Season 22 league 2 statistics

A summary statistics table of previous stages and seasons.  

Draw rate, wins

Final draw rate was 57.1%. 

Game termination

The three most common game termination causes were:

41.1% - SyzygyTB
29.5% - TCEC draw rule
20.5% - Mate

There were one crash/loss on time in the stage, ClassicAra failes to move though it had more than a minute left.

Moves per game

Median= 67.8
Average= 78.9

There were 20 games longer than 100 moves, the longest was 268 moves (ClassicAra - Halogen, game 38, draw). 

Time per game (hours)

Median= 1:02
Average= 1:02

Openings

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

The engines had some freedom to choose the opening variant, 82.1% of the game pairs repeated the same ECO code and 78.6% repeated the opening variant twice. In 7.1% of the game pairs the first letter of the ECO code was not repeated.

Reverse pairs, wins

Reverse pairs, same moves

Pairs of reverse games diverged very quickly, 35.7% diverged immediately out of book, 71.4% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 9 plys (Halogen - Koivisto, games 24 and 52, Old Indian, Ukrainian variation, Koivisto won as white)

Season 22 league 2

Final standings

Koivisto and Minic advance to league 1. Koivisto led the league from the start and its promotion was never in doubt. It won all its game pairs except one (two white wins against Vajolet in the first DRR). Seer was always close to Minic, Seer beat Minic in one game pair but Minic had a better score against the lower ranking engines. Seer did not recover from its loss to ClassicAra, and it finished 3rd.

Winter and Vajolet are relegated to league 3. ClassicAra and Halogen also struggled against relegation. ClassicAra was last after RR2, it lost game pairs to Winter and Vajolet. However it improved in the second DRR with game pair wins against Seer, Winter and Vajolet. Halogen survived after winning two game pairs against Winter.

Koiovisto and Seer promoted from league 3, while Berserk did not after finishing a close 3rd. Considering the results of league 2 I think it is reasonable that Berserk would have been in the top half of league 2 if it had played there. It is difficult to predict if it would have promoted to league 1. Koivisto was better when they played together in league 3, but I think there would have been a race between Minic, Seer and Berserk for the second promotion spot. Anything can happen with such a small sample size.

Koivisto and Minic will join the following engines in league 1:
played in season 21 premier division: Ethereal
played in season 21 league 1: SlowChess, Revenge (previously known as Pedone), rofChade, Nemorino.

Interesting games

game 3, Halogen - Winter: Halogen had a small eval advantage from the start, with almost no exchanges. On move 17 Winter started a series of moves which didn't seem right. It traded an active knight for a passive bishop, then lost a pawn and gave a rook for a bishop. Finally it gave two more pawns and the other rook for a knight. On move 27 Halogen had a large material advantage, Winter had a very questionable attack on the white king. Halogen exchanged pieces and won easily.

game 4, Koivisto - Vajolet: Koivisto was a pawn up with a passer on the queen side, the center was blocked and Koivisto had more space and an eval advantage. Somehow Koivisto moved a rook into a trap on the king side, the engines started to shuffle and evals drifted slowly down. On move 92 Koivisto gave its trapped rook for a knight and pawn, the shuffle continued with a few pawn moves. Vajolet blundered in time trouble, on move 166 Koivisto exchanged queens and then managed to get enough passers forward to win material. The game reached a RN vs R ending and there were enough pawns for a white win, mate on move 221.

game 10, Halogen - ClassicAra: ClassicAra was a pawn up from the start. Both kings did not castle, there were many exchanges and the game reached a rook ending with ClassicAra still ahead by a pawn. The black rook was more active, ClassicAra managed to extend its leads to 3 pawns, enough to win.

game 18, Koivisto - Minic: Minic tried to block the board with a long pawn line. Koivisto used exchanges to open holes in the line and create connected passers behind the black pawns. Minic tried to attack the white king but was not strong enough. Koivisto forced its way on the queen side, gained material and won. 

game 25, Koivisto - Fritz: Fritz grabbed a pawn, a few moves later Koivisto opened the king side and attacked the black king. Fritz lost material to find safety for its king and the game reached a RRB vs Q position. Koivisto was careful to keep its pieces protected, the material advantage was enough for a win 30 moves later.

game 27, Winter - Minic: Winter had an eval advantage from the start, it had a queen side passer that Minic blocked. Evals came down and the engines mostly shuffled, evals became negative as Minic gained space but still the engines blitzed and shuffled. On move 136 Winter exchanged a pair of rooks creating a passer for Minic. Minic then reduced to a queen ending two pawns up, Winter delayed with check as much as it could but was mated in the end on move 180.

game 30, Seer - Minic: Minic concentrated forces on the king side with doubled rooks in an open file. The white king moved to the safer queen side, then Seer opened a file on the queen side and attacked. In a QRB vs QRB position the white king moved forward but Minic could not threaten it, Seer captured two pawns and reduced to a winning king and pawns ending. 

