Season 9, rapid tournament stats

Draw rate, wins

Final draw rate was 27.3%. Putting all engines in one group resulted in huge differences in engine strength in many games, most of which were decisive. Looking at the subtable of only the top 10 engines the draw rate was 63.3%. The top 3 engines played 6 games, all draws.
There was a small preference for white wins. This may have to do with the openings, or perhaps it is just the general bias for white in chess.

Game termination

The three most common game termination causes were:
66.2% - TCEC win rule
12.6% - TCEC draw rule
9.0% - TB position

There were 37 cases of time loss or crash and 4 cases of mate on the board. The most curious case was a loss due to an illegal move by Delphil, I've never seen something like that happen to an engine on TCEC.

Moves per game

Median= 55
Average= 61.7

The distribution has a long tail due to several long games. For example there were 4 games with more than 200 moves, the maximum was 274 for Jellyfish - Chiron, round 50. On the other hand there were a few very short games, the minimum was 10 moves for Critter - Laser, round 10.

Time per game (hours)

Median= 1:01
Average= 1:01

The time distribution is almost symmetric, when playing many moves the engines played faster.

Openings

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

Open games (C) and indian openings (E) were under-represented, very similar to stages 1a and 1b that also had 2-move openings. Is this a Cato preference or do the engines prefer to transpose to other openings? 

If we use the opening 'family name' (using format FAMILY_NAME: VARIANT....) the top 3 are:
Sicillian - 151 times
English - 107 times
QGD - 78 times

The engines had a lot of freedom to choose the opening variant. Only 40.7% of the game pairs repeated the same ECO code twice, and only 21% repeated the same opening variant. In 15.7% of the game pairs the ECO family was not repeated twice.

Reverse pairs, wins

With such a low draw rate it's hard to draw conclusions from this histogram. There were 22/496 openings that had a two win 1-1 biased result, and some of the openings were one-sided but only a few. I think luck and weak engines are more important factors here.

Reverse pairs, same moves 

The reverse games diverged very quickly, half diverged in the first move and 83% diverged at or before the third ply. Only 7 games repeated more than 6 plys.

Season 9, rapid tournament, rounds 56-62

Rapid tournament, final results

Houdini wins the rapid tournament !! That's not really a surprise, right? A solid 6 points out of the last 7 was more than it needed to keep first place. Very few engines managed to slow Houdini down. Fizbo and Nirvana are the only ones that held Houdini to two draws, other than the top 3 engines. Well done Houdini !

Komodo kept its small lead over Stockfish and finished second. Both remained unbeaten in the tournament, and it was their worse performance against weak engines that made them lose the race to the top. I think this says more about the tournament than it does on the relative strength of the top engines.

In the second trio of engines Fire finished fourth comfortably, finishing the second RR without loss. Jonny overtook Ginkgo and finished fifth.

My opinion of the rapid tournament has not changed. There were too many games and many of them too one-sided. The games went by too fast, it was impossible to follow them or to get excited by them. There was some entertainment value in the race but Houdini opened up a gap and was hardly in danger most of the time.

And what about the superfinal? Remember that? A 100-game match between Stockfish and Houdini, long games like we used to have in TCEC? So far there have been no news as to when this should start. Anton from chessdom has not posted anything in the chat or on the facebook page for a while and it was said he had health issues. I hope he gets well soon. I also hope we will not have to wait too much for the superfinal. Note also that the world chess championship match between Carlsen and Karjakin starts in a few weeks, will we have both matches at the same time? Worlds colliding.

Games that caught my eye

Round 56:
Gull - Jonny: Jonny was sure it had an advantage with eval over 1, but after a series of exchanges its eval came back down. When only opposite colored bishops remained the engines agreed on a draw.

Houdini - Rybka: Rybka held its position against Houdini for over 30 moves. Rybka's center was strong and Houdini attacked on the queen side, quickly opening files and creating an advanced passer. Rybka managed to stop the passer for the price of a deadly pawn-bishop pair in the corner. The only blocking piece was the black queen, leading to an easy win for Houdini. Another obstacle cleared by Houdini.

Stockfish - Komodo: Komodo had an effective pawn line that stopped any attack attempts by Stockfish. Stockfish tried to open the position by giving a rook for a bishop, both evals then fell to 0 and a draw was just a matter of time. Houdini's lead is 3 points with 6 games remaining.

