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Pages: [1] 2
Author Topic: Imitator - definition, features, implementation
Julia
Administrator
Posts: 13
Julia
Post Imitator - definition, features, implementation
on: November 7, 2014, 18:02

The discussion about Imitator has started in the comments to the problem No.638 - http://juliasfairies.com/problems/jf-2014-iii/no-638/#comments

Julia
Administrator
Posts: 13
Julia
Post Re: Imitator - definition, features, implementation
on: November 11, 2014, 16:53

There're many cases when combinations of fairy conditions give surprising results, and there're also many cases when they don't work together. I believe that maybe it's not really needed (or so important now) to test Imitator with all possible conditions. Or we can think about it, and wonder, and discuss when some problem will show a debatable combination.

But thinking about a better definition and understanding of Imitator, I've made some "research" and this is what I've found:

1) Imitator was invented by Theodorus Cornelis Louis Kok in 1939. And the same year the definition of it was published in "Fairy Chess Rewiew" by T.R.Dawson. (I don't have it, maybe somebody does)

2) I've got a copy of later publication, from "A GUIDE TO FAIRY CHESS (1967)" by Anthony Dickins, with a following definition of Imitator:

The IMITATOR (I), invented by Dr. Kok (FCR 8/18/p.140/Paper 198), is non-checking, non-capturing, non-capturable piece that exactly imitates in length and direction the moves made by each man of either colour. It moves simultaneously with the White or Black man, like a kind of 'shadow', and if in imitating the move the Imitator would have to enter an occupied square, then that move is illegal; for the Imitator may only enter an unoccupied square. It may be drawn along one step behind an advancing pawn, Rook, etc., or pushed along one step ahead. With an Imitator on the board the two Kings may legally occupy adjacent squares, for if the Imitator cannot imitate the 'move' that would enable one King to capture the other one, then the latter is not in 'check'.

3) In Popeye the implementation of Imitator was done by Thomas Maeder, who has kindly explained me that he has allowed a promotion into Imitator in Popeye as it was originally defined as a piece;
but on another hand it mostly works as a condition, restricting moves as
some other fairy conditions, that's why it was implemented as a condition.

So, it seems like "condition" in Popeye is more like technical instrument for implementation, than an essence of Imitator.

Also, I've got to know, that Popeye has an option to switch off a promotion adding a condition: NoIProm - No Promotion to Imitator allowed.

-----------------------------
What I would offer is -
To use the original definition being correct to the inventor;
To add something like a Note to the original definition, explaining some nuances we've found, regarding the behavior in general and promotion in Popeye/WinChloe.

Or maybe another option is to write a new, more laconic definition, based on the one proposed by Peter Harris, but mentioning that in original definition Imitator was called as a piece, but its behavior combines the features of the both - a piece and a condition.

Kjell-
Widlert
Visitor
Posts: 3
Post Re: Imitator - definition, features, implementation
on: November 12, 2014, 00:29

The original source (Fairy Chess Review, April, 1939, 5-minute Paper 34) indicates another Dutchman as the inventor: Gerrit Jansen! The later publication referred to by Dickins (FCR Oct. 1954) doesn't mention any inventor at all. So which is right, Kok or Jansen?

The original definition in 1939 is the following:
The Imitator (...) is a neutral man which imitates EVERY move like a shadow. In other words, when any White or Black man moves, the imitator moves simultaneously in a parallel direction for the same distance.
The imitator may not be captured and may never capture, so that any move of White or Black which would bring one or more imitators to occupied squares (or, of course, off the board) is inadmissible and may not be played. Incidentally this includes the fact that the imitator is a non-checking man.
It must be realised, also, that the ability of the imitator to prevent various moves makes it readily possible for the Kings to stand in what would normally be checks, because the capture of the King has ceased to be admissible.
(...) With the final remark that Pawns may promote to Imitators as well as normally, No. 3615 may be left to the reader.

