Season 27 league 1 statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

Final draw rate was 65.9%. 

Game termination

The three most common game termination causes were:
54.9% - TCEC draw rule
27.3% - SyzygyTB
10.2% - Mate

There were no crashes in the stage.

Moves per game

Median= 68.5
Average= 73.6

There were 39 games longer than 100 moves, the longest was 233 moves (Caissa - Revenge, game 87, Caissa won). 

Time per game (hours)

Median= 1:03
Average= 1:01

Openings

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

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

Reverse pairs, wins

Reverse pairs, same moves

Pairs of reverse games diverged quickly, 26.5% diverged immediately out of book, 60.6% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 29 plys, twice (Uralochka - Revenge, games 135 and 201, Modern defence, two white wins ; Caissa - Viridithas, games 193 and 259, Nimzo-Indian, two draws) 

Season 27 league 1

Final Standings

Obsidian and Caissa advance to the premier league. From the start there were three engines leading: Obsidian, Caissa and Ceres. After the first two RRs Obsidian led with 8 game pair wins and one loss to Ceres, Caissa was second with 6 game pair wins (including against Ceres) and no loss, and Ceres was 3rd with 6 game pair wins and one loss. In RR3 Obsidian increased its lead while Caissa and Ceres were tied. It appeared that Ceres had a better chance of qualifying because Caissa drew 3 games as white against lower ranked engines. However, RR4 was a disaster for Ceres. It lost 3 games (one to Obsidian) and only managed one win, drawing 4 times against lower ranked engines. Caissa also missed chances in RR4, with one loss and only two wins, but this was enough to ensure 2nd place before the last round.

Ceres started this season in the qualifying league, first time playing in TCEC. It easily reached league 1 and was considered a strong candidate to play in the premier division, perhaps even close in strength to Leela and Stockfish. As it turns out its journey ended in league 1 this season, it will get another chance next season. League 1 is a tough league with 12 strong engines and only 2 advancing. Recall that last season Obsidian and Caissa were tied with Seer in 2nd place, and Seer advanced only on a tiebreak. This season Obsidian and Caissa will test their strength against the strongest TCEC engines.

Obsidian and Caissa will play in the premier division together with Stockfish, Leela, Berserk, KomodoDragon, Ethereal and Seer.

Interesting games

game 8, rofChade - Caissa: The center was blocked, the engines exchanged a pair of knights and rofChade captured a pawn, creating a passer on the queen side. The engines exchanged a few pawns and pieces, then mostly shuffled for a long time. After a series of exchanges the game reached a rook ending with rofChade two pawns up. The engines traded pawns and the game ended in a tablebase win.

game 12, Obsidian - PlentyChess: Obsidian captured a rook for a knight and pawn early, the engines reduced to a RRB vs RBB position. After some shuffling PlentyChess captured a pawn but one of its bishops became trapped. Obsidian captured two pawns before the black bishop was freed, the engines exchanged rooks and the game ended in a tablebase win.

game 17, Caissa - RubiChess: RubiChess gave a rook for a bishop and pawn, it created a passer that Caissa captured. RubiChess avoided exchanging queens, after a while Caissa captured a pawn. The game reached a QRR vs QRB position, RubiChess delayed by attacking the exposed white king. Caissa exchanged a pair of rooks and captured a pawn. After finally exchanging queens the game ended in a tablebase win. 

game 23, Obsidian - Devre: After a series of exchanges there was a material imbalance of R vs BB with white two pawns up. Obsidian moved two rooks forward, then captured a rook for a knight leading to a RR vs BBN position. The engines traded pawns, Obsidian had a passer on both sides and its rooks threatened the black king. Devre lost material and the game ended in a tablebase win.

game 26, Devre - PlentyChess: The engines exchanged all bishops, after some shuffling they exchanged a pair of knights. Devre moved a rook forward, captured a pawn and then moved the second rook forward. The game reached a RRN vs RRN position and Devre captured a second pawn. PlentyChess captured one pawn back but its knight was trapped and captured. Devre exchanged all rooks, queened a pawn and mated.

