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Subject: Easy or hard test position: an evaluation issue.

Author: Albert Silver

Date: 13:48:00 03/09/02


There is a friendly match between my club, the Tijuca Tenis Clube (the chess
department) and the Clube De Xadrez Gunabara, over 8 boards. Both are among the
most victorious and long-lasting clubs in Rio de Janeiro. The event comes with
the blessing of the president of the Brazilian federation and will be worth some
trophy they created that will be swapped back and forth over the next few years
as I saw it had inscriptions for all winners until 2006 on it. There are two
rounds at 90 min KO + 30 sec increment (though no increment today) played over
this weekend, and I played 4th board. My game went well for me (especially
considering how monstrously rusty I am) and I eventually arrived at the
following position with about 5 minutes left.

[D]6k1/4bp1p/2b3p1/2N1p3/1PP5/4N1P1/5P1P/6K1 w - - 0 1

Obviously, many roads must lead to Rome here, but I saw a short winning sequence
that made it clear and simple. The main line goes 1.b5! Bxb5 2.cxb5 Bxc5 3.Nd5
f5 4.b6 Bd6 5.b7 Kf7 6.Nb4 Ke6 7.Nc6 and I win a piece and the game quite
easily. The line is quite simple, and above all, with my knight fighting alone,
there is little thinking to do after. I fed it to a few engines and was
surprised to see how many fumbled around. Tiger found it in a few seconds but
Junior 7 after about 6 minutes (and 22 half plies) gave me a line that had it
win the piece in almost the same way in about 5 more moves. No idea why it
preferred this. Fritz 7 also had a line that didn't seem like any great
improvement and also preferred to take a bit longer. Obviously the issue must be
one of evaluation, since they clearly don't think much of the knight fighting
the pawns. This is a mistake as winning it after the line I gave above is a
piece of cake AND it's quick. I say stray because the line they give is
unconvincing usually.

Here is Junior 7 (1.10/22) and its idea of an 'improved' final position: 1.Na6
Bb7 2.Nd5 Bxa6 3.b5 Bxb5 4.cxb5 Bd6 5.b6 Kg7 6.Nc3 f5 7.Nb5 Bb8 8.f3 e4 9.fxe4
fxe4 10.b7

[D]1b6/1P4kp/6p1/1N6/4p3/6P1/7P/6K1 b - - 0 10



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