End of quote. Judging from the language, I assume that T. R. Dawson himself was involved in the writing, although the paper is signed by Gerrit Jansen and A. Wijker.
At least two noteworthy points: the paper implicitly allows several imitators on the board, and it explicitly allows pawn promotions to imitators!

Julia
Administrator
Posts: 13
Julia
Post Re: Imitator - definition, features, implementation
on: November 12, 2014, 09:40

Yes, in the copy of the definition I've got the name of Gerrit Jansen was struck out, and a name of Kok written by hand... The same time I've checked the Chess Composers blog by Eric Huber & Vlaicu Crişan - the page http://chesscomposers.blogspot.com/2012/11/november-23rd.html says that Theodorus Cornelis Louis Kok invented the Imitator in 1939. Maybe authors have found some another source? Also, there're no problems with Imitator by Dawson, but they are by Kok in 1939.

It would be interesting to prove the inventor's name.. The same time, I guess, that there're many fairy elements with many times revised definitions, and unknown authors.
Is it right, that there're no rules on copyright protection for inventions in chess composition? I'm thinking, that on the one hand, it would be correct and polite to use the original authors' definitions, but on another hand, some fairy elements were invented long time ago, but a new fairy elements coming later may require changes to the old definitions. Same, as the language always gets some changes with the time, and some terms as well. (I'm thinking about a definitions I should use in Original Problems and Fairy terms)

Anyway, the main things we wanted to know are found and pointed by Kjell, that several Imitators on the board and pawn promotions are allowed!

About other fairy conditions, like Take&Make, there're no defined rules as these conditions were invented later. To my opinion, either combinations should be not allowed, or somehow defined and implemented in accordance with that definition. I believe, that the primary thing is still a definition, but not an implementation in any solving program.

Julia
Administrator
Posts: 13
Julia
Post Re: Imitator - definition, features, implementation
on: November 15, 2014, 22:53

I should say that I've started to enjoy Imitator, its features with a different moves and conditions, implementation by Popeye and WinChloe.. and how much of it is based on the definition.

At first, I've tried to find more about the inventor's definition, but all I have is:
I've got to know that on Chess Composers blog the information about Imitator's inventor came from the Retro Corner - http://www.janko.at/Retros/Glossary/Imitator.htm (written by Philippe Schnoebelen) - where it is said:

The Imitator (invented by Th. Kok in 1939) is a fairy piece depicted as a big black spot, and denoted by "I". It does not move by itself, but it imitates every move by normal pieces. Moves that cannot be imitated are illegal, so that the Imitator acts as a constraint on possible moves.
The Imitator does not belong to any side. It cannot be captured.

And one more interesting addition - I don't know either it is a part of the definition, or it is based on the implementation is solving programs:

Castling is imitated by decomposing into a King move followed by a Rook move.

This addition made me think about the features Imitator can add to the castling move:

IMITATOR with Castling

(Imitator's behavior is analogical in the last versions of the both programs – Popeye and WinChloe)

1. Castling short – the both moves are imitated in a sequence, the first is a King, the second is a Rook. But as a result Imitator returns on its initial square.
F.i., in the scheme below:
white ke1 qe5 rh1 | bla kf3 pg4 | imitator a4
after Kg1 Imitator goes to c4, but after Rf1 Imitator returns again on a4!

Image

1.0-0{Ia4}‡!

Popeye (Imitator is a condition)

beg sti #1
pie whi ke1 qe5 rh1
bla kf3 pg4
con imitator a4 end

  #1                          3 + 2
             Imitator a4

   1.0-0[Ia4] # !

2. Castling long – again, the both moves are imitated in a sequence, the first is a King, the second is a Rook. But this time a place of return for Imitator is one square right from its initial square.
F.i., in the scheme (2) below:
white ke1 qe5 ra1 | bla kd3 pc4 | imitator g4
after Kc1 Imitator goes to e4, but after Rd1 Imitator returns to the right and comes on h4 (one square to the right from its initial position)!

