Tuesday, August 16, 2016

Season 9, stage 3, RR 4

Table after 4 RR

(I will stop anouncing the draw rate, it is clearly around 65%. The final rate will appear in the statistcal report of the stage)

Stockfish extended its lead to 2 points, drawing the rematch against Komodo and beating Fire (only the second loss for Fire this stage). Could this be Stockfish's season?
Komodo and Houdini are tied in second place in a very close race. With half of the stage over, only 1/12 games within the top 3 engines has been decisive so far. The race may be determined by the results of the games against less strong opponents.

Some of the game highlights

Komodo had an eval advantage against Houdini but did not have enough for a win. Houdini still second by half a point.

Jonny had a significant eval advantage against Stockfish (Jonny 2.5 vs Stockfish 1), but when Stockfish exchanged pieces the evals came down. Jonny could only get a draw in a QBB vs QNN position.

Gull had a significant eval advantage from the start against Jonny. There were many early exchanges and the game reached a RN vs RB position, with Gull's rook controling the 7th rank. Gull had a queen side passer that marched quickly, and through a knight sacrifice it was able to queen and force Jonny to lose a rook for it. This was Gull's first win of the stage, with a lot of help from Cato (Jonny won the reverse game in RR 3).

Stockfish - Rybka reached a RB vs RN endgame, Stockfish had an eval advantage but the evals were stable for a long while even when Stockfish won a pawn. Evals started to rise rapidly around move 65, Stockfish outplayed Rybka in the endgame forcing a bishop and knight exchange leading to a won rook ending. Stockfish extended its lead by another 0.5 point.

Komodo had a pawn advantage and eval over 1.5 early in the game against Andscacs. For many moves Komodo didn't find a way to improve its position, even after trapping a black bishop. The breakthrough came when Komodo moved its king to a safer location and forced Andscacs to give a rook for a bishop to avoid a mating net. The QR vs QB endgame was far from easy, but Komodo had no problem getting the win. A double win for Komodo against Andscacs in this opening.

Houdini maintained pressure for 50 moves against Stockfish, but it was all over after most pieces were exchanged resulting in a drawn RB vs RB ending. Komodo is tied with Houdini, 1.5 points behind Stockfish.

Fire - Rybka got into a static pawn line standoff, Fire's eval a bit over the draw rule threshold. As the game approached the 50-move draw Rybka saw an opportunity to win a pawn, leading to a higher eval and more moves. Then with time running out Fire found an opening and created a passer on the 7th rank while its king hid behind a black pawn. Rybka had to use a bishop to block the pawn, then it lost a rook for a bishop and lost the game very quickly. 

Komodo - Stockfish: the rematch. This was the game everyone was waiting for, following the 1-0 result of the previous RR. Komodo fans wanted Komodo to win, so they could blame Cato's opening for the results and get Komodo back to a superfinal position. Stockfish fans wished for a draw so they can prove Stockfish is the best engine. Both claims are ridiculous based on one game, but we're talking about fans, not statistics experts. There was an interesting post by LPZ, a frequent chat contributor, showing the results of a 5-game simulation he ran of this game using similar hardware and conditions. With 4 draws and one Komodo win there was hope for everyone. The actual game followed the simulations for about 20 moves, Komodo with an eval of 0.8 and Stockfish with an awkward king side. Komodo held the tension for another 20 moves but then pieces started to be exchanged and Stockfish untangled itself. Komodo couldn't penetrate the white fortress, draw.

Andscacs was a pawn up early in the game against Gull, and then it exchanged pieces until only QNN vs QBN were left. With a passer on the 7th row, a pawn advantage and an active king after further exchanges, Andscacs had no problem to get the win.

Gull had an eval advantage against Stockfish, but Stockfish defended well and nothing came out of Gull's attempts. Stockfish's eval started to increase after 40 moves, but it only went up to 0.6 in a QRN vs QRB position. Then after what looked like shuffling moves Stockfish found a way to exchange pieces and reach a winning 6-man rook ending. Gull's lack of tablebase support was probably a factor in its loss. A double win for Stockfish in this opening, extending its lead in the crosstable.

Komodo started with an eval advantage against Gull and soon found a way to improve. It sacrificed two pawns to destroy the black pawn structure, then it won a rook for a knight. In a RR vs RN position the engines exchanged pawns until Komodo found a way to exchange pieces and reach a winning R vs N ending. First win for Komodo against Gull this stage. Second loss in a row for Gull, again tablebases could surely help it.

Houdini crushed Rybka in one of the shortest wins of the stage. Rybka's king side was filled with pieces that could hardly move, and when trying to defend against Houdini's passers it lost a rook for a knight and then another bishop. The material advantage was enough for an easy win for Houdini.

Featured game: Stockfish - Fire
Stage 3, round 28
Link to game on TCEC

The game started with evals close to zero, a sure sign of a draw. Fire was very hard to beat in the stage, another sign. Then Stockfish's eval started to increase following an inaccuracy by Fire.

Stockfish applied pressure on the black king with its rooks and through the long diagonal. Fire tried to defend but then its knight got trapped.

After taking the knight the g file opened and the white king was exposed. Stockfish had to be careful not to allow Fire counterplay. After the king side attacks were over Fire created a dangerous passer on the queen side.

Stockfish calmly let the pawn reach the second rank before taking it. Fire had no more offensive options, and with pieces being exchanged the white bishop advantage became bigger. The game ended in a winning RB vs R position. This was only the second loss of the stage for Fire, Stockfish firmly leading the table.

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