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Subject: Re: Underpromotions

Author: Uri Blass

Date: 12:39:49 09/25/00

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On September 25, 2000 at 13:51:32, Carlos del Cacho wrote:

>On September 25, 2000 at 06:45:34, Ricardo Gibert wrote:
>
>>Which of the following is the most effective for a chess playing computer
>>program:
>>(1) Never consider underpromotions.
>>(2) Allow consideration of underpromotions.
>>(3) Only consider underpromotions if promoting to a Queen leads to a stalemate
>>or if underpromoting to a Knight gives check.
>
>I think the correct one is 2.

I agree.

 Most of the time you are going to fail high with
>the queening moves so promotions to other pieces won't get considered.

The cases when promotion to other pieces won't get considered are cases in the
search when the other side(not the side that did the promotion) made an
illogical move and promotion to queen is enough to prove that it is illogical
move.

Failing high is a necessary condition for it but it is not enough.
You need to fail high in the right nodes.

A simple example

[D]8/4P3/8/8/8/8/2PP3p/2K3k1 w - - 0 1

a)1.e8Q fails high for white but the program has to consider also
underpromotions like 1.e8N to prove that they are weaker.

b)the case that you meant with the same position:
1.Kd1 h1Q fails high for black so the program does not have to consider
1.Kd1 h1N

Uri



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