game 32, Vajolet - Koivisto: Both engines had advanced passers, Vajolet with a knight and two pawns for a rook. Koivisto overlooked the possibility of a pawn promoting to a knight with check on its king, its eval jumped immediately. Vajolet had time to protect its king and capture a pawn, the engines reduced to a BNN vs RBN position. Vajolet pushed one passer and forced exchanges that left only BN vs BN, then captured all black pawns. The ending with two isolated white pawns was long and tricky, it took more than 50 moves to queen a passer and win. There were two white wins in this opening, but the result is more related to the engines than directly to the opening.

game 38, ClassicAra - Halogen: Halogen was a pawn up with an eval advantage from the start. The black queen moved forward on the queen side, this let ClassicAra develop a strong attack on the king side. Evals became positive and high, eventually the engines reduced to a RB vs RN position with white two pawns up. However, despite having two passers ClassicAra failed to convert though it kept playing, the game was finally adjudicated on move 268.

game 39, Seer - Koivisto: Koivisto was a pawn up with an eval advantage from the start. The engines exchanged several minor pieces and queens, there were no exchanges after move 23, only shuffles and pawn pushes. On move 73 Koivisto exchanged a few pawns and opened the king side, with (negative) evals increasing. On move 94 Koivisto captured another pawn and only RRN vs RRN remained. Koivisto pushed pawns very slowly, it took more than 40 moves to mate.

game 41, Winter - Fritz: Fritz captured two pawns on the queen side, and then castled long with its king open to attacks on semi open files. Evals jumped as the engines reduced to a BB vs B position. It took Winter a while to break up the black pawn structure, but then its bishops captured the pawns gradually. The game ended in a tablebase win for white.

game 47, ClassicAra - Vajolet: ClassicAra was a pawn up in a N vs B ending. Progress was very slow but eventually ClassicAra managed to capture two more pawns and finally queen a pawn on move 127. However, 3 moves later in a 7-man winning position it failed to move on time (though it had over a minute left on the clock).

game 49, Seer - Fritz: Seer was a pawn up with an advanced passer, but from move 41 it started to shuffle without a plan. I don't know if it could have won, but in any case since Seer has no awareness of the 50-move rule the game ended in a draw before we could find out.

game 51, Vajolet - Minic: Vajolet gave up a perpetual check draw and had to deal with a passer on the 2nd rank instead. Vajolet gave checks for as long as it could, but eventually Minic queened and mated.

Standings after RR2: Koivisto +6, Minic +4, Seer +2, Fritz 0, Halogen Vajolet -2, Winter -3, ClassicAra -5. Koivisto has a comfortable lead after winning game pairs against all the other engines except Vajolet. Minic lost game pairs to Koivisto and Seer, but was better against the lower ranked engines including two double wins. Seer is a point behind Minic, it only has 2 game pair wins against lower ranked engines to add to its win against Minic. At the bottom ClassicAra was even after the first RR but had 5 losses in the reverse games, including a time loss/crash in a winning position. Halogen, Vajolet and Winter are struggling against relegation.

game 59, Halogen - Winter: Halogen gave a pawn but its pieces were better, it had a protected knight on the 6th rank and one of the black bishops was very passive without an open diagonal. Halogen doubled rooks on the a file and equalized material, then with a rook on the back rank it forced a series of exchanges and won a piece. The game ended in a tablebase win for white.

game 63, Seer - Halogen: The position was closed with all pawns on the board until move 45. When the position opened the engines reduced to a QRR vs QRB position with black two pawns up. Seer threatened the black king, Halogen gave its queen for two rooks to stop the attack. In a Q vs RB ending Seer's queen captured all the black pawns and secured the win with passers.

game 65, Minic - Fritz: All pieces were on the board until Fritz gave a rook for a bishop on move 33. Mintz reduced to a RRN vs RBB position, then gave back the exchange and went a pawn up in a N vs B ending. Fritz lost its bishop for a passer, Minic queened and mated.

game72, Minic - Halogen: The engines shuffled for a long time with almost all pieces and pawns on the board. Both engines were in blitz mode when evals started to jump after move 95. Minic opened the g file and attacked the black king. The engines reduced to a rook ending, Minic used mating threats and passers to win.

game 74, Koivisto - Minic: Koivisto had an eval advantage which gradually increased. The engines opened the queen side and Koivisto moved its major pieces there. Minic had a passer on the queen side, Koivisto blocked it and for a long time nothing happened. On move 78 Minic gave a pawn, not sure if that was necessary, evals jumped immediately. Koivisto captured the black passer, and then trapped a black rook that moved forward. Minic gave the rook for a bishop, Koivisto gradually gained more material until the game ended in a tablebase win.

