Season 22 is about to start with a qualification league. It has been almost 6 months since the season 21 superfinal ended, during this time TCEC ran a cup, a swiss tournament, an FRC championship, and other bonus events.
There are 14 engines in the qualification league trying to win one of 4 spots that move on to the next stage. The participating engines are:
played in Season 21 league 4: ChessFighter
played in Season 21 qualification league: Berserk, Invictus, Bagatur, tomitankChess, Cheese
returning after not playing for a few seasons: Counter, Chiron, Asymptote
new: Zahak, Bit-Genie, Velvet, BlackMarlin, Mantissa
Berserk became much stronger since last season. Judging by its performance in the swiss event Berserk will be hard to beat in the lower leagues, it may be heading straight to the premier division. Chiron is another interesting engine, it used to be quite strong and even played in the premier division in seasons 11-13. It gradually dropped down since then, but now it's trying to make a comeback after skipping two seasons.
Final standings
Berserk, Bit-Genie, Chiron and Zahak qualify for league 4.
Berserk and Chiron were unbeaten in the qualification league, while Bit-Genie's only loss was a loss on time in a winning position against Counter. In the final rounds there were 4 engines racing for 4th place, in the end it was Zahak that qualified with a comfortable margin.
Beserk and Chiron are on their way up as I thought from the beginning, Bit-Genie also had a great performance and had potential to move up the leagues. Based on the swiss event Berserk should be strong in league 4, Chiron and Bit-Genie did not play so there is no direct evidence. Zahak may find the competition harder, considering that Weiss, Drofa and Monolith had better scores in the swiss.
The four qualifiers will join Weiss, Monolith, Amoeba, Stash, Cheng, Nirvana, MrBob, and Drofa in league 4. Weiss played in league 3 in season 21, the other engines played in league 4.
Interesting games
game 5, tomitankChess - BlackMarlin: The game reached a Q vs NN ending, tomitankChess held a fortress for 30 moves but its defense collapsed in the end. BlackMarlin used zugzwangs to win.
game 9, Velvet - Zahak: Zahak slowly turned a small advantage with a better pawn structure in a RBBN vs RBNN position, to a winning rook ending with a pawn up.
game 16, Invictus - ChessFighter: Invictus had an early R for B exchange advantage, it was able to reduce to a winning R vs N ending.
game 20, Zahak - BlackMarlin: Zahak blundered in a QQ vs QQ position, BlackMarlin was able to reduce to a winning king and pawns ending with a pawn up.
game 28, Berserk - Invictus: Evals slowly increased with equal material, until Berserk reduced to a winning rook ending a pawn up.
game 29, Invictus - Asymptote: The game reached a Q vs RR position with Invictus 4 pawns up. Evals were high but somehow Invictus couldn't find a way to advance its pawns safely and Asymptote held the draw.
game 34, Bit-Genie - Counter: Bit-Genie outplayed Counter in a knight ending, it went two pawns up to win.
game 46, Zahak - ChessFighter: The black queen moved forward to attack, allowing Zahak to capture a pawn. Zahak stopped the attack on its king and reduced to a winning rook ending.
game 49, BlackMarlin - Counter: Counter blundered in a knight ending, BlackMarlin created connected passers that won the game.
game 52, Chiron - Velvet: Velvet gave a rook for a knight and pawn to create a passer in a RR vs RB ending. Chiron stopped the passer on the 3rd rank and countered with a passer on the 7th rank. Chiron gave the material back and secured the queening to win.
game 54, Berserk - Zahak: Berserk exposed the black king with a knight for pawns sacrifice. Zahak had to give material to avoid mate, Berserk used two connected passers facing the black king to get a decisive advantage and win.
game 59, Zahak - Invictus: Zahak gave a rook for a bishop and developed a strong king side attack. Invictus protected its king and exchanged pieces until the game reached a B vs R position. Zahak went 3 pawns up and eventually reduced to a winning king and pawns ending.
game 62, BlackMarlin - Chiron: Evals were close to 0 for 35 moves, then Chiron's (negative) eval started to increase. It used the exposed white king to reduce to a RN vs RB position two pawns up. BlackMarlin got the pawns back but lost its rook for the bishop, the game ended in a tablebase win for Chiron.
game 66, ChessFighter - BlackMarlin: ChessFighter had a significant eval advantage in a RRB vs RRB position, despite being a pawn down. However, BlackMarlin exchanged a pair of rooks and ChessFighter couldn't find a winning path. Evals came slowly down and the game ended in a draw.
game 90, Mantissa - Berserk: There were very few exchanges and Mantissa was a pawn up. Evals became negative and slowly increased, Berserk used an open file to attack the white king and gain material. In a RB vs RR position Berserk gave the material back to create an unstoppable passer and win.