Naum - Ginkgo: There were may early exchanges, Naum was a pawn up but it was a doubled pawn. On move 32 only B vs N remained, the engines continued to shuffle for more than 90 moves before declaring a draw.

Round 57:
Ginkgo - Stockfish: Stockfish came out of the opening in a better position, with rooks controling the center and a queen side passer. After a pair of rooks was exchanged only RB vs RB remained, Stockfish was able to get a two pawn lead and exchange down to a winning 6-man rook ending. That was the last serious opponent for Stockfish in the RR, it has a chance to get second place.

Komodo - Houdini: Komodo had an eval advantage for a short while but Houdini was never in any danger. Evals came back to 0 and the engines shuffled and exchanged until adjudication. Komodo's last chance of geting closer to Houdini is gone, and it is tied with Stockfish in second.

Jonny - Andscacs: Jonny was very happy with the opening, getting an eval advantage of over 1. Andscacs remained calm with low eval, and when the shuffling began it proved it was right. It took more than 150 more moves of mostly nothing for a draw to be declared. Jonny is tied with Ginkgo in fifth place.

Round 58:
Chiron - Jonny: Chiron was outplayed by Jonny in a closed position. Chiron started with an eval advantage but after less than 20 moves Jonny took the initiative on the king side. While Chiron's pieces defended Jonny captured two pawns on the queen side, and eventually after many exchanges the queen side passers were enough to win. Surprising how easily Jonny won here.

Fire - Protector: Fire had an eval advantage for over 60 moves when the game reached a BN vs R position. Protector could have perhaps held on with better play, it came down to which engine had the better passers. Fire had an extra piece to block the black pawns' advance, and the white pawns won the game.

Nirvana - Komodo: Nirvana had the opening advantage and it took Komodo 30 moves to turn things around and get the initiative. Komodo took over the center and won a pawn with eval getting over 1. Nirvana held its position for another 40 moves or so but after queens were exchanged Komodo's eval started to climb again. With a nice combination Komodo reduced the board to a rook ending with two pawns advantage. It took Nirvana a while to see it was losing.

Houdini - Ginkgo: Houdini had an eval advantage of almost 1 when Ginkgo started an effective blockade. The engines shuffled for 40 moves, then Houdini exchanged rooks and in an QRB vs QRN position the evals started to rise gradually. With evals over 2 suddenly Ginkgo crashed for no apparent reason. Houdini got the win but from its PV it was aiming for a R vs N ending with king side pawns, is that a sure win? Jonny is now 1 point ahead of Ginkgo in fifth place.

Stockfish - Gaviota: Stockfish couldn't get anything going in this game, even though it played white. By move 23 only minor pieces remained and the rest of the game was shuffling and further exchanges. With this draw Stockfish is third again, 0.5 points behind Komodo.

Round 59:
Fizbo - Stockfish: The engines started to shuffle on move 19, Fizbo thought it had some advantage while Stockfish's eval was 0. After a series of exchanges Fizbo's eval came down, with only QBN vs QNN left. The game was close to adjudication when Stockfish's eval jumped close to over 0.5 where it stayed for 15 moves. Fizbo managed to exchange down to a drawn knight ending. The third draw in 4 games for Stockfish, quite a bad result for such a strong engine.

Ginkgo - Nirvana: Ginkgo thought it had a small advantage from the opening. After the rooks were exchanged the engines started to shuffle, and after queens were exchanged the game was a dead draw, though Ginkgo had to lower its eval first for adjudication.

Hannibal - Fire: A series of exchanges removed almost all pieces with only QB vs QN remaining. Fire forced a repetition draw a few moves after that.

Jonny - Critter: After the opening the engines fought for control of the center. Critter had an advantage with a rook for a bishop and pawns and an eval of 1. After several exchanges the center struggle was resolved and only RB vs RR remained. Despite the material advantage Critter was stuck and after a long rook shuffle the engines agreed on a draw. Jonny keeps a 1 point lead over Ginkgo.

Round 60:
Laser - Jonny: By move 26 only QRB vs QRB remained, and the engines settled for a repetition draw not long after that.

