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start moving evaluation heuristics into functions
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@Icerath
Icerath committed Jan 11, 2025
1 parent f6aaee4 commit b071b32
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Showing 2 changed files with 109 additions and 71 deletions.
177 changes: 107 additions & 70 deletions src/engine/evaluation.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
use movegen::PAWN_ATTACKS;

use super::mobility::raw_mobility_eval;
use crate::prelude::*;
use crate::{core::board::Pieces, prelude::*};

const ROOK_SAME_FILE_BONUS: i32 = 20;

Expand All @@ -19,12 +19,14 @@ pub fn raw_evaluation(board: &Board) -> i32 {
let friendly = board.side_bitboards(side);
let enemy = board.side_bitboards(!side);

// king safety
earlygame -= (enemy[Queen] & king.nearby3()).count() as i32 * 80;
earlygame -= (enemy[Knight] | enemy[Bishop] & king.nearby3()).count() as i32 * 40;

earlygame -= (enemy[Queen] & king.nearby2()).count() as i32 * 80;
earlygame -= (enemy[Knight] | enemy[Bishop] & king.nearby2()).count() as i32 * 30;
earlygame += king_safety(&enemy, king);
earlygame += punish_open_kings(king, &friendly, &enemy);
total += punish_double_pawns(&friendly);
total += reward_pawns_close_to_king(&friendly, king);
total += reward_outposts(side, &friendly, &enemy);
total += reward_rooks_on_open_file(&friendly, board);
total += reward_lined_up_rooks(&friendly, board);
total += has_bishop_pair(board, side) as i32 * 50;

// punish pieces in front of enemy pawns
let mut pawn_attacks = Bitboard::EMPTY;
Expand All @@ -33,22 +35,6 @@ pub fn raw_evaluation(board: &Board) -> i32 {
let non_pawns = friendly[Knight] | friendly[Bishop] | friendly[Rook] | friendly[Queen];
total -= (pawn_attacks & non_pawns).count() as i32 * 40;

// punish kings adjacent to an open file
for pawns in [friendly[Pawn], enemy[Pawn]] {
let file = king.file();

let left_open = file.sub_int(1).is_some_and(|file| (pawns & file.mask()).is_empty());
let middle_open = (pawns & file.mask()).is_empty();
let right_open = file.add_int(1).is_some_and(|file| (pawns & file.mask()).is_empty());

let num_open_files = left_open as i32 + middle_open as i32 + right_open as i32;
earlygame -= num_open_files * [40, 35, 25, 10, 10, 25, 35, 40][file.usize()];
}
// punish double pawns
for file in File::ALL {
let pawns_in_file = (friendly[Pawn] & file.mask()).count() as i32;
total -= pawns_in_file.saturating_sub(1) * 25;
}
friendly[Pawn].for_each(|sq| {
// reward non-isolated pawns
if !(sq.file().adjacency_mask() & friendly[Pawn]).is_empty() {
Expand All @@ -61,57 +47,12 @@ pub fn raw_evaluation(board: &Board) -> i32 {
total += [0, 10, 20, 30, 40, 50, 70, 90][offset];
}
});
// reward outposts
(friendly[Knight] | friendly[Bishop]).for_each(|sq| {
if sq.rank().relative_to(side).u8() < 4 {
return;
}
let is_outpost = (sq.outpost_mask(side) & enemy[Pawn]).is_empty();
if is_outpost {
total += 20;
}
});
// reward pawns close to king
(friendly[Pawn] & king.nearby2() & (king.file().adjacency_mask() | king.file().mask()))
.for_each(|sq| {
const BONUSES: [[i32; 3]; 8] = [
[18, 18, 14],
[15, 15, 10],
[13, 13, 9],
[8, 8, 4],
[8, 8, 4],
[13, 13, 9],
[15, 15, 10],
[18, 18, 14],
];
let dif_rank = sq.rank().u8().abs_diff(king.rank().u8());
unsafe { std::hint::assert_unchecked(dif_rank < 3) };
total += BONUSES[sq.file().usize()][dif_rank as usize];
});
// reward rooks on an open file
friendly[Rook].for_each(|sq| {
if (board[Pawn] & sq.file().mask()).is_empty() {
total += 20;
} else if (friendly[Pawn] & (sq.file().mask())).is_empty() {
total += 10;
}
});
if friendly[Rook].count() >= 2 {
let rook_a = unsafe { friendly[Rook].bitscan_unchecked() };
let rook_b = unsafe { friendly[Rook].rbitscan_unchecked() };

let rook_attacks = rook_attacks(rook_a, board.all_pieces());
if rook_attacks.contains(rook_b) {
total += 20;
total += (rook_a.file() == rook_b.file()) as i32 * ROOK_SAME_FILE_BONUS;
}
}
total += has_bishop_pair(board, side) as i32 * 50;

