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Fairy-MaxA computer program . Free open source chess variant software.[All Comments] [Add Comment or Rating]
💡📝H. G. Muller wrote on Mon, Jan 11, 2010 05:46 PM UTC:
ShaMax and Fairy-Max use the same fmax.ini file, so the automatically play each other's variants. But the search engine of ShaMax is altered to score stalemated as a loss (actually by deleting the code that makes an exception for it and scores it as a draw), and score a bare opponent King as a win.

If I understood the description correctly, you would not need that for Makruk, and it might lead to some really stupid mistakes in the late end-game. (For the rest of the game you would not notice the difference.)

The promotion on 6th is a problem for Fairy-Max. The only way around this I see at the moment is that you would perform the promotion by hand, by using 'Edit Position' in stead of doing your move, or using Edit Position after Fary-Max' move. Pawns on 6th already get a bonus in Fairy-Max, so it might also strive for promotions and resist yours. The bonus is not very high, though: to have it play Shatranj better, I devide the bonuses for normal Chess that were originally hard-coded in the program by 8 if the value of the piece you promote to is less than 250. In Chess you get 64 for a Pawn on 6th, and 128 for a Pawn on 7th. So that would be reduced to 8 and 16, not very much. But in Shatranj (and presumably Makruk) a 'Queen' is of course hardly worth more than a Pawn. So it might not hurt too much, sacrificing a Pawn to make another promote is probably always wrong anyway, so a large bonus is not really needed.

The problem with using Edit Position is that WinBoard considers what you play afterwards as a new game, so you cannot save the entire game if you do that. If there is much interest, I could of course make a dedicated version of Fairy-Max for playing Makruk, which promotes at 6th rank, just like I made ShaMax for Shatranj (micro-Makrux?).

Fairy-Max is indeed an amazingly tough opponent, for an IA of only ~100 lines of code. I guess that tells you how powerful hardware is nowadays. Currently I am trying to have it play Chess with Different Armies. (The Color-bound Clobberers seem to lose pretty badly to the FIDE army, though; perhaps I should revise my piece values!)