Fire - Rybka: Evals stayed close to 0 the whole game, Rybka ended the game with a bishop sacrifice and perpetual check.

Houdini - Fizbo: Houdini had an eval advantage from the opening, Fizbo defended and exchanged pieces until only QRR vs QRR remained on move 23. Houdini's eval came down and then it was Fizbo's turn to be optimistic. However, with a pair of rooks exchanged the engines started to shuffle, and with the queens gone the draw came quickly. Despite the draw Houdini is now officially the winner of the rapid tournament. With only two games left Houdini leads Komodo by 2.5 points.

Round 61:
Komodo - Fire: Komodo had an eval advantage that grew to about 1 when Fire started to exchange pieces. By move 28 only QN vs QN remained and evals were on the way down. Fire created a passer that forced Komodo to draw with perpetual check. Komodo is only 0.5 points ahead of Stockfish.

Round 62:
Jonny - Raptor: Jonny got its queen into a tight spot in the corner, and the only way out allowed Raptor to exchange all pieces and reach a drawn rook ending. Ginkgo has a chance to catch up with Jonny in its last game if it wins against Fire.

The Baron - Komodo: The Baron held out for 25 moves against Komodo but it was all downhill from there. Komodo created a passer and opened up the position a little, its evals started to jump. The Baron had to give a bishop to get rid of the dangerous passer giving Komodo a decisive lead. After this win Komodo guarantees second place.

Fire - Ginkgo: Both engines had strong pawn lines and they began to shuffle on move 26. After another 40 moves a draw was agreed. Jonny keeps fifth place.

Season 9, rapid tournament, rounds 48-55

Table after 55 rounds

Remember I said things were getting exciting. Well, not anymore. Houdini's lead is back to 2.5 points after a perfect 8 points in the last 8 games. I don't see anything that can stop it from winning the rapid tournament. Komodo in second place scored only 6.5 points, drawing against some of the weaker opponents: Naum, Arasan and Vajolet2. This is quite a surprise after Komodo's performance so far in this RR. The minor excitement left is the fight for second place, with Stockfish only 0.5 points behind Komodo. Fifth place is also contested by Ginkgo and Jonny. Some of the remaining games will be interesting (Komodo and Ginkgo will face Stockfish, Houdini and Fire), but I doubt they will change the overall standings by much.



Games that caught my eye

Round 48:
Houdini - Chiron: The engines played a very interesting middlegame where Houdini's king side was very exposed while Chiron's pieces were not well developed and it couldn't take advantage of this. Both kings moved to the center to find a safe spot, and Houdini's threats on the black king became very effective with eval jumping high. Chiron's pieces couldn't protect each other and the king, and when Houdini added an advanced passer Chiron's position crumbled. An excellent game by Houdini against a strong opponent.

Stockfish - Critter: The game reached a QRN vs QRN position by move 28 and the engines started to shuffle. After a few pawn moves and exchanging the knights the position became static and a draw was agreed. Stockfish is firmly in third place, 2.5 points behind Houdini.

Naum - Jonny: The game was reduced to a queen ending by move 34. For a while the evals were 0 and the game was close to adjudication but Naum's eval climbed a little so the game continued. Naum had two pawns to Jonny's one but Jonny's queen gave checks and it seemed they would go on indefinitely. Still Naum's eval rose gradually, and suddenly Jonny's eval shot up to 15, as if it saw the loss and resigned. It took Naum another 15 moves to see it... Queen endings can be very challenging even for top engines.

Round 49:
Jonny - Stockfish: Stockfish equalized quickly though it was a pawn down. Jonny saw an opportunity to win more material, it was up RPP for B for a while, but this left its king exposed against a rook and a strong bishop pair. In the end it was Stockfish that was up a piece in a N vs BN ending, and though it wasn't easy Stockfish was able to take out Jonny's extra pawns and get a winning position.

Round 50:
Fire - Gull: Gull thought it had an advantage most of the game. The engines exchanged pieces gradually, and though Gull's pawns were more advanced Fire had no real problem defending. When all the pieces were gone Gull admitted it was a draw.

