Skip to content

Evaluate passed pawns based on their square relative to the kings #233

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
FitzOReilly merged 2 commits into from
Jan 30, 2026
Merged

Evaluate passed pawns based on their square relative to the kings #233

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
525cf2d
Evaluate passed pawns relative to kings
FitzOReilly Jan 29, 2026
d578de1
Update tuned params
FitzOReilly Jan 29, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
78 changes: 66 additions & 12 deletions eval/src/hand_crafted_eval.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -256,24 +256,24 @@ impl HandCraftedEval {
match p.piece_side() {
Side::White => {
self.squares_relative_to_king += diff as Score
* piece_table.square_relative_to_friendly_king
* piece_table.piece_relative_to_friendly_king
[(OFFSET + square.relative_to(kings[Side::White as usize])) as usize];
self.squares_relative_to_king -= diff as Score
* piece_table.square_relative_to_enemy_king[(OFFSET
* piece_table.piece_relative_to_enemy_king[(OFFSET
+ square
.flip_vertical()
.relative_to(kings[Side::Black as usize].flip_vertical()))
as usize];
}
Side::Black => {
self.squares_relative_to_king -= diff as Score
* piece_table.square_relative_to_friendly_king[(OFFSET
* piece_table.piece_relative_to_friendly_king[(OFFSET
+ square
.flip_vertical()
.relative_to(kings[Side::Black as usize].flip_vertical()))
as usize];
self.squares_relative_to_king += diff as Score
* piece_table.square_relative_to_enemy_king
* piece_table.piece_relative_to_enemy_king
[(OFFSET + square.relative_to(kings[Side::White as usize])) as usize];
}
}
Expand Down Expand Up @@ -328,33 +328,87 @@ impl HandCraftedEval {

fn update_passed_pawn_scores(&mut self, eval_data: &EvalData) {
#[cfg(feature = "trace")]
self.coeffs.passed_pawn.fill(Coeff(0));
{
self.coeffs.passed_pawn.fill(Coeff(0));
self.coeffs
.passed_pawn_relative_to_friendly_king
.fill(Coeff(0));
self.coeffs
.passed_pawn_relative_to_enemy_king
.fill(Coeff(0));
}

const OFFSET_RELATIVE_TO_KING: i8 = ((Rank::NUM_RANKS - 2) * File::NUM_FILES) as i8;
self.passed_pawn_scores = ScorePair(0, 0);
// Ignore the rank just before promotion (7th for white, 2nd for black).
// Pawns on these ranks are always passed, so they are already
// considered by the pawn PSTs.
let mut white_passed = Self::passed_pawns_one_side(
eval_data.pawns[Side::White as usize],
eval_data.pawns[Side::Black as usize],
Side::White,
) & !Bitboard::RANK_7;
);
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_RELATIVE_TO_FRIENDLY_KING
[(OFFSET_RELATIVE_TO_KING
+ square.relative_to(eval_data.kings[Side::White as usize]))
as usize];
self.passed_pawn_scores -= params::PASSED_PAWN_RELATIVE_TO_ENEMY_KING
[(OFFSET_RELATIVE_TO_KING
+ square
.flip_vertical()
.relative_to(eval_data.kings[Side::Black as usize].flip_vertical()))
as usize];
#[cfg(feature = "trace")]
(*self.coeffs.passed_pawn[square.fold_to_queenside().idx()] += 1);
{
// White pawns on the 7th rank are always passed, so they are
// already considered by the pawn PSTs.
if square.rank() != Rank::R7 {
*self.coeffs.passed_pawn[square.fold_to_queenside().idx()] += 1;
}
*self.coeffs.passed_pawn_relative_to_friendly_king[(OFFSET_RELATIVE_TO_KING
+ square.relative_to(eval_data.kings[Side::White as usize]))
as usize] += 1;
*self.coeffs.passed_pawn_relative_to_enemy_king[(OFFSET_RELATIVE_TO_KING
+ square
.flip_vertical()
.relative_to(eval_data.kings[Side::Black as usize].flip_vertical()))
as usize] -= 1;
}
}
let mut black_passed = Self::passed_pawns_one_side(
eval_data.pawns[Side::Black as usize],
eval_data.pawns[Side::White as usize],
Side::Black,
) & !Bitboard::RANK_2;
);
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_RELATIVE_TO_FRIENDLY_KING
[(OFFSET_RELATIVE_TO_KING
+ square
.flip_vertical()
.relative_to(eval_data.kings[Side::Black as usize].flip_vertical()))
as usize];
self.passed_pawn_scores += params::PASSED_PAWN_RELATIVE_TO_ENEMY_KING
[(OFFSET_RELATIVE_TO_KING
+ square.relative_to(eval_data.kings[Side::White as usize]))
as usize];
#[cfg(feature = "trace")]
(*self.coeffs.passed_pawn[square.flip_vertical().fold_to_queenside().idx()] -= 1);
{
// Black pawns on the 2nd rank are always passed, so they are
// already considered by the pawn PSTs.
if square.rank() != Rank::R2 {
*self.coeffs.passed_pawn[square.flip_vertical().fold_to_queenside().idx()] -= 1;
}
*self.coeffs.passed_pawn_relative_to_friendly_king[(OFFSET_RELATIVE_TO_KING
+ square
.flip_vertical()
.relative_to(eval_data.kings[Side::Black as usize].flip_vertical()))
as usize] -= 1;
*self.coeffs.passed_pawn_relative_to_enemy_king[(OFFSET_RELATIVE_TO_KING
+ square.relative_to(eval_data.kings[Side::White as usize]))
as usize] += 1;
}
}
}