game 81, Koivisto - Fritz: Koivisto had an eval advantage, but for a long while the engines either shuffled or moved a pawn with evals not changing. On move 47 there was a minor piece exchange and shuffling resumed. On move 65 evals started to increase, Koivisto created passers on the queen side and captured all the black pawns. Fritz lost more material and was soon mated.

game 84, Seer - ClassicAra: Seer had an eval advantage from the start, the center was blocked, Seer pushed pawns on the queen side and ClassicAra on the king side. ClassicAra gave a pawn and opened the king side, then concentrated forces facing the white king. Somehow Seer was not careful enough about the safety of its king, evals became negative. In a series of exchanges the game reached a RB vs RB position with black a pawn up, it took ClassicAra another 60 moves to reduce to a tablebase win.

Standings after RR3: Koivisto +9, Minic +7, Seer +3, Fritz -1, Halogen -3, ClassicAra -4, Vajolet -5, Winter -6. Koivisto and Minic extended their lead with a +3 score in RR3. Seer is losing touch with the leaders after its unexpected loss to ClassicAra. ClassicAra had a positive score in RR3, it climbs to 6th place and may avoid relegation.Vajolet and Winter drop down with a -3 score each.

game 94, ClassicAra - Halogen: The game reached a RB vs RB position on move 87, material was equal but ClassicAra had an eval advantage. It is possible ClassicAra could have won, but it only managed to capture a pawn and then to shuffle. Evals came slowly down and the game was adjudicated on move 196. 

game 95, Seer - Koivisto: Seer had an eval advantage from the start, the engines exchanged pieces and pawns and evals came down, even though Seer was two pawns up with a queen side passer. Seer neglected its king and when Koivisto moved its queen forward to the king side evals became negative and started to jump. Koivisto captured the passer and two more pawns, the white king was vulnerable and Seer gave a bishop in desperation. The game reached a winning QN vs Q ending. 

game 99, Koivisto - ClassicAra: The engines exchanged a pair of pawns and a pair of knights, and there were no more exchanges until move 48. Koivisto had an eval advantage but evals drifted slowly down. On move 73 evals started to increase, with both engines in blitz mode. Koivisto gave a pawn, opened the king side and moved a passer to the 7th rank. ClassicAra could not prevent loss of material and mate followed.

Standings with 3 rounds to go: Koivisto +12, Minic +7, Seer +3, Fritz 0, Halogen -3, ClassicAra -5, Vajolet Winter -7. Koivisto adds 3 wins and will finish first. Minic drew four games, but it will probably be second as it is 2 points ahead of Seer. Seer lost to Koivisto and drew against Minic, its chances of promotion are slim. Vajolet and Winter are last but both still have to face ClassicAra, so the relegation race is still active.

game 103, ClassicAra - Vajolet: There were many early exchanges and the game reached a doube rook ending. Vajolet had a passer but it couldn't push it beyond the 3rd rank. ClassicAra went a pawn up after exchanging a pair of rooks. Vajolet moved its king forward to support the passer, allowing ClassicAra to capture the remaining black pawns. ClassicAra gave its rook for the passer, its 4 remaining pawns were stronger than the black rook with no king support. The game ended in a tablebase win for white.

In round 26 ClassicAra beat Vajolet while Winter managed a draw against Seer. Scores at the bottom with two rounds to go: ClassicAra -4, Winter -7, Vajolet -8.

In round 27 Winter and ClassicAra drew their game, Vajolet survived against Minic. Winter and Vajolet are relegated with one round left to play.

 

Season 22 league 3 statistics

A summary statistics table of previous stages and seasons.   

Draw rate, wins

Final draw rate was 44.7%.

Game termination

The three most common game termination causes were:

41.7% - SyzygyTB
26.5% - Mate
22.7% - TCEC draw rule

There were no crashes in the stage, Bit-Genie lost once on time in a drawn position.

Moves per game

Median= 62.5
Average= 69.1

There were 14 games longer than 100 moves, the longest was 168 moves (Weiss - Arasan, game 65, draw). 

Time per game (hours)

Median= 1:00
Average= 1:00

Openings

There were variable length (1-8 plys) book openings in this stage chosen by Eduardo Saucedo and Bastiaan J. Braams. The first letter of the ECO codes was distributed as follows:

The engines had some freedom to choose the opening variant, 78.8% of the game pairs repeated the same ECO code twice, and 74.2% repeated the same opening variant. Only in two (3.0%) game pairs the ECO first letter was not repeated twice.

Reverse pairs, wins

Reverse pairs, same moves 

Pairs of reverse games diverged quickly, 25.8% diverged immediately out of book, 65.2% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 20 plys (Tucano - Drofa, games 37 and 103, Petrov, Damiano variation, two draws) 

Season 22 league 3

Final standings

Koivisto and Seer advance to league 2. There were three engines leading the league from the start, Koivisto, Seer and Berserk. Seer lost to the other two in their direct matches, but it won more games against the weaker engines. Koivisto also beat Berserk in their head-to-head match, so of the three it deserved to be first. Berserk was very close to Seer during the whole RR2, but it was unable to catch up.