Houdini - Jonny: The engines kept their pieces on the board for a long time, Houdini had a small eval advantage that grew to over 1 when it created a queen side passer. Jonny had to keep an eye on the passer and Houdini could move more freely. Houdini gradually increased the pressure on Jonny's pieces until it could hardly move, finally trapping the black queen for the win. The third straight loss for Jonny, falling behind Ginkgo to 6th place.

Round 51:
Jonny - Nirvana: The engines exchanged almost all their pieces and were at a B vs N position by move 28. After a while the pawn lines stabilized and the game was adjudicated. Only a draw for Jonny, now 1 point behind Ginkgo in fifth place.

Andscacs - Fire: Evals were virtually 0 from move 16, the engines exchanged pieces until getting a tablebase draw. 

Round 52:
Fire - Chiron: Fire outplayed Chiron in a double rook ending. Chiron's connected passers did not have enough support, and after exchanging a rook pair Fire managed to capture a pawn and create connected passers on the queen side. After clearing the center Fire was two pawns up in a winning rook ending.

Vajolet2 - Komodo: Vajolet2 managed to hold Komodo to a draw, forcing a 3-fold repetition by move 29. A big and unexpected setback for Komodo which had an excellent performance this RR, this was only its second draw after beating many opponents much better than Vajolet2. It is back to 1.5 points behind Houdini.

DisasterArea - Ginkgo: Another game with many early exchanges, reaching a RN vs RB position by move 29. DisasterArea had the tablebase advantage that allowed it to give the knight for the black pawns. The remaining R vs RB ending was a tablebase draw. Ginkgo and Jonny are losing sight of Fire in fourth place.

Round 53:
Ginkgo - Vajolet2: Ginkgo got into an imbalanced QR vs QBN position and evals favored Vajolet2 at about 0.7. After exchanging queens and with only a few pawns left both engines could not push pawns without losing, forcing a draw.

Protector - Stockfish: Stockfish gave two pawns and got open files for its rooks and a deadly king side attack. Protector gave material to keep its king alive, giving Stockfish an extra rook and an easy win.

Critter - Fire: The game reached a pawn blockade position by move 23, and a long boring shuffle started. With a few pawn moves and some exchanges the game continued until move 227 before adjudication.

Round 54:
Fire - Jonny: Jonny set up a pawn line across the board and Fire shuffled for a long time hesitating whether to advance pawns on the king side. When finally the king side opened up Jonny thought it had an advantage for a short while with eval over 1.5 before coming back to 0. After exchanging most pieces the remaining N vs B with a passer for each engine was a drawn position.

Houdini - Protector: Houdini had an eval advantage from the opening. Evals did not move a lot until about move 30 when Houdini's eval started to rise. It took control of the center and opened a file on the king side for its rooks. Protector had very little room to move its defending pieces and its position crumbled when Houdini's king side pawns started to advance. Another strong engine that Houdini beats easily, not many more to go that can stop it.

Arasan - Komodo: At move 25 only BB vs RB remained with Arasan two pawns up. Komodo could not find a weakness in Arasan's position and Arasan did not blunder until a draw was declared. This result is a big surprise and a major setback for Komodo. After closing the gap Komodo is now back to 2 points behind Houdini with very low chances of getting near the lead again.

Round 55:
Komodo - Naum: After queens were exchanged at move 18 the engines mainly shuffled behind their pawn lines. Naum was two pawns up while Komodo managed to trap a rook and Naum exchanged material to release it. With only rooks on the board Komodo had a small eval advantage. This later turned into a 7-man rook ending, Komodo was a pawn up but the position was a draw. Another disappointing draw for Komodo against a weaker opponent.

Rybka - Stockfish: Evals stayed close to 0 the whole game. Stockfish temporarily sacrificed a bishop but it got the material back a few moves later. Other than that the engines did not try anything fancy, just exchanged pieces until only pawns were left and a draw.

Season 9, rapid tournament, rounds 40-47

Table after 47 rounds

Houdini's lead over Komodo is down to 1 point, and things are getting exciting. Komodo's success against the top half of the table this RR is paying off now that Houdini is facing these opponents. Komodo had 7.5 points from the last 8 games, first draw this RR. Houdini had only 6.5, already 4 draws this RR against strong opponents. Stockfish with a solid 7 points is third, and at this rate I don't think it can catch up with Houdini, especially since their opponent list is almost identical.
In the second group Jonny had a 7.5 score, closing the gap to Fire. Ginkgo is now 2.5 points behind, it probably won't be able to close this gap.


