Season 16 league 2, first half

Standings after 15 rounds:
Stoofvlees +7, Arasan +6, ScorpioNN and Pedone +4, Fritz and Nemorino +3, Texel +1, Wasp Vajolet and Nirvana 0, chess22k RubiChess and Gull -2, Pirarucu -6, Marvin -7, Topple -9.

The two NN qualifiers, Stoofvlees and ScorpioNN, are doing well in league 2 and have a good chance of moving up again. Stoofvlees has the most wins so far, but it makes mistakes occasionally and loses to weaker opponents. ScorpioNN has no losses so far, but it has many draws against the bottom half of the table.

Arasan is also doing well in this league. It appeared in TCEC at least from season 7, never getting great results. It played the last two seasons in division 3, this time it appears to be better than other engines that were in division 3 last season.

There are 4 qualifiers in this league, the race is still open and there are at least 6 engines with a good chance.

Of the 4 AB qualifiers only Wasp and chess22k have a chance to stay in league 2, Marvin and Topple are on their way back down.

There are 6 engines that will be relegated, and one of these may well be Gull. Gull has been in TCEC at least from season 4, the first season I saw. In season 8 it was 3rd in stage 3 which was the last stage before the superfinal, with a better score than Houdini. It has not been updated since then and it has slowly drifted downward in the divisions. If it relegates it may not play again in TCEC, since engines currently under development are preferred.

Of the other engines at the bottom of the table it is interesting to note that RubiChess has two wins against the table leaders, Arasan and Stoofvlees, and a draw against ScorpioNN. It needs to lose less against the lower ranked engines if it wants to get away from the danger zone.

Notable games


Game 22, Pedone - Stoofvlees: Pedone blundered in a N vs B ending, Stoofvlees was able to capture a pawn. Using zugzwang the black king infiltrated behind the white pawns and won the game.

Game 26, ScorpioNN - RubiChess: ScorpioNN gave two pawns but had a strong king side attack in a closed position. After the position opened RubiChess lost a piece, the game reduced to a RB vs R ending and ScorpioNN could only get a draw.

Game 27, Stoofvlees - Nemorino: Stoofvlees missed a long move sequence by Nemorino and its king got caught in a mating net. Stoofvlees had no tablebase support and it failed to see that the resulting RN vs Q position was a loss.

Game 39, RubiChess - Stoofvlees: Stoofvlees gave a pawn early, then gave more and more material and tried to attack the white king. RubiChess held on, the white king escaped and the material advantage gave RubiChess an easy win.

Game 63, Arasan - Gull: The game reached a QN vs QR position with Arasan three pawns up. Gull thought it was safe enough to exchange rook and knight, without tablebase support it didn't realize the queen ending was a win for Arasan.

Game 84, RubiChess - Arasan: RubiChess gave a bishop for a crushing attack on the black king. Arasan gave the piece back, the game reduced to a BN vs BN ending and the white king charged forward and cleared the black queen side pawns. This created a passer that won the game for RubiChess.

Game 108, Arasan - Stoofvlees: In a position with a closed center Arasan opened the queen side and neglected the long black pawn line closing on its king on the king side. Stoofvlees used a pawn on g3 to open the king side and win material, reaching a BN vs Q imbalance that was enough to win the game.