 

At the bottom Topple and Pirarucu are heading to league 4, if relegation works properly next season. Marvin and Drofa may be joining them.

 

It is somewhat disappointing that Berserk did not advance to league 2. It seemed to be a strong engine based on its performance in the swiss event, and I thought (like others in the chat) that it would be more successful in the leagues. Unfortunately there were only two promotion spots, and the competition was hard. It is still quite possible that Berserk is stronger than most engines in league 2. It will have to wait for the next season to try again.

 

Seer was much better that expected. In RR1 it beat all engines except Koivisto and Berserk, to which it lost. In RR2 its score was more normal with 7 draws. Tucano was also a surprise, in the swiss event it was behind Topple and Pirarucu while here it finished 4th with a +6 score.

 

Koivisto and Seer join the following engines in league 2:
played in season 21 league 2: Fritz, Minic, Halogen, Vajolet, Winter, ClassicAra

 

This season only 8 engines will play in league 2, Booot and Defenchess do not participate this season. There was no relegation from league 1 because of engines dropping out in higher leagues (Xiphos and AllieStein). League 2 will be a 2 DRR event.

Interesting games

game 1, Seer - Drofa: Drofa went up a pawn but the white pieces were much more active. Seer pushed a pawn to the 7th rank, then gave its queen for two minor pieces. Drofa felt safe for a while, but Seer captured two pawns and Drofa blocked the passer with a rook, both engines realized Seer had a clear advantage. Drofa was forced to lose a rook for the passer, in the end Seer reduced to a B vs pawns tablebase win.

game 3, Wasp - Weiss: Wasp created a passer on the queen side, Weiss pushed the h pawn until it was also a passer but its king remained uncastled. Wasp gave a knight and connected a second passer on the queen side, Weiss lost a bishop to stop one passer. In a series of exchanges Weiss stopped the second passer and the game reached a RRB vs RR position. Eventually Wasp was able to reduce to a bishop vs pawns tablebase win.

game 11, Bit-Genie - Wasp: Wasp was up a pawn from the KGA opening book line. The engines gradually exchanged pieces and (negative) evals increased. The game reached a N vs B ending, Bit-Genie was forced to give its knight to stop a passer and Wasp had enough pawns to win.

game 12, Seer - Arasan: Evals increased after the start, but then stayed mostly constant for a long time, with the engines shuffling and pushing pawns. On move 68 Arasan traded a knight for 3 pawns, it had 3 passers but Seer used the extra piece to gradually capture pawns. The game reached a RN vs R position, Seer captured all the black pawns and had enough of its own to win.

game 14, Wasp - Seer: The game started with an eval advantage for white, but after the engines castled in opposite directions evals became negative. Seer opened the f file and the white king was exposed to attack. Wasp tried to open the queen side, the black king remained safe and Seer went up a pawn with a passer. Seer gave a rook for a knight and reduced to a R vs N ending 3 pawns up. Wasp had to give the rook to stop a passer, Seer had enough pawns to win.

game 16, Koivisto - Weiss: After a slow increase in evals the game reached a QRR vs QRR position with Koivisto a pawn up. The engines exchanged a pair of rooks and then Koivisto captured two more pawns. Koivisto was not in a hurry, it took 25 moves to exchange all pieces and promote a passer to a queen. It had a million ways to win but Koivisto shuffled for 50 moves and captured a pawn before finally mating.

game 27, Koivisto - Seer: Seer went up a pawn, letting Koivisto take control of a file in the center. The black king side pawns advanced leaving the black king vulnerable. Koivisto reduced to a QB vs QB position and used attacks on the black king to capture pawns. Koivisto was a pawn up when both engines promoted a pawn, 4 queens on the board. Koivisto had a big advantage since its king was safe, it reduced to a winning queen ending two pawns up.

game 36, Wasp - Tucano: Tucano pushed pawns on the queen side and (negative) evals increased slowly. For a while the engines shuffled, then Tucano gave a rook for a knight and attacked in the center. Wasp exchanged pieces quickly and reduced to a QRB vs QBB position. Tucano was two pawns up, it pushed a passer to the 2nd rank, and that was enough to win after almost all pieces were exchanged.

game 38, Koivisto - Wasp: There were only a few exchanges after the start, Koivisto had an eval advantage but for a long time evals did not change and it seemed the game was heading for a draw. On move 61 evals started to increase again, the engines reduced to a QRR vs QRR position. Koivisto used an advanced passer and threats on the black king to gain materlal, the game reached a rook vs pawns ending which Koivisto dragged on for 25 moves before matng.

