[Retros] Two-pawns chess

[Francois Labelle]

On 09/15/2012 07:04 AM, Nicolas Dupont wrote:

>> I don't see where the discussion about the 'checks' comes from. I think

>> Eric was clear about the rules. I quote: 'orthodox rules + just one

>> unorthodox rule: if your opponent captures a second pawn (of yours), you

>> have lost the game.'

>

> The sentence "you have lost the game" certainly makes sense for an otb 

> player but, as a problemist, I don't know what it means!

>

> So, in my humble opinion, "you have lost the game" should be changed 

> in "you are checkmated", if one wants to define "N-pawns chess" as a 

> fairy condition.

I don't see what change this makes. Both checkmate and the capture of 
the one's Nth pawn are terminating conditions. Note that in chess, there 
is no rule saying that players must prevent a mate-in-1, so I don't see 
why many people think it's natural to prevent the "capture of my Nth 
pawn in 1". Sure, you can add such a rule if you want, but this should 
be called "the Nth pawn is royal" -- that rule doesn't follow from 
Eric's description any more than it follows from orthodox chess rules 
that we should play "no mate-in-1 chess".

By the way I've just programmed the following interpretation of Eric's idea:
  - players win by either checkmating or by capturing N pawns,
  - moves must be orthodox-legal, i.e. players can't capture the Nth 
pawn by putting (or leaving) their own king in check,
  - promoting a pawn makes it no longer a target.

For N=1, White wins in 3 moves and 1.c3 and 1.c4 are the only winning 
moves (congrats Pascal!)
For N=2, all I know is that White has no win in 6 moves. I'll see if I 
can analyze more moves.

My program is slow because my chess engine was not designed for 
directmate (it has no transposition table). If someone is interested in 
a computer analysis, it would probably be better to add the condition to 
Popeye and run that.

     Francois