Wednesday, July 18, 2007

Some Negative Aspects of Chess Programs

Albert Frank Headshot by Albert Frank

In my previous articles "Computers, chess and A.I.", I have presented some dramatically positive aspects of the best chess software programs concerning a quasi human understanding of the chess positions. Today, on the contrary, I'm going to present some extremely negative aspects, especially concerning the defence of a position.

A "fortress" is a pieces' configuration against which the challenger is unable to do anything, despite a huge material superiority, and that involves a draw.

I will present and comment three fortresses. A beginner, or a weak player, will easily understand all of them.

These three configurations have been analysed for five hours by the following strong chess programs: Rybka (the best chess software existing that can be run on a PC), Fritz (which won a match by 6/4 against the world champion Valdimir Kramnik), and Hiarcs on a 3 GHz PC, with 1 GB of RAM.

All the three softwares continued going round in circles indefinitely, giving a winning evaluation to the side which has the material superiority, without realizing that it was impossible to gain a victory.

We can then make the statement that they didn't display any sign of "intelligence".

Fortress 1: White to move

Fortress 1 chess diagram

It's one of the simplest known fortresses: White, if not in check, will move back-and-forth with his rook from f3 to h3; if he is in check, he will move the king, protecting the g3 pawn. Even a very weak chess player will understand this without difficulty.

We must notice that if this position is given to the Shredder chess software, it will immediately be recognized as a draw, because all the positions with a maximum of 6 pieces are recorded ("hard force").

Fortress 2: Black to move

Fortress 2 chess diagram

This more complex fortress is comprised exclusively of pawns.

How could Black progress?

- The King has no entry into the white position;

- If they push forward their pawn a to a5 and then a4, White will answer by b4;

If they push forward their pawn b to b4, White will answer by a4.

-As long as their rook stays on the h column, The white king will go back and forth between g1 and g2; if their rook goes to the f or g columns, the white king will go back and forth between f2 and g2; if their rook goes to the e column, the white king will go back and forth between f1 and f2.

No progression is possible, and the game will be a draw.

While the position of the fortress 1 was quite simple and let us hope for an eventual solution by the computer without having to resort to a "hard force", the fortress 2 seems to be too difficult for any of such expectation.

Nevertheless even a weak player understands quite easily why Black can not do anything.

Fortress 3: Black to move

Fortress 3 chess diagram

Here is another type of fortress.

The black king has no available square and the h5 pawn is blocked by the king.

Black can only move with his queen: if she stays on the first line, between a1 and d1 or in f1, White answers g3 to mate, winning the game. If he goes on e1, the following move is also g3+, and if he goes on g1 or h1, the white king captures the queen, and Black is stalemated (impossible to make a legal move, and the game is draw). If Black's queen leaves the first line, for example if the queen takes control of the diagonal b8-h2, White will operate back-and-forth with their king between g1 and h1.

Once again, chess programs persist in giving a noticeable advantage to the black position.

A possible improvement concerning these wrong evaluations could be the following:

Add to the program a condition such as "if no improvement is reached after twenty moves - analyse deepness - or in other words if the evaluation function, which will be very positive in the beginning (due to the material advantage), stays unchanged, then tackle the position analysis in another way.

1 comment:

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