I was sad to hear that Guy Haworth died last week. Guy was a reader of this blog, I suppose one of the few who read through my statistical reports where he would sometimes comment and point out an error I made - for which I was thankful. Together with Nelson Hernandez (Cato) he wrote the summary articles of TCEC seasons that can be found on the TCEC website, their writing skills obviously better than mine. I always got mentioned in these summaries, for which I'm also greatful. During season 20 I reached out to Guy and we corresponded a few times by mail. He was very friendly and easy to talk to, both about computer chess and about personal matters. I didn't know he would be gone a few months later.
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Final standings
Igel and Ethereal advance to the Premier division. Igel started strong, it led the table at the half with a +5 score without loss. In the second half it lost 3 games, yet it won 5 and held on to first place. Ethereal only had a +1 score at the half, it secured 2nd place with a +5 score in the second half of the league. RubiChess was their only competitor but it couldn't keep up with the leaders and ended in 3rd.
rofChade and Nemorino are relegated back to league 2. The race at the bottom of the league was very tight to the very end. rofChade had a -4 score at the half, it was alone in last place and appeared to be weakest. In the second half it performed better while other engines lost games. Pedone and Nemorino in particular dropped down, and together with Xiphos formed a group of 4 engines fighting for survival. The standings were determined only in the last few rounds, with rofChade losing to Xiphos on a head to head tiebreak.
Ethereal dropped from the premier division to league 1 on season 19, in season 20 it qualified for the premier division and was relegated again. It may repeat this in season 21. On the other hand rofChade also qualified for the premier division and was relegated in season 20, this season it is relegated to league 2. A little bit surprising, it shows that it is very hard to keep up unless you keep improving.
The final draw rate was 58%, there were 5/56 openings where both engines won a game. Biased but much less so than in season 20.
Igel and Nemorino will compete in the premier league together with:
Stockfish, Leela, KomodoDragon, AllieStein, Stoofvlees, ScorpioNN, all played in the season 20 premier division.
Interesting games
game 57, Pedone - RubiChess: RubiChess was a pawn up from the start, while Pedone had a bishop pair advantage. Pedone created a passer on the queen side in a RRB vs RRN position, then pushed it forward. The engines reduced to a rook ending, the white passer was on the 7th rank and RubiChess pushed a passer in the center to the 2nd rank as well. Both passers were removed leaving pawns only on the king side. One white pawn was isolated and vulnerable, the white king was too far to help. Once RubiChess captured the white pawn it had enough material to win.
game 59, Igel - rofChade: rofChade had an eval advantage of around (negative) 1 from the start. The engines exchanged pieces until reaching a rook ending. All the white pawns were isolated, rofChade gradually captured them. Igel was always one pawn behind until it was left with one last pawn. rofChade found the right moves to capture the white pawn while keeping two of its own, resulting in a tablebase win.
game 61, RubiChess - Nemorino: RubiChess attacked on the king side, it exposed the black king with a rook sacrifice. To get its king out of trouble Nemorino had to give material back and the game reached a NN vs R imbalance. RubiChess picked up isolated black pawns and reduced to a BNN vs RB position. Nemorino lost its bishop for an advanced passer, the remaining white pawns gave the win to RubiChess.
game 64, Pedone - Ethereal: Pedone had an eval advantage from the start in a closed position without queens. The engines opened the center with a few exchanges, Ethereal created a king side passer and evals came down. Ethereal gave a rook for a bishop, it lost its king side passer and created another on the queen side. Evals turned negative in a RRB vs RBN position with a black passer on the 3rd rank. Pedone saw the problem too late, it gave the bishop to clear the black pawns on the queen side. In a patient endgame Ethereal captured the white pawns, and the last black pawn secured the tablebase win.
