[Retros] More on Retro-Strategy and Retro-Volage
G.A.Rol at umcutrecht.nl
Wed Jun 20 13:50:43 EDT 2007
Thanks to Valery for his great example in Retro-Volage posted on the 7th of june. I have reproduced an excerpt from his post below. What can be seen in this problem is no less than "the future of retro-synthesis and retro variants". Dittman's book "der blick zurück" does not reserve a lot of space for these subjects and why this is the case becomes clear when you read his comments on help-retractors. He divides them in 2 categories: the analytical and synthetic kind, and he tells us that the synthetic kind is much more interesting in terms of "chess content" while its analytical counterpart mainly depends on "initially surprising but soon familiar tricks with e.p. moves and castling" [my phrasing]. And in fact, Dittman is quite right in the orthodox domain. Retro-Volage problems however do not only show more sophistication in retro-strategical methods but include good chess play as well.
One of the things I will try to add to the theory of these areas is the idea that there are at least two different classes of factors that may deliver "facts" for Post Factum evalutions (a) the changing profile of capabilities of piece movement during a game as in castling, e.p. or retro-volage pieces (b) the game enforcers - everything that justifiably avoids draws, mates and even king captures. I have shown one example in R309 where the potential of a repetition draw delivers the crucial "fact" for completing the solution. I will now present another one which uses "mate avoidance" in the same manner. The funny part is that we can stay pretty close to the orthodox domain since "game enforcers" (to my knowledge) are as yet unexplored territory in Retro Strategy. Not 100% orthodox though as Reflex-mate problems actually contain a play-rule that separates them out from help- and selfmates. Every legal chess game is also legal as a helpmate or selfmate game but not as a reflexmate game!
I invite you to solve this yet unpublished challenge and comment on its logic or chess solution. Familiarity with AP (a posteriori) logic is required to discover how the generic AP principles are applied in a new way:
White: Kd6, Bg7, Sd7, P:b6,c4,f5,g6
Black: Ke8, Ra8, Rh8, Bd8, P:b7,c6,f6,f7.
Solution to follow in a few days.
(excerpt from Valery's post of june 7, 2007)
V.Liskovets and N.Plaksin, feenschach, h.81, 1986
W: Kg1 Rb5 Rf3 Sb1 Sc3 Pd3;
B: Ke1 Rd2 Rf2 Pc4
a)#2 b)#2 pRA or RV
a) (implicit) PF logic: 1.Rb2=bR! - 2.Re3(=wR!)#! (2... Rde2=wR??/Rfe2=wR??).
b) By the opposite pRA logic, there are 4 retro-variants (RVs)
known in advance and 4 corresponding partial solutions. The latter
contain W's moves without recoloring. E.g., if Rf3 and Rf2 are
(known to be) volage (hence Rb5 and Rd2 are normal), then
1.Re5(=wR)+ Rde2(=bR) 2.Rxe2#!
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