[Retros] Proof games with loss of tempo

[Kevin Begley]

I'll second what Andrew has said -- congratulations Francois... PG b) is
quite remarkable!

In hindsight, I now realize that I had come in close contact with your very
idea, over a year ago -- but, from the perspective of a heterodox PG.

The chess pieces kept telling me there were rich temporizing possibilities
with Bc1xg5/h6, but focused to achieve a particular heterodox idea, I
remained completely deaf to the orthodox implications.

I never published what I did manage to achieve, because I had a strong
feeling something better was possible... I just never imagined that it
might be an orthodox PG.

Well done!


On Mon, Mar 19, 2012 at 9:31 AM, Andrew Buchanan <andrew at anselan.com> wrote:


> b) n=4.5: 1.d3 g5 2.Bxg5 h6 3.Bxh6 Rh7 4.Bg7 Rxg7 5.d4

> (b) has the additional property that the solution is unique in 3.0, 3.5,

> 4.0, and 4.5 moves, so that question is settled too. (Andrew Buchanan

> claimed to have a solution to that problem on

> http://anselan.com/STAsols.html but it might not have been shortest.)

>

> My heartiest congratulations! That's so much simpler than I could have

> thought possible. (Note: I didn't just *claim* to have a solution :) but

> mine was longer and had promoted force.)

>

> -----Original Message-----

> From: retros-bounces at janko.at [mailto:retros-bounces at janko.at] On Behalf

> Of

> Francois Labelle

> Sent: 19 March 2012 13:45

> To: retros at janko.at

> Subject: [Retros] Proof games with loss of tempo

>

> For each value of t, what is the smallest n with a PG that has

> a) a unique solution in n moves and some solution(s) in n - t moves?

> b) a unique solution in both n and n - t moves?

>

> Version (b) is harder and more "publishable", but (a) is also interesting

> from a mathematical point of view. Below are some results.

>

> The first two values of t are easy:

>

> t=0.5

> a,b) n=1.5: 8*20 = 160 combinations of a white pawn double-jump and any

> black move.

>

> t=1.0

> a,b) n=2.0: 8*8 = 64 combinations of a white pawn double-jump and a black

> pawn double-jump.

>

> Here are the results of a computer search up to 5.0 moves:

>

> t=1.5

> a) n=4.0: 1.g3 d6 2.g4 Bxg4 3.h3 Bf3 4.Nxf3 d5

> b) n=4.5: 1.d3 g5 2.Bxg5 h6 3.Bxh6 Rh7 4.Bg7 Rxg7 5.d4

> (b) has the additional property that the solution is unique in 3.0, 3.5,

> 4.0, and 4.5 moves, so that question is settled too. (Andrew Buchanan

> claimed to have a solution to that problem on

> http://anselan.com/STAsols.html but it might not have been shortest.)

>

> t=2.0 (impossible)

>

> t=2.5

> a,b) n=5.0: 1.d4 c5 2.Bf4 c4 3.Bc7 c3 4.Nxc3 Nf6 5.Nb1 Nd5 That problem was

> used in the Messigny 2011 retro solving competition

> http://www.pairlist.net/pipermail/retros/2011-June/003569.html .

>

> And here are current records that I could find on the Chess Problem

> Database:

>

> t=3.0

> a,b) n=10.0 (Michel Caillaud, 3074 Probleemblad 09/1996, 1st prize)

> http://www.softdecc.com/pdb/search.pdb?expression=PROBID=%27P0008478%27

>

> t=3.5 ?

>

> t=4.0 (impossible)

>

> t=4.5

> a,b) n=12.0 (Gerd Wilts, R226 Probleemblad 02/2004)

> http://www.softdecc.com/pdb/search.pdb?expression=PROBID=%27P1013079%27

>

> Any other result?

>

>        Francois

>

>

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