Games that caught my eye

Round 40:
Stockfish - Nirvana: Stockfish gave a rook for a bishop, partially exposing the black king to attacks. It seemed Nirvana could hold its position but when Stockfish got a rook behind the black line its evals started to climb rapidly. Nirvana gave the material back and soon lost a piece, and Stockfish converted the RN vs R ending to a winning 6-man rook ending with connected pawns.

Komodo - Protector: Protector left its king almost unguarded in a QRN vs QRB position, when its pieces tried to attack the white king. Komodo used this to capture a few pawns and exchange down to a winning rook ending.

Round 41:
Hannibal - Komodo: Hannibal stopped Komodo's wining streak with this draw. The game wasn't very interesting, evals stayed close to 0 with a gradual piece exchange until reaching a tablebase draw.

Protector - Ginkgo: Ginkgo's eval was at 0 from move 12, the position was a RRN vs RRN at move 22, the game ended in 3-fold check repetition not too long after that.

Nirvana - Houdini: Most of the queen side was cleared by move 17. Both engines couldn't get an advantage in the game. Houdini tried a pawn storm on the king side, nothing came out of it and evals stayed low. The game was adjudicated in a QRN vs QRN position. With this draw Houdini does not extend the lead, it is 2 points ahead of Stockfish and Komodo. 

Round 42:
Naum - Fire: Fire won as white but only got a draw as black. Naum had an eval advantage out of the opening, Fire's eval dropped to 0 after the queen side became locked. A series of exchanges opened up the position and Fire was a pawn up, but with only RB vs RB left and opposite color bishops the game ended in a draw.

Ginkgo - Hannibal: Both engines did not want to fight in this game, evals were at 0 from move 9. There were still many pieces on the board, an advanced passer for white, an exposed white king open for attack, yet the engines chose a quick repetition draw. Ginkgo is falling behind Jonny and Fire, but also had a tougher set of opponents so far in the second RR.

Komodo - Rybka: The queen side pawns were gone by move 18 with a drawish position. Rybka weakened its king side and Komodo found ways to use its queen and bishop to threaten mate while taking control of the center. Finally after a series of exchanges the position was a won 6-man queen ending. Komodo continues to impress this RR, but it still needs Houdini draws to get closer to the leader.

Round 43:
Rybka - Ginkgo: Rybka had material advantage up to three pawns, offset by Ginkgo's threats on the white king. By move 33 the position was QRN vs QRN with Rybka one pawn ahead, and the game was heading for a draw. As the 50-move rule was approaching Ginko's eval started to rise. It had Rybka's knight in a pin and found a way to attack it with all three pieces, more than Rybka's available defenders. The resulting QN vs Q ending took another 30 moves but it was a clear win for Ginkgo, well done.

Fire - Stockfish: Fire had the opening advantage but Stockfish defended well and did not let Fire develop anything substantial. The game reached a rook ending with pawns only on the king side, another draw. Stockfish losing 0.5 points to Komodo and Houdini.

Round 44:
Houdini - Fire: Houdini had an eval advantage out of the opening, and the advantage started to increase from move 30 until reaching almost 2, clearly Houdini was winning. Fire's king was under attack while on the queen side it had two connected passers. Houdini got the passers exchanging a rook for two minors to get a QBN vs QR position with pawns only on the king side. In this position Fire's queen started to harass the white queen, and though Houdini refused to exchange it couldn't hide. When the queens were finally gone the engines just shuffled for 50 moves until the draw. Great defense by Fire.

Ginkgo - Komodo: Ginkgo thought it had an advantage, very dangerous when playing Komodo. It left its king exposed in a R for BN imbalance, and then saw a chance to capture the black queen. This was a mistake as Komodo's eval's jumped immediately. In the resulting QR vs RBB position Komodo had a pawn on the 2nd rank and a strong bishop pair for support and attacks on the white king and queen. Ginkgo's situation became hopeless very quickly. Komodo reduces the gap to 1.5 points.