game 27, Ceres - Obsidian: The engines started to exchange pieces on move 25. Ceres went a pawn up and then the game reached an opposite color bishop ending and Ceres captured a second pawn. Ceres pushed a passer to the 7th rank, the black king had to block while the white king was free to move forward. Obsidian couldn't cover all squares with its bishop, Ceres captured another pawn and promoted a passer (to a knight?) to win.

game 38, Ceres - Uralochka: All pieces were on the board until move 40, except for one minor piece exchange. Ceres created a passer on the queen side and evals started to increase. Uralochka captured the passer, Ceres created another and pushed it to the 7th rank. In a series of exchanges Uralochka captured the passer and lost some material, the game reached a RB vs R position. Uralochka was two pawns up with a passer but the extra bishop was stronger. Ceres exchanged rooks and the game ended in a tablebase win. 

game 39, Caissa - PlentyChess: The engines castled in opposite directions, evals increased steadily though there were only a few exchanges. Caissa placed its major pieces behind the e pawn, PlentyChess gave a knight for a pawn to block the e file. In desperation PlentyChess gave a rook for a knight and created an advanced passer. Caissa captured the passer and exchanged queens, PlentyChess lost more material and was mated.

game 50, Caissa - Devre: The engines exchanges pieces and pawns, first Devre was up a pawn, then Caissa equalized and the game reached a QRB vs QRB position. Devre had connected passers in the center, Caissa captured both and went a pawn up. After exchanging bishops Caissa used the exposed black king to reduce to a queen ending two pawns up. Caissa pushed a passer forward to win.

game 63, rofChade - Devre: The game started with a black bias and a Q vs BN imbalance. Devre was two pawns up with a passer in the center. After the pawns stabilized the engines shuffled for a long time, after move 75 evals increased as the engines reduced to a Q vs RB position. Devre created a second passer, rofChade captured one but Devre gave its pieces to queen the other. The queen ending was long, eventually Devre reduced to a winning king and pawn ending.

Standings after RR1: Obsidian +4, Ceres Caissa +3, RubiChess +1, rofChade Uralochka PlentyChess Devre 0, Revenge Viridithas -2, Igel -3, Stoofvlees -4. Obsidian, Ceres and Caissa are at the top. Ceres is without loss, yet Obsidian leads despite losing to Ceres. There are 5 engines which can still close the gap with a good reverse RR. 

game 70, RubiChess - Devre: RubiChess had a pawn majority on the queen side, and the black king was vulnerable on the king side. The engines exchanged pieces until only RN vs RB were left, RubiChess gave two pawns for the bishop. There was only one white pawn left, RubiChess captured all remaining black pawns to win.

game 74, Caissa - rofChade: The engines opened the queen side and after a series of exchanges the game reached a QRR vs QRB position with black two pawns up. Caissa exchanged a pair of rooks and captured a pawn, rofChade still had a passer in the center. Caissa pinned the bishop and captured the passer, then the engines shuffled for a long time. Eventually Caissa found a way to capture a pawn, rofChade lost more material and the game ended in a tablebase win.

game 80, Obsidian - Uralochka: The engines exchanged a few minor pieces, when the c file opened Obsidian moved a rook forward and Uralochka gave its queen for two rooks. The game reached a QN vs RRN position, Obsidian captured a pawn and Uralochka gave a rook for a knight. The white king moved forward and Uralochka lost more material, leading to a tablebase win.

game 83, RubiChess - Caissa: The engines exchanged pieces until only QRB vs QRB remained. RubiChess captured a pawn, Caissa decided to not equalize pawns but exchange rooks instead. RubiChess reduced to a queen ending with a pawn up and connected passers. The game ended in a tablebase win.

game 90, Uralochka - PlentyChess: There were a few exchanges after the start, the engines castled in opposite directions, Uralochka gave a pawn but managed to push a pawn to h6. PlentyChess gave a rook for a bishop and captured the h6 pawn and the game reached a QRB vs QBN position. The black king was vulnerable and PlentyChess exchanged queens but lost the knight, the game ended in a tablebase win.

game 101, Ceres - PlentyChess: Ceres kept its king in the center and opened the king side. PlentyChess gave a trapped bishop for 3 pawns and the engines reduced to a RN vs R position. Ceres captured black pawns and kept one white pawn to secure the win.

