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Merged
FitzOReilly merged 1 commit into from
Feb 7, 2026
Merged

Refactor evaluation of piece square tables #234

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12 changes: 8 additions & 4 deletions eval/src/hand_crafted_eval.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -209,8 +209,11 @@ impl HandCraftedEval {
fn add_pst(&mut self, p: Piece, square: Square, diff: i8) {
let pst = PIECE_TABLE_REFS[p.piece_type().idx()].pst;
match p.piece_side() {
Side::White => self.pst_scores += diff as Score * pst[square.idx()],
Side::Black => self.pst_scores -= diff as Score * pst[square.flip_vertical().idx()],
Side::White => self.pst_scores += diff as Score * pst[square.fold_to_queenside().idx()],
Side::Black => {
self.pst_scores -=
diff as Score * pst[square.flip_vertical().fold_to_queenside().idx()]
}
}
#[cfg(feature = "trace")]
self.coeffs.add_pst(p, square, diff);
Expand Down Expand Up @@ -347,7 +350,7 @@ impl HandCraftedEval {
);
while white_passed != Bitboard::EMPTY {
let square = white_passed.square_scan_forward_reset();
self.passed_pawn_scores += params::PASSED_PAWN[square.idx()];
self.passed_pawn_scores += params::PASSED_PAWN[square.fold_to_queenside().idx()];
self.passed_pawn_scores += params::PASSED_PAWN_RELATIVE_TO_FRIENDLY_KING
[(OFFSET_RELATIVE_TO_KING
+ square.relative_to(eval_data.kings[Side::White as usize]))
Expand Down Expand Up @@ -382,7 +385,8 @@ impl HandCraftedEval {
);
while black_passed != Bitboard::EMPTY {
let square = black_passed.square_scan_forward_reset();
self.passed_pawn_scores -= params::PASSED_PAWN[square.flip_vertical().idx()];
self.passed_pawn_scores -=
params::PASSED_PAWN[square.flip_vertical().fold_to_queenside().idx()];
self.passed_pawn_scores -= params::PASSED_PAWN_RELATIVE_TO_FRIENDLY_KING
[(OFFSET_RELATIVE_TO_KING
+ square
Expand Down
169 changes: 56 additions & 113 deletions eval/src/params.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,12 @@ use movegen::{file::File, rank::Rank, square::Square};

use crate::{score_pair::ScorePair, Score};

pub type PieceSquareTable = [ScorePair; 64];
// Piece square tables:
// We use symmetrical PSTs, so we only define values for half the board. Squares
// on the kingside (right side) will be mirrored to the queenside (left side)
// during evaluation.
const PST_LEN: usize = 32;
pub type PieceSquareTable = [ScorePair; PST_LEN];

pub const KNIGHT_MOB_LEN: usize = 9;
pub const BISHOP_MOB_LEN: usize = 14;
Expand All @@ -27,7 +32,7 @@ const MATERIAL_PAWN: ScorePair = ScorePair(0, 0);
pub const TEMPO: ScorePair = ScorePair(29, 29);

#[rustfmt::skip]
const PASSED_PAWN_MG_EG: ([Score; 32], [Score; 32]) = (
const PASSED_PAWN_MG_EG: ([Score; PST_LEN], [Score; PST_LEN]) = (
[
0, 0, 0, 0,
0, 0, 0, 0,
Expand Down Expand Up @@ -329,11 +334,8 @@ const PASSED_PAWN_RELATIVE_TO_ENEMY_KING_MG_EG: (
],
);

// Piece square tables:
// We only define values for the queenside (left side) and mirror them to the
// kingside (right side) so that we end up with symmetrical PSTs.
#[rustfmt::skip]
const PST_PAWN_MG_EG: ([Score; 32], [Score; 32]) = (
const PST_PAWN_MG_EG: ([Score; PST_LEN], [Score; PST_LEN]) = (
[
0, 0, 0, 0,
111, 153, 152, 164,
Expand All @@ -356,7 +358,7 @@ const PST_PAWN_MG_EG: ([Score; 32], [Score; 32]) = (
],
);
#[rustfmt::skip]
const PST_KNIGHT_MG_EG: ([Score; 32], [Score; 32]) = (
const PST_KNIGHT_MG_EG: ([Score; PST_LEN], [Score; PST_LEN]) = (
[
185, 278, 255, 307,
300, 294, 398, 325,
Expand All @@ -379,7 +381,7 @@ const PST_KNIGHT_MG_EG: ([Score; 32], [Score; 32]) = (
],
);
#[rustfmt::skip]
const PST_BISHOP_MG_EG: ([Score; 32], [Score; 32]) = (
const PST_BISHOP_MG_EG: ([Score; PST_LEN], [Score; PST_LEN]) = (
[
303, 309, 292, 252,
296, 356, 337, 342,
Expand All @@ -402,7 +404,7 @@ const PST_BISHOP_MG_EG: ([Score; 32], [Score; 32]) = (
],
);
#[rustfmt::skip]
const PST_ROOK_MG_EG: ([Score; 32], [Score; 32]) = (
const PST_ROOK_MG_EG: ([Score; PST_LEN], [Score; PST_LEN]) = (
[
540, 567, 560, 560,
564, 539, 560, 550,
Expand All @@ -425,7 +427,7 @@ const PST_ROOK_MG_EG: ([Score; 32], [Score; 32]) = (
],
);
#[rustfmt::skip]
const PST_QUEEN_MG_EG: ([Score; 32], [Score; 32]) = (
const PST_QUEEN_MG_EG: ([Score; PST_LEN], [Score; PST_LEN]) = (
[
958, 968, 965, 987,
983, 957, 946, 883,
Expand All @@ -448,7 +450,7 @@ const PST_QUEEN_MG_EG: ([Score; 32], [Score; 32]) = (
],
);
#[rustfmt::skip]
const PST_KING_MG_EG: ([Score; 32], [Score; 32]) = (
const PST_KING_MG_EG: ([Score; PST_LEN], [Score; PST_LEN]) = (
[
15, 8, 33, 5,
-13, 3, 35, -1,
Expand All @@ -471,21 +473,37 @@ const PST_KING_MG_EG: ([Score; 32], [Score; 32]) = (
],
);

