuffling continued. On move 119 The engines started to open the position with exchanges, reaching a drawn knight ending.

Game 55 started with Stockfish a pawn up and Houdini's king in the center unable to castle. Stockfish's eval was over 1 but more or less stable. The position became static, then after a series of exchanges only QNN vs QNN were left. After exchanging a pair of knights Stockfish's queen moved forward, and Houdini managed to trap it in the corner. For a while Stockfish thought it was ahead with eval approaching 2, but it soon realized there was no way to improve. After exchanging queens the evals dropped to 0, the game continued until getting a tablebase draw. In game 56 Houdini chose a different line, not forcing the black king to move but winning a rook temporarily. Stockfish countered with an attack on the white king, forcing it to move without castling. Stockfish regained the material by move 17 and evals were close to 0. The game reached a knight ending and a draw.

Stockfish had an eval advantage close to 1 in game 57. It went a pawn up on move 16, and after a series of exchanges only BN vs BN were left on move 28. The extra pawn was not enough, the game reached a tablebase draw. In game 58 evals came down to 0 faster. Material was balanced as the engines exchanged pieces. Houdini grabbed a pawn before exchanging queens, reaching a N vs B ending on move 34. Stockfish got the pawn back and the game was adjudicated a few moves later.

There were many early exchanges in game 59, with only RRB vs RRN remaining on move 22. Stockfish's eval jumped over 1 when it took over the 7th rank, and jumped again over 1.5 after trading minor pieces. It appeared that Stockfish was ahead with an advanced queen side passer, however Houdini put its rooks on the 2nd rank and could end the game with a perpetual check. Houdini chose to play on, only delaying the draw by a few moves. In game 60 evals were low throughout the game. After move 13 there were no exchanges for 20 moves. After the position opened up the white king was exposed. Stockfish attacked and started a series of exchanges that led to a drawn B vs N ending. 

Season 11 superfinal, games 41-50

After 50 games Stockfish leads 13-1 with 36 draws. At the halfway point Houdini has still not won an opening minimatch, Stockfish is constantly better as white and as black.

Stockfish had an eval advantage in game 41, with more space for its pieces. Stockfish opened the king side and threatened the black king through open files. Houdini traded pieces and the evals dropped to 0. The game reached a drawn rook ending.
Evals were low in game 42, Houdini had more space. On move 25 Houdini gave a pawn, opening files on the queen side for its pieces. Stockfish blocked the file with its knight, and when Houdini exchanged the knight both engines had passers on the queen side.

Essentially nothing happened in the next 90 moves. The engines shuffled pieces and made a few pawn moves. Both engines had very little time left when Stockfish opened the position. Evals became negative but still small, the expected outcome was still a draw.



The engines were in blitz mode, Stockfish's eval started to increase as it exploited its control on the dark squares. It gave a pawn to open a diagonal for its bishop and soon Houdini's king was in a mating net. Houdini gave a rook for a bishop and Stockfish's eval jumped.



Stockfish exchanged queens, the B vs R ending was a win for white. The game should have been a draw but Houdini lost it in time trouble.

Stockfish started game 43 with an eval advantage. There were several early exchanges, material was even, Stockfish had a bishop pair and a pawn advantage on the queen side.



Evals continued to increase, after exchanging queens Stockfish won a pawn. This didn't change the pawn structure, only removed the black double pawn, yet Stockfish's eval was already over 3. A few moves later the game reached a rook ending.



There were pawns on both sides of the board, with a pawn advantage for white on the queen side. This was enough for a Stockfish win, the game was adjudicated 10 moves later.
In game 44 evals stayed low throughout the game. The engines gradually exchanged pieces until reaching a rook ending, this time with even material. Houdini had a queen side passer but that was only good for a draw.

Stockfish had an eval advantage in game 45, it captured a pawn and had more space with eval over 1. Houdini exchanged pieces when it could, reducing to a QR vs QR position. The engines shuffled with evals slowly dropping, until reaching a 50-move draw. In game 46 Houdini was a pawn up in a more open position with evals close to 0. Stockfish reduced to a QR vs QR position, it used an attack on the white king to get the pawn back. After exchanging queens the rook ending was drawn.