game 108, Revenge - RubiChess: The engines opened the queen side, in a series of exchanges Revenge traded Q for RB, then RubiChess gave a knight for two pawns. Revenge moved both its rooks to the 7th rank and RubiChess traded its queen for the rook pair, resulting in a BBN vs RB position. Revenge pushed a passer to the 7th rank and RubiChess lost its rook for it, game over. 

game 113, Caissa - Uralochka: Caissa went a pawn up, then Uralochka gave a rook for a knight and pawns and exposed the white king. The game reached a RRB vs RBB position, Caissa captured pawns and was a pawn up. Caissa pushed a passer and Uralochka gave a bishop to stop it. Caissa gained more material and the game ended in a tablebase win.

game 119, Obsidian - RubiChess: The engines opened the queen side, RubiChess moved its queen forward to capture a pawn. Obsidian trapped the queen and traded RB for it. RubiChess was two pawns up, after some time the game reached a QR vs RRB position. Obsidian created an advanced passer and started to gain material, first the black bishop and then a rook to win.

game 126, Caissa - Ceres: The engines exchanged many pieces and pawns, leading to a R vs BN imbalance with white two pawns up. Caissa captured another pawn and all its 4 pawns were passers. The game reached a RR vs RBN position, Ceres captured one pawn back and reduced to a rook ending. Ceres avoided captured to delay but the game ended in a tablebase win.

game 130, Uralochka - RubiChess: The game started with a Q vs BN imbalance and a black bias. RubiChess was two pawns up, there were many early exchanges and the game reached a Q vs RB ending. The engines traded pawns and evals were low, but Uralochka was inaccurate and evals jumped. RubiChess pushed a passer to the 2nd rank, then found a safe square for its king and Uralochka had to give its queen for a rook to avoid a queening. The black king moved forward and Uralochka couldn't prevent a queening and mate.

Standings after RR2: Obsidian +7, Caissa +6, Ceres +5, RubiChess +2, forChade 0, Viridithas Igel Stoofvlees -2, PlentyChess Uralochka Revenge -3, Devre -5. The 3 leaders haven't changed, and there are only two qualifying spots in this league. Obsidian leads, Caissa is in 2nd place ahead of Ceres. There are no engines without loss, Ceres has one game pair loss to Caissa, Obsidian has one game pair loss to Ceres. Caissa has no game pair losses. RubiChess is not too far behind, it has only one game pair loss but not enough wins to join the leaders. PlentyChess, Uralochka and Devre dropped after a weak RR2.

game 137, Ceres - rofChade: Ceres gave a pawn but rofChade had weak pawns on the queen side including isolated doubled pawns. The engines exchanged pieces, Ceres had a strong bishop pair and rofChade gave a rook for one of the bishops, with RBN vs BBN remaining. The engines slowly traded pawns until each engine had only one left. After exchanging knights it took Ceres a long time to force a bishop exchange and a tablebase win. 

game 177, Obsidian - rofChade: After a series of exchanges Obsidian was a pawn up and only minor pieces remained. Obsidian captured another pawn and had doubled passers in the center. rofChade tried to blockade and all pieces were in the center, eventually Obsidian managed to reduce to a BN vs NN position. rofChade lost a knight for one passer, Obsidian queened the other and mated.

Standings after RR3: Obsidian +12, Caissa Ceres +9, RubiChess +3, Stoofvlees Igel Viridithas -2,  rofChade -3, Revenge PlentyChess -5, Uralochka -6, Devre -8. Obsidian increased its lead after winning all 5 games with white against non-top3 engines. Ceres and Caissa are tied in 2nd place and only one will qualify, Ceres won all 4 games with white against non-top3 engines while Caissa drew 3 of 6 such games it played. This gives Ceres a better chance of qualifying. On the other hand Ceres has to play as black against both Caissa and Obsidian. 

game 203, rofChade - Ceres: rofChade created doubled passers in the center, one was gone in a minor piece trade, but the other was protected and Ceres had to block it. rofChade gave a rook for a bishop, the game reached a QB vs QR position with white two pawns up. Ceres blocked the passer with its queen, the engines mostly shuffled for a while. Eventually the white queen moved forward to prevent a second passer on the king side. After a few pawn trades the queens were exchanged, Ceres captured the passer in the center and rofChade created more passers on the sides. rofChade pushed a slowly pushed a passer to the 7th rank, the game ended in a tablebase win.