game 47, Wasp - Marvin: Wasp gave 3 pawns and exposed the black king to attack. The white king was also exposed and uncastled, but Marvin had no time to exploit this. Wasp gradually increased the pressure, and in a series of exchanges it won material and reduced to a BNN vs N position, game over.

game 49, Koivisto - Drofa: In a RBB vs RRN position Koivisto trapped the black king and a rook in the corner, then used its king as an additional piece to attack and gain material. The black king was mated still in the trap with its rook.

game 53, Berserk - Seer: There was only one exchange of a pair of pawns which opened the a file, the engines formed long pawn lines and stayed behind them. Berserk had more space and an eval advantage, but for a very long time the engines just shuffled. On move 81 there was an exchange of bishops, by move 96 all rooks were gone and finally a pawn exchange but still evals did not change. The engines were in blitz mode, after more exchanges only QN vs QB remained and evals started to increase. All the black pawns were on squares the same color of the black bishop, which was basically trapped and passive. After exchanging queens Berserk had two passers that only the black king could stop. Berserk used the time to go two pawns up and win.

game 55, Drofa - Bit-Genie: The engines started to shuffle on move 26, with a few pawn moves that reset the 50-move counter. Bit-Genie's clock came slowly down and on move 159 it lost on time.

game 57, Arasan - Berserk: Berserk was up a pawn from the start, (negative) evals increased gradually as the engines exchanged pieces and reduced to a double rook ending. The engines shuffled for a while, then Berserk exchanged a pair of pawns and evals moved up again. Berserk had passers on the queen side, eventually Arasan had to give a rook to stop one. The game ended in a tablebase win.

game 62, Pirarucu - Koivisto: The engines shuffled in a QBB vs QBN position. On move 98 Pirarucu offered a queen exchange, Koivisto accepted and (negative) evals increased. It took Koivisto another 25 moves to move its king forward, and 10 more moves to force a bishop exchange. The white pawns were weak, Koivisto captured them all to reach a tablebase win on move 149.

game 64, Berserk - Wasp: Berserk was up a pawn after the opening with a queen side passer. The engines quickly reduced to a QRR vs QRR position, after some shuffling and exchanges the game reached a queen ending. Wasp delayed as much as it could, but Berserk slowly pushed its passer forward. Wasp captured 2 pawns but couldn't prevent a queening, game over.

Standings after RR1: Koivisto Seer +7, Berserk +6, Tucano +2, Wasp 0, Bit-Genie Arasan Drofa -1, Marvin -2, Weiss -3, Topple Pirarucu -7. There are 3 engines leading the table, but only two will advance. Seer has an unusual result of 11 games without draws, it lost to the two other leaders but won all other games. At the bottom Topple and Pirarucu are losing most of their games. 

game 75, Koivisto - Berserk: The center was blocked and there were no exchanges after the start. The first pawn exchange opened a file on the queen side where Koivisto had rooks doubled. Berserk tried to react on the king side, it gave a knight and moved a pawn to h2. Koivisto hid its king behind the black pawn, gave a rook for a bishop and pushed a passer on the queen side forward. Koivisto avoided opening the king side, Berserk exchanged pieces and managed to capture the white passer but this led to a dangerous attack on the black king. Berserk had to give material and was eventually mated.

game 76, Tucano - Weiss: Weiss blundered in a RB vs RN position, Tucano managed to trap the black rook with a passer and its bishop. The black pawns were all isolated and Weiss couldn't defend them all. Tucano used the passer to reduce to a winning bishop vs pawns tablebase win. 

game 82, Weiss - Koivisto: Evals started positive but became negative after move 20. Weiss pushed the king side pawns forward, leaving its king without pawn support. Koivisto gave two pawns and attacked through the center, with its queen threatening on the diagonal. Weiss struggled to defend its king, after a series of exchanges only RN vs RR remained. Koivisto captured all the white pawns and reduced to a tablebase win.

Standings with 6 rounds to go: Koivisto +10, Seer +8, Berserk +7, Tucano +4, Drofa 0, Wasp Arasan -1, Bit-Genie Marvin -3, Weiss -4, Topple -8, Pirarucu -9. Koivisto takes the lead after winning 3 games, including one against Berserk. Seer only won one game and drew 4, after not drawing a single game in RR1. Seer and Koivisto drew their game. Berserk had one loss but it won two games for a total score of +1. It only drew against Pirarucu, which could be significant in the final standings. The game between Seer and Berserk may decide the engine in 2nd place.

game 97, Berserk - Drofa: There were a few minor piece exchanges and one pawn exchange after the start, Berserk had an eval advantage. After move 18 there were no exchanges, the engines shuffled and pushed pawns and evals did not change. On move 60 Berserk exchanged pawns on the king side and threatened the black king. Evals increased rapidly as Berserk went 2 pawns up and reduced to a RRB vs RRB position. After Drofa lost a rook for a passer the win was a matter of time.

