Tuesday, June 2, 2020

Season 18 premier division, after RR2

Crosstable after RR2

Stoofvlees is leading with a +4 score, followed by AllieStein, Leela and Stockfish with +2 each. Stoofvlees is the surprise of the division so far, I don't think anyone expected it to perform so well. The leading group is unbeaten so far, there is a clear divide between engines with positive scores and those with negative scores.

Fire and rofChade, the promoting engines, are at the bottom. I think rofChade will relegate, Fire still has a chance to survive. Komodo is dangerously close to relegation, which I didn't expect.

The division started with 5 straight decisive games, but the draw rate has increased significantly since then to around 80%.

There are three NN engines in the leading group, it is quite possible that Stockfish will not reach this season's superfinal. The last time TCEC had a superfinal without Stockfish was in season 10 (Houdini - Komodo), this was the only season this happened since season 4.

Interesting games
Game 1, Leela - rofChade: Leela gave two pawns and developed a strong king side attack. rofChade exchanged pieces and reduced to a QRN vs QRN position, its king behind a white pawn. In desperation rofChade gave a rook and exposed the white king to checks. Leela moved its king to safety and reducd to a RN vs N ending, 4 pawns down but still winning.
Game 2, Stockfish - Fire: The game reached a same color bishop ending., Stockfish a pawn up with a passer. The engines shuffled for a few moves with evals constant. Then Stockfish saw a win, though Fire didn't think it blundered. It took Fire a few moves to see what happened, Stockfish found a way to push the black bishop away and moved its king forward. The game was adjudicated before we saw the win played. 
Game 3, AllieStein - Ethereal: AllieStein had an eval advantage from the start, the black king stayed in the center uncastled and evals increased steadily. The black king side rook was effectively trapped, Ethereal traded it for a knight to slow AllieStein on the king side. The game reached a RR vs RN position, AllieStein's eval was winning though the game continued for another 20 moves.
Game 4, Komodo - Stoofvlees: Stoofvlees went a pawn up and created a pawn majority on the king side. The queen side opened and Stoofvlees' (negative) eval started to increase. Komodo did not defend accurately, Stoofvlees reduced to a QBN vs QBN position and targeted the white backward e pawn. The white king and knight couldn't reach the pawn in time, Stoofvlees exchanged queens and captured it. The two pawns advantage was enough for a win.
Game 5, rofChade - Stoofvlees: rofChade went a pawn up and opened a file on the queen side, Stoofvlees' eval became negative. Stoofvlees threatened the white king on a long diagonal, forcing the white pieces back to defend. The black pieces moved forward on the queen side, Stoofvlees regained the pawn and reduced to a RN vs RB position. Both engines had passers but Stoofvlees' pieces were stronger. It managed to capture all the white pawns, 4 pawns up when the game was adjudicated.
Game 9, Stockfish - rofChade: The game reached a RBN vs Q imbalance, black two pawns up. After some shuffling, and perhaps inaccuracies from rofChade, Stockfish found a combination to capture two pawns and exchange a pair of rooks. rofChade then traded a promoting passer with a bishop and only RN vs Q remained, white two pawns up. rofChade thought it could hold until it realized Stockfish had an unstoppable passer. 
Game 15, Leela - Komodo: The engines castled on opposite sides and the center was blocked. All pawns were on the board and the engines mostly played behind their pawn lines. On move 42 the first pawns were exchanged, Komodo opened a file on the queen side and then sacrificed a knight for pawns to attack the white king. Leela exchanged queens and found safety for its king, the game reached a RRB vs RR position with black 3 pawns up. Leela made slow progress, it made sure to keep one pawn safe and won the RB  vs R ending. 
Game 22, Leela - Ethereal: The game reached a BBN vs Q imbalance early. Leela thought it had an advantage, its eval got close to 1.5. However, after exchanging all rooks Ethereal defended well and evals slowly came down. The engines reduced to a 7-man drawn position and Leela kept playing until move 176. 
Game 25, Komodo - rofChade: Komodo had a strong king side attack. It forced the black king to run to the center, evals were around 2. Most pieces were exchanged and only Q vs RR remained, Komodo couldn't break rofChade's defense and the game ended in a draw after 149 moves. 

Scores after RR1: Stockfish Leela Stoofvlees +2, AllieStein +1, Fire Ethereal -1, Komodo -2,  rofChade -3. The table is split into positive and negative scoring engines. At the top Stoofvlees is in the lead together with Leela and Stockfish, after winning two games playing black. At the bottom rofChade is last, which was expected. Komodo is weaker than I assumed, it used to be be better that Fire and Ethereal. Still many games to be played, the reverse games may change everything.

Game 33, Stoofvlees - rofChade: Stoofvlees' eval increased quickly from the start. It pushed the black pieces back with its pawns, then gave a pawn and attacked on the king side. rofChade gave back the pawn and gave a bishop to force a queen exchange. The black king was out of immediate danger, but Stoofvlees created an advanced passer, both engines agreed that together with the extra piece Stoofvlees was winning.
Game 35, AllieStein - Fire: AllieStein sacrificed a knight for pawns and exposed the black king. Fire kept its king safe, while AllieStein went 3 pawns up with two advanced passers. A series of exchanges reduced to a RB vs RB postion, AllieStein had a protected passer on the 7th rank that kept the black pieces busy, it captured the remaining black pawns and the game was adjudicated. 

After round 9 Stoofvlees moves into the lead, and AllieStein joins the chasing group together with Leela and Stockfish.

Game 42, Stoofvlees - Fire: See featured game below. 
Game 44, AllieStein - Stockfish: The engines opened two files, their remaining pawns locked in three pawn islands. All pieces were on the board until move 44, AllieStein had more space and its eval was around 2. Stockish's eval went over 2 for a short while, then came back down after the queens were exchanged. Stockfish covered all entry points, AllieStein couldn't break the fortress. The game ended in a 50 move draw. 

After round 11 Stoofvlees increases its lead to a full point, with a good chance of being first at the end of the first double RR. 

Featured game: Stoofvlees - Fire
Premier division, game 42 
Link to game on TCEC

Fire went two pawns up from the start, also exposing the white king. Stoofvlees thought it had a small advantage, it had a bishop pair and the black king couldn't castle. Stoofvlees pushed the black pieces back, gave two more pawns and captured a knight.

Fire had all its pawns on the board until move 41. The engines mainly shuffled behind the pawn lines and exchanged pieces. Evals stayed low, the game reached a RB vs R ending on move 47. 

Fire was 3 pawns up and evals were drawish. The white king came forward while the bishop kept watch over the black queen side pawns. AllieStein's eval increased above 1, Fire was close to zugzwang. All the black pawns could not move safely, the black king was trapped in the corner, only the black rook moved and it had no safe square behind its pawns. I'm not sure what was Stoofvlees' threat, but somehow Fire felt it had to move its pawns on move 68. Fire lost control of the position very quickly and its eval jumped over 5.

Stoofvlees was careful to keep its a pawn safe, the bishop made sure the black passers couldn't advance. The white king and rook had more freedom to operate, it took a while but Stoofvlees captured the black passers and the game was adjudicated in a 7-man winning position.

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