250 lines
9.6 KiB
Rust
250 lines
9.6 KiB
Rust
//! Board statistics used for heuristics.
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use crate::board::*;
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use crate::rules::GameState;
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/// Storage for board pieces stats.
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#[derive(Debug, Clone, PartialEq)]
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pub struct BoardStats {
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pub num_pawns: i8,
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pub num_bishops: i8,
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pub num_knights: i8,
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pub num_rooks: i8,
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pub num_queens: i8,
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pub num_kings: i8,
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pub num_doubled_pawns: i8, // Pawns that are on the same file as a friend.
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pub num_backward_pawns: i8, // Pawns behind all other pawns on adjacent files.
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pub num_isolated_pawns: i8, // Pawns that have no friend pawns on adjacent files.
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pub mobility: i32,
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}
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impl BoardStats {
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pub const fn new() -> BoardStats {
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BoardStats {
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num_pawns: 0, num_bishops: 0, num_knights: 0, num_rooks: 0, num_queens: 0,
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num_kings: 0, num_doubled_pawns: 0, num_backward_pawns: 0, num_isolated_pawns: 0,
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mobility: 0,
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}
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}
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pub fn reset(&mut self) {
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self.num_pawns = 0;
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self.num_bishops = 0;
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self.num_knights = 0;
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self.num_rooks = 0;
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self.num_queens = 0;
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self.num_kings = 0;
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self.num_doubled_pawns = 0;
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self.num_backward_pawns = 0;
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self.num_isolated_pawns = 0;
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self.mobility = 0;
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}
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/// Fill `stats` from given `board` and `game_state`.
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///
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/// Only the current playing side stats are created,
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/// prepare the game_state accordingly.
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pub fn compute(&mut self, board: &Board, game_state: &GameState) {
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self.reset();
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let color = game_state.color;
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// Compute mobility for all pieces.
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self.mobility = rules::get_player_moves(board, game_state, true).len() as i32;
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// Compute amount of each piece.
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for (piece, p) in get_piece_iterator(board) {
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let (pos_f, pos_r) = p;
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if piece == SQ_E || !is_color(piece, color) {
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continue
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}
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match get_type(piece) {
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SQ_R => stats.num_rooks += 1,
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SQ_N => stats.num_knights += 1,
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SQ_B => stats.num_bishops += 1,
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SQ_Q => stats.num_queens += 1,
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SQ_K => stats.num_kings += 1,
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SQ_P => {
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stats.num_pawns += 1;
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let mut doubled = false;
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let mut isolated = true;
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let mut backward = true;
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for r in 0..8 {
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// Check for doubled pawns.
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if
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!doubled &&
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is_piece(get_square(board, &(pos_f, r)), color|SQ_P) && r != pos_r
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{
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doubled = true;
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}
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// Check for isolated pawns.
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if
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isolated &&
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(
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// Check on the left file if not on a-file...
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(
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pos_f > POS_MIN &&
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is_piece(get_square(board, &(pos_f - 1, r)), color|SQ_P)
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) ||
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// Check on the right file if not on h-file...
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(
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pos_f < POS_MAX &&
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is_piece(get_square(board, &(pos_f + 1, r)), color|SQ_P)
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)
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)
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{
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isolated = false;
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}
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// Check for backward pawns.
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if backward {
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if color == SQ_WH && r <= pos_r {
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if (
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pos_f > POS_MIN &&
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is_type(get_square(board, &(pos_f - 1, r)), SQ_P)
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) || (
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pos_f < POS_MAX &&
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is_type(get_square(board, &(pos_f + 1, r)), SQ_P)
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) {
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backward = false;
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}
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} else if color == SQ_BL && r >= pos_r {
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if (
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pos_f > POS_MIN &&
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is_type(get_square(board, &(pos_f - 1, r)), SQ_P)
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) || (
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pos_f < POS_MAX &&
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is_type(get_square(board, &(pos_f + 1, r)), SQ_P)
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) {
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backward = false;
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}
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}
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}
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}
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if doubled {
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stats.num_doubled_pawns += 1;
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}
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if isolated {
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stats.num_isolated_pawns += 1;
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}
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if backward {
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stats.num_backward_pawns += 1;
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}
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},
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_ => {}
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}
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}
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}
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}
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impl std::fmt::Display for BoardStats {
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fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
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write!(
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f,
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"{}P {}B {}N {}R {}Q {}K {}dp {}bp {}ip {}m",
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self.num_pawns, self.num_bishops, self.num_knights, self.num_rooks,
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self.num_queens, self.num_kings,
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self.num_doubled_pawns, self.num_backward_pawns, self.num_isolated_pawns,
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self.mobility
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)
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}
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}
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/// Create two new BoardStats objects from the board, for both sides.
