# [Retros] rstan

Francois Labelle flab at wismuth.com
Fri Oct 4 14:46:56 EDT 2013

On 10/02/2013 09:14 PM, Andrew Buchanan wrote:

> Shorter again:

>

> 1. d4 ... 2. dxe5 ... 3. Qxd7+ ... 4. Qd6+ ... 5. Qd7+ ...

> then:

> 1004. Qc6 ... 1005. Qc4 ...#

C+ again. Here's the solution with 2.0 moves added to the shortest line:
1. d4 e5 2. dxe5 Ba3 3. Qxd7+ Kf8 4. Qd6+ Ke8 5. Qd7+ Kf8 6. Qc6 Qg5 7.
Qc4 Qxc1#

On 10/02/2013 08:53 PM, Richard Stanley wrote:

>

> One could also look at "half proof games" with various conditions. For

> instance, does there exist such a game that ends in mate by a pawn

> promoting to a knight? The moves of the side being mated are specified.

Interesting. We don't know the full potential of "half proof games" yet,
but right now I worry that the genre isn't well-defined. The problem is
what to do with the disambiguating moves in algebraic notation.

Take for example the white moves
1. Nf3 ... 2. Nd4 ... 3. Na3 ... 4. Ndb5 ...

We could take any of the following viewpoints:

a) Half proof games never use disambiguation. In the example we would
write "4. Nb5" and determining which knight moved would be part of the
problem.

b) Half proof games always use disambiguation. In the example we would
write "4. Ndb5" even if Black captured Na3 in move 3, so as not to give
information about whether Na3 was captured or not. In other words, all
the white moves are crystal clear as if we used long-hand notation
everywhere (1. Ng1-f3 ... 2. Nf3-d4 ... 3. Nb1-a3 ... 4. Nd4-b5 ...).

c) Half proof games use disambiguation according to algebraic notation
rules (
https://en.wikipedia.org/wiki/Algebraic_notation_%28chess%29#Disambiguating_moves
). In the example, writing "4. Ndb5" would imply that Black didn't
capture Na3, and writing "4. Nb5" would imply that Black captured either
Na3 or Nd4. In other words, a half proof game is obtained by taking the
solution as written in algebraic notation and blanking the hidden plies.

I wonder which viewpoint people think is best. So far the problems
people have posted aren't affected by this, but if the genre takes off,
someone is going to test those boundaries someday...

François