Season 8 stage 3 rounds 26-30 and final results

The final results for stage 3 are:

Congratulations to Komodo and Stockfish, the finalists of season 8 !!!
This was the obvious result but the strength of Gull in the first half of the stage, together with Stockfish losing several games on time, made the path to qualification very much unexpected.

There were some more problems with web access and down time of the live website, but after some code fixes the site was back faster than ever, and no need to reload for updates.

Stockfish lost on time again, unbelievable. It happened against Hannibal when qualification was almost determined theoretically so the crowd response was not so loud, but still - this was the version that was supposed to have better time management. Obviously the bug is still there, and according to the chat it could still be there in the finals. Any long game that gets Stockfish near the increment is going to be touch and go unless something is done soon. Against Komodo there will be no chance of getting easy points, and losing a few games on time can determine the match outcome.


Hannibal-Protector was another short draw, this time 24 moves. Hannibal-Komodo took 28 moves to draw. The engines had enough of stage 3 and wanted to go home and rest for the finals or for next season.

Gull-Stockfish was the last chance for Gull to get close to the leaders. However it was Stockfish who tried to win with black, but it could only get a pawn advantage which was not enough for the endgame. Only a draw for Gull against Houdini and it was two points away from Stockfish with two games left. Stockfish prolonged the theoretical possibility when it lost on time against Hannibal. Stockfish beat Protector in a beautiful come-back into a difficult ending RB vs RBN, and Gull's run was over officially.

The last Stockfish-Komodo game before the finals ended in an uneventful draw. This completes 6 straight draws between them in stage 3, very likely that we will see many more draws in the finals (hopefully not a lot of crashes and bugs...)

Notable game
Komodo-Gull, round 26
Game on TCEC archive

On move 35 the position was:

Gull seemed to be on the sure path towards a draw. Komodo had an isolated passed pawn while Gull had a pawn advantage on the queen side. There were only a few pieces left on the board, but Komodo found a way to create some excitement. The white knight moved forward, sacrificing the a4 pawn to get to e6.

That knight was in a strong position, and the black king was starting to feel pressure. Komodo advanced the g pawn trying to open the king side, and in the process sacrificed another pawn and then a rook sacrifice?!?

False alarm, Qf4 and the threat of Qb8 saves the rook. Moreover Komodo's eval jumped above 1 as Gull's king became exposed. Gull's eval soon followed, was this another loss for Gull? After a second long think by Gull the path forward became clear, both engines agreed on their moves for over 20 moves in their PV.

Komodo was going to win some material but only to reach a QB vs Q ending with almost no pawns. Indeed the game followed along this line, and Komodo's eval started drifting downwards. The excitement was over - once the pawns started to disappear it was clear the game was heading to a tablebase draw. Gull pulled a great defense against Komodo - something only very strong engines can do.

Season 8 stage 3 full stats

Draw rate, wins

Final draw rate was 56.6%, only a little higher that in stage 2. 


Moves per game

Average= 76.85
Median= 69.25

These numbers are similar to stage 2.

Time per game (hours)

Average= 5:16
Median= 5:27

The games are about an hour longer than in stage 2. There is a pattern here, every stage the games are longer by an hour. Why? because the engines are given half an hour more (each) than they had in the previous stage. We can expect a median of 6:15 hours for the final.

Openings


There were 8-move book openings in this stage chosen by Cato, so the engines had almost no say. The first letter of the ECO codes was distributed as follows:

Looking at The histogram shows that Cato chose a wide variety of openings with some preference to Sicilians.

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

Sicillian - 20 times
QGD - 6 times
French, Spanish, King's Indian, Nimzo-Indian - 4 each

Reverse pairs, wins

Cato chose biased openings intentionally so that there would be more decisive results. However, as the graph shows there were very few openings (2 actually) so biased that each engines won a game. The strength of the engines was such that there were only a few openings with a 2-0 result. Excellent job, Cato !!!


Reverse pairs, same moves

How many plys did the engines play after book until the first divergence in the reverse games? 

Divergence was usually within the first move (2 plies). This shows that Cato chose openings that didn't have forced continuations so that each engine could try its own strategy. As always, it's Cato's fault. Cato is the best !!!

Season 8 stage 3 rounds 21-25

After 25 rounds (5RR) the crosstable is:

Gull continued losing points and it is now 2.5 points behind Stockfish in second place. After losing to both Komodo and Stockfish it is now difficult to imagine Gull making a comeback and reaching the final.