game 206, Caissa - rofChade: Caissa gave a pawn but opened the king side and exposed the black king. rofChade gave the pawn back and countered with an attack on the white king that wasn't effective. The engines reduced to a RBN vs RBN position with white a pawn up. Caissa captured a second pawn and created connected passers on the queen side. One passer slowly advanced and rofChade lost the rook to stop it. The game ended in a tablebase win.

game 214, Revenge - Ceres: Early exchanges opened the queen side and Revenge was up a pawn with a passer. After another series of exchanges only RBN vs RBB were left and Revenge captured a second pawn. Ceres captured one pawn back and the game reached a rook ending. After trading pawns it was a 7-man position which Revenge converted. 

game 215, RubiChess - Caissa: There were many early exchanges, the game reached a RRB vs RRN position and evals were stable. Evals started to increase after RubiChess exchanged a pair of rooks and moved a rook forward. RubiChess captured a pawn, Caissa did the same but its knight couldn't retreat to safety. Instead Caissa gave the knight for more pawns, it was two pawns up and there was only one white pawn left. RubiChess pushed its pawn forward, it gave its pieces and queened. In the Q vs R ending the black pawns were too slow to promote and too far from the black king, the game ended in a tablebase win.

game 225, Obsidian - Ceres: There were many early exchanges and the game reached a RN vs RB position, Ceres was a pawn up while the white rook and king were more active. Evals suggested a draw but Ceres made the wrong move, allowing Obsidian to reduce to a king and pawns ending. Obsidian quickly equalized material, and using its active king it forced the black king back and captured another pawn to win.

Standings with 5 rounds to go: Obsidian +13, Caissa +9, Ceres +6, RubiChess +4, Stoofvlees rofChade -1, Viridithas -2, Igel -3, Revenge PlentyChess -5, Uralochka -7, Devre -8. Obsidian continues to lead, it is very likely to finish first in the league. Ceres had a terrible RR4 so far with 3 losses and no wins, including 3 games it only drew as white against weaker engines. Caissa lost one game as well, but it also won a game and drew as white only once against weaker engines. As a result Caissa has a 3 win gap in 2nd place and Ceres needs a miracle to close this gap in 5 rounds. One of the remaining games is Caissa as white against Ceres. 

game 251, Obsidian - RubiChess: Obsidian gave two pawns and attacked the king side, RubiChess gave a rook for a bishop to protect its king. The game reached a QRR vs QRB position and Obsidian moved a rook to the 7th rank. After a while the white queen moved forward as well, Qbsidian captured a pawn and created an advanced passer. RubiChess gave the bishop so its queen could check the white king, but Obsidian eventually found safety for its king. RubiChess lost more material and was mated.

Standings with 2 rounds to go: Obsidian +15, Caissa +10, Ceres +6, RubiChess +4. The 3 leaders drew their games as black. Obsidian won twice as white and ensured first place. Caissa increased its 2nd place lead to 4 wins after it won its game as white and Ceres only drew. Caissa will finish 2nd almost surely. 

game 254, Revenge - Obsidian: Revenge captured a pawn and the engines exchanged queens, they continued to exchanged pawns and pieces until the queen side was cleared and only BBN vs BBN were left. Revenge created a passer in the center and slowly pushed it forward. Obsidian captured a pawn but had to give a bishop for the passer. Obsidian lost more material, Revenge queened and mated.

Ceres held a draw against Caissa, with this result Caissa ensured 2nd place.

Season 27 league 2 statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

Final draw rate was 69.7%. 

Game termination

The three most common game termination causes were:
54.9% - TCEC draw rule
25.0% - SyzygyTB
9.5% - Mate

There were no crashes in the stage.

Moves per game

Median= 63.5
Average= 71.3

There were 35 games longer than 100 moves, the longest was 195 moves (akimbo - PlentyChess, game 153, draw). 

Time per game (hours)

Median= 1:02
Average= 1:01

Openings

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

The engines had very little freedom to choose the opening variant, 97.7% of the game pairs (all but 3) repeated the same ECO code and 93.2% repeated the opening variant twice. In all of the game pairs the first letter of the ECO code was repeated.