Round 45:
Jonny - Vajolet2: Jonny managed to equalize despite the bad opening and had a pawn advantage for a short while. Vajolet2 gave up its bishop pair to regain the pawn and reach a QRB vs QRB position, and then the engines shuffled for 80 moves to get to a draw by repetition.

Gull - Stockfish: Gull thought it had an advantage, Stockfish calmly defended and got the evals to 0. When only bishops were left Gull's eval increased a little, prolonging the game until it reached a tablebase draw. Stockfish dropping back to 2.5 points behind Houdini, 1 point behind Komodo.

Fire - Nirvana: The engines exchanged pieces quickly and got a check repetition by move 30.

Round 46:
Houdini - Gull: The position was closed and the engines exchanged pieces gradually. On move 62 it was just RB vs RB left, with a draw as the likely outcome. However, Houdini short on time let Gull take a pawn, getting a passer and much better piece activity. Gull had to give the rook for a bishop to stop Houdini from queening, giving Houdini an easy R vs B winning position. A great game of patience by Houdini.

Stockfish - Andscacs: After many early exchanges the position at move 27 was a closed RRB vs RRB and the engines started to shuffle. With both engines short on time and the 50-move draw getting close the evals started to rise, somehow Stockfish had a plan. First it created a passer and opened up a few files. Then it offered a rook for a bishop and Andscacs took it, probably a blunder because the evals shot up immediately. Stockfish had a second passer and Andscacs had to give a rook to stop it, resulting in an RB vs R winning position for Stockfish.

Round 47:
Ginkgo - Fizbo: Ginkgo seemed to have a promising lead in eval while there were many pieces on the board. However, after a series of exchanges the evals dropped to 0 even though Ginkgo was two pawns up. The white king was too exposed and Fizbo could try a perpetual check or more exchanges, both engines agreed to a draw.

Chiron - Stockfish: Stockfish managed to equalize and be a liitle ahead in eval in a RRB vs RRB position.The position looked drawish but Stockfish outplayed Chiron, marching the king to the queen side and creating a pawn advantage there. Chiron's passer was not supported enough to make a diference and in the end it was Stockfish's queen side passer that could not be stopped, giving Stockfish the win.

Andscacs - Houdini: The game reached a RRB vs RRB position by move 22. Andscacs was able to push a pawn to the 7th rank but no further. The opposite colored bishops ensured the draw after a pair of rooks was exchanged. Houdini with another draw gets Komodo to within 1 point of the lead.

Season 9, rapid tournament, rounds 32-39

Table after 39 rounds

Houdini is in the lead, Komodo gained 0.5 points on Houdini and Stockfish and is second 2 points behind. These three remain unbeaten, in fact they have won all of their last 8 games except the draw between Houdini and Stockfish. Komodo's opponents have been much tougher than those of Houdini and Stockfish, and Komodo has some hope of closing the gap to the leader later in the RR.
In the second group of leaders Fire opened a 1.5 point gap to Jonny and Ginkgo with 7.5 points in the last 8 games. Fire's opponents have been quite weak so this gap is probably temporary (recall that Fire started led the table after 8 wins in the first RR).



Games that caught my eye

Round 32:
Komodo - Gull: Gull was a pawn up but Komodo had the initiative. For a long time Gull fought hard in a RNN vs RBN position. Komodo was able to crack Gull's defense after 70 moves, capturing pawns and getting a decisive lead. Komodo with a good start after a draw in the reverse game.

Hannibal - Chiron: Chiron was up a pawn in a closed position with low evals, when Hannibal saw an opportunity for a king side attack. Hannibal opened the king side with charging pawns and managed to win a bishop. Chiron's queen side pawns were still a threat but the extra piece was winning in the end. Each engine with a win in this mini-match.

Round 33:
Jonny - Protector: A 12-move miniature draw.

Andscacs - Komodo: Komodo improved its position very slowly for 60 moves. Then in a RN vs RN position Komodo took a pawn and another, and it was just winning. A second win for Komodo against a tough opponent after drawing the reverse game. Stockfish and Houdini are also winning but they have much weaker opponents.

Gull - Ginkgo: Ginkgo managed to get a pawn advantage and evals above 1 in a N vs B ending. Gull's king was more active in the center and was enough to get the pawn back and get a draw.

