Friday, July 29, 2016

Season 9, stage 3, RR 1

Stage 3 has started, 8 of the best chess engines fight for a place in the superfinal of the season. We have a new version of Houdini, will it change the balance of powers, can it compete with Stockfish and Komodo? In this stage each engine is given 150 minutes + 15 seconds increment per move. Many games are more than 5 hours long, everything is slower than the previous stages.

Important Note: In the next two weeks I will be busy with other summer activities. Therefore I may be late in posting and my posts may be less detailed.

Table after 1 RR

The draw rate is 19/28 (68%). Cato did his best to choose openings that give advantage to white but do not force a win, and in most cases black manages to get a draw. Only one black win so far, and that was quite a surprise.
Komodo and Stockfish are at their natural 1-2 places, Houdini's new version seems better than before but I don't think it will be able to challenge the leaders. Rybka will probably be the easiest engine to beat this stage, recall it qualified last as well. It remains to be seen if Jonny can perform as well as it did in stage 2.
The games of the next RR will complete the reverse color game pairs, and then the rankings will be more meaningful.

Some of the game highlights

Houdini - Komodo: What a start to the stage. In the opening game the new Houdini used the opening advantage to defeat the champion Komodo. As this was going on, while Houdini fans were declaring its return to greatness, the Komodo developers noticed that the settings for Komodo were not what they instructed. The organizers decided to replay the match using the right settings for Komodo, and you can imagine the craziness that went on in the chat around this decision.
In the replayed game Houdini had an eval advantage and an imbalance of RPP for BN. There were only a few pawns but many pieces on the board, Komodo had to defend but it wasn't in any apparent danger. The RB vs BBN endgame was long but always a draw. Did the settings change anything? Was the first win just luck? Who knows.

More problems at the start: 6 hours down time, no live coverage of games 2-3.

Andscacs had an eval advantage from the start against Rybka. Rybka played defensively from the start, not moving a pawn for more than 45 moves and just waiting to see what Andscacs will do. Evals increased a little after the pawn move, and then the game became static and it seemed the 50-move rule would be applied. Eventually, with both engines in blitz mode with very little time, Andscacs did find a way to break Rybka's defenses on the king side, creating a significant mating threat and winning the game. Did Rybka blunder in time trouble?

Stockfish took advantage of the favorable opening it had against Jonny. Without stopping to castle it applied pressure on Jonny's pieces, forcing them to retreat until they almost could not move. An opening on the king side was enough for Stockfish to attack Jonny's king, evals jumping fast. The game ended before the action started, but the PVs showed significant material advantage for Stockfish.

In its second game Komodo was back to normal with no technical problems. It started with an eval advantage against Fire and kept it alive for 30 moves. It repeated a move twice to confuse Fire, and us, but then found the path to victory. A strong king side attack led to a superior ending with an advanced passer and a bishop pair.

Houdini - Andscacs: Very early in the game Andscacs created a defensive line and played waiting moves, challenging Houdini to try to attack. When Houdini finally attacked it gave a rook for a bishop but exposed the black king, with evals climbing to around 1. Andscacs defended well, exchanging down to a Q vs RR position with very few pawns, and the game ended in a draw.

Stockfish was able to get a pawn advantage against Houdini, but Houdini exchanged everything and got a draw.

Komodo had a big eval advantage right from the start against Jonny. Jonny gave a rook for a bishop with the hope that a bishop pair will be enough as defense. It also tried a king side attack but it was weak. Komodo was about to win material in a QR vs QB ending when the game was stopped. Will Komodo hold the reverse game?

Houdini got into a double rook ending with Gull, and although material was equal Houdini's had the initiative. That was enough to win a pawn and reach a winning pawn ending.

Andscacs - Stockfish reached a RR vs RBN ending. Andscacs had what looked like dangerous connected passers but Stockfish kept calm with eval at zero. There was some excitement near the end when Andscacs' eval jumped to nearly 4, but this was due to lack of tablebases, the final RP vs B position was a draw.

Stockfish - Komodo: another draw, third one this season.

Jonny had a pawn advantage and an eval advantage right from the start against Rybka. However, with Jonny's performance so far in the stage and its tendency to exaggerate it was doubtful it would win the game. Then the endgame was RB vs RB with opposite color bishops, and the pawn advantage was a doubled pawn, sure signs of a draw. Yet the eval advantage persisted. Somehow, Jonny found a way to infiltrate with a king and rook, to create a passer and to get a winning position. A big surprise for me.

Komodo had a small eval advantage from the start against Rybka, and Rybka was able to hold for about 30 move before it started to play inaccurately. In the RN vs RB endgame Rybka had an advanced passer but Komodo controlled the center and had a stronger rook. It was a slow process but Komodo succeeded in taking out the passer, and then the central pawns started marching and it was all over. Two defeats in a row for Rybka.

Stockfish eval advantage against Gull became a position where material was equal but Gull had weak pawns and an exposed king. The game reached a queen ending with a pawn advantage for Stockfish. The win was clear for Stockfish, especially after it took another pawn. Gull, with no tablebase support, took longer to convince.

Fire used the opening bias to get an eval advantage against Stockfish, and it slowly increased to about 1. To get out of trouble Stockfish sacrificed a knight and got an attack on the white king. This led to a series of exchanges and a QN vs Q position, and the white king was too exposed for anything but perpetual checks. 

Featured game: Andscacs - Fire
Stage 3, round 6
Link to game on TCEC

Andscacs had the opening advantage, but the evals did not go over 1. After several exchanges in the center, including the queens, Andscacs was able to reach the 6th rank with a passed pawn supported by a bishop.

This looked encouraging for white. But Fire blocked any more support for this pawn and it couldn't advance further. The evals came back down to zero, so probably a draw, right? Then Andscacs made an unexpected move.

Fire liked a4 quite a bit, causing Fire's eval to jump to (negative) 0.33. I don't know what was behind Andscacs' move, it allowed Fire to have a supported passer and to free its bishop. The evals continued to rise for black and a few moves later Andscacs chose to give a rook for a knight.

Most probably Andscacs valued the bishop pair and the two passed pawns, and was willing to lose some material for them. This turned out to be a serious mistake. After trading bishops suddenly the white pawns were very weak and easy targets for the black rook.

It wasn't long before the king side pawns were all gone, and the black passer was going to cost at least the white bishop for a nice black win.This was a very surprising result, the only black win, Fire's only win of the round and Andscacs' only loss.

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