Reverse pairs, wins

Reverse pairs, same moves

Pairs of reverse games diverged quickly, 23.5% diverged immediately out of book, 58.3% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 19 plys (Minic - Arasan, games 27 and 93, Scandinavian, Marshall variation, two draws) 

Season 27 league 2

Final standings

Ceres, PlentyChess, Devre and Uralochka advance to league 1. Ceres and PlentyChess led the league from the start. After RR2 PlentyChess was ahead, both engines had no loss. In the second half Ceres took the lead, PlentyChess won less games and even lost one and finished second. Many engines were in the race for the other two qualification spots. After RR2 Uralochka was in 3rd place, Devre in joint 4th place and without loss. After RR3 Devre was in 3rd place though it lost twice, close behind were Uralochka, Ginkgo, Stormphrax and Velvet. In RR4 Devre pulled away and secured qualification, only in the last round Uralochka ensured it was ahead of the chasing engines. Devre and Uralochka finished with tied scores, Devre was given 3rd place on a tiebreak.

The four qualifying engines will play in league 1 with:
played in season 26 premier division - RubiChess, Stoofvlees
played in season 26 league 1 - Caissa, Obsidian, rofChade, Viridithas, Igel, Revenge

Interesting games

game 1, Arasan - Stormphrax: The game started with a bias for black, Stormphrax grabbed an early pawn and Arasan gave a rook for a bishop. Arasan had a trapped knight and no real compensation, Stormphrax was a rook up for pawns after it captured the knight. Stormphrax gained more material and mated.

game 4, Uralochka - BlackMarlin: The engines exchanged pieces and pawns, Uralochka created a passer on the queen side. The game reached a RBN vs RBN position, Uralochka captured a pawn and created a second passer. Uralochka captured the remaining black pawns to win.

game 23, Arasan - Uralochka: Arasan went a pawn up and created a passer in the center. The engines exchanged pieces and pawns, it took Arasan a while to arrange its major pieces and then all rooks were exchanged and the game reached a QN vs QB position. Uralochka delayed but couldn't avoid a queen exchange, Arasan gave the passer but captured the remaining black pawns to win. 

game 28, PlentyChess - Ginkgo: After exchanging queens PlentyChess had a passer in the center. The engines reduced to a RN vs Rn position and PlentyChess captured a pawn. The white pieces were more active, PlentyChess captured a second pawn and the white king moved forward. PlentyChess used the passer to win.

game 36, Ceres - Uralochka: The black queen grabbed a pawn on the queen side and it was late coming back when Ceres attacked on the king side. Ceres gave a rook for a bishop, it threatened the black king with a queen and a bishop on the light squares. Uralochka gave the material back and Ceres captured a pawn, the game reached a same color bishop ending with white two pawns up which Ceres converted.

game 39, PlentyChess - Velvet: There were many early exchanges and the game reached a RN vs RB position. PlentyChess captured a pawn and created a passer on the queen side, Velvet tries to attack and gave up another pawn. Velvet regained the pawns but lost its bishop, the last white pawn secured the win.

game 50, PlentyChess - Uralochka: After a series of exchanges PlentyChess was up a pawn and the engines cleared the queen side pawns. The engines slowly exchanged pieces, PlentyChess gave two pawns but captured rook for a bishop. The RN vs BN ending was slow, eventually PlentyChess exchanged minors and forced mate.

game 61, PlentyChess - Stormphrax: There were no exchanges until move 43, the engines shuffled behind their pawn lines until move 78. When the king side opened the game reached a BNN vs BNN position, PlentyChess was a pawn up with a passer. The white king moved forward, Stormphrax gave a knight and captured pawns but its bishop was trapped. PlentyChess captured the bishop and was on time to stop the black pawns, it queened to win.

