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Subject: Re: Does your program understand castling/en passant rights on 3x repetition

Author: Daniel Clausen

Date: 08:19:04 02/27/00

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Hi

On February 27, 2000 at 00:15:14, Richard A. Fowell (fowell@netcom.com) wrote:

>I noticed today that six of the seven chess programs that I tried
>(three freeware, four commercial) failed to pass the two tests below.
>
>(my congratulations to Will Bryant, who programmed Screamer right!)
>
>The others don't understand how castling rights and en passant capture
>rights effect the ability to claim draw by three-fold repetition of position.
>
>The FIDE Laws of Chess (1997, but unchanged from when I learned chess 26 years
>ago) say:

[snip]
>#1 Check for knowledge of castling rights on triple repetition draw =
>
>1. Nf3 Nf6
>2. Rg1 Rg8
>3. Rh1 Rh8   (second occurrence of this visible piece pattern, but first
>occurrence w/o castling rights)
>4. Rg1 Rg8
>5. Rh1 Rh8 ( No draw, yet - this is the original piece pattern, but there
>             both sides had castling rights. To put it another way, the EPD
>             strings for the starting position and this one are different.)
>6. Rg1 Rg8 - draw by triple repetition of position.
>
>#2 Check for knowledge of en passant opportunity of triple repetition draw =
>
>1.  a4  a6
>2.  a5  b4
>3. Nf3 Nf6
>4. Ng1 Ng8 (second occurrence of this visible piece pattern, but first
>occurrence w/o en passant capture option)
>5. Nf3 Nf6
>6. Ng1 Ng8 (again, no draw yet - there is no en passant capture possible here,
>            as there was after Black's second move).
>7. Nf3 - draw by triple repetition of position.

>Which chess programs (other than Screamer) get these right?

Not that anyone cares, but my engine gets these right. :) But only
if blacks 2nd move in the 2nd mini-game is b5. (instead of b4)

Kind regards,
 -sargon



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