const fn human_readable_to_file_rank(piece_value: Score, pst: [Score; 32]) -> [Score; 64] {
let mut res = [0; 64];
const fn human_readable_to_file_rank(
material_value: Score,
pst: [Score; PST_LEN],
) -> [Score; PST_LEN] {
let mut res = [0; PST_LEN];
let mut idx = 0;
while idx < 32 {
while idx < PST_LEN {
let rank = 7 - idx / 4;
let file = idx % 4;
let new_idx = Square::from_file_and_rank(File::from_idx(file), Rank::from_idx(rank)).idx();
let mirrored_idx = Square::from_idx(new_idx).mirror_horizontal().idx();
res[new_idx] = piece_value + pst[idx];
res[mirrored_idx] = piece_value + pst[idx];
res[new_idx] = material_value + pst[idx];
idx += 1;
}
res
}

const fn convert_pst(
material_value: ScorePair,
mg_eg: ([Score; PST_LEN], [Score; PST_LEN]),
) -> PieceSquareTable {
let mg = human_readable_to_file_rank(material_value.0, mg_eg.0);
let eg = human_readable_to_file_rank(material_value.1, mg_eg.1);
let mut table = [ScorePair(0, 0); PST_LEN];
let mut idx = 0;
while idx < PST_LEN {
table[idx] = ScorePair(mg[idx], eg[idx]);
idx += 1;
}
table
}

const fn convert_square_relative_to(
mg_eg: (
[Score; PIECE_RELATIVE_TO_KING_LEN],
Expand Down Expand Up @@ -594,89 +612,14 @@ pub const PASSED_PAWN_RELATIVE_TO_FRIENDLY_KING: [ScorePair; PASSED_PAWNS_RELATI
pub const PASSED_PAWN_RELATIVE_TO_ENEMY_KING: [ScorePair; PASSED_PAWNS_RELATIVE_TO_KING_LEN] =
convert_passed_pawn_relative_to(PASSED_PAWN_RELATIVE_TO_ENEMY_KING_MG_EG);

pub const PASSED_PAWN: PieceSquareTable = {
let mg = human_readable_to_file_rank(0, PASSED_PAWN_MG_EG.0);
let eg = human_readable_to_file_rank(0, PASSED_PAWN_MG_EG.1);
let mut table = [ScorePair(0, 0); 64];
let mut idx = 0;
while idx < 64 {
table[idx] = ScorePair(mg[idx], eg[idx]);
idx += 1;
}
table
};

pub const PST_PAWN: PieceSquareTable = {
let mg = human_readable_to_file_rank(MATERIAL_PAWN.0, PST_PAWN_MG_EG.0);
let eg = human_readable_to_file_rank(MATERIAL_PAWN.1, PST_PAWN_MG_EG.1);
let mut table = [ScorePair(0, 0); 64];
let mut idx = 0;
while idx < 64 {
table[idx] = ScorePair(mg[idx], eg[idx]);
idx += 1;
}
table
};

pub const PST_KNIGHT: PieceSquareTable = {
let mg = human_readable_to_file_rank(MATERIAL_KNIGHT.0, PST_KNIGHT_MG_EG.0);
let eg = human_readable_to_file_rank(MATERIAL_KNIGHT.1, PST_KNIGHT_MG_EG.1);
let mut table = [ScorePair(0, 0); 64];
let mut idx = 0;
while idx < 64 {
table[idx] = ScorePair(mg[idx], eg[idx]);
idx += 1;
}
table
};