Standings after RR1: PlentyChess +5, Ceres +4, Devre +2, Stormphrax Ginkgo +1, Uralochka akimbo 0, Velvet -1, Arasan -2, BlackMarlin Minic -3, DeepSjeng -4. PlentyChess and Ceres are in the lead, both without loss. PlentyChess won all its games with bias while Ceres drew twice with bias (some of the games had black bias so not all wins are in white and not all draws are in black). Devre is also without loss but with only 2 wins. At least 4 more engines are in the race for the 3rd and 4th qualifying places.

game 76, Uralochka - akimbo: The game reached a QRB vs QRB position with the queen side pawns cleared and Uralochka a pawn up. The engines exchanged queens, akimbo regained the pawn but its bishop was pinned. Eventually Uralochka captured the bishop, its last pawn secured the win.

game 88, Minic - Ginkgo: Minic was a pawn up from the start, the engines exchanged pieces until the game reached a rook ending. The engines slowly traded pawns until only 3 were left, Minic managed to convert the 7-man win.

game 90, Ceres - Velvet: The engines castled in opposite directions, Ceres had more space and a pawn majority in the center. Ceres gave two pawns and reduced to a RRN vs RRN position with an advanced passer. Ceres regained the pawns, then captured another and added a second passer. The white king moved forward, Velvet lost material for the passers, game over.

Standings after RR2: PlentyChess +7, Ceres +6, Uralochka +3, Devre Stormphrax +2, Ginkgo +1, Velvet 0, akimbo -1, BlackMarlin Arasan -4, Minic -5, DeepSjeng -7. PlentyChess and Ceres are still leading without loss. Uralochka had 3 wins and no loss in RR2 and it jumps to 3rd place. Devre is still without loss in the league, it is part of the group trying to finish in the top 4 places.

game 142, akimbo - Uralochka: The engines opened the queen side, Uralochka had two isolated pawns there that akimbo eventually captured. The black queen moved forward but was not effective there, Uralochka captured a rook for a bishop but later lost material to stop a passer. The game reached a BNN vs RN position, Uralochka lost the knight for another passer and was mated.

game 157, Ceres - Stormphrax: The center was blocked, all pawns were on the board and Ceres had more space. After exchanging a pair of pawns Stormphrax had a passer in the center and Ceres had a pawn majority on the queen side. After some shuffling the a file opened, the engines exchanged pieces and reduced to a RRB vs RRB position. Ceres captured two pawns and created 3 passers. Ceres queened a passer and the game ended in a tablebase win.

game 161, Devre - akimbo: akimbo captured a pawn on the queen side while Devre weakened the black pawns on the king side and threatened the black king. In a QRB vs QRN position Devre regained the pawn, then went a pawn up and reduced to a rook ending. Devre created a passer on both sides, enough to win.

game 165, Ginkgo - Devre: Devre gave a rook for a bishop early, weakening the white pawns on the king side. Devre was strong in the center but Ginkgo slowly improved with an attack on the king side. The engines exchanged pieces, Ginkgo gave back the material and the game reached a rook ending. Ginkgo captured black pawns and was 3 pawns up to win.

game 168, Ceres - Uralochka: The engines exchanged pieces slowly and evals remained constant. When the game reached a B vs N ending evals started to increase. Uralochka gave a pawn to create a passer, Ceres controlled the promotion square with its bishop and pushed its own passer forward. Uralochka allowed a queening to keep its knight but was then mated.

game 171, PlentyChess - Velvet: The engines slowly exchanged pieces with most pawns on the board. Velvet gave a knight for two pawns and exposed the white king, but PlentyChess kept its king safe and blocked all black passers. In a RBN vs RB position PlentyChess captured black pawns, then reduced to a tablebase win. 

game 178, Velvet - Devre: The game reached a QBB vs QBB position, Devre had connected passers on the queen side but its king was exposed. Evals started to increase as Velvet captured one of the passers and exchanged queens. After exchanging a pair of bishops Velvet created a passer, then captured the second black passer. Velvet queened a passer and mated.

game 193, PlentyChess - Stormphrax: PlentyChess had a bishop pair advantage, Stormphrax offered a rook for a bishop but PlentyChess refused the exchange. PlentyChess opened the king side, after exchanging queens it placed a rook on the 7th rank and captured two pawns. The engines reduced to a RB vs RN position and the game ended in a tablebase win. 

