PDN long notation disambiguation

Discussion about development of draughts in the time of computer and Internet.
TAILLE
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Re: PDN long notation disambiguation

Post by TAILLE » Thu Mar 21, 2013 10:36

Wieger Wesselink wrote:
julien007 wrote:I maintain that the path or «turning points» belongs to literature rather than the position of the game.
Hi Julien, sorry that I misunderstood your point about sorted orders. Your formulation of disambiguated capture sequences does not look exact, since "a cycle with two possible orders for a sub-sequence" is not a well-defined notion. If you want to make it precise, you can use something like lexicographical ordering. To give an exact definition of a unique short notation takes even more effort.

Anyhow, as long as there are no official rules for the notation, I don't think there is a reason to change the PDN standard. Perhaps the current formulation should be improved. I'm open for suggestions.
I agree with you Wieger, without any change in the official rules for the notation I do not see any need for an improvment of PDN 3.0. standard. Though PDN 3.0 concerns programmers I agree with Julien that the notation used in PDN 3.0 should also reflect the human notation. My view is the following:
1) The notation in the PDN 3.0 should not be an invention for programmers but should follow common human practice. Should the standard PDN 3.0 recommend a given notation, then this notation should be easily build by a human. Using the smallest lexicographical notation is a non-sense for a human so I do not like this suggestion
2) The notation has not to be a constraint for the human player and in addition, for the reader, the notation shoud be an help for decoding a move. The official rule states in particular:
4.9. A multiple capture has to be indicated clearly, putting the capturing piece down on the empty square after each jump and putting that piece on the final square. Absence of a clear indication is incorrect, and rectification can be requested by the opponent
That means that human players MUST show clearly each turning squares, mustn't they? Without any change in the official rule the prefered notation should help the human player to execute the capture. Giving the ordered turning point is only most natural approach.
3) Creating a unique notation is only a very theoritical advantage. In practise I do not see any need for such unique notation. Draughts lived for many years with several possible notations for an ambiguous move and I never heard a difficulty with that. The rule of the game allow to choose between several paths for certain captures and so, it is only natural to have several notations for such move. We have not to try to recommand a prefered path because it would be just unnatural.
Gérard

julien007
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Re: PDN long notation disambiguation

Post by julien007 » Thu Mar 21, 2013 12:07

Hi Wieger,

Thank for your attention. Sorry my English is not very fluently. I'm not sure to always use the right word at the right place...

I hope you understand what I mean with cycle. It's clear that, in certain cases, the capture can be made in both directions to traverse a loop (which is anecdotal for positions). It's happened with the starting point 48 with Gérard example.

Then to sequences are possibles 48x9x20x48 and 48x20x9x48 for the same positional move. The proposal consists to choose the sub-sequence 9x20 between two possibles sub-sequences 9x20 and 20x9. I do not know if the lexicographical order has something to do with this simple transposition, although the wording of this rule could probably be improved...

More generally, this can happened many times and it can allow permutations as product of transpositions. But this happened probably rarely in competitions and more often with problems of multiple captures like the first example (I verify, It's leads to 16 different moves for the 955 pseudo-variants).

I can not speak about the respective tasks of the federation and PDN Standards, but thank you for the work that marks real progress and contains useful informations and essential details to the community of players.

Sorry for criticism, Progress are within our reach...

Julien de Prabère

Rein Halbersma
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Re: PDN long notation disambiguation

Post by Rein Halbersma » Thu Mar 21, 2013 14:34

julien007 wrote: Image
The position before 43. ... 48x45x42x17x40

I propose only to write : 48x17x45

Image
The position before 45. ... 50x28x48

I propose only to write 50x32x48
I find your proposed notations terribly confusing because it mixes empty squares with captured pieces! For me, the PDN notations 48x26x12x45 and 50x28x37x48 are much easier to visualize. The reason is that it focusses on only 1 piece, namely the black king that is travelling. With your notation I have to mentally switch between the capturing and the captured piece when reading the sequence.

I therefore strongly agree with Wieger that no modification is necessary to the PDN standard.

julien007
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Re: PDN long notation disambiguation

Post by julien007 » Thu Mar 21, 2013 17:04

You are right, if it's only to describe the movement of the player, but the preceding examples show that different movements can reach the same position. In all cases you have to mentally switch between the capturing piece (a king in this case) and the captured pieces or the turning points. I do not really see other differences that captured pieces change the position, never turning points...

Further more, PDN files are not uniquely made for humans, (the names and date are specially formatted for computer sorting, the PDN 3.0 Grammar is eloquent at this regard). They are most of the time used with software. Then this readability is also to appreciate. As noted previously, the reference to many empty cells does not facilitate the identification of the destination square which do not figure always at the end of the list !

I only try to propose a solution to reach an unique notation and to clarify the rules of notation.
That is the unique question.

Rein Halbersma
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Re: PDN long notation disambiguation

Post by Rein Halbersma » Thu Mar 21, 2013 19:36

julien007 wrote:You are right, if it's only to describe the movement of the player, but the preceding examples show that different movements can reach the same position. In all cases you have to mentally switch between the capturing piece (a king in this case) and the captured pieces or the turning points. I do not really see other differences that captured pieces change the position, never turning points...

Further more, PDN files are not uniquely made for humans, (the names and date are specially formatted for computer sorting, the PDN 3.0 Grammar is eloquent at this regard). They are most of the time used with software. Then this readability is also to appreciate. As noted previously, the reference to many empty cells does not facilitate the identification of the destination square which do not figure always at the end of the list !

I only try to propose a solution to reach an unique notation and to clarify the rules of notation.
That is the unique question.
So which ambiguities in the current PDN standard do you want to resolve? In my opinion there are none: the full turning point sequence (including endpoints) is enough to determine the next position.

The fact that you can capture a full circle of 4 or more piece in clockwise or counter-clockwise direction is not really a problem because the lead to the same successor position. If you want a unique notation, you can always write only the lexicographically least of two or more sequences.

julien007
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Re: PDN long notation disambiguation

Post by julien007 » Fri Mar 22, 2013 01:59

You are right PDN Standards are perfect.
All is perfect. No change !

What for is made PDN ?
What's the notation to use in tournament ?
The World Draughts federation rules are silent about disambiguation and PDN notation ?
Maybe it is advisable to apply other rules ?

Nevertheless, It seems yet necessary to clarify all these points !

Good Luck...

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