No.584 
Seetharaman K.
(India)

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Original Problems, Julia’s Fairies – 2014 (II): May – August

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No.584 by Seetharaman K. – Three interesting variations of white pawn’s play with Back-to-Back! (JV)


Definitions:

Back-To-Back: When pieces of opposite colors stand back-to-back with each other on the same file (white piece is on the top of black!), they exchange their roles. A pawn on the first rank cannot move. Any piece can make an en passant capture when it has got a role of Pawn by Back-To-Back.


No.584 Seetharaman K.
India

original – 15.08.2014

Solutions: (click to show/hide)

White Kc8 Pb2 Black Ka8 Qa5 Ra7 Ra6 Pc4 Pe5

h#3        3 solutions         (2+4)
Back-To-Back


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seetharaman
seetharaman
6 years ago

Thanks to Julia for testing several versions of this problem in Winchloe. Popeye 4.67 (which has bugs reg. Backtoback) failed to point out any cooks even without the black pawns.

See also: https://juliasfairies.com/57th-wccc-composing/
Joost Dee Heer and Dmitri Tureveski have made some corrections and this modified version of Popeye 4.67 (unofficial) seems to be free of the known bugs (in BTB). Those who are composing for the Japanese tourney can try it at their own risk (as Dmitri says !). here:
http://yacpdb.org/download/py-20140814.zip

Kenneth Solja
Kenneth Solja
6 years ago

Please tell me why solution:
1. Da2 Kc7 2. Ta3 b3 3. T7a4 bxa4#
doesn’t work?

Kenneth Solja
Kenneth Solja
6 years ago

Sorry, of course not that doesn’t work, but following should:
1. Da2 Kd8 2. Tc7 Kxc7 3. Ta3 bxa3#
I have some twist with my WinChloe .. I can see only three solutions at the time ..

seetharaman
seetharaman
6 years ago
Reply to  Kenneth Solja

1. Da2 Kc7 2. Ta3 b3 3. T7a4 bxa4# This does not work because
1…..Kc7 is not legal move !
1. Da2 Kd8 2. Tc7 Kxc7 3. Ta3 bxa3# is not mate because black can play 4.Qa1 (the queen has pawn power and so can make this pawn-like move !). After queen moves away a3 reverts to pawn power!

Laco Packa
Laco Packa
6 years ago
Reply to  seetharaman

The move Qa1 is not promotion?
It is therefore possible such selfmate?
Kh1, Ra4, Pb2 – Kh3, Ra2, Pa3 – S#1
1.bxa3+ Ra1#

dupont
dupont
6 years ago
Reply to  Laco Packa

I already asked for some precisions on the BTB main rule, namely which is the exact meaning of “role”? Your question about Qa1 is another illustration that the term “role” needs a definition!

Anyway, neither Popeye nor WinChloe considers that Qa1 should be promoted, the reason being probably that Qa2 is still considered as a Queen, even if it must move (temporaly) like a Pawn. In particular your s#1-scheme is correct for both programs.

seetharaman
seetharaman
6 years ago
Reply to  dupont

You are right Dupont about the ambiguity of the term “role”. I have understood it to be the moving/capturing ability. The programmers have also taken that view.

Dominique Forlot
Dominique Forlot
6 years ago
Reply to  dupont

BTB condition seems logic. The pieces don’t change of type , they adopte only the moving-mode of the piece on their back.

on the position:

white Pe6a2c3 Ka1
black Qc2 Pe7 Kf8

Black to move can play :Qb2-b1#
White to move can play :b3-h8=Q#

The pieces don’t change of type , they adopte only the moving-mode of the piece on their back.

on the position:

white Pe6a2c3 Ka1
black Qc2 Pe7 Kf8

Black to move can play : 1…Qb2-b1#
White to move can play : 1. b3-h8=Q#

in BTB condition, a pawn, after a queen’s move, can promote because “it’s still a pawn”!
in BTB condition, a queen can move like a pawn, make possibly a pep, but cannot (under)promote because “it’s still a Queen”!

seetharaman
seetharaman
6 years ago

Good example Dominique (though repeated!). I think your explanation makes the position clear !

Dominique Forlot
Dominique Forlot
6 years ago
Reply to  seetharaman

sorry for the repetition, i have Stumbled on the key: “return”! 🙁

Ganapathi
Ganapathi
6 years ago

Dear Dominique,
In your last ,black’s Qb2-b1 mate is not possible because with WP above it, it can only move as a P (BTB condition). Do you agree?

Dominique Forlot
Dominique Forlot
6 years ago

Dear Ganapathi,
You are right, I made a mistake ( File c and not file b):
the two solutions are:
Black to move can play : 1…Qc2-c1#
White to move can play : 1. c3-h8=Q#

sorry fo this confusion!