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Goals and Step Functions

The third group of advisors is concerned with goals and regressed goals for this class of games.

vital:this measures dynamic progress by both players on their goals to eradicate some set of piece types. As a given goal becomes closer to achievement, exponentially more points are awarded to that player. In addition, if the number of such remaining pieces is below some threshold, the remaining pieces are considered vital, in which case any potential threats against them automatically become potent.

arrival-distance:this is a decreasing function of the abstract number of moves it would take a piece to move (i.e. without capturing) from its current square to a goal on an otherwise empty board, where this abstract number is based on the minimum distance to the destination plus the cost/difficulty of clearing the path. This applies only to destinations for which the game has a defined arrival-goal for a piece-type consistent with the piece, and succeeds separately for each way in which this is true.

promote-distance:for each target-piece that a piece could promote into (by the player's choice), this measures the value of achieving this promotion (using the other advisors), but reduces this value based on the difficulty of achieving this promotion, as discussed for arrival-distance above. The result is the maximum net value (to a player) of the discounted promotion options, or the minimum value if the opponent gets to promote the piece instead.

init-promote:This applies in a position where a player is about to promote the opponent's piece (on some square) before making a normal move. For each promoting-option defined for that piece, this calculates the value that option would have on the given square in the current position. The value returned is the maximum of the values of the options, from the perspective of the promoting player (and thus the minimum from the perspective of the player who owned the piece originally).