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MatPlus.Net Forum General Kontrawechsel
 
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(1) Posted by Jacques Rotenberg [Sunday, Jul 25, 2021 20:01]

Kontrawechsel


what does mean « Kontrawechsel »?
 
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(2) Posted by Joost de Heer [Monday, Jul 26, 2021 07:17]

Literal translation is counterchange.
 
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(3) Posted by Martin Minski [Monday, Jul 26, 2021 08:11]

I wrote in an article in "Problem-Forum" 2010:

"Der Begriff „Kontrawechsel“ rührt von A. Trilling („Die Schwalbe“, 1938, S. 285 ff.) her, dem auch die theoretische Erforschung dieser Erscheinung zu verdanken ist. Dieses logische Gefüge sieht man oft als spezielle Form des Banny-Themas im Zwei- und Dreizüger sowie gelegentlich im logischen Mehrzüger (Siehe „Beispiele zur Ideengeschichte des Schachproblems“ von Josef Breuer oder „Das logische Schachproblem“ von Werner Speckmann)."
 
 
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(4) Posted by Jacques Rotenberg [Monday, Jul 26, 2021 08:47]

very interesting : you mean Kontrawechsel=Banny ?
How is it bound to logic-school ?
 
   
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(5) Posted by Joose Norri [Monday, Jul 26, 2021 09:12]

It is not the same as Banny, but very closely related. A free translation from Breuer: "Black has two defences; White must choose his move so that he has an answer to each defence. If White changes (wechselt) his move, then Black counters accordingly."
 
   
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(6) Posted by Hauke Reddmann [Monday, Jul 26, 2021 09:46]

1...a 2.A! (2.B?)
1...b 2.B! (2.A?)
Observe that it is both less than a Banny (where this scheme
happens after the correct move order) and more (since Banny
is a #2 theme exclusively by definition).
Whether Kontrawechsel it is "logical" depends on whether you
could split off a genuine common "Grundplan" from the moves A,B
and declare the play an "Auswahlkombination".
 
   
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(7) Posted by Jacques Rotenberg [Monday, Jul 26, 2021 10:10]

As far as I understand Banny is not only a 2# theme.
It was defined first in 2#, but the definition is rather formal :
1.A? a!
1.B? b!
1.X! a/b 2.B/A

I did not really understand yet what Kontrawechsel is
 
 
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(8) Posted by Joose Norri [Monday, Jul 26, 2021 10:16]

Interpreting two move themes in threemovers has long been popular. Entirely by chance I have Die Schwalbe 167 Okt 1997 to hand. Kuhlmann and Zirkwitz discuss the Banny in threemovers on page 220. On page 221 they indeed equate Banny and Kontrawechsel, although they note that not every Banny is a logical Kontrawechsel.
 
   
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(9) Posted by Jacques Rotenberg [Monday, Jul 26, 2021 11:37]

Can you please
1) explain the "logical" structure
2) give details when they are equal, when not ?

Thank you very much
 
   
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(10) Posted by shankar ram [Monday, Jul 26, 2021 11:54]

Jacques,

Here's an example by myself and Juraj: https://juliasfairies.com/problems/no-1224/
Kjell Widlert comments on it: "The basic mechanism is indeed simple and well-known: it has been known under the German name “Kontrawechsel” since 1938, and it has been shown with as little as 4 pieces. (There is no established English term, but in Hans Peter Rehm’s new book on logic in fairy chess it is translated as “Interchanged counter”.)

The idea is that Black has two moves (in this problem: a5 and axb5); one requires White to play the moves A and B… (where “…” indicates that there may some further moves connected with B), the other requires White to play A and C… So White must start with A which is common to both variations; if he starts with B or C, Black can choose to continue with the “wrong” variation. With the right first move by White, Black must decide on which variation to play before White has committed himself."
 
   
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(11) Posted by Andrew Buchanan [Monday, Jul 26, 2021 12:57]

V&V Encyclopaedia says:

 QUOTE 
COUNTER EXCHANGE

An English equivalent to the German "Kontrawechsel", which is one form of Option Combination, one of the basic forms being: 1. A? a! (l. ... b? 2. B), 1. B? b! (l. ... a? 2. A); 1. X! a/b 2. B/A. This is in fact a little extended form of what in two-movers is known as Banny Theme, but logical renderings tend to be three or more-movers. The pattern may be different e.g. l. X? b! (l. ... a 2. A), 1. Y? a! (l. ... b 2. B); l. Z! a/b 2. B/A#, where White's 1st and 2nd moves, are made by different pieces. The combination can also find a cyclic rendering, for instance: 1. X? a! 1. Y? b! 1. Z? c! 1. W! a/b/c Z/X/Y.

It should be noted that the combination cannot always be easily translated into the patterns above, because in essence the letters signify plans, not just particular moves.

The last sentence expresses how, even if the Banny is extended to beyond 2#, it is still a subset of Kontrawechsel, as the latter admits logical plans.
 