Standings after RR3: Ceres +10, PlentyChess +9, Devre +3, Ginkgo Uralochka +2, Stormphrax Velvet +1, akimbo -3, Arasan BlackMarlin -4, Minic -7, DeepSjeng -10. Ceres and PlentyChess lead after RR3, both without loss. Ceres had a better RR and it overtakes PlentyChess. Devre lost twice in RR3, despite this it is now in 3rd place. Ginkgo and Uralochka are right behind, Stormphrax and Velvet are also in the qualification race.

game 205, Devre - Stormphrax: There was one pawn exchange after the start but evals increased steadily. After move 24 the engines started to exchange pieces and pawns, resulting in a NN vs R imbalance. Stormphrax gave a rook for a knight and tried to hold a QBN vs QB position, Devre exchanged queens and reduced to a tablebase win.

Standings with 5 rounds to go: Ceres +11. PlentyChess +10, Devre +5, Uralochka Ginkgo Velvet +2, Stoemphrax +1, akimbo -2, BlackMarlin -5, Arasan -7, Minic -9, DeepSjeng -10. Devre improved its position and it has a 3 win lead over the chasing group of 4 engines. 

game 242, BlackMarlin - Ginkgo: All pawns were on the board and one exchange of a pair of bishops. On move 35 BlackMarlin captured a rook for a knight, and then the engines shuffled for a long time. When the exchanges started BlackMarlin created a passer on the queen side. The game reached a RRN vs RNN position, BlackMarlin gave back the exchange but captured a pawn and created a second passer. Ginkgo couldn't stop the passers, BlackMarlin queened and mated. 

game 248, Uralochka - PlentyChess: There were almost no exchanges until move 37, Uralochka gave a pawn and created a passer in the center. Uralochka regained the pawn and captured a rook for a knight, PlentyChess equalized material and the game reached a RBN vs RBN position. Uralochka created two more passers, PlentyChess captured one but lost its bishop and knight for the other two passers. The game ended in a tablebase win.  

game 249, Ceres - Devre: The center was blocked and there were no exchanges after the start. After move 28 all bishops were exchanged and the king side opened, the exposed white king walked to the center. Both engines pushed a passer on the king side and shuffled for a while, after move 55 there was a series of exchanges that reduced to a RN vs RN position. Both king side passers were captured, Ceres captured a pawn and had a passer in the center. In a slow endgame Ceres gave up its passer but managed to capture all the black pawns. The game ended in a tablebase win.

Standings with 2 rounds to go: Ceres +13, PlentyChess +9, Devre +4, Uralochka Velvet +3, Stormphrax Ginkgo +2, akimbo -2, BlackMarlin -6, Arasan -7, DeepSjeng -10, Minic -11. Ginkgo lost to BlackMarlin and only drew against DeepSjeng, Uralochka beat PlentyChess and held against Stormphrax, Devre lost to Ceres and only drew against Velvet. It is hard to imagine Devre not qualifying despite its loss, but four engines still have a chance of getting the 4th qualification spot.

game 255, BlackMarlin - Velvet: The black king moved without castling, the engines opened the board with exchanges. BlackMarlin moved its queen forward and went a pawn up, the engines reduced to a BB vs BN position. BlackMarlin captured a second pawn, the game ended in a tablebase win.

Ginkgo drew against Stormphrax, Devre drew against Uralochka, Velvet lost to BlackMarlin. Uralochka is in 4th place with a small lead over the other 3 engines, one last round to go.

Devre held a draw against Minic and qualified. Uralochka beat DeepSjeng to secure 4th place. 

Season 27 entrance league statistics

A summary statistics table of previous stages and seasons.  

Draw rate, wins

Final draw rate was 54.2%. 

Game termination

The three most common game termination causes were:
39.2% - TCEC draw rule
32.9% - SyzygyTB
20.0% - mate

There was one crash in the stage, Booot crashed in a 7-man drawn position.

Moves per game

Median= 69.8
Average= 74.7

There were 38 games longer than 100 moves, the longest was 189 moves (Halogen - Ceres, game 157, draw). 

Time per game (hours)

Median= 1:03
Average= 1:02

Openings

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

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

Reverse pairs, wins

Reverse pairs, same moves

Pairs of reverse games diverged quickly, 27.5% diverged immediately out of book, 62.5% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 25 plys (Devre - BlackMarlin, games 78 and 198, QGD semi-Slav, anti-Meran, Lilienthal variation, two draws)