game 65, Ethereal - RubiChess: Ethereal started with an eval advantage that increased steadily. The black LS bishop was trapped and it also blocked the queen side rook. By the time RubiChess opened a path for its bishop Ethereal had connected passers on the king side. In a an attempt to find a counter RubiChess gave two pawns to create a passer, then gave a rook and bishop to queen the passer. Ethereal used its rooks to clear the remaining black pawns, then gave both rooks and queened a pawn. The remaining QN vs Q ending with 3 pawns was a win for white.
game 66, Igel - Pedone: Evals stayed around 1 for a long time with most pieces and pawns still on the board. Pedone tried to open the queen side, it created two pawns but something went wrong and Igel captured both. The black king became vulnerable on the back rank, Igel used this to reduce to a Q vs RN ending. The black pieces were soon captured using fork attacks, game over.
game 72, Ethereal - Igel: Ethereal started with an eval advantage. It went a pawn up and created a passer on the queen side. After exchanging queens evals were around 2 for a while, Ethereal connected a second passer and the game reached a RN vs RN position. Igel captured one passer, but Ethereal added another on the king side. Eventually Igel lost its knight for a passer and the game ended in a tablebase win.
game 73, Igel - RubiChess: The game reached a QRB vs QRN position on move 40. Evals were over 1 for a long time, Igel created a passer in the center but it was blocked. For a while Igel was a pawn up and evals increased to around 2, then RubiChess captured the white passer and evals came back down a little. The engines started to shuffle on move 73, evals slowly increased as RubiChess tried to protect its isolated pawns. On move 113 finally Igel captured a pawn, this created an unstoppable passer and a win.
game 79, Ethereal - Nemorino: The engines castled in opposite directions, evals increased steadily without almost any exchanges. Nemorino was two pawns up when it gave a rook for a bishop, the game reached a RRN vs RBN position. Ethereal captured the black pawns until they were all gone, and reduced to a winning R vs B ending 5 pawns up.
game 80, Igel - SlowChess: Igel had an eval of 1 from the start, it was a pawn down but SlowChess did not castle and there were two pairs of black doubled pawns in the center. Evals slowly increased, Igel regained the pawn and SlowChess had little room to move. SlowChess gave a bishop and opened files on the king side, Igel created a passer on the queen side. SlowChess gave more material, it captured the passer and the black queen moved forward and threatened the exposed white king. Igel made sure to avoid a perpetual check, the material advantage was huge and mate was just a matter of time.
Standings after RR3: Igel +6, Ethereal +5, RubiChess +2, SlowChess -1, Pedone -2, Nemorino Xiphos -3, rofChade -4. Ethereal joins Igel at the top with a +4 score including a win against Igel. Igel also lost to rofChade. Only RubiChess is close to the leaders. The bottom is more crowded, Pedone dropped with a -3 score, Nemorino scored -2. rofChade imroved its survival chances with a 0 score.
game 88, Nemorino - SlowChess: SlowChess was up a pawn from the start, the engines reduced to a rook ending. SlowChess captured all the white pawns, the win was just a matter of time.
game 89, Nemorino - RubiChess: Nemorino went a pawn up early, evals increased as the engines exchanged pieces. Nemorino traded a rook for a knight and two pawns, then reduced to a RN vs RR position. Nemorino had passers on both sides and RubiChess could not stop them all, game over. There were two white wins in this opening.
game 92, Ethereal - Pedone: Ethereal had an eval advantage from the start that increased steadily. The black king moved without castling and the black queen was far on the queen side, Ethereal gathered forces and pressed on the king side. Ethereal used its pawns to expose the black king, a series of exchanges left a BN vs N position and Ethereal had enough pawns to win. A double win for Ethereal in this opening.
game 93, RubiChess - Ethereal: RubiChess had an eval advantage from the start, it placed a knight on e5 in a closed position and evals increased slowly. Ethereal played waiting moves while RubiChess prepared, it started the attack with a knight sacrifice and a rook on the back rank. Ethereal gave the material back to save its king, after a series of exchanges only RN vs RB remained with white a pawn up. RubiChess captured two more pawns and reduced to a winning rook ending. There were two white wins in this opening.