Image

1.0-0-0{Ih4}

Castling with Imitator gives some special features, like in the Scheme (3):

Image

The only solution here is 1.0-0+! - where Imitator goes together with Kg1 (If1) and than with Rf1 (Id1) – returns to its initial position!
A check with 1. Rf1?? is impossible as together with this move Imitator goes to b1, and a Rook from f1 can't give a check as a capture RxKe8 can't be imitated as b8 is blocked!

------------
Also, the en passant-discussion of the last weeks couldn't leave me indifferent, so I've checked the

IMITATOR with En Passant
(Imitator's behavior is analogical in the last versions of the both programs – Popeye and WinChloe)

Image

Without an Imitator the mates would be:
1.b4! axb3 e.p.‡; 1.b3+! axb3‡.

Adding the Imitator in a Scheme (5) changes a situation cardinally! Now it is important, where should play the white Pawn – on b4 or b3. It is not very visible from the first glance why 1.b3+? Doesn't work for (a) and 1.b4? doesn't work for (b).

Image

a) 1.b4{If6}! axb3 e.p.{Ig5}# (1.b3?(If5) axb3+(Ig4) but 2.Kb2(Ih4)!! and the capture cxb3 is impossible because the Imitator h4 is blocked and can't come on g3!!)
b) 1.b3{If5}! axb3 {Ig4}# (1.b4(If6)? 2.axb3 e.p(Ig5)+ but 2.Sxc3(Ih7)!! and the capture bxa2 is impossible because the Imitator h7 is blocked and can't come on g6!!)

--------------

That's all for today :). But further I'd like to discuss with you some combinations of Imitator with other conditions, especially differently implemented in Popeye and WinChloe.
And.. I've started to compose my first problem with Imitator!

shankar-
ram
Visitor
Posts: 10
Post Re: Imitator - definition, features, implementation
on: November 16, 2014, 17:12

Great to see you use the forum, Julia!

Whether the imitator is a piece or a condition or both.. is an old discussion point.. something like whether the electron is a particle or a wave..! btw.. such quantum references were also made in a recent lengthy discussion in the matplus forum..

Have you got any example problems where a pawn promotes to imitator? Would there be black, white or neutral imitators? In sentinelles, would an imitator leave behind a pawn?

More research for you..!

Kjell-
Widlert
Visitor
Posts: 3
Post Re: Imitator - definition, features, implementation
on: November 18, 2014, 22:51

Another non-trivial question is this:
When an imitator is imitating a move by a hopper (grasshopper, lion, etc) - does the imitator need a hurdle too? Or does the imitator move like a normal line-piece (a rider) even when imitating a hopper?

Some small tests indicate that Popeye 3.69 and WinChloe 3.30 agree that the imitator needs a hurdle too, at least as long as the hopper is a grasshopper.
When the hopper is a lion, Py doesn't want to play at all ("Too much fairy for an imitator"), and WC still requires a hurdle - but it must be in the same relative position to the imitator as the other hurdle is relative to the lion! (So with wKd4 wLId1 - bKb1 - Imitator f4, LId1-a1(Ic4) is legal. But with wK moved to e4, LId1-a1 is no longer legal in WC, even though f4-c4 would still be a legal lion move.)
When the hopper is a leo, we have the funny situation that with wKd4 wLEd1 - bKb1 bSa1 - Imitator f4, White can play LEd1xa1(Ic4), so the imitator doesn't need something to capture like the piece it imitates does ... in fact, it is not even allowed to have something to capture. This is in WC; as expected, Py doesn't want to play with the combination imitator + leo either.

Julia
Administrator
Posts: 13
Julia
Post Re: Imitator - definition, features, implementation
on: November 19, 2014, 17:45

I've also found that Popeye doesn't solve a combination of Imitator and Chinese pieces. Most probably, there're many other fairy elements (pieces and conditions) which are "too much fairy for an imitator" 🙂
I don't know why Imitator is implemented this way. I hope to convince Thomas Maeder to extend the implementation and I also hope that nobody minds it. But for that we should provide the rules and examples.

