Overtom's Computer Chess Weblog

Paw In The Bottle   (15 October 2008)

According to writer James Hadley Chase, monkeys in Brazil are caught in the following way:

They put a nut in a bottle and tie the bottle to a tree. The monkey grasps at the nut, but the neck of the bottle is too narrow for the monkey to withdraw its paw along with the nut. You’d think that the monkey would let go of the nut and escape? But alas! The monkey is so greedy that it never does!

As self-appointed curator of the Overtom Chess Computer Museum, I play hundreds of games with chess computers, if only to heed Arno Kreuzberg's advice that chess computers should be used at least once a year.

Yesterday I witnessed a game between Fritz-5-ply and Mephisto Rebell, which reminded me of James Hadley Chase's story.

Mephisto Rebell

On the 55th move, the following situation came about:

It is clear that white has a won game. But there is one little problem: black can delay checkmate as long as he can give checks; white may not capture the rook because then black has no moves left and is stalemated. Black realizes this and keeps giving checks.

After a series of fifteen checks, black gave check again with 70...Rd1-e1+ .


The last fifteen moves would have taught a human player that he had to find a way to put an end to the stalemate threat. At this point white had the chance to stave off this threat with 71. Nf6-e4.

But Fritz turned out to be the monkey with the paw in the bottle. He held on to his knight, which seemed to be positioned so favourably but in reality contributed considerably to his plight, and played 71. Ke5-d5.

To make a long story short, on the 81st move, the game was drawn, as can be seen in the game below:

White: Fritz 8 (5 ply)

Black: Mephisto Rebell 5 (± 60 seconds / move)

1.d4 Nf6 2.Nf3 d5 3.c4 e6 4.Nc3 Be7 5.Bf4 O-O 6.e3 c5 7.dxc5 Nc6 8.Qc2 Bxc5 9.Rd1 Nb4 10.Qd2 Bd6 11.Bxd6 Qxd6 12.a3 Na6 13.cxd5 Nc7 14.dxe6 Qxd2+ 15.Rxd2 Bxe6 16.Nd4 Rfd8 17.Bd3 Rac8 18.Ke2 Nfd5 19.Rc1 Bg4+ 20.f3 Bd7 21.Be4 a6 22.Nxd5 Nxd5 23.Rxc8 Bxc8 24.Nc2 Nf4+ 25.exf4 Re8 26.Ne3 f5 27.Bd5+ Kf8 28.Kf2 h5 29.h4 Ke7 30.Re2 Kf8 31.Rc2 g6 32.Rc7 Rd8 33.Rf7+ Ke8 34.Rf6 Ke7 35.Rxg6 Rh8 36.Rb6 a5 37.Bxb7 Be6 38.Bd5 Bxd5 39.Nxd5+ Kd7 40.Nf6+ Ke7 41.b4 axb4 42.axb4 Kf7 43.b5 Kg7 44.Nd5 Rd8 45.Ne7 Rf8 46.Ra6 Rb8 47.Nxf5+ Kg8 48.Nd6 Kg7 49.g4 Rh8 50.g5 Rd8 51.f5 Kh7 52.Ne4 Kg7 53.Ra7+ Kg8 54.Nf6+ Kf8 55.g6 Rd2+ 56.Ke3 Rd3+ 57.Kf4 Rxf3+ 58.Ke4 Rf4+ 59.Ke3 Rf3+ 60.Kd4 Rf4+ 61.Kd3 Rf3+ 62.Kd2 Rd3+ 63.Ke2 Re3+ 64.Kd1 Re1+ 65.Kd2 Rd1+ 66.Ke2 Re1+ 67.Kd3 Rd1+ 68.Ke4 Re1+ 69.Kd4 Rd1+ 70.Ke5 Re1+ 71.Kd5 Rd1+ 72.Kc4 Rc1+ 73.Kb3 Rb1+ 74.Kc3 Rc1+ 75.Kb4 Rb1+ 76.Ka5 Rxb5+ 77.Ka4 Rb4+ 78.Ka3 Rb3+ 79.Ka2 Rb2+ 80.Ka1 Rb1+ 81.Kxb1= An animation of this game can be seen if you have Java installed.

A few other games played by these two computers can be seen on this page.

On the same page you can see that Rebel also played a much stronger game against Fritz-5-ply, which game was also drawn (probably an unnecessary draw as well).

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