Round 34:
Ginkgo - Andscacs: Both engines were sure the game was heading to a perpetual check when Andscacs blundered and Ginkgo found a way to win a bishop. The QB vs Q ending was a win for Ginkgo. An impressive double win for Ginkgo against Andscacs.

Komodo - Chiron: Chiron left its king a little exposed and Komodo used this for a deadly attack. Chiron exchanged as many pieces as it could but Komodo still won a piece, leading to a winning QRN vs QR position. Komodo starting the RR with 3 wins, compared to 3 draws in the first RR. 

Round 35:
Jonny - Rybka: After 22 moves the position was QRR vs QRR with almost all pawns. Pawn lines were quickly established and the game ended in a 50-move draw. Jonny won the reverse game with black pieces, only a draw in white.

Chiron - Ginkgo: Ginkgo had an eval advantage as well as a rook for a bishop but the position was blocked and both engines started shuffling. Ginkgo avoided the 50-move rule, and as the rule approached again suddenly Chiron was clearly ahead in eval. Although after exchanging pieces the position was an opposite bishop ending Chiron had two passers and black couldn't stop both. Ginkgo should have taken the draw.

Round 36:
Fruit - Fire: Fire was down two pawns when it initiated a series of moves that ended in a perpetual check. Only a draw against Fruit.

Komodo - Jonny: In a balanced position Jonny allowed Komodo to get control of the center, followed by a series of exchanges where Komodo won a rook for a bishop. After exchanging queens the remaining R vs B ending was a win for Komodo. 

Round 37:
Jonny - Ginkgo: The game reached a RRB vs RRB position at move 27, and though Jonny had some false hopes it had an advantage the game ended in a quick draw.

Andscacs - Fridolin: This should have been a very easy win for Andscacs. Instead Andscacs crashed 2 plys before adjudication in a clearly winning position. That's just sad.

Round 38
Ginkgo - Texel: The game looked like it was heading for a big shuffle when Texel exchanged queens and evals jumped to over 1 in its favor. For a few moves Texel was a pawn ahead in a RN vs RB position, then a pawn race started. Texel had to gave its bishop to stop the white pawns, and the RN vs R left was a tablebase draw.

Round 39:
Raptor - Ginkgo: Ginkgo sacrificed a bishop for a pawn in an attempt to start a king side attack. The attack faded a few moves later when Raptor gave an exchange back and created a BN to R imbalance. After a long shuffle the game ended in a tablebase draw.

Houdini - Stockfish: The last game of the round was also the most anticipated, the last time these engines meet before the superfinal. The game itself was not so interesting, perhaps that was expected? Stockfish equalized quickly and by move 25 only rooks and knights were left. Then the rooks were exchanged, evals became 0 and stayed there until a tablebase draw was reached. The main result is that Komodo gained 0.5 point on its two rivals.

Season 9, rapid tournament, rounds 25-31

Table after 31 rounds

The first RR is over and we are at the halfway point. Houdini is in front, increasing the gap after 6 points in the last 7. Stockfish and Komodo are tied in second 2.5 points behind. The three leaders are still uneaten in this tournament. A little behind are Ginkgo, Jonny and Fire, forming a second group of 3. Of the under-3000 engines only Texel's performance remains notable in the top half. Fruit and Laser are doing well in the bottom half.

Draw rate of games within the top 10 engines is 29/45 (64%), much higher than the total draw rate.

The Stockfish - Delphil draw stands out as the most outrageous result of the RR, considering that this is half of Delphil's score in the full RR.

What will happen in the reverse games? My feeling is that Houdini will win this tournament, that it is simply playing better, beating the weaker engines where Stockfish and Komodo sometimes slip. A gap of 2.5 points is quite a lot to close in 31 games, especially if Houdini remains unbeaten.  


Games that caught my eye

Round 25:
Jonny - Gull: The game had a RN for Q imbalance, and evals favored Gull. As pieces were exchanged the evals continued to climb, reaching over 1 in a RRN vs QR position. With pawns running out Jonny saw a draw coming. Gull without tablebase support did not see it and thought it was winning, playing a 6-man draw for over 50 moves.

Rybka - Houdini: Houdini sacrificed a bishop to get a strong king side attack that turned into a RR vs Q ending. Houdini's two extra pawns were enough to win.

