# [Retros] No (1+1) SPG at x=5

Francois Labelle flab at EECS.Berkeley.EDU
Thu Apr 1 15:17:18 EST 2004

Some of the computer-composed problems that I announced earlier appear in
Problemesis 38.

[R142a-b] vertical symmetry
[R143] at-home (most depleted)

The rest is delayed because of my desire to publish the best problem for

For the (1+1) SPGs, I want to investigate all the diagrams with few
solutions. There's a small chance I can find one with independent
solutions.

For the SPGs enabled by A1.3, I want to investigate if there are any with
more pieces on the board.

For the stalemate SPGs I'm torn, because Popeye solves the (7+3) one at
x=5 in 77 min, and the (4+1) one at x=4 in 12 min. So the latter might be
an easier problem, and it's theoretically more interesting (by being the
only stalemate SPG at x<=4), but of course its diagram is less furnished.

For the at-home AND mirror-symmetric SPGs, I thought it had nothing to do
with massacres and that there must be better examples of this task at low
plies.

So instead I published a task where massacre probably gives the best
example:

[R144] fullest at-home position with no pawns

A short note about computer testing: problems [R142] and [R144] have been
independently verified by Popeye. [R143] was computer created, but not
computer tested. Personally I think that the problem shouldn't be
considered C+, but Christian chose to publish it as C+. I wonder what's
the right thing to do in this case. For [R143] everything was done to a
very high standard, but I would like to have the right to be sloppy with
my programming in the future.

Joost de Heer wrote:

> Perhaps you can do something like Gerd Wilts and Norbert Geissler did

> with one of the 17.0 move 1+1-proofgames: 'Black captured on the second

> move. How did the game go?' [...] In this case it probably is something

> like 'Black's 9th move was with a bishop. How did the game go?'.

That would work, but it might be overkill. A condition like this can
probably be used to turn a problem with hundreds of solutions into a sound
one too. I need very very little. Even specifying that the 9th move was
from a light square might be too much. Let's see if I can find a good
multi-solution SPG first.

Francois