Komodo-Hannibal got into a knight for 3 pawns imbalance.The game reached a RRN vs RR ending with Komodo losing all its pawns. I don't know what the theory is for this ending, but Hannibal managed to hold a draw even with no tablebase help.

Stockfish managed to beat Gull in a Rook ending, turning a passed pawn on one side to a winning advantage on the other. Stockfish saw the win long before Gull caught on, having no tablebase assistance. In the next Stockfish game, black against Hannibal, Stockfish fought hard for a two pawn advantage. Unfortunately the game reached a opposite color bishop ending and two pawns were not enough, Hannibal holding another draw.

The RR ended with the Komodo-Stockfish game. On move 28 of the game things started to get exciting when Komodo's eval jumped suddenly and Stockfish was under pressure, a rare occurance in this season so far. Stockfish defended well, first exchanging a rook for a bishop and trading queens, and then getting the exchange back. Komodo had an extra pawn but the opposite bishops ending was a sure draw. Another feature of this game was that a little after the excitement started the website went offline for a long time, and the viewers were left in the dark as to how the game was unfolding. The web host apparently was undergoing maintainance, could it be something to do with the end of the daylight saving period?? Hopefully this will not happen again, it is very annoying to have no access to the live games.

Notable game
Protector-Komodo, round 23
Game on TCEC archive

The game was balanced and not many pieces were left on move 34:

 Here Protector decided to go after the queen side pawns with its queen. In the process the queen walks into a trap:

The white queen can't move! On the other hand the black queen is neccesary for the trap, so altogether the position is still balanced with the queens out of the way. A few moves later Komodo finds an unexpected maneuver to create a decisive advantage: the king goes on a walk:

It walked from g8 to c3 with no pawns or pieces to stop it. Komodo sacrificed a pawn in the process, but with the king as an additional piece behind the white lines it has more than enough compensation. When Komodo releases the white queen the game soon enters a queen ending, but black has a two pawn advantage, enough for a win.

Season 8 stage 3 rounds 16-20

After 20 rounds (4 RR) the crossable is:

What a turn-around. Gull drops from first to third in the fourth RR. Komodo is now comfortably in the lead, and Stockfish is second (remember its two losses on time in the first RR, losing 1.5 points including 0.5 to Gull). This is what was expected so there is less tension for the fans (especially SF fans like me). However, Gull has proven it is very strong and hard to beat, and with only 10 games per Engine left anything can still happen.

Komodo was on fire this RR with a result of 4.5/5. Only Stockfish could get a draw against it.

Protector-Hannibal managed to find a draw faster than the reverse game, this time in 19 moves. Protector also had two wins in the fourth RR, after only one in the first 3 RR (not counting the game against Stockfish which was lost). The first win was against Houdini after a long shuffling match. The second win was against Gull with the assistance of the king's gambit opening.

Hannibal held for 30 moves against Komodo, but blundered in the end to allow Komodo to reach a won rook ending.

Stockfish managed to get a draw out of its hard opening against Gull.

Notable game
Komodo-Gull, round 16
Game on TCEC archive

The opening favoured white but nothing Gull couldn't handle, right? On move 22 the position was:

The queen side was locked with pawns but the g file was open after Gull advanced its king side pawns. That left both kings a bit open to attack, not clear where black's king can go and how to develop black's queen and rook. Komodo then placed two rooks on the g file while Gull tried to untangle itself by attacking the center:

This was a serious mistake because Komodo used a bishop and knight on both sides of the board to trap Gull's king in the center and freeze the queen side entirely:

Komodo then opened up the king side, temporarily giving up a rook for a bishop but clearly in the lead. Gull gave back the exchange to get rid of the knight on b6 and was only a pawn down when the dust settled:

The evals show the reality of the position. After exchanging the rook and queen the combination of a passed f-pawn and all the black pawns on white squares ensures the win for white.

Season 8 stage 3 rounds 11-15

After 15 rounds (3 RR) the crosstable is:

Gull is still in the lead !! Stockfish and Komodo are 1.5 points behind and need to start working hard if they want to both qualify for the final. There is a real possibility that only one will qualify against Gull, an enormous surprise if that happens. Stockfish managed to equalize with Komodo in the third RR, but Gull had the same record as Stockfish, 3.5 points without loss. Looking forward to the reverse games in the next RR the Komodo-Gull has potential of a loss for Gull. On the other hand the Gull-Stockfish is dangerous for Stockfish since Gull had to work hard to get a draw in the opening they had.