   
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(12) Posted by Jacques Rotenberg [Tuesday, Jul 27, 2021 00:06]

Thank you Shankar Ram,
1)
your problem is nice!
2)
The pattern you explain fits well the Banny
3)
It is a small surprise for me that this belongs to the so called - neo-german logic - because generally, I had in mind that a characteristic of this is to be able to cut the solution in "main plan" and "foreplans". It does not seem to be so here.

Thank you Andrew, this wording of the encyclopedia looks a bit more difficult...
 
   
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(13) Posted by Joose Norri [Tuesday, Jul 27, 2021 07:18]

As always, there are complications.

A Banny is not necessarily a Kontrawechsel, at least in the pure sense, because the moves that fit the Banny pattern perhaps do not satisfy New German ideals. Kuhlmann & Zirkwitz quote P1023182, which satisfies the Banny pattern, but is not a Kontrawechsel in the strict sense, because the key is not pure in aim.

On the other hand, in a Banny the mates should not be set. Valtonen proposes to call such problems pseudo-Banny. But in a Kontrawechsel this has no significance, if I understand correctly.

In Chlubna's Keller-book there is some discussion about this, with references, p. 116 ff. Must try to understand that...
 
   
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(14) Posted by Joose Norri [Tuesday, Jul 27, 2021 07:26]

As an aside, I should like to mention that the Banny is quite an usual occurrence in OTB chess: you play a move that leaves both options open, serving both ends, waiting for your opponent's reply.
 
   
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(15) Posted by shankar ram [Tuesday, Jul 27, 2021 08:16]

Jacques,

>>> "It is a small surprise for me that this belongs to the so called - neo-german logic - because generally, I had in mind that a characteristic of this is to be able to cut the solution in "main plan" and "foreplans". It does not seem to be so here."

Well... It surprised me too! I think there are many similar problems with New-German logic which the composers had no conscious intent to include. ;-)
I think the Banny/Kontrawechsel scheme can be explained to be New-German logical as follows:
- W tries 1.B? and 1.C? hoping for B to play 1...x and 1...y when W can continue successfully with 2.A! (fore plan)
- But B refutes by playing 1...y and 1...x (refutation of foreplan)
- So W goes with 1.A! (main plan)

Thus changing the SEQUENCE of his moves becomes the main plan. Of course, some other criteria may need to be fulfilled like purity, etc.
 
   
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(16) Posted by Joose Norri [Tuesday, Jul 27, 2021 08:26]

This is an option combination I think, long established in New German tradition. There is little to be found in the English language, but Grasemann's Eines Reverends Einfall (and the texts by Rehm & Eisert) is available in English, I believe. There must be much else.
 
 
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(17) Posted by shankar ram [Tuesday, Jul 27, 2021 08:31]

Joose,

>>> "Kuhlmann & Zirkwitz quote P1023182, which satisfies the Banny pattern, but is not a Kontrawechsel in the strict sense, because the key is not pure in aim."
This problem has the solution:
1.C×é3? [2.Tç4‡] 1…F×ç3!
1.Cb6? [2.Tç4‡] 1…C×ç3!

1.Fé6! [2.Té4+ F×é4 3.Fé5‡]
1…F×ç3 2.D×é3+ Rç4 3.Cb6‡
1…C×ç3 2.Fb6+ Rç4 3.C×é3‡

The two Banny tries of W come back in the solution only on the 3rd move, not the 2nd. So, "not a Banny in the strict sense" too! (WinChloe's theme discovery logic didn't catch it either).
 
   
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(18) Posted by Joose Norri [Tuesday, Jul 27, 2021 13:55]

Yes, the key has the additional element of creating a battery.
 
   
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(19) Posted by Joose Norri [Tuesday, Jul 27, 2021 18:25]

Sorry, I think I made a bit of a mess of it. The last comment was meant to emphasize Zweckreinheit.

The simplest Banny I can think of is https://www.yacpdb.org/#294053

1.c3/c4? 1. a7! Is it also a Kontrawechsel? I think so.
 
   
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(20) Posted by Andrew Buchanan [Wednesday, Jul 28, 2021 05:44]

An observation, a question, and a suggested answer.

Observation: A position in the two player game Nim comprises various piles of matches. Each player in their turn must remove some matches (at least one) from just one pile. If they can't (because all the matches are gone) they lose. So the position 1,2,2 shows (two-fold) Banny:
1. 1,2,1? 1,1,1!
1. 1,2,0? 1,0,0!
1. 0,2,2! 0,2,1/0,2,0 2. 0,1,1/0,1,1.
This shows how natural and non-paradoxical Banny is.

Question: taking a step back: where do we want to end up? What needs to be specified? How specific/definite should the descriptions of these terms be? Where should they be published?

Suggested answer: Here it seems Banny is a single pattern, which can manifest in different ways in different schools of thought (alphabet vs logical). I think we should have self-contained online pages describing each of the two schools. Do they already exist? Banny can be an excellent worked example of a pattern, and it is instructive to see how this is worked through in the different schools.
 
   
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MatPlus.Net Forum General Kontrawechsel