game 104, Wasp - Koivisto: Wasp had an eval advantage after the start, but Koivisto's eval became negative after move 23. Koivisto attacked through the center and the game reached a QBB vs QRB position with white a pawn up. After a very long shuffle Wasp grabbed a pawn and (negative) evals started to increase again. The engines exchanged queens and Wasp pushed a passer to the 7th rank. Koivisto blocked and captured the passer, pawn captures continued until there was only one black pawn in a 7-man position on move 114. It took Koivisto another 27 moves to promote its pawn and win.

game 110, Berserk - Bit-Genie: Berserk had an eval advantage from the start but for a long time evals did not change or drifted down a little. The game reached a RRN vs RRB position on move 51, after some shuffling evals started to increase. Bit-Genie captured a pawn but Berserk moved its rooks forward and managed to capture the black bishop. The engines reduced to a RN vs R ending, a win for white.

game 111, Topple - Seer: Topple had an eval advantage from the start and it was a pawn up. Seer managed to place a strong knight on the 3rd rank and evals became negative. Topple got rid of the black knights with exchanges, Seer regained the pawn and took over the center in a QRR vs QRR position. It pushed a passer slowly forward, won a piece for it and won.

Standings at the top with 3 rounds to go: Koivisto +11, Seer +10, Berserk +9. Koivisto still leads, though it won only one game in 3 rounds. Seer and Berserk won two games, Seer is still ahead by 0.5 points. They still have to play each other.

game 119, Seer - Berserk: Evals increased from the start, Seer had a protected passer on the 6th rank, it was a pawn up in a QRB vs QRB position. After exchanging queens Seer captured a second pawn and it appeared to be heading for a win. However, Berserk exchanged rooks and only opposite color bishops remained. Despite the high evals the position was a draw. Seer wouldn't lower its eval and the game ended by the 50 move rule.

In round 20 Berserk managed somehow to hold a draw against Seer and to keep its hope of promoting alive. Berserk has a head-to-head advantage over Seer in case of a tiebreak. Koivisto only managed a draw against Drofa, no change in scores at the top. Standings with 2 rounds to go: Koivisto +11, Seer +10, Berserk +9.

In round 21 the 3 leaders drew their games, scores remain unchanged. The final standings will be determined in the last round. Standings before the last round:  Koivisto +11, Seer +10, Berserk +9. 

In the last round Koivisto beat Pirarucu easily to ensure first place. Berserk as black drew its game against Wasp. In the last game of the league Seer was white against Bit-Genie in a KGA with advantage for black. Seer only needed a draw to promote, in the end it managed to turn the tables and win. Final standings: Koivisto +12, Seer +11, Berserk +9.

Season 22 league 4 statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

Final draw rate was 56.1%.

Game termination

The three most common game termination causes were:

32.6% - SyzygyTB
30.3% - TCEC draw rule
23.5% - Mate

There was one crash in the stage by MrBob.

Moves per game

Median= 61
Average= 66.3

There were 12 games longer than 100 moves, the longest was 263 moves (Amoeba - Nirvana, game 47, draw).

Time per game (hours)

Median= 0:58
Average= 0:57

Openings

There were 4-move book openings in this stage chosen by Cato. The first letter of the ECO codes was distributed as follows:

The engines had a little freedom to choose the opening variant, 77.3% of the game pairs repeated the same ECO code twice, and 77.3% repeated the same opening variant. In 4.5% 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, 36.4% diverged immediately out of book, 66.7% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 14 plys (Zahak - Drofa, games 19 and 85, KGA Kieseritsky, Berlin defence, two draws) 

Season 22 league 4

Final standings

Berserk, Weiss, Bit-Genie and Drofa advance to league 3. Berserk had an remarkable first RR with 10 wins and a draw, it was obviously the best engine in the league. Weiss was second at the half point and kept its position with a good +9 score. Bit-Genie, Drofa and Chiron fought to get in the top 4. Bit-Genie finished 3rd after beating the other two engines in their head to head matches. Drofa and Chiron were close until the end, Drofa had an unexpected loss to Amoeba but Chiron missed its opportunity to catch up and Drofa qualified in the final round.

Berserk and Bit-Genie advance for the second time this season. Judging by Berserk's scores it appears league 4 was weaker than the qualification league, but keep in mind that there were no opening books in the qualification league so it is difficult to compare. The other two qualifiers, Chiron and Zahak, stop in league 4. 

The 4 qualifiers will join the following 8 engines in league 3:
played in season 21 league 2 - Seer, Arasan
played in season 21 league 3 - Wasp, Tucano, Koivisto, Marvin, pirarucu, Topple

There are only two qualifiers in league 3 and it is going to be tougher. In the swiss event Koivisto and Arasan were close to Berserk, Weiss and Drofa were close behind. It is unknown how they compare to Bit-Genie.