Hannibal-Protector was a very quick draw by repetition after 23 moves. All the spectators were grateful (perhaps not all).

Gull-Houdini reached a fascinating RNN vs RBN with pawns ending, Gull with a pawn advantage. Gull gradually increased its eval until it was well over 2, Houdini steered the game to a NN vs R endgame. Here Houdini used its tablebase advantage to make sure the outcome is a draw, sacrificing the rook to get to a KNN vs KP 5-man position. This is also a game to look out for in the reverse matches.

Hannibal-Stockfish seemed to be heading to a draw as well. Stockfish was slightly ahead with a BP vs R exchange, but there seemed to be not enough pieces and pawns on the board, and the evals were static for many moves. Somehow the queens were exchanged and Stockfish managed to convert the RB vs RR ending.

The Komodo-Stockfish is last in the RR. This time Stockfish pushed for an advantage but could only reach a rook and pawns ending which soon reached a tablebase draw. We'll see if Komodo can do better in the rematch.

Season 8 stage 3 rounds 6-10

After 10 rounds (2RR) the crosstable is

Gull in the lead !!
And I thought that a Komodo-Stockfish final was guaranteed. Now we have a real fight on our hands and the tension is rising.

Draw rate is up to 50%. There were many draws in the reverse matches. Although Cato promised unbalanced openings only one opening resulted in two same color wins. The most common result was win+draw, showing that the openings can be defended if played right (against a weaker opponent). To me this is an indication that the openings were chosen well. Well done Cato!! Let's hope the next openings work out just as well.

Stockfish reverted to the stage 2 version and it is doing ok (3/5) so far. The newer version gave 1.5 points to opponents by losing on time, and I hope Stockfish will be able to compensate for that in the following rounds. Gull is currently leading without loss, drawing most of its games but still winning a few. It would be a big surprise if it reaches the superfinal, but if it stays unbeaten this could happen.

There were several long boring draws. In particular Hannibal drew against Protector and Houdini (record 212 moves). One of the reasons for these long draws is that Hannibal is using a contempt of -0.16, making it more cautious. This has a side effect that a drawn position gets an eval of 0.16, too high for the TCEC draw rule, so draws are not adjudicated early.

Notable game
Protector-Houdini, round 7
Game on TCEC archive

The game reached a RR vs Q with pawns ending after 40 moves. After most pawns were taken the following position was reached:

Houdini was relaxed. All it had to do was keep the king hidden and let the white rooks run around under the black queen's supervision so as not to be mated. However, Protector managed to drive the black king out:

 With clever maneuvering of the rooks Protector led the black king away from the pawns.

With the 50-move counter reaching 1 Protector managed to take a pawn before the forced draw, and then it was easy to get the second pawn and win the game. Very impressive, but the question remains: could Houdini have held the draw?

Season 8 stage 3 rounds 1-5

After 5 rounds (1 RR) the crosstable is:

Cato promised unbalanced openings (he even posted a video - on vid.me, not available now - explaining this decision), and that's what we got. So far the draw rate is 33%. The real strength of the engines will appear only after considering the reverse games in the second RR.

The main issue in the starting rounds of stage 3 is Stockfish. Huge volumes of discussion were spent on this and will continue to do so for the near future, but here's a short digest:
- Stockfish was updated for this stage, the new version was supposed to be stronger because of better usage of the many cores available on TCEC.
- However, the update caused Stockfish to use more time (season 7 deja vu), and to make things worse when it came close to the 30s increment a bug caused it to use a little too much time and to lose games on time. This happened twice, against Gull in a drawn position, and against Protector just before it won by adjudication. Martin posted a video - on vid.me, not available now - to explain what had happened.
- This caused a heated discussion about what to do, and in the end the decision was to revert Stockfish to the stage 2 version and to let it play on. Hopefully the games will continue smoothly from here on.

Houdini surprised everyone by beating Komodo. After a balanced opening Houdini got into a RPP vs BN game. It took a few moves until Komodo realized it is in trouble, and from then the evals increased gradually until the end. We will see how Komodo reacts in the reverse game.
 
Gull-Hannibal reached a KBB vs KNP ending. The position was drawn according to 6-man tablebases. However, both engines did not use the available 5-man of TCEC, Gull thought it was winning and Hannibal thought not. Both engines made several mistakes along the way until Gull managed to take the pawn. The resulting 5-man position was adjudicated as won for Gull, but it was a mate in 59 and it's far from clear if Gull could have really won on its own.