Standings after RR1: Berserk +8, Chiron Bit-Genie +6, Zahak +4, Mantissa BlackMarlin +3, Invictus +1, Velvet 0, ChessFighter -1, Counter -2, Asymptote -4, Bagatur -6, tomitankChess Cheese -9. Berserk, Chiron and Bit-Genie are the only engines without a loss in RR1, they will probably finish in the top 4. Zahak is currently 4th, Mantissa and BlackMarlin are also in the race for 4th place, only 0.5 points behind.
game 92, Asymptote - ChessFighter: ChessFighter insisted on attacking the white king, this backfired when Asymptote moved its rooks forward and went 3 pawns up. ChessFighter lost more material until the game was over.
game 103, Bagatur - Mantissa: Bagatur played this game better and the game reached a RR vs RB position. Evals were high, the engines reduced to a 7-man R vs B ending which was a draw. Both engines had no tablebase support, as play continued it became a 7-man win and then a draw again. The game was adjudicated a draw after Bagatur captured a pawn.
game 107, ChessFighter - Invictus: ChessFighter was a pawn up, The black queen came forward and captured a pawn, by the time it came back ChessFighter developed an attack on the black king. Invictus gave material to stop the attack, the game reached a R vs B ending and a tablebase win.
game 114, Bit-Genie - BlackMarlin: Bit-Genie created a passer in a RRN vs RRB position, then reduced to a rook ending. The black king was too far to help and BlackMarlin was forced to give its rook to stop the passer.
game 115, Zahak - Counter: Counter surprised Zahak by sacrificing a rook for a knight, leading to a deadly attack on the white king. Zahak gave material to save its king, the game reached a RN vs Q ending. The white queen was strong, Counter went 4 pawns up to win.
game 116, Cheese - Mantissa: Mantissa was better in a QB vs RRB position a pawn up with a passer. However, without tablebase support it chose to reduce to a pawns vs bishop ending and the game reached a tablebase draw.
game 125, Counter - Bit-Genie: The engines shuffled for a long time in a closed RRB vs RRN position. After the position opened Bit-Genie managed to reduce to a rook ending with two pawns up, but then it lost on time. Counter gets a point for free.
Standings with 6 rounds to go: Berserk +13, Chiron +9, Bit-Genie +7, Mantissa +5, Zahak BlackMarlin, +4, Counter +3, Invictus +1, ChessFighter -1, Velvet -2, Asymptote -3, Bagatur -12, tomitankChess Cheese -14. Berserk and Chiron will be in the top 4 unless something unusual happens, Bit-Genie probably as well. The main race is for 4th place with 4 engines in the race. Mantissa has a small lead over Zahak and BlackMarlin, Counter had a remarkable +5 in the last 7 games to join the leaders (though one win was a gift from Bit-Genie). However, judging by the remaining games Zahak has the best chance. It has yet to play the bottom 3 engines, and the other contestants have at most one such game remaining.
game 154, Mantissa - Counter: Counter was careless in a knight ending, Mantissa was able to exchange knights and create a passer. Counter stopped the passer but couldn't block the white king which moved forward and captured pawns to win.
Race for top 4 with 3 rounds to go: Berserk +13, Chiron Bit-Genie +9, Mantissa +6, Zahak +5, BlackMarlin, +4, Counter +2. Mantissa is still leading the race for 4th place, its win against Counter keeps it ahead of the other engines. Counter is almost surely out of the race. Zahak has 3 games against weak engines, while both BlackMarlin and Mantissa have to face Berserk, and Mantissa has a game against Chiron as well.
game 166, Berserk - BlackMarlin: Berserk outplayed BlackMarlin in a RN vs RR position with white two pawns up. It took Berserk 20 moves to capture one black pawn, BlackMarlin could not stop the slow march of the white pawns. Berserk captured a rook for one passer, it had one last pawn left to win in a RN vs R ending.
game 167, ChessFighter - Counter: ChessFighter gave two pawns and attacked the black king side, this time the attack succeeded. The game reached a RBB vs RBN position, ChessFighter got the pawns back and trapped the black knight. Counter gave a rook for a bishop to free its knight, ChessFighter created an unstoppaable passer to win.
After round 24: Mantissa Zahak +6, BlackMarlin +3. BlackMarlin lost to Berserk and it is probably out of the race. Zahak beat tomitankChess and Mantissa held against Chiron, they are tied with two games left.
game 171, Counter - Berserk: In a QRN vs QRN position Berserk found a way to move its rook forward and threaten the white king. After 20 moves of increasing pressure the engines exchanged pieces and reduced to a king and pawns ending. Berserk used zugzwang to win.
After round 25: Zahak +7, Mantissa +6, BlackMarlin +4. Mantissa only managed a draw against ChessFighter, Zahak beat Cheese and is now in 4th place. Mantissa plays Berserk in its last game, Zahak probably needs only a draw against Asymptote to qualify. BlackMarlin is formally out despite winning against Invictus.
game 181, Berserk - Mantissa: There were very few exchanges from the start, Berserk had a space advantage and it pushed all the black pieces back. When the position opened Berserk went two pawns up, it used two advanced passers to win.
In the last round Zahak only managed a draw against Asymptote, but that was enough to qualify since Mantissa lost its last game against Berserk.