let [mg, eg] = material_and_square_table_values(board, side);
earlygame += mg;
endgame += eg;
total += earlygame * phase.earlygame() + endgame * phase.endgame();

total += earlygame * phase.earlygame() + endgame * phase.endgame();
final_total += total * side.positive();
}
// mop up evaluation
Expand All @@ -129,6 +70,102 @@ pub fn raw_evaluation(board: &Board) -> i32 {
final_total + raw_mobility_eval(board)
}

fn king_safety(enemy: &Pieces, king: Square) -> i32 {
let mut total = 0;
total -= (enemy[Queen] & king.nearby3()).count() as i32 * 80;
total -= (enemy[Knight] | enemy[Bishop] & king.nearby3()).count() as i32 * 40;

total -= (enemy[Queen] & king.nearby2()).count() as i32 * 80;
total -= (enemy[Knight] | enemy[Bishop] & king.nearby2()).count() as i32 * 30;
total
}

fn punish_open_kings(king: Square, friendly: &Pieces, enemy: &Pieces) -> i32 {
let mut total = 0;
for pawns in [friendly[Pawn], enemy[Pawn]] {
let file = king.file();

let left_open = file.sub_int(1).is_some_and(|file| (pawns & file.mask()).is_empty());
let middle_open = (pawns & file.mask()).is_empty();
let right_open = file.add_int(1).is_some_and(|file| (pawns & file.mask()).is_empty());

let num_open_files = left_open as i32 + middle_open as i32 + right_open as i32;
total -= num_open_files * [40, 35, 25, 10, 10, 25, 35, 40][file.usize()];
}
total
}

fn punish_double_pawns(friendly: &Pieces) -> i32 {
let mut total = 0;
for file in File::ALL {
let pawns_in_file = (friendly[Pawn] & file.mask()).count() as i32;
total -= pawns_in_file.saturating_sub(1) * 25;
}
total
}

fn reward_pawns_close_to_king(friendly: &Pieces, king: Square) -> i32 {
let mut total = 0;
(friendly[Pawn] & king.nearby2() & (king.file().adjacency_mask() | king.file().mask()))
.for_each(|sq| {
const BONUSES: [[i32; 3]; 8] = [
[18, 18, 14],
[15, 15, 10],
[13, 13, 9],
[8, 8, 4],
[8, 8, 4],
[13, 13, 9],
[15, 15, 10],
[18, 18, 14],
];
let dif_rank = sq.rank().u8().abs_diff(king.rank().u8());
unsafe { std::hint::assert_unchecked(dif_rank < 3) };
total += BONUSES[sq.file().usize()][dif_rank as usize];
});
total
}

fn reward_outposts(side: Side, friendly: &Pieces, enemy: &Pieces) -> i32 {
let mut total = 0;
(friendly[Knight] | friendly[Bishop]).for_each(|sq| {
if sq.rank().relative_to(side).u8() < 4 {
return;
}
let is_outpost = (sq.outpost_mask(side) & enemy[Pawn]).is_empty();
if is_outpost {
total += 20;
}
});
total
}

fn reward_rooks_on_open_file(friendly: &Pieces, board: &Board) -> i32 {
let mut total = 0;
friendly[Rook].for_each(|sq| {
if (board[Pawn] & sq.file().mask()).is_empty() {
total += 20;
} else if (friendly[Pawn] & (sq.file().mask())).is_empty() {
total += 10;
}
});
total
}

fn reward_lined_up_rooks(friendly: &Pieces, board: &Board) -> i32 {
let mut total = 0;
if friendly[Rook].count() >= 2 {
let rook_a = unsafe { friendly[Rook].bitscan_unchecked() };
let rook_b = unsafe { friendly[Rook].rbitscan_unchecked() };

let rook_attacks = rook_attacks(rook_a, board.all_pieces());
if rook_attacks.contains(rook_b) {
total += 20;
total += (rook_a.file() == rook_b.file()) as i32 * ROOK_SAME_FILE_BONUS;
}
}
total
}

fn material_and_square_table_values(board: &Board, side: Side) -> [i32; 2] {
let [earlygame, endgame] = material_values(board, side);
let [earlygame2, endgame2] = square_table_values(board, side);
Expand Down
3 changes: 2 additions & 1 deletion src/main.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -209,7 +209,8 @@ impl Application {
print!(" {sq}");
});
println!();
println!("Direct Eval: {:?}", raw_evaluation(&self.engine.board));
println!("Endgame: {:?}", phase(board).endgame().as_float());
println!("Direct Eval: {:?}", raw_evaluation(board));
}
}

Expand Down

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