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///
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/// See `compute_stats_into` for details.
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pub fn compute_stats(board: &Board, game_state: &GameState) -> (BoardStats, BoardStats) {
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let mut stats = (BoardStats::new(), BoardStats::new());
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compute_stats_into(board, game_state, &mut stats);
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stats
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}
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/// Compute stats for both the current player and its opponent.
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///
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/// The playing color will have its stats filled in the first
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/// BoardStats object, its opponent in the second.
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pub fn compute_stats_into(
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board: &Board,
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game_state: &rules::GameState,
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stats: &mut (BoardStats, BoardStats)
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) {
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let mut gs = game_state.clone();
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compute_color_stats_into(board, &gs, &mut stats.0);
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gs.color = opposite(gs.color);
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compute_color_stats_into(board, &gs, &mut stats.1);
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_compute_stats() {
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// Check that initial stats are correct.
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let b = new();
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let gs = rules::GameState::new();
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let initial_stats = BoardStats {
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num_pawns: 8,
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num_bishops: 2,
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num_knights: 2,
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num_rooks: 2,
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num_queens: 1,
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num_kings: 1,
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num_doubled_pawns: 0,
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num_backward_pawns: 0,
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num_isolated_pawns: 0,
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mobility: 20,
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};
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let mut stats = compute_stats(&b, &gs);
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eprintln!("{}", stats.0);
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eprintln!("{}", stats.1);
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assert!(stats.0 == stats.1);
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assert!(stats.0 == initial_stats);
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// Check that doubled pawns are correctly counted.
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let mut b = new_empty();
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set_square(&mut b, &pos("d4"), SQ_WH_P);
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set_square(&mut b, &pos("d6"), SQ_WH_P);
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compute_color_stats_into(&b, &gs, &mut stats.0);
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assert_eq!(stats.0.num_doubled_pawns, 2);
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// Add a pawn on another file, no changes expected.
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set_square(&mut b, &pos("e6"), SQ_WH_P);
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compute_color_stats_into(&b, &gs, &mut stats.0);
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assert_eq!(stats.0.num_doubled_pawns, 2);
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// Add a pawn backward in the d-file: there are now 3 doubled pawns.
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set_square(&mut b, &pos("d2"), SQ_WH_P);
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compute_color_stats_into(&b, &gs, &mut stats.0);
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assert_eq!(stats.0.num_doubled_pawns, 3);
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// Check that isolated and backward pawns are correctly counted.
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assert_eq!(stats.0.num_isolated_pawns, 0);
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assert_eq!(stats.0.num_backward_pawns, 2); // A bit weird?
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// Protect d4 pawn with a friend in e3: it is not isolated nor backward anymore.
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set_square(&mut b, &pos("e3"), SQ_WH_P);
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compute_color_stats_into(&b, &gs, &mut stats.0);
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assert_eq!(stats.0.num_doubled_pawns, 5);
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assert_eq!(stats.0.num_isolated_pawns, 0);
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assert_eq!(stats.0.num_backward_pawns, 1);
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// Add an adjacent friend to d2 pawn: no pawns are left isolated or backward.
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set_square(&mut b, &pos("c2"), SQ_WH_P);
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compute_color_stats_into(&b, &gs, &mut stats.0);
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assert_eq!(stats.0.num_doubled_pawns, 5);
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assert_eq!(stats.0.num_isolated_pawns, 0);
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assert_eq!(stats.0.num_backward_pawns, 0);
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// Add an isolated/backward white pawn in a far file.
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set_square(&mut b, &pos("a2"), SQ_WH_P);
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compute_color_stats_into(&b, &gs, &mut stats.0);
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assert_eq!(stats.0.num_doubled_pawns, 5);
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assert_eq!(stats.0.num_isolated_pawns, 1);
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assert_eq!(stats.0.num_backward_pawns, 1);
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// Check for pawns that are backward but not isolated.
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let mut b = new_empty();
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// Here, d4 pawn protects both e5 and e3, but it is backward.
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set_square(&mut b, &pos("d4"), SQ_WH_P);
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set_square(&mut b, &pos("e5"), SQ_WH_P);
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set_square(&mut b, &pos("e3"), SQ_WH_P);
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compute_color_stats_into(&b, &gs, &mut stats.0);
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assert_eq!(stats.0.num_doubled_pawns, 2);
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assert_eq!(stats.0.num_isolated_pawns, 0);
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assert_eq!(stats.0.num_backward_pawns, 1);
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}
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}
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