About Hoppers I'd agree with WinChloe's realization: if Imitator should fully imitate the moving piece, then it should jump if/when a piece jumps. So, I'd prefer Popeye to have the same implementation, where an Imitator needs a hurdle and it should be on the same relative position as an imitated piece.
I agree, a situation with LEO (PAO, VAO, ...) looks funny. An Imitator can't capture anything and if it was LEO then it won't need a hurdle for non-capturing move. But it is not LEO, just an imitation (like a shadow) - so I believe it's correct that it jumps together with LEO. With orthodox pieces the imitation doesn't include capturing as well, just the move till the square of capture/arrival. But maybe there're another views?

Julia
Administrator
Posts: 13
Julia
Post Re: Imitator - definition, features, implementation
on: November 19, 2014, 22:01

An interesting fact - the name of the inventor!
About a week ago Thomas Maeder advised me to turn to Hans Gruber with a questions about Imitator's inventor and definition.
And this is what I've got today:

1). "it is true that Gerrit Jansen (a pseudonym used by Theodorus Kok) presented the Imitator in the Fairy Chess Review, which was at that time edited by Thomas Dawson."
So, Gerrit Jansen and Theodorus Kok is just one and the same person!

2). Some more materials below are in German. Maybe German friends would comment or translate the main things:

Imitator [Gerrit Jansen (Pseudonym von Theodorus Kok), The Fairy Chess Review, Band 3, Nr. 17, IV/1939, S. 180‑181]

Der Imitator ist ein Schatten [Gerhard Wolfgang Jensch, Schachmatt 55, 16.11.1947], der die Bewegung jedes ziehenden Steins auf einer Parallelen in derselben Richtung mitmacht. Er kann selbst weder schlagen noch Schach bieten. Für den Imitator gelten die gleichen Zugregeln wie für den gerade ziehenden Stein: Die Transitfelder müssen (bei Langschrittlern) leer sein. Ein Zug, durch den der Imitator über besetzte Felder oder über den Brettrand hinaus bewegt würde, ist nicht zulässig. Kommen mehrere Imitatoren in einer Stellung vor, so imitieren alle in der beschriebenen Art.

Der Imitator wird in der Originaldefinition als neutraler Stein beschrieben, in den sich ein Bauer umwandeln darf.

Thur Row sagt, dass die Figur besser Companion genannt worden wäre, was aber nun nicht mehr ginge [Chess Ultimates, Band 3, Nr. 2, VII/1973, S. 81]. In Rows Version darf man in Stellungen mit Imitator nicht rochieren; eine Bauernumwandlung in einen Imitator ist erlaubt [Chess Ultimates, Band 1, Nr. 7, X/1970, S. 25].

Ein schwarzer Imitator [E. W. Bennett, 7669. The Fairy Chess Review, Band 6, Nr. 18, VI/1948, S. 135] imitiert nur schwarze Züge, ein weißer Imitator nur weiße.

Ein Lone Imitator [Thur Row, Chess Ultimates, Band 1, Nr. 8, XI/1970, S. 32, sowie Nr. 10, I/1971, S. 38 (Definition)] ist ein einsamer Imitator Rowscher Version: Außer ihm darf es keinen weiteren Imitator auf dem Brett geben; eine Bauernumwandlung in einen Lone Imitator ist nicht erlaubt.

shankar-
ram
Visitor
Posts: 10
Post Re: Imitator - definition, features, implementation
on: November 20, 2014, 10:15

how about imitation of moves by nightrider, rose, mao, moa, other riders..?
would the imitator need the intervening squares also to be free..?
as for imitator combined with take and make... it's "too much fairy" for me even..!

moral: when inventing a new piece, condition, board or stipulation, the inventor should clearly state the scope of it's combination with other pieces, conditions, boards and stipulations..
else composers, programmers and forum posters will make their own assumptions..
simplest would be to state a minimum scope for combinations.. all other combinations should stated as "undefined"..

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