The Peace-Chess Challenge

[hgm]

I some of the older rule descriptions (e.g. on the first kickstarter page) the huggig pairs were immobile, but the side that formed or mutated one would have the option to take it off the board, rather than keeping it around. This would allow the number of pieces to decrease. I don't kow why they changed the rules to moving the pairs, instead of deleting them.

I agree that the King seems quite defenseless under the current rules.

[Sven]

Is it allowed to move a non-pawn piece that hugs a pawn to an empty square on the opponent's first rank, where pawns usually are never located? I guess it is disallowed, but by which rule?

[hgm]

This is allowed, and Pawns also have a double push on the first rank.

[Arpad Rusz]

"Repeated moves: When the same move has been played by both players three times in a row with the same piece in the same position on the board, the players will automatically draw."

But there is nothing in the rules to avoid a cycle during a single move. There could be four solutions:
During a move it is forbidden
1) to move the same piece twice
2) to move on the same square twice with any piece
3) to move the same piece twice to a given square
4) to repeat positions

[hgm]

I met with the inventor today, and he was convinced it would be best to have no restrictions at all on the release chains. So you can for instance use two of your Rooks on the same rank (both hugging some opponent) as a 'conveyor belt' to transport a Queen sideways:
[d] q7/8/8/3r2r1/7K/8/8/8 w
Qa8-d5, Rd5-g5, Rg5-d5, Qd5-g5, Rg5-d5, Rd5-g5, Qg5xh4

For engines this would mean you would not need to search moves that would repeat an earlier position in the same chain, as these would be pointless detours.

I wrote a small JavaScript engine, using fractional plies, where a release move counts as 0.5 ply, and release chains that cannot be completed before the horizon score -INF. This prevents search explosions that could happen when the pair density gets high ('super-critical'), when you would not count release plies towards the depth at all. For the moment the engine plays almost randomly, (except when there is a King hug within the horizon), for lack of an evaluation to distinguish good and bad positions. All I have is centralization. Which is probably the wrong thing to do; I think it would be better to draw pieces to the opponent King. You would have to completely recalculate that every time a King moves, though.

We also discussed the issue of the poor King being so defenseless. One of the solutions he coined was to allow a King to embrace pieces, immobilizing the latter (so they cannot abduct the King to a place where it cannot survive).

[Arpad Rusz]

We also discussed the issue of the poor King being so defenseless. One of the solutions he coined was to allow a King to embrace pieces, immobilizing the latter (so they cannot abduct the King to a place where it cannot survive).

After the king embraces it becomes immune to all attacks because one cannot hug a union. Its hugging partner can be changed but the king survives. So if both kings manage to hug a piece the game is over.

I know that this is Peace-Chess but I feel that some mechanism of eliminating pieces from the board is missing.

"During a move it is forbidden to repeat positions" is a good practical rule not only for computers but also for human play. (You don't want to see your opponent switching two rooks 100 times before he decides to finish the move.)

[hgm]

After the king embraces it becomes immune to all attacks because one cannot hug a union. Its hugging partner can be changed but the king survives. So if both kings manage to hug a piece the game is over.

No, that is not how it works. You can move into a union, to release your own piece there, and hug the oppoent. So a union of the King would be just as sensitive to check as a lone King.

I know that this is Peace-Chess but I feel that some mechanism of eliminating pieces from the board is missing.

Perhaps you could allow paired pieces to disappear by stepping over the edge of the board. Then weak pieces can not so easily abduct stronger pieces.

(You don't want to see your opponent switching two rooks 100 times before he decides to finish the move.)

Why not? If his clock is running... You can drag out a move as long as you want, even without touching any pieces.

[Arpad Rusz]

Rule proposal:
If a piece finds a matching piece of the same kind their union have to be removed from the board. So Qq, Rr, Bb, Nn and Pp pairs never survive on the board. This also removes most of the annoying repetitions.

[hgm]

Interesting rule variation. I will mention it to the inventor.

I made a simple JavaScript engine, which plays a little bit better than random (I hope). I award it some points for moving a unit towards the opponent King (in proportion to the value of the piece). And for having a virtual attack on the King. I put up a demo page at http://hgm.nubati.net/paco . (Just the upper half of the page. I did not set up a server for it.)

[Arpad Rusz]

Thanks for the engine, it was a great fun to play with it! Probably there is no need even to change the rules.
There is a bug: the engine got into a perpetual cycle when tried to play a move. Its rook and queen were exchanging places forever (both of them hugging some other pieces).