[Retros] Distance-PG = Fastest "n"

Mon Aug 29 06:12:29 EDT 2016

Hi,
I guess the ply number is meant to be part of the stipulation? Or should the stipulation ask for the quickest solution?

For example:
"find a game with total move length of 6 + 5*sqrt(2) + 0*sqrt(5) ending in checkmate".1. f4 e5 2. fxe5 Qe7 3. g4 Qh4#In what sense is this ply 6 non-unique solution not a cook of the problem as stated?

And on reflection, I think it's nicer *not* to subtract 1 for en passant: because if you do then many problems will be cooked. Good to be able to force en passant in a novel way, without relying on pins etc.
Thanks,Andrew

      From: Eric Angelini <Eric.Angelini at kntv.be>
 To: The Retrograde Analysis Mailing List <retros at janko.at> 
 Sent: Monday, August 29, 2016 5:38 PM
 Subject: Re: [Retros] Distance-PG = Fastest "n"

#yiv5154785312 #yiv5154785312 -- _filtered #yiv5154785312 {panose-1:2 4 5 3 5 4 6 3 2 4;} _filtered #yiv5154785312 {font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;} _filtered #yiv5154785312 {font-family:Consolas;panose-1:2 11 6 9 2 2 4 3 2 4;}#yiv5154785312 #yiv5154785312 p.yiv5154785312MsoNormal, #yiv5154785312 li.yiv5154785312MsoNormal, #yiv5154785312 div.yiv5154785312MsoNormal {margin:0cm;margin-bottom:.0001pt;font-size:12.0pt;color:black;}#yiv5154785312 a:link, #yiv5154785312 span.yiv5154785312MsoHyperlink {color:blue;text-decoration:underline;}#yiv5154785312 a:visited, #yiv5154785312 span.yiv5154785312MsoHyperlinkFollowed {color:purple;text-decoration:underline;}#yiv5154785312 pre {margin:0cm;margin-bottom:.0001pt;font-size:10.0pt;color:black;}#yiv5154785312 span.yiv5154785312PrformatHTMLCar {color:black;}#yiv5154785312 span.yiv5154785312EmailStyle19 {color:#1F497D;}#yiv5154785312 .yiv5154785312MsoChpDefault {font-size:10.0pt;} _filtered #yiv5154785312 {margin:70.85pt 70.85pt 70.85pt 70.85pt;}#yiv5154785312 div.yiv5154785312WordSection1 {}#yiv5154785312 Many thanks, François, this is what I was looking for !  > length of a + b*sqrt(2) + c*sqrt(5)  ... this is what I like too: those a, b and c give justthe right amount of information about the game (straitone-square movements, oblique one-square movements, jumps).  > tempting to use sqrt(2)-1 to retroactively shrink the previous move.  ... brilliant idea !  Merci encore !É.        De : Retros [mailto:retros-bounces at janko.at] De la part de Francois Labelle
Envoyé : dimanche 28 août 2016 21:37
À : retros at janko.at
Objet : Re: [Retros] Distance-PG = Fastest "n"  Hi Eric,

If I programmed things correctly, then these problems should have unique solutions:

ply 5
  6,5,0

ply 6
  2,6,0
  3,6,0 (similar to previous)
  3,8,0
  3,9,0 (similar to previous)
  3,10,0 (similar to previous)
  3,11,0
  6,11,0
  8,2,0
  9,6,0 (similar to 3,6,0)
  10,7,0 (similar to 6,11,0)

where a,b,c means "find a game with total move length of a + b*sqrt(2) + c*sqrt(5) ending in checkmate".

I also found problems with unique solutions without the "checkmate" condition:

ply4
  5,0,2
  7,4,0

ply5
  5,5,2

ply6
  14,9,0
  16,6,0
  16,7,0
  16,8,0
  17,5,0

For example, the solution to "ply4 5,0,2" is "1. Nc3 d5 2. Nxd5 Qxd5".

There's still the question of the length of an e.p. capture. I assumed sqrt(2), blindly using the maximummer definition (see "length of a move" from http://christian.poisson.free.fr/problemesis/condus.html which doesn't say anything special about e.p.). But in this case, because we're adding all the lengths, I admit that it's tempting to use sqrt(2)-1 to retroactively shrink the previous move.

    FrançoisOn 28/08/16 12:15 PM, Eric Angelini wrote:
  The herunder game ending in checkmate has the same length 4(1+SQR2) asthe "Black version" seen before:1. e2 -- g52. Be2 -- f63. Bh5++But this checkmate is not as fast asthe Black's one. So what do "fast"and "fastest" mean? Well, this deals obviously with the quantity of moves.If this type of problem has no name,it could be baptised "Fastest n" -- "n" being a quantity in square-side units.At least this type of problem doesn't need any diagram -- what a relief forprinted magazines !-))  
Le 28 août 2016 à 17:08, Eric Angelini <Eric.Angelini at kntv.be> a écrit :
For instance, the fastest Distance-PG of total length 4(1+SQR2) ending in checkmate comes of course after thewell known:1.f3 -- e62.g4 -- Qh4++... but as the White moves can beexchanged, this is not a uniquesolution.
à+ É.Catapulté de mon aPhone  
Le 28 août 2016 à 16:20, Eric Angelini <Eric.Angelini at kntv.be> a écrit :
Yes Roberto,a sound proof game of this (total) length,and, in my dreams, the shortest one,hopefully unique, I have in mind.  More generally, one can assign for any past, present and future a single such number, if I'm not wrong.It would be nice to have uniquenumbers "n" for precise tasks like:-find the SPG of total length "n" ending in a checkmate;-find the SPG of total length "n" with a casling;-find the SPG of total length "n" with an en passant capture, etc.BTW, what would be the geometrical length of an e.p. capture?But this is old hat, I'm sure, no?
à+ É.Catapulté de mon aPhone  
Le 28 août 2016 à 13:53, roberto osorio <osorio.arg at gmail.com> a écrit :
Hi Eric,   with SQR5 you surely mean a knight move, so the PG has to include 6 knight moves plus  straight displacements total 20 long.  Many unsound sequences  fit whit these requirements. When you say "Find a PG", do you mean "a sound PG"?  best,Roberto Osorio        2016-08-27 10:17 GMT-03:00 Eric Angelini <Eric.Angelini at kntv.be>:

Hello Retro-fans,
This is for sure old hat, but do you know
a nicer example than my attempt
to produce an unique solution?

"Find a PG ending in checkmate where the pieces have  browsed
the distance of 20 + 6SQR5 units"

(read "twenty plus six times the
square roots of five" - the unit being
the side of a square, of course)
Best,
É.

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