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Subject: Re: Repetitions: is this code correct?

Author: Robert Hyatt

Date: 13:40:21 07/12/02

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On July 12, 2002 at 09:52:03, Ricardo Gibert wrote:

>On July 12, 2002 at 09:27:43, José Carlos wrote:
>
>>On July 12, 2002 at 09:19:10, Richard Pijl wrote:
>>
>>><snipped irrelevant part>
>>>
>>>>>>>- Game history should be counted, but make sure you do not evaluate repetitions
>>>>>>>in the rootnode as you need a move to be played ...
>>>>>>
>>>>>>  Not if your opponent has made a move such that there's a 3 times repeated
>>>>>>position on the board. In that case, you can simply claim the draw.
>>>>>>
>>>>>Not by FIDE rules where you have to state a move you want to play which results
>>>>>in the third time the position occurred. E.g. when from the startposition white
>>>>>moves its kings knight to f3 and back, and black does the same with its knight
>>>>>(g8-f6 and back) black can claim a draw before making its fourth move stating
>>>>>the intention to play f6-g8. If black doesn't, white can by stating the move
>>>>>g1-f3. However, if white had played the sequence 1.Nf3 2.Ng1 3.Nc3 4.Nb1 it
>>>>>cannot claim a draw on any move as on either Nc3 or Nf3 the position only
>>>>>occurred twice.
>>>>
>>>> I play white, you play black. The game goes: 1. Nf3 Nf6 2. Ng1 Ng8 3. Nf3 Nf6
>>>>4. Ng1 Ng8 5. Nf3 Nf6 6. Ng1 Ng8 7. Nf3 Nf6 ... It's perfectly legal because 3rd
>>>>repetition must be claimed by the players. In this game, either you or me can
>>>>claim draw by third repetition whenever we want, with or without making a move,
>>>>because there have been some positions (4 in this case) repeated 3 or more
>>>>times.
>>>>  I'm 100% sure about this point.
>>>>
>>>You're right. Either something changed in the rules over time or my memory is
>>>failing me ;-). From the FIDE rules:
>>>
>>>'9.2 The game is drawn, upon a correct claim by the player having the move, when
>>>the same position, for at least the third time (no necessarily by sequential
>>>repetition of moves)
>>>a) is about to appear, if he first writes his move on his scoresheet and
>>>declares to the arbiter his intention to make this move, or
>>>b) has just appeard, and the player claiming the draw has the move.
>>>
>>>Positions as in (a) and (b) are considered the same, if the same player has the
>>>move, pieces of the same kind and colour occupy the same squares, and the
>>>possible moves of all the pieces of both players are the same.
>>>Positions are not the same if a pawn that could have been captured en passant
>>>can no longer be captured or if the right to castle has been changed temporarily
>>>or permanently.'
>>>
>>>(From FIDE Laws of Chess, in force since July 1st 2001)
>>>
>>>Richard
>>
>>  Thanks for the info.
>>  Luckily I don't have a bug in third repetition then :)
>>
>>  José C.
>
>How should this next position be handled?
>
>[D]8/6k1/1b6/2p5/3pP3/3P4/1B4K1/8 b - e3 0 1
>
>White has just played e2e4 and the reply de3 e.p. is not a legal move. Should
>this position recur, is it counted as a repetition since the same set of legal
>moves for Black are available? Either way, do programs handle this case
>corrrectly?

This is one most chess programs probably get wrong.  the EP capture is not
possible, so that the position is the same whether white had just played
e2-e4 or e3-e4, since they are equivalent with the black pawn pinned.

Therefore this would be a repetition if the same position happens two
more times by shuffling kings.



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