game 96, rofChade - Nemorino: The engines castled in opposite directions, rofChade pushed pawns on the king side and one pawn reached h6. Nemorino sacrificed a knight for two pawns to free a trapped bishop, but it did not have enough compensation for the piece. The engines exchanged pieces until only RB vs R remained and rofChade captured two pawns. Nemorino reduced to a king and pawns ending which was a win for white.
game 99, SlowChess - Pedone: The black king was forced to move without castling, Pedone wasted time getting its king to safety. SlowChess attacked from the queen side, went a pawn up and reduced to a B vs N ending. It captured two more pawns and the win was a matter of time.
Standings with 3 rounds to go: Igel +7, Ethereal +5, RubiChess +2, SlowChess +1, rofChade -3, Pedone Nemorino Xiphos -4. The top is more or less settled, unless there are last minute surprises. The survival race at the bottom is very close with 4 engines within 0.5 point. Pedone and Nemorino continue to drop, while rofChade is 0.5 points ahead of the rest after beating Nemorino.
game 103, Pedone - Nemorino: Pedone kept its king uncastled, it opened the king side and attacked the black king. Nemorino tried to block with its pieces, Pedone was a pawn up and evals increased slowly. Nemorino gave a rook for a bishop, then the engines reduced to a R vs N ending. Pedone captured black pawns until they were all gone to win.
game 104, Xiphos - rofChade: Xiphos grabbed an early pawn with its queen. Evals slowly increased as the engines exchanged pieces until only RN vs RN were left. Xiphos created connected passers on the queen side, rofChade could not stop their advance. Xiphos queened a pawn and mated.
After round 26 the race at the top is over, Ethereal beat SlowChess and RubiChess drew against Igel. Two head to head games at the bottom, Pedone and Xiphos won while Nemorino and rofChade lost. Standings at the bottom: Pedone Xiphos -3, rofChade -4, Nemorino -5.
game 106, rofChade - Pedone: Evals increased quickly after the start. There were no exchanges, the black pieces were pushed back, Pedone didn't castle and it had very little room to move. rofChade opened a file on the king side, it captured a bishop while the black king ran to the queen side. rofChade's attack continued and it gained material quickly. It was two pieces and 3 pawns up, mate came not long afterwards.
game 107, Nemorino - Ethereal: Evals increased after the start though there were almost no exchanges and material was equal. Nemorino had a space advantage and the black king did not castle. On move 40 Nemorino opened the queen side and then went a pawn up. Ethereal gave another pawn and tried to free its king side rook without success. Ethereal opened the position by giving two more pawns, then it lost its rook for a passer. The game ended in a tablebase win. There were two white wins in this opening.
Standing after round 27: Xiphos rofChade -3, Pedone Nemorino -4. The last round will determine which engines will survive and which will be relegated.
game 110, Igel - Nemorino: Evals increased from the start, Nemorino gave a knight for two pawns and tried to build a wall across the board to prevent attacks. After some shuffling and preparations Igel pushed pawns on the king side and opened a way through the wall. Nemorino had to give its queen to save its king, Igel's material advantage in a QR vs RB position was enough to win.
With this loss Nemorino is relegated.
game 111, Ethereal - rofChade: rofChade gave a pawn early but did not get enough compensation for it and evals increased. The engines exchanged pieces, in a QR vs QR position Ethereal captured a second pawn and then exchanged queens. A rook on the 7th rank and advancing passers gave Ethereal the win.
game 112, Pedone - Xiphos: Pedone outplayed Xiphos in a QB vs RRN position. It threatened the exposed black king and Xiphos had to play defensively. In the end Xiphos had to give material to avoid losing, reducing to a winning Q vs R ending.
The final standings at the bottom: Pedone -3, Xiphos rofChade -4, Nemorino -5. The last game determined the final result at the bottom of the table, Pedone is safe while Xiphos survives with a head to head tiebreak against rofChade.
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