Expand Down
75 changes: 38 additions & 37 deletions eval/src/hand_crafted_eval_coeffs.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -61,16 +61,18 @@ pub struct HandCraftedEvalCoeffs {
pub rook_mobility: [Coeff; params::ROOK_MOB_LEN],
pub queen_mobility: [Coeff; params::QUEEN_MOB_LEN],
pub bishop_pair: Coeff,
pub pawn_square_relative_to_friendly_king: [Coeff; params::SQUARE_RELATIVE_TO_KING_LEN],
pub pawn_square_relative_to_enemy_king: [Coeff; params::SQUARE_RELATIVE_TO_KING_LEN],
pub knight_square_relative_to_friendly_king: [Coeff; params::SQUARE_RELATIVE_TO_KING_LEN],
pub knight_square_relative_to_enemy_king: [Coeff; params::SQUARE_RELATIVE_TO_KING_LEN],
pub bishop_square_relative_to_friendly_king: [Coeff; params::SQUARE_RELATIVE_TO_KING_LEN],
pub bishop_square_relative_to_enemy_king: [Coeff; params::SQUARE_RELATIVE_TO_KING_LEN],
pub rook_square_relative_to_friendly_king: [Coeff; params::SQUARE_RELATIVE_TO_KING_LEN],
pub rook_square_relative_to_enemy_king: [Coeff; params::SQUARE_RELATIVE_TO_KING_LEN],
pub queen_square_relative_to_friendly_king: [Coeff; params::SQUARE_RELATIVE_TO_KING_LEN],
pub queen_square_relative_to_enemy_king: [Coeff; params::SQUARE_RELATIVE_TO_KING_LEN],
pub pawn_square_relative_to_friendly_king: [Coeff; params::PIECE_RELATIVE_TO_KING_LEN],
pub pawn_square_relative_to_enemy_king: [Coeff; params::PIECE_RELATIVE_TO_KING_LEN],
pub knight_square_relative_to_friendly_king: [Coeff; params::PIECE_RELATIVE_TO_KING_LEN],
pub knight_square_relative_to_enemy_king: [Coeff; params::PIECE_RELATIVE_TO_KING_LEN],
pub bishop_square_relative_to_friendly_king: [Coeff; params::PIECE_RELATIVE_TO_KING_LEN],
pub bishop_square_relative_to_enemy_king: [Coeff; params::PIECE_RELATIVE_TO_KING_LEN],
pub rook_square_relative_to_friendly_king: [Coeff; params::PIECE_RELATIVE_TO_KING_LEN],
pub rook_square_relative_to_enemy_king: [Coeff; params::PIECE_RELATIVE_TO_KING_LEN],
pub queen_square_relative_to_friendly_king: [Coeff; params::PIECE_RELATIVE_TO_KING_LEN],
pub queen_square_relative_to_enemy_king: [Coeff; params::PIECE_RELATIVE_TO_KING_LEN],
pub passed_pawn_relative_to_friendly_king: [Coeff; params::PASSED_PAWNS_RELATIVE_TO_KING_LEN],
pub passed_pawn_relative_to_enemy_king: [Coeff; params::PASSED_PAWNS_RELATIVE_TO_KING_LEN],
}

