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MatPlus.Net Forum Competitions Back-Home Tourney
 
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(1) Posted by Dupont Nicolas [Sunday, Jun 30, 2013 07:45]

Back-Home Tourney


ChessProblems.ca organizes a thematic tournament dedicated to the new Back-Home fairy condition I recently invented. The tourney announcement is online at http://tt5.chessproblems.ca/

Hope you will enjoy this tournament!

Nicolas.
 
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(2) Posted by Thomas Brand [Sunday, Jun 30, 2013 17:08]

A notification in German can be found here:

http://www.thbrand.de/2013/06/30/nach-hause/

Much fun with this interesting new fairy condition!

Regards, Thomas
 
 
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(3) Posted by Jacques Rotenberg [Monday, Jul 1, 2013 09:14]

Some questions about back-home :

1 may a back-home move be a capture ?
2 it is said that a back home move must be played first whatever happens on the board
-2 a does it mean for example that a check could be parried by giving the opponent the opportunity of a back-home move?
-2 b does it mean that when your king is threatened, if you have back-home moves, none of them being a defence, you are mate ? If yes, may a back-home move be a self check ?
3 in case you can demonstrate (retro) the origin of a pawn or a piece, does the back-home square change ? If not,
-3 a does it mean that a back-home diagram has no past ?
-3 b does it mean that the past was orthodox till the diagram, and only then 'back-home'?
-3 c does it mean that the past was back-home till the diagram and then the home squares changed ?
 
   
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(4) Posted by Dupont Nicolas [Monday, Jul 1, 2013 13:08]

@ Jacques,

Thanks for your questions, they give me the opportunity to precise some back-home rules:

1. Yes, going back-home is mandatory, even if the back-home square is occupied by an opponent piece.

2a. Yes, giving the opponent side a back-home move possibility is a way to parry a check, as this opponent side is no more threatening to capture the King.

2b. No, such back-home moves would be self-checks and back-home moves must be legal.

3. No, the back-home square of a given unit is the one it occupies in the diagram position, except for proof games when it is the one it occupies in the initial game array. So 3a is correct except for proof games. And for proof games there is no ambiguity about the back-home square of each unit as the past of the diagram-position is known from the solution.

PS: I haven’t thought about the possibility of a back-home retro-analysis problem, but it might be interesting. Of course a set of new rules must be defined, for example is the retro-diagram the result of an orthodox game or of a back-home game?
 
   
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(5) Posted by Jacques Rotenberg [Tuesday, Jul 2, 2013 01:32]; edited by Jacques Rotenberg [13-07-02]

Thank you for your quick answer.
"...So 3a is correct..." Why should you forbid pep key or 0-0-0 ?
3b or 3c are without doubt better.

I would even propose 3d :

If 3b or 3c can be a basis to demonstrate that a pep is possible, then this pep is a possible key.
If 3b or 3c can be a basis for a 0-0-0 (0-0) to be valid, the 0-0-0 (0-0) is valid.
 
   
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(6) Posted by Jacques Rotenberg [Tuesday, Jul 2, 2013 04:42]

About the questions 2, if I understand well what you say, it means that a side under check (side I) (after move A) by the opponent (side II) has to play in that order :

1- a back-home move that is capturing the opponent's king (that means that A was illegal)

if there is no such move

2- a back-home move B that is a defence against the check or that gives the opponent (side II) a possibility of a back-home move C (not capturing the king) This move C may itself put its king under check if in the same time it gives its opponent (side I) a back home move etc. the chain may long till you decide if B is legal or not ?

if there is no such move

3- a non back-home move that is capturing the opponent's king (that means that A was illegal)

if there is no such move

4- a non back-home move B that is a defence against the check or that gives the opponent (side II) a possibility of a back-home move C (not capturing the king) This move C may itself put its king under check if in the same time it gives its opponent (side I) a back home move etc. the chain may long till you decide if B is legal or not ?

Am I right ?
 
   
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(7) Posted by Dupont Nicolas [Tuesday, Jul 2, 2013 13:20]

Yes. As said in the foundation article, "(back-home) rules may actually lead to rather complex reasoning, in particular to detect legal moves [..] It implies that some induction process may appear in order to verify back-home move legality."

In particular, suppose the side-on-move has a back-home move possibility letting its own King under (orthodox) attack. Then this back-home move is legal if the opponent side has, in its turn, a legal back-home move which prevent the orthodox King's capture.

So you are right, "chains" of back-home moves may appear while looking if the first one is legal or not. I haven't proved that such a chain is never closed. If it exists such a closed chain (would be interesting to find one!) it leads to an un-decidable situation (a back-home move A is legal if and only if the back-home move A is legal).
 
   
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(8) Posted by Dupont Nicolas [Sunday, Mar 30, 2014 14:41]

Judgment is online!

http://Bulletin.ChessProblems.ca
 
 
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MatPlus.Net Forum Competitions Back-Home Tourney