pub const PST_BISHOP: PieceSquareTable = {
let mg = human_readable_to_file_rank(MATERIAL_BISHOP.0, PST_BISHOP_MG_EG.0);
let eg = human_readable_to_file_rank(MATERIAL_BISHOP.1, PST_BISHOP_MG_EG.1);
let mut table = [ScorePair(0, 0); 64];
let mut idx = 0;
while idx < 64 {
table[idx] = ScorePair(mg[idx], eg[idx]);
idx += 1;
}
table
};

pub const PST_ROOK: PieceSquareTable = {
let mg = human_readable_to_file_rank(MATERIAL_ROOK.0, PST_ROOK_MG_EG.0);
let eg = human_readable_to_file_rank(MATERIAL_ROOK.1, PST_ROOK_MG_EG.1);
let mut table = [ScorePair(0, 0); 64];
let mut idx = 0;
while idx < 64 {
table[idx] = ScorePair(mg[idx], eg[idx]);
idx += 1;
}
table
};

pub const PST_QUEEN: PieceSquareTable = {
let mg = human_readable_to_file_rank(MATERIAL_QUEEN.0, PST_QUEEN_MG_EG.0);
let eg = human_readable_to_file_rank(MATERIAL_QUEEN.1, PST_QUEEN_MG_EG.1);
let mut table = [ScorePair(0, 0); 64];
let mut idx = 0;
while idx < 64 {
table[idx] = ScorePair(mg[idx], eg[idx]);
idx += 1;
}
table
};
pub const PASSED_PAWN: PieceSquareTable = convert_pst(ScorePair(0, 0), PASSED_PAWN_MG_EG);

pub const PST_KING: PieceSquareTable = {
let mg = human_readable_to_file_rank(MATERIAL_KING.0, PST_KING_MG_EG.0);
let eg = human_readable_to_file_rank(MATERIAL_KING.1, PST_KING_MG_EG.1);
let mut table = [ScorePair(0, 0); 64];
let mut idx = 0;
while idx < 64 {
table[idx] = ScorePair(mg[idx], eg[idx]);
idx += 1;
}
table
};
pub const PST_PAWN: PieceSquareTable = convert_pst(MATERIAL_PAWN, PST_PAWN_MG_EG);
pub const PST_KNIGHT: PieceSquareTable = convert_pst(MATERIAL_KNIGHT, PST_KNIGHT_MG_EG);
pub const PST_BISHOP: PieceSquareTable = convert_pst(MATERIAL_BISHOP, PST_BISHOP_MG_EG);
pub const PST_ROOK: PieceSquareTable = convert_pst(MATERIAL_ROOK, PST_ROOK_MG_EG);
pub const PST_QUEEN: PieceSquareTable = convert_pst(MATERIAL_QUEEN, PST_QUEEN_MG_EG);
pub const PST_KING: PieceSquareTable = convert_pst(MATERIAL_KING, PST_KING_MG_EG);

#[cfg(test)]
mod tests {
Expand All @@ -697,19 +640,19 @@ mod tests {
];

let res = super::human_readable_to_file_rank(100, arr);
assert_eq!(156, res[Square::A1.idx()]);
assert_eq!(148, res[Square::A2.idx()]);
assert_eq!(100, res[Square::A8.idx()]);
assert_eq!(157, res[Square::B1.idx()]);
assert_eq!(149, res[Square::B2.idx()]);
assert_eq!(142, res[Square::C3.idx()]);
assert_eq!(135, res[Square::D4.idx()]);
assert_eq!(127, res[Square::E5.idx()]);
assert_eq!(118, res[Square::F6.idx()]);
assert_eq!(109, res[Square::G7.idx()]);
assert_eq!(101, res[Square::G8.idx()]);
assert_eq!(156, res[Square::H1.idx()]);
assert_eq!(108, res[Square::H7.idx()]);
assert_eq!(100, res[Square::H8.idx()]);
assert_eq!(156, res[Square::A1.fold_to_queenside().idx()]);
assert_eq!(148, res[Square::A2.fold_to_queenside().idx()]);
assert_eq!(100, res[Square::A8.fold_to_queenside().idx()]);
assert_eq!(157, res[Square::B1.fold_to_queenside().idx()]);
assert_eq!(149, res[Square::B2.fold_to_queenside().idx()]);
assert_eq!(142, res[Square::C3.fold_to_queenside().idx()]);
assert_eq!(135, res[Square::D4.fold_to_queenside().idx()]);
assert_eq!(127, res[Square::E5.fold_to_queenside().idx()]);
assert_eq!(118, res[Square::F6.fold_to_queenside().idx()]);
assert_eq!(109, res[Square::G7.fold_to_queenside().idx()]);
assert_eq!(101, res[Square::G8.fold_to_queenside().idx()]);
assert_eq!(156, res[Square::H1.fold_to_queenside().idx()]);
assert_eq!(108, res[Square::H7.fold_to_queenside().idx()]);
assert_eq!(100, res[Square::H8.fold_to_queenside().idx()]);
}
}