Komodo - Stockfish: Komodo looked good in the start with evals rising to 0.6 and a great spot for a knight. Stockfish remained calm and the game became static with both engines just shuffling. This didn't improve when the position opened up 50 moves later, only the evals coming slowly down until the draw. Houdini was the real winner of the game, extending its lead.

Ginkgo - Naum: Ginkgo was happy to win a pawn leading to a QB vs QB position, evals climbing above 1. Since the bishops were of opposite color Naum tried to force a queen exchange, and the evals came back down as this was achieved. Then it was just a long wait for adjudication. A missed chance for Ginkgo.

Round 26:
Stockfish - Ginkgo: Nothing in this game, just exchanging pieces and waiting for the draw.

Houdini - Komodo: Houdini had a little more space than Komodo, but Komodo had a strong pawn line that together with a bishop closed all files. Both engines shuffled pieces until draw was declared. Both head-to-head matches of the top engines were draws, Houdini remains 2 points in front.

Andscacs - Jonny: Andscacs exchanged down to a rook ending a pawn up, with evals approaching 1. Jonny then used its tablebase knowledge to reach a drawn 6-man, with Andscacs playing on for 20 moves thinking it has a winning chance. Only Fire improving its score at the top in this round.

Round 27:
Critter - Laser: A 10 move/11 minute miniature repetition draw.

Jonny - Chiron: The game started with an unusual imbalance of BN and pawns for Q. Both engines thought they were better, and even though Jonny exchanged a bishop for a rook the RRB for QR ending was a draw.

Protector - Fire: Fire had no problem defending against Protecor but could get no more the a draw out of the game. Fire and Jonny starting to fall back behind the top 3 in the table.

Komodo - Nirvana: Komodo had an eval advantage from the start, by move 25 only RBB vs RBN were left. Nirvana defended well and Komodo could only get an opposite color bishop ending, a sure draw. Komodo is now tied with Stockfish in second.

Ginkgo - Houdini: Ginkgo thought it had a better position for 20 moves with a passer on the king side. Houdini countered on the queen side (where both kings castled), exposing white's king for attack as well as advancing a passer of its own. Houdini's pawn storm in front of the white king was much more threatening than Ginkgo's passers, and was enough to ensure a win for Houdini. Nothing seems to be able to stop Houdini, this was its last serious opponent of the RR. This was only Ginkgo's second loss of the tournament.

Round 28:
Nirvana - Ginkgo: Ginkgo thought it had an advantage with a bishop pair against Nirvana's two knights. Nirvana managed to exchange down to a N vs B ending which resulted in a quick draw. Four straight games without a win for Ginkgo.

Fire - Hannibal: After many exchanges the position was RN vs RN after 26 moves. The game continued until reaching a drawn tablebase position.

Critter - Jonny: Jonny couldn't get past Critter's defense, its initial eval advantage slowly came down to zero as more pieces came off the board. The Fire - Ginkgo - Jonny group has lost touch with the table leaders, a full point behind.

Round 29:
Jonny - Laser: Jonny's eval jumped above 1.5 in a QB vs QB position. Laser defended well and Jonny couldn't find an opening, evals dropping back to zero. Laser continues to play better than what its TCEC rating suggests.

Rybka - Fire: Rybka thought it was better in a R vs BN ending, Fire just exchanged pawns until reaching a drawn 6-man position.

Fizbo - Houdini: Fizbo succeeded where most engines failed, it held Houdini to a draw. Fizbo had a queen side pawn advantage, while Houdini was a pawn up with doubled central passers. Houdini was able to take out the queen side pawns, leaving its king exposed, enough for Fizbo to force a draw.

Round 30:
Fire - Komodo: Neither engine could get something going in the game. By move 33 only B vs N were left and evals were at 0 until adjudication.

Round 31:
Ginkgo - Fire: Fire had an advanced passer but could not get it far enough. Ginkgo closed the game with a bishop sacrifice and a forced repetition by Fire to avoid mate. The second engine group is 1.5 points behind.

Fruit - Stockfish: Stockfish managed to get a small eval advantage in the game but there were not enough pieces left on the board in a QB vs QB ending. A surprise draw to close the RR.