Season 17 league 1 (CPU) after RR1

Four engines that were supposed to play in league 1 were not compatible with the new hardware: Chiron, Jonny, ChessBrain and Booot. As a result four additional engines promoted from league 2: Pedone, Nemorino, Winter and PeSTO.

This is the CPU part of league 1. There is still no update regarding the GPU hardware nor which engines will play in a GPU league 1. The rules page states that the top 4 CPU engines and 2 GPU engines are going to have a playoff to determine the 4 engines that continue to the premier division.

Scores after RR1
Ethereal +7, Xiphos +5, rofChade KomodoMCTS +4, Laser +3, Fire +2, Andscacs Arasan +1, RubiChess DefenChess 0, Vajolet -1, Pedone -2, PeSTO Nemorino Winter -5, Fizbo -9.

There are many engines in the race for the top 4 places. The first 6 engines are still without loss and they have the best chance in my opinion. Ethereal has a small gap at the top with 7 wins against lower ranking engines. rofChade is a surprise, it was close to relegation from league 1 last season, this season it seems to have improved significantly.

The lower half of the table contains 7 of the 8 engines that played in league 2. Of the 4 that were added at the last minute only Pedone is above the relegation zone. Fizbo is last with 9 losses, it has problems with the hardware and is using only 32 threads out of the possible 176.

The draw rate is just under 70%, unusually high for this stage. Comparing to previous seasons we see that draw rates this high were only seen in the premier division and superfinal stages. In 28 games within the top 8 engines in the table there are only two decisive games so far, two Ethereal wins against places 7 and 8. There are many games yet to play in the league, things may of course change.

Notable games

Game 22, rofChade - Vajolet: rofChade was a pawn down in a QRR vs QRR position, but the black king was exposed to attack. Vajolet tried to escape, rofChade avoided exchanges and gradually closed a mating net around the black king.
Game 44, Nemorino - Arasan: Nemorino had an eval over 1.5 with a lot of pressure on the black king, but Arasan defended well and countered on the queen side. Evals turned negative, Arasan doubled rooks on the 2nd rank and reduced to a QB vs QN position. Then it captured two pawns and exchanged queens for the win.
Game 46, KomodoMCTS - Fizbo: The game reached a QN vs QN position with white a pawn up. KomodoMCTS tried but couldn't find how to convert, even after it captured the knight and the game reached a 7-man tablebase win.
Game 50, Andscacs - Ethereal: Ethereal gave a pawn and exposed the white king, then created a central passer on the 3rd rank. Then Ethereal took over the 2nd rank and exchanged down to a RB vs RN position, Andscacs lost a rook for the black passer, game over.
Game 53, Arasan - Winter: The game reached a Q vs QB ending with white two pawns up. Winter managed to capture two pawns and was very close to winning, its lack of tablebase support is probably the reason it chose to exchange queens, leading to a tablebase draw.
Game 64, Xiphos - Andscacs: Andscacs held a fortress draw in a Q vs BN ending.
Game 78, Ethereal - Arasan: Ethereal created a central passer and pushed it to the 7th rank. Arasan gave a bishop to stop the passer, it was 3 pawns up in a RB vs R ending. Ethereal kept one pawn safe and gradually captured black pawns until the game was adjudicated.
Game 86, RubiChess - KomodoMCTS: RubiChess was up 3 pawns but its king was exposed to attack. The engines exchanged most pieces and only R vs RB remained, KomodoMCTS kept one pawn and that was enough to secure the win.
Game 93, Ethereal - DefenChess: DefenChess went two pawns up and its queen ended up nearly trapped in the corner. Ethereal gave a rook for a bishop and regained the pawns, it broke the black defense and reduced to a winning QB vs QB position two pawns up.
Game 108, Ethereal - Vajolet: The game reached a QN vs QR position with white two pawns up and seemed to be heading for a draw. Vajolet was not careful enough in the endgame, it let Ethereal push a passer to the 6th row and Ethereal found a way ot make it unstoppable. Vajolet started to give checks and the game was adjudicated, the PV shows that the white king eventually finds a safe spot and Ethereal can promote the pawn.
Game 116, RubiChess - Andscacs: Andscacs gave a rook for a bishop and pawns, opened the queen side and created two passers. After reducing to a QR vs QN position the passers were enough to secure the win for black.