Interesting games

game 10, Chiron - Stash: Evals were close to 0, Stash had a strong passer yet its queen was almost trapped. The black king moved to the center, Stash was surprised by a pawn sacrifice by Chiron that was followed by an attack on the king, with evals jumping. Most pieces were exchanged and the game reached a queen ending. The queens were exchanged, both engines queened again but Chiron was first and the black king was exposed. This was enough to get a two pawn lead and win.

game 12, Weiss - Monolith: Monolith gave a rook for a bishop early, it thought that the exposed white king in the center compensated for the material. Weiss gradually exchanged pieces, its king was not threatened and it castled eventually. The game reached a R vs N ending and Weiss had enough pawns to win.

game 20, Berserk - MrBob: The game reached a RRB vs RRN position, Berserk had an eval advantage but evals did not change for a long time. On move 68 MrBob deserted the back rank and a white rook immediately took over. After exchanging rooks the white king came forward, the black pieces were too far to help. Material was equal but Berserk used the threat on the black king to promote a passer and win.

game 31, Zahak - Berserk: The game reached a BNN vs RBN position, white was two pawns up with 3 connected passers on the queen side. Zahak started to push a passer forward but (negative) evals increased. Berserk reduced to a N vs R ending, the white passer was unprotected too far ahead and was captured. The last black pawn became a passer on the king side, Zahak lost its knight to stop it giving Berserk the win.

game 41, Drofa - Bit-Genie: The game reached a RR vs RB position, black a pawn up with two connected passers. Drofa was not accurate enough, Bit-Genie was able to push its passers safely forward. Drofa lost a rook for one passer, Bit-Genie queened the other passer to win.

game 42, Berserk - Chiron: Evals slowly increased in a closed position with only a few exchanges. On move 43 Chiron gave a rook for a bishop to keep the queen side closed. After a while Berserk opened the king side and reduced to a RR vs RN position. The white rooks were strong, Berserk went 3 pawns up to win. 

game 44, Bit-Genie - Berserk: Berserk opened the center with a rook sacrifice. The white king was exposed, Berserk had a strong knight on d3, and the white pieces were misplaced, balancing the material advantage that Bit-Genie had. However, Bit-Genie was not careful enough, Berserk (negative) evals jumped and it created connected passers. Bit-Genie lost material to stop the passers, the game reached an opposite color bishops ending with Berserk two pawns up. The black king managed to protect its pawns, the remaining white pawns were vulnerable. The game ended in a tablebase win for Berserk.

game 52, Drofa - Monolith: The position was closed with almost all pawns on the board, evals started to increase after move 43. The position opened up and the engines exchanged pieces until only QN vs QN remained, material was equal but Drofa had a queen side passer. Monolith could not block the passer, eventually Monolith queened and won.

game 53, Berserk - Weiss: The game reached a QBN vs QR position on move 43 after both engines queened a pawn. Berserk had a queen side passer that slowly moved forward, Weiss blocked with its rook when the passer was on the 7th rank. Weiss had passers on the king side that slowly moved forward, somehow Berserk found the right moves to stop the passers and eventually force the black rook to move. The game reached a 7-man QBN vs QP position, a win for white.

game 55, Zahak - Bit-Genie: Zahak had a small eval advantage after the start, evals turned negative after Zahak missed a strong attack by the black pieces on the long diagonal. Many exchanges followed and when the dust cleared only BB vs RB remained. It was a long endgame, Zahak defended with its bishops, but after almost 40 moves Bit-Genie captured a bishop and then mated.

game 66, Bit-Genie - Weiss: Weiss was a pawn up early, Bit-Genie tried to threaten the black king on the queen side but nothing came out of it. Evals turned negative though Bit-Genie regained the pawn. Weiss gave a bisיop and attacked the white king, it regained the material and the game reached a QRB vs QRB position. Weiss used the exposed white king to eventually reduce to a winning queen ending two pawns up.

Standings after RR1: Berserk +10, Weiss +4, Drofa +3, Bit-Genie +2, Chiron +1,  Zahak MrBob -1, Monolith Stash -2, Cheng -3, Amoeba -5, Nirvana -6. Berserk with a remarkable score of 10.5/11, no doubt it will finish first. The 3 remaining spots for advancing are more contested, the 4 engines with a positive score are the probable candidates. Amoeba and Nirvana are at the bottom with no wins and losing half of their games.

game 67, Zahak - Weiss: There were almost no exchanges, evals were close to 0 and the first piece exchange was on move 42. On move 49 Zahak missed Weiss' move, and it lost a knight for 2 pawns. Weiss attacked the white king and gained material, mate came quickly.

game 88, Cheng - Bit-Genie: Bit-Genie didn't see its king was in danger, evals jumped as Cheng attacked on the king side. The center was blocked and most of the black pieces were too far to help. After some preparation Cheng reduced to a Q vs R ending and won. 

game 96, Berserk - Drofa: Drofa moved its queen to the queen side, Berserk saw an opportunity to attack the king side. Drofa exchanged pieces but still Berserk was a pawn up in a RRB vs RRN position. Eventually Berserk reduced ro a rook ending and captured a second pawn to win. 

