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piece square evaluation

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Moritz Eigenauer 2025-11-18 11:44:36 +01:00
parent 4a8e1ce52c
commit 32be42e283
5 changed files with 248 additions and 15 deletions
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84
src/eval/basic.rs
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@ -1,18 +1,74 @@
use crate::board::{Board, Color, PieceType};
use crate::board::*;
use crate::eval::piece_square_tables::PSQT;
// Pawn, Knight, Bishop, Rook, Queen
pub const MATERIAL_WEIGHTS: [i32; 5] = [100, 300, 300, 500, 900];
pub const PHASE_WEIGHTS: [i32; 5] = [0, 1, 1, 2, 4];
pub fn evaluate_board(board: &Board) -> i32 {
let mut score = 0_i32;
score += board.pieces[PieceType::Pawn as usize][Color::White as usize].count_ones() as i32 * 100;
score += board.pieces[PieceType::Knight as usize][Color::White as usize].count_ones() as i32 * 300;
score += board.pieces[PieceType::Bishop as usize][Color::White as usize].count_ones() as i32 * 300;
score += board.pieces[PieceType::Rook as usize][Color::White as usize].count_ones() as i32 * 500;
score += board.pieces[PieceType::Queen as usize][Color::White as usize].count_ones() as i32 * 900;
let mut mg_score = 0_i32;
let mut eg_score = 0_i32;
let mut phase = 0_i32;
score -= board.pieces[PieceType::Pawn as usize][Color::Black as usize].count_ones() as i32 * 100;
score -= board.pieces[PieceType::Knight as usize][Color::Black as usize].count_ones() as i32 * 300;
score -= board.pieces[PieceType::Bishop as usize][Color::Black as usize].count_ones() as i32 * 300;
score -= board.pieces[PieceType::Rook as usize][Color::Black as usize].count_ones() as i32 * 500;
score -= board.pieces[PieceType::Queen as usize][Color::Black as usize].count_ones() as i32 * 900;
// --- WHITE PIECES ---
// Iterating Pawn (0) to Queen (4) for Material + Phase + PSQT
for pt in 0..5 {
let mut pieces = board.pieces[pt][Color::White as usize];
let count = pieces.count_ones() as i32;
mg_score += count * MATERIAL_WEIGHTS[pt];
eg_score += count * MATERIAL_WEIGHTS[pt];
phase += count * PHASE_WEIGHTS[pt];
score
}
while pieces > 0 {
let sq = pieces.trailing_zeros() as usize;
pieces &= pieces - 1; // Clear LS1B
// Access: [Piece][Color][Phase (0=MG, 1=EG)][Square]
mg_score += PSQT[pt][Color::White as usize][0][sq];
eg_score += PSQT[pt][Color::White as usize][1][sq];
}
}
// King (Index 5) - No Material/Phase weight, only PSQT
let mut white_king = board.pieces[5][Color::White as usize];
if white_king > 0 {
let sq = white_king.trailing_zeros() as usize;
mg_score += PSQT[5][Color::White as usize][0][sq];
eg_score += PSQT[5][Color::White as usize][1][sq];
}
// --- BLACK PIECES ---
// Iterating Pawn (0) to Queen (4)
for pt in 0..5 {
let mut pieces = board.pieces[pt][Color::Black as usize];
let count = pieces.count_ones() as i32;
mg_score -= count * MATERIAL_WEIGHTS[pt];
eg_score -= count * MATERIAL_WEIGHTS[pt];
phase += count * PHASE_WEIGHTS[pt];
while pieces > 0 {
let sq = pieces.trailing_zeros() as usize;
pieces &= pieces - 1;
mg_score -= PSQT[pt][Color::Black as usize][0][sq];
eg_score -= PSQT[pt][Color::Black as usize][1][sq];
}
}
// King (Index 5) for Black
let mut black_king = board.pieces[5][Color::Black as usize];
if black_king > 0 {
let sq = black_king.trailing_zeros() as usize;
mg_score -= PSQT[5][Color::Black as usize][0][sq];
eg_score -= PSQT[5][Color::Black as usize][1][sq];
}
// Tapered Evaluation Interpolation
let phase = phase.min(24); // Clamp to 24 max
let mg_phase = phase;
let eg_phase = 24 - phase;
((mg_score * mg_phase) + (eg_score * eg_phase)) / 24
}