squareTableEval.go

package buba

import "github.com/notnil/chess"

var pawnSquareTable = []float64{
	0, 0, 0, 0, 0, 0, 0, 0,
	50, 50, 50, 50, 50, 50, 50, 50,
	10, 10, 20, 30, 30, 20, 10, 10,
	5, 5, 10, 25, 25, 10, 5, 5,
	0, 0, 0, 20, 20, 0, 0, 0,
	5, -5, -10, 0, 0, -10, -5, 5,
	5, 10, 10, -20, -20, 10, 10, 5,
	0, 0, 0, 0, 0, 0, 0, 0,
}

var knightSquareTable = []float64{
	-50, -40, -30, -30, -30, -30, -40, -50,
	-40, -20, 0, 0, 0, 0, -20, -40,
	-30, 0, 10, 15, 15, 10, 0, -30,
	-30, 5, 15, 20, 20, 15, 5, -30,
	-30, 0, 15, 20, 20, 15, 0, -30,
	-30, 5, 10, 15, 15, 10, 5, -30,
	-40, -20, 0, 5, 5, 0, -20, -40,
	-50, -40, -30, -30, -30, -30, -40, -50,
}

var bishopSquareTable = []float64{
	-20, -10, -10, -10, -10, -10, -10, -20,
	-10, 0, 0, 0, 0, 0, 0, -10,
	-10, 0, 5, 10, 10, 5, 0, -10,
	-10, 5, 5, 10, 10, 5, 5, -10,
	-10, 0, 10, 10, 10, 10, 0, -10,
	-10, 10, 10, 10, 10, 10, 10, -10,
	-10, 5, 0, 0, 0, 0, 5, -10,
	-20, -10, -10, -10, -10, -10, -10, -20,
}

var rookSquareTable = []float64{
	0, 0, 0, 0, 0, 0, 0, 0,
	5, 10, 10, 10, 10, 10, 10, 5,
	-5, 0, 0, 0, 0, 0, 0, -5,
	-5, 0, 0, 0, 0, 0, 0, -5,
	-5, 0, 0, 0, 0, 0, 0, -5,
	-5, 0, 0, 0, 0, 0, 0, -5,
	-5, 0, 0, 0, 0, 0, 0, -5,
	0, 0, 0, 5, 5, 0, 0, 0,
}

var queenSquareTable = []float64{
	-20, -10, -10, -5, -5, -10, -10, -20,
	-10, 0, 0, 0, 0, 0, 0, -10,
	-10, 0, 5, 5, 5, 5, 0, -10,
	-5, 0, 5, 5, 5, 5, 0, -5,
	0, 0, 5, 5, 5, 5, 0, -5,
	-10, 5, 5, 5, 5, 5, 0, -10,
	-10, 0, 5, 0, 0, 0, 0, -10,
	-20, -10, -10, -5, -5, -10, -10, -20,
}

var kingMiddleGameSquareTable = []float64{
	-30, -40, -40, -50, -50, -40, -40, -30,
	-30, -40, -40, -50, -50, -40, -40, -30,
	-30, -40, -40, -50, -50, -40, -40, -30,
	-30, -40, -40, -50, -50, -40, -40, -30,
	-20, -30, -30, -40, -40, -30, -30, -20,
	-10, -20, -20, -20, -20, -20, -20, -10,
	20, 20, 0, 0, 0, 0, 20, 20,
	20, 30, 10, 0, 0, 10, 30, 20,
}

var kingEndGameSquareTable = []float64{
	-50, -40, -30, -20, -20, -30, -40, -50,
	-30, -20, -10, 0, 0, -10, -20, -30,
	-30, -10, 20, 30, 30, 20, -10, -30,
	-30, -10, 30, 40, 40, 30, -10, -30,
	-30, -10, 30, 40, 40, 30, -10, -30,
	-30, -10, 20, 30, 30, 20, -10, -30,
	-30, -30, 0, 0, 0, 0, -30, -30,
	-50, -30, -30, -30, -30, -30, -30, -50,
}

func squareTableEval(pt chess.PieceType, c chess.Color, s chess.Square, isEndGame bool) float64 {
	color_inv := -1.0 // black

	if c == chess.White {
		s = 63 - s // reverse squareTable, 63 is MAX_SQUARE_TABLE_INDEX
		color_inv = 1.0
	}

	switch pt {
	case chess.Pawn:
		return pawnSquareTable[s] * color_inv
	case chess.Knight:
		return knightSquareTable[s] * color_inv
	case chess.Bishop:
		return bishopSquareTable[s] * color_inv
	case chess.Rook:
		return rookSquareTable[s] * color_inv
	case chess.Queen:
		return queenSquareTable[s] * color_inv
	case chess.King:
		if isEndGame {
			return kingEndGameSquareTable[s] * color_inv
		}
		return kingMiddleGameSquareTable[s] * color_inv
	default:
		return 0
	}
}