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cheeseonamonkey/ChessPositionAnalyzer.js

Created September 6, 2024 22:38
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ChessPositionAnalyzer.js
// Piece values
const piece = {
"P": 100,
"N": 280,
"B": 320,
"R": 479,
"Q": 929,
"K": 60000
};
// Piece-Square Tables (PSTs)
const pst = {
'P': [
0, 0, 0, 0, 0, 0, 0, 0,
78, 83, 86, 73, 102, 82, 85, 90,
7, 29, 21, 44, 40, 31, 44, 7,
-17, 16, -2, 15, 14, 0, 15, -13,
-26, 3, 10, 9, 6, 1, 0, -23,
-22, 9, 5, -11, -10, -2, 3, -19,
-31, 8, -7, -37, -36, -14, 3, -31,
0, 0, 0, 0, 0, 0, 0, 0
],
'N': [
-66, -53, -75, -75, -10, -55, -58, -70,
-3, -6, 100, -36, 4, 62, -4, -14,
10, 67, 1, 74, 73, 27, 62, -2,
24, 24, 45, 37, 33, 41, 25, 17,
-1, 5, 31, 21, 22, 35, 2, 0,
-18, 10, 13, 22, 18, 15, 11, -14,
-23, -15, 2, 0, 2, 0, -23, -20,
-74, -23, -26, -24, -19, -35, -22, -69
],
'B': [
-59, -78, -82, -76, -23, -107, -37, -50,
-11, 20, 35, -42, -39, 31, 2, -22,
-9, 39, -32, 41, 52, -10, 28, -14,
25, 17, 20, 34, 26, 25, 15, 10,
13, 10, 17, 23, 17, 16, 0, 7,
14, 25, 24, 15, 8, 25, 20, 15,
19, 20, 11, 6, 7, 6, 20, 16,
-7, 2, -15, -12, -14, -15, -10, -10
],
'R': [
35, 29, 33, 4, 37, 33, 56, 50,
55, 29, 56, 67, 55, 62, 34, 60,
19, 35, 28, 33, 45, 27, 25, 15,
0, 5, 16, 13, 18, -4, -9, -6,
-28, -35, -16, -21, -13, -29, -46, -30,
-42, -28, -42, -25, -25, -35, -26, -46,
-53, -38, -31, -26, -29, -43, -44, -53,
-30, -24, -18, 5, -2, -18, -31, -32
],
'Q': [
6, 1, -8, -104, 69, 24, 88, 26,
14, 32, 60, -10, 20, 76, 57, 24,
-2, 43, 32, 60, 72, 63, 43, 2,
1, -16, 22, 17, 25, 20, -13, -6,
-14, -15, -2, -5, -1, -10, -20, -22,
-30, -6, -13, -11, -16, -11, -16, -27,
-36, -18, 0, -19, -15, -15, -21, -38,
-39, -30, -31, -13, -31, -36, -34, -42
],
'K': [
4, 54, 47, -99, -99, 60, 83, -62,
-32, 10, 55, 56, 56, 55, 10, 3,
-62, 12, -57, 44, -67, 28, 37, -31,
-55, 50, 11, -4, -19, 13, 0, -49,
-55, -43, -52, -28, -51, -47, -8, -50,
-47, -42, -43, -79, -64, -32, -29, -32,
-4, 3, -14, -50, -57, -18, 13, 4,
17, 30, -3, -14, 6, -1, 40, 18
]
};
// Function to parse a FEN string and calculate the advantage
function calculateAdvantage(fen) {
const pieceValues = {
'P': piece['P'], 'N': piece['N'], 'B': piece['B'],
'R': piece['R'], 'Q': piece['Q'], 'K': piece['K'],
'p': piece['P'], 'n': piece['N'], 'b': piece['B'],
'r': piece['R'], 'q': piece['Q'], 'k': piece['K']
};
// Convert FEN to 8x8 board
const board = fen.split(' ')[0]
.split('/')
.map(row => row.replace(/(\d)/g, d => ' '.repeat(Number(d))) // Replace numbers with spaces
.split('')) // Split into characters
.flat(); // Flatten into a single array
let materialWhite = 0;
let materialBlack = 0;
let positionWhite = 0;
let positionBlack = 0;
for (let i = 0; i < board.length; i++) {
const square = board[i];
if (square !== ' ') {
const value = pieceValues[square];
const pstValue = getPstValue(square, i);
if (square === square.toUpperCase()) {
materialWhite += value;
positionWhite += pstValue;
} else {
materialBlack += value;
positionBlack += pstValue;
}
}
}
const materialAdvantage = materialWhite - materialBlack;
const positionAdvantage = positionWhite - positionBlack;
const combinedAdvantage = materialAdvantage + positionAdvantage;
return combinedAdvantage;
}
// Get PST value based on piece and position index
function getPstValue(piece, squareIndex) {
// Index adjustment for black pieces
const adjustedIndex = piece === piece.toUpperCase() ? squareIndex : 63 - squareIndex;
return pst[piece.toUpperCase()][adjustedIndex];
}
// Test FEN
const fen = 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1';
console.log(calculateAdvantage(fen));
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