Game 47 started with Stockfish a pawn up. Houdini exchanged queens early and the engines continued to trade pieces until reaching a rook ending and a draw. In game 48 evals were low. Houdini's king was exposed in the center and Stockfish won the pawn back by attacking the king. The engines traded pieces with evals at 0, the game continued for 30 moves in a drawn rook ending until the pawns stopped moving.

In game 49 Stockfish had an eval over 1. The engines exchanged pieces in an open position, by move 30 only RRB vs RRN remained. Stockfish captured a pawn and had a queen side passer, but with the kings exposed the rooks could give checks and the game reached a repetition draw. Houdini kept its king uncastled in game 50. Stockfish gave two knights for a rook and attacked the white king. Stockfish then sacrificed a rook and got a perpetual check draw.

Season 11 superfinal, games 31-40

After 40 games Stockfish leads 11-1 with 28 draws. Houdini finally achieved its first win. Stockfish won the same opening as white, perhaps the opening was too biased. The match continues to be one-sided, though there were a few more draws compared to the previous two games.

Stockfish had a small eval advantage from the start of game 31. The center was blocked and all pieces were on the board. Stockfish had more space on the king side, its king a little exposed. Houdini was better on the queen side, but its king had little support from the black pieces due to the pawn wall. Stockfish's queen side rook looked awkward, blocked by its own bishop.



Stockfish sacrificed a bishop for pawns to expose the black king, its eval jumped above 2. Houdini countered by opening the queen side and attacking the white king. The white back ranks were weak and Houdini's pieces drove the white king forward. However, the black king was in grave danger, once the checks stopped Stockfish sent a knight to join the attack, offering a rook to Houdini.



Stockfish was RB down, but it had the black king in a mating net. Houdini had to give its queen to stay alive, and with three passers and a queen facing the black king Stockfish was about to gain more material when the game was adjudicated. A spectacular win in 36 moves.
Game 32 started with evals close to 0. Stockfish kept its king uncastled in the center, it gave a pawn to open a file for its king side rook. On the queen side Stockfish had a pawn advantage and a strong knight.



Houdini's eval started to increase gradually. It got rid of the white queen side knight and gave the pawn back. Stockfish had a pawn majority on the queen side, while Houdini created a passer in the center with support from behind. Evals were close to 2, could this be Houdini's first win?



Houdini formed a pawn line on the king side and secured its passer. Stockfish gave a pawn in the center to try and threaten the exposed white king, Houdini exchanged pieces until only RN vs RB remained, evals over 3.5.



Stockfish had to keep an eye on the d pawn, allowing Houdini's king to walk to the queen side. With the additional piece Houdini started to capture the black pawns on queen side and the game was soon adjudicated. A win for Houdini, finally. Stockfish won the previous game so the opening is also a factor.

In game 33 Houdini gave a rook for a bishop early in the game. Stockfish had an eval close to 1 and the engines started to shuffle on move 22. A few pawn moves and exchanges got the engines to move 100 with the 50-move counter down to 1, but Stockfish avoided the draw and opened the position. The game continued for another 25 moves, reaching a queen ending and a perpetual check draw. Game 34 started with early exchanges, the engines started to stabilize and shuffle from move 16. Stockfish concentrated forces on the king side and evals became negative for a while. Houdini just traded all the pieces and got a drawn rook ending. After 6 openings with decisive results we finally got back to "normal" with two draws in a row.

Stockfish started game 35 with a small eval advantage. After a while the evals started to increase, the reason was not evident at first. Houdini had a central passer while Stockfish had a pawn majority on the queen side. The black LSB was trapped on the queen side.

Stockfish pushed its queen side pawns forward and created two connected passers. Houdini started a series of exchanges, with a net result of being a rook for a knight up in a RBN vs RRB position. However Stockfish had a pawn on the 7th rank. 

Stockfish advanced with a second pawn and Houdini was forced to lose a rook to stop the two passers. The game reached a RB vs R ending, Houdini two pawns up. Evals were over 3 and climbing.

Stockfish took its time and slowly captured the black pawns. After 15 moves the game was over. 
Evals stayed low in game 36. The engines exchanged queens on move 27 and the game reached a RN vs RN position on move 32. The engines continued to trade, the game ended in a quick tablebase draw.