Standings with 6 rounds to go: Berserk +13, Weiss +7, Drofa Bit-Genie +3, Chiron +2,  Zahak 0, MrBob -1, Monolith -2, Stash -3, Cheng -5, Amoeba -8, Nirvana -9. Berserk and Weiss will qualify, the race for 4th place is very close between Drofa, Bit-Genie and Chiron. Bit-Genie was hit by its unexpected loss to Cheng. 

game 97, Berserk - Zahak: Zahak was up a pawn early, but it had a trapped bishop on the queen side and its king side rook could not develop. Berserk regained the pawn and the game reached a RBB vs RBN position. Berserk forced a bishop for knight exchange, removing the only effective black piece. The engines reduced to a rook ending, Berserk went 4 pawns up to win. 

game 99, MrBob - Bit-Genie: MrBob crashed on the opening move, giving Bit-Genie a free point. 

game 110, Berserk - Bit-Genie: The black queen was on the queen side from the start. After blocking the center Berserk waited for the right moment to open the king side. It went a pawn up, created a passer and captured a bishop. Bit-Genie countered by attacking the white king with its queen, but it was too weak and too late. Berserk exchanged queens and created a second passer, mate followed.

Race for 4th place with 3 rounds to go: Drofa Bit-Genie +3, Chiron +2. No change in the scores. The direct matches between Drofa and both Chiron and Bit-Genie were draws. Chiron held against Berserk, Drofa held against Weiss, Bit-Genie lost to Berserk and got a free point from a crash against MrBob.  Drofa has the easiest remaining games so its chances are greatest to qualify. The direct match between Bit-Genie and Chiron may decide their final standings, if the game is not drawn.

game 118, Monolith - Drofa: Drofa had a promising eval advantage in a QRB vs QRB position, it allowed a queen exchange at the wrong time and allowed Monolith to hold. Drofa ended the game in a KBP vs K ending, not realizing this was a draw with a flank pawn and the wrong colored bishop.

game 120, Bit-Genie - Chiron: Evals increased as the engines played mostly behind their pawn lines. Chiron had a bishop that was very passive and almost trapped, after exchanging all rooks Bit-Genie went 2 pawns up and reduced to a N vs B ending. The black bishop found space but it had no targets. Bit-Genie queened a pawn and won.

In round 20 Bit-Genie beat Chiron, Bit-Genie moves to 3rd place while Chiron is probably out of the race. Drofa only managed a draw against Monolith and it is in 4th place. Standings with 2 rounds to go: Bit-Genie +4, Drofa +3, Chiron +1. 

game 121, Bit-Genie - Zahak: There were no exchanges until move 20, the engines castled in opposite directions. Evals increased as Bit-Genie went a pawn up and opened the king side. The engines reduced to a QRB vs QRB position and Bit-Genie captured a second pawn. After exchanging queens the white passers secured a win for Bit-Genie.

game 124, Drofa - Amoeba: Amoeba castled long after the g file opened, the black king was much safer than the white king. Drofa pushed a pawn to a6 and tried to attack on the queen side, it was not careful enough while Amoeba doubled rooks on the g file. Amoeba used a mating threat to capture two pawns, then reduced to a rook ending. The game ended in a tablebase win.

In round 21 Bit-Genie secured 3rd place with a win. Drofa lost to Amoeba (!) while Chiron held against Weiss, Chiron is only 0.5 points behind in the race for 4th place. Standings before the last round: Bit-Genie +5, Drofa +2, Chiron +1. 

In the last round Drofa only managed a draw against Stash. Chiron still could tie the score but its last game against Monolith was a draw, Drofa finishes in 4th place.

Season 22 qualification league statistics

A summary statistics table of previous stages and seasons. 

The season 22 qualification league was a bookless event. Therefore the game pairing is not relevant and statistics related to it are not shown.

Draw rate, wins

Final draw rate was 46.1%.

Game termination

The three most common game termination causes were:

49.5% - SyzygyTB
21.4% - TCEC draw rule
20.3% - Mate

There were no actual crashes in the stage, but Bit-Genie lost one game on time.

Moves per game 

Median= 65.5
Average= 69.8

There were 16 games longer than 100 moves, the longest was 218 moves (Invictus - Asymptote, game 29, draw).

Time per game (hours) 

Median= 1:05
Average= 1:04

Openings

Books were not used in this stage. The first letter of the ECO codes was distributed as follows: