[Retros] Distance-PG = Fastest "n"

Mon Aug 29 15:32:10 EDT 2016

Hi Francois,
Thanks for this. 

How deep have you plied, please? Just to give us an idea of where it's not worth searching.
Cheers,
Andrew

      From: Francois Labelle <flab at wismuth.com>
 To: andrew buchanan <andrew at anselan.com>; The Retrograde Analysis Mailing List <retros at janko.at> 
 Sent: Monday, August 29, 2016 9:52 PM
 Subject: Re: [Retros] Distance-PG = Fastest "n"

 Hi Andrew,

 The ply number is meant to be part of the stipulation, sorry for not having been clear. For the problems I listed it is also possible to instead ask for the shortest solution.

 An example of a non-shortest problem would be to ask for a checkmate of total move length (2,6,0) in 3.5 moves. The solution is unique, 1. e3 d6 2. Qe2 Kd7 3. Qd3 Kc6 4. Qb5# , but non-shortest because there is also a solution in 3.0 moves: 1. d3 e6 2. Kd2 Qe7 3. Kc3 Qb4# .

 For the moment I don't have an example of a problem that is sound without specifying the number of moves or asking that it be shortest, but "checkmate (2,6,0)" comes close with only the two solutions above and nothing else. The problem "checkmate (7,1,0)" is also a close call, with 2 solutions in 3.5 moves,
 1. d3 e6 2. Qd2 e5 3. Qe3 Ke7 4. Qxe5#
 1. d3 e6 2. Qd2 Ke7 3. Qe3 e5 4. Qxe5#
 and nothing else.

     François

 On 29/08/16 06:12 AM, andrew buchanan wrote:

  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"

  #yiv1629342007 -- filtered {panose-1:2 4 5 3 5 4 6 3 2 4;}#yiv1629342007 filtered {font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;}#yiv1629342007 filtered {font-family:Consolas;panose-1:2 11 6 9 2 2 4 3 2 4;}#yiv1629342007 p.yiv1629342007MsoNormal, #yiv1629342007 li.yiv1629342007MsoNormal, #yiv1629342007 div.yiv1629342007MsoNormal {margin:0cm;margin-bottom:.0001pt;font-size:12.0pt;color:black;}#yiv1629342007 a:link, #yiv1629342007 span.yiv1629342007MsoHyperlink {color:blue;text-decoration:underline;}#yiv1629342007 a:visited, #yiv1629342007 span.yiv1629342007MsoHyperlinkFollowed {color:purple;text-decoration:underline;}#yiv1629342007 pre {margin:0cm;margin-bottom:.0001pt;font-size:10.0pt;color:black;}#yiv1629342007 span.yiv1629342007PrformatHTMLCar {color:black;}#yiv1629342007 span.yiv1629342007EmailStyle19 {color:#1F497D;}#yiv1629342007 .yiv1629342007MsoChpDefault {font-size:10.0pt;}#yiv1629342007 filtered {margin:70.85pt 70.85pt 70.85pt 70.85pt;}#yiv1629342007 div.yiv1629342007WordSection1 {}#yiv1629342007    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 just the right amount of information about the game (strait one-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.

     François  On 28/08/16 12:15 PM, Eric Angelini wrote:  
      The herunder game ending in checkmate    has the same length 4(1+SQR2) as   the "Black version" seen before:   1. e2 -- g5   2. Be2 -- f6   3. Bh5++   But this checkmate is not as fast as   the 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 for   printed 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 the   well known:   1.f3 -- e6   2.g4 -- Qh4++   ... but as the White moves can be   exchanged, this is not a unique   solution.
 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 unique   numbers "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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