Stockfish kept its king uncastled in game 37. It created an advanced passer in the center and Houdini was concentrated on stopping it and did not attack the exposed white king. After most pieces were exchanged Houdini got rid of the passer, and the game reached a drawn tablebase position. In game 38 there were many early exchanges and only RN vs RB remained after move 21. Evals dropped to 0 quickly and the game was adjudicated.

Game 39 started with Stockfish a pawn up. Stockfish's eval stayed below 1. After queens were exchanged the engines stablized the pawn lines. Then all the rooks were traded off and the engines started to shuffle in a BN vs BN position. It took more than 40 moves for Stockfish to lower its eval enough for the draw rule to apply. There were many early exchanges in game 40. The game reached a RR vs RR position on move 27, Houdini still a pawn up. Evals dropped to 0, Stockfish regained the pawn and the game reached a drawn rook ending.

Season 11 superfinal, games 27-30

After 30 games Stockfish leads 9-0 with 21 draws. Stockfish continues to amaze. It won 3 of the last 4 games, including a win in white and in black of the same opening.

Stockfish had an eval advantage close to 1 from the opening in game 27. There were many early exchanges and by move 21 only RBN vs RBB remained. Stockfish had a slightly better pawn structure, Houdini seemed solid enough and had a bishop pair.



The engines shuffled for a while with evals about the same. Houdini locked the queen side pawns, Stockfish thought this was a mistake and its eval jumped close to 2. Houdini's pieces were blocked and Stockfish's king slowly walked all the way to g4 on the king side. 



The additional piece on the king side was enough to cause Houdini's defense to crumble. Stockfish could play h5, or it could free a piece for another task as the king takes over, while the black pieces could only stand and watch. After carefully arranging its pieces Stockfish forced a bishop exchange and created a passer on the king side. The game was adjudicated before Houdini lost a piece.
In game 28 more pieces and pawns remained on the board. Houdini had a small eval advantage when the engines began to shuffle after move 20. About 45 moves later, with a few pawn moves here and there, the engines exchanged the remaining knights and continued to shuffle. Eventually Stockfish opened the position, leading to many exchanges and a tablebase draw on move 155. This was the fourth opening in a row with a 1.5-0.5 score for Stockfish.

Game 29 started with a long book sequence and an eval advantage for Stockfish. People on the chat didn't like Stockfish's early c6 move, though who can argue with such a strong engine. After several exchanges the position on the board was simplified with low evals. On move 32 the white c pawn became an advanced passer.



The c pawn advanced to c7 where Houdini blocked it. Stockfish's eval climbed over 1 yet Houdini thought it could hold the position. The engines exchanged queens and then Houdini decided to give a rook for a bishop in order to get rid of the advanced passer. The result was a RR vs RB ending with very few pawns, both evals were over 1, it was not clear what Stockfish could do to improve.



Stockfish's eval started to increase, slowly at first and then it jumped over 10, Boom! Suddenly the black king was in danger of a backrank mate. The 3 pawns in the center also restricted its movement. Houdini's eval stayed around 1 for 6 moves before it saw the danger, unbelievable.



The game was adjudicated quickly, the PV showed how Houdini was going to lose a piece. We haven't seen an engine blind to the danger for so long in a late stage game in TCEC for a long time. I was reminded of a similar situation in season 5, but I wouldn't have believed this could happen in this superfinal.

In game 30 Stockfish stormed the king side and created a hole in the pawn wall. Stockfish's eval was over 1, Houdini still felt safe though its king was exposed and its pawns were blocking the way for its own pieces.



Houdini was a pawn up and it made a weak attempt to counter on the queen side. Stockfish had many pieces on the king side, Houdini was forced to give back the pawn and allow its pieces to help. The white king was under a lot of pressure, unable to move and facing two black pawns supported from behind.



Houdini exchanged all the pieces it could to save its king. In the process Houdini lost a knight, and the game reached a RRN vs RR position with black a pawn up, a win for Stockfish. This is the fifth straight opening that Stockfish wins, and this time it won with white and with black. The last time this happened in a TCEC superfinal was in season 5, Komodo had a double win in games 25-26 against Stockfish.