impl Default for HandCraftedEvalCoeffs {
Expand All @@ -93,18 +95,20 @@ impl Default for HandCraftedEvalCoeffs {
rook_mobility: Default::default(),
queen_mobility: Default::default(),
bishop_pair: Default::default(),
pawn_square_relative_to_friendly_king: [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN],
pawn_square_relative_to_enemy_king: [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN],
knight_square_relative_to_friendly_king: [Coeff(0);
params::SQUARE_RELATIVE_TO_KING_LEN],
knight_square_relative_to_enemy_king: [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN],
bishop_square_relative_to_friendly_king: [Coeff(0);
params::SQUARE_RELATIVE_TO_KING_LEN],
bishop_square_relative_to_enemy_king: [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN],
rook_square_relative_to_friendly_king: [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN],
rook_square_relative_to_enemy_king: [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN],
queen_square_relative_to_friendly_king: [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN],
queen_square_relative_to_enemy_king: [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN],
pawn_square_relative_to_friendly_king: [Coeff(0); params::PIECE_RELATIVE_TO_KING_LEN],
pawn_square_relative_to_enemy_king: [Coeff(0); params::PIECE_RELATIVE_TO_KING_LEN],
knight_square_relative_to_friendly_king: [Coeff(0); params::PIECE_RELATIVE_TO_KING_LEN],
knight_square_relative_to_enemy_king: [Coeff(0); params::PIECE_RELATIVE_TO_KING_LEN],
bishop_square_relative_to_friendly_king: [Coeff(0); params::PIECE_RELATIVE_TO_KING_LEN],
bishop_square_relative_to_enemy_king: [Coeff(0); params::PIECE_RELATIVE_TO_KING_LEN],
rook_square_relative_to_friendly_king: [Coeff(0); params::PIECE_RELATIVE_TO_KING_LEN],
rook_square_relative_to_enemy_king: [Coeff(0); params::PIECE_RELATIVE_TO_KING_LEN],
queen_square_relative_to_friendly_king: [Coeff(0); params::PIECE_RELATIVE_TO_KING_LEN],
queen_square_relative_to_enemy_king: [Coeff(0); params::PIECE_RELATIVE_TO_KING_LEN],
passed_pawn_relative_to_friendly_king: [Coeff(0);
params::PASSED_PAWNS_RELATIVE_TO_KING_LEN],
passed_pawn_relative_to_enemy_king: [Coeff(0);
params::PASSED_PAWNS_RELATIVE_TO_KING_LEN],
}
}
}
Expand All @@ -126,21 +130,16 @@ impl HandCraftedEvalCoeffs {
}

pub fn clear_squares_relative_to_king(&mut self) {
self.pawn_square_relative_to_friendly_king =
[Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN];
self.pawn_square_relative_to_enemy_king = [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN];
self.knight_square_relative_to_friendly_king =
[Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN];
self.knight_square_relative_to_enemy_king = [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN];
self.bishop_square_relative_to_friendly_king =
[Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN];
self.bishop_square_relative_to_enemy_king = [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN];
self.rook_square_relative_to_friendly_king =
[Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN];
self.rook_square_relative_to_enemy_king = [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN];
self.queen_square_relative_to_friendly_king =
[Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN];
self.queen_square_relative_to_enemy_king = [Coeff(0); params::SQUARE_RELATIVE_TO_KING_LEN];
self.pawn_square_relative_to_friendly_king.fill(Coeff(0));
self.pawn_square_relative_to_enemy_king.fill(Coeff(0));
self.knight_square_relative_to_friendly_king.fill(Coeff(0));
self.knight_square_relative_to_enemy_king.fill(Coeff(0));
self.bishop_square_relative_to_friendly_king.fill(Coeff(0));
self.bishop_square_relative_to_enemy_king.fill(Coeff(0));
self.rook_square_relative_to_friendly_king.fill(Coeff(0));
self.rook_square_relative_to_enemy_king.fill(Coeff(0));
self.queen_square_relative_to_friendly_king.fill(Coeff(0));
self.queen_square_relative_to_enemy_king.fill(Coeff(0));
}

pub fn add_squares_relative_to_king(
Expand Down Expand Up @@ -224,5 +223,7 @@ impl HandCraftedEvalCoeffs {
.chain(self.rook_square_relative_to_enemy_king.iter())
.chain(self.queen_square_relative_to_friendly_king.iter())
.chain(self.queen_square_relative_to_enemy_king.iter())
.chain(self.passed_pawn_relative_to_friendly_king.iter())
.chain(self.passed_pawn_relative_to_enemy_king.iter())
}
}
Loading