feat: piece square table
no tapered eval yet
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src/eval.rs
229
src/eval.rs
@ -13,7 +13,8 @@ Copyright © 2024 dogeystamp <dogeystamp@disroot.org>
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//! Position evaluation.
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use crate::{Board, Color, N_PIECES};
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use crate::{Board, Color, Piece, Square, N_COLORS, N_PIECES, N_SQUARES};
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use core::ops::Index;
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/// Signed centipawn type.
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///
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@ -25,31 +26,217 @@ pub trait Eval {
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fn eval(&self) -> EvalInt;
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}
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impl Eval for Board {
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fn eval(&self) -> EvalInt {
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use crate::Piece::*;
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let mut score: EvalInt = 0;
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pub(crate) mod eval_score {
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//! Opaque "score" counters to be used in the board.
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// scores in centipawns for each piece
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let material_score: [EvalInt; N_PIECES] = [
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500, // rook
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300, // bishop
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300, // knight
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20000, // king
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900, // queen
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100, // pawn
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];
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use super::{EvalInt, Pst};
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use crate::{ColPiece, Square};
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for pc in [Rook, Queen, Pawn, Knight, Bishop, King] {
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let tally_white = self[Color::White][pc].0.count_ones();
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let tally_black = self[Color::Black][pc].0.count_ones();
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let tally =
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EvalInt::try_from(tally_white).unwrap() - EvalInt::try_from(tally_black).unwrap();
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/// Internal score-keeping for a board.
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///
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/// This is kept in order to efficiently update evaluation with moves.
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#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Default, Debug)]
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pub struct EvalScores {
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/// Middle-game perspective evaluation of this board.
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pub midgame: EvalScore,
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/// End-game perspective evaluation of this board.
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pub endgame: EvalScore,
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}
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score += material_score[pc as usize] * tally;
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/// Score from a given perspective (e.g. midgame, endgame).
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#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Default, Debug)]
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pub struct EvalScore {
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pub(crate) score: EvalInt,
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}
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impl EvalScore {
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/// Remove the value of a piece on a square.
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pub fn del_piece(&mut self, pc: ColPiece, sq: Square, pst: &Pst) {
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self.score -= pst[pc.pc][pc.col][sq] * EvalInt::from(pc.col.sign());
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}
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score
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/// Add the value of a piece on a square.
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pub fn add_piece(&mut self, pc: ColPiece, sq: Square, pst: &Pst) {
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self.score += pst[pc.pc][pc.col][sq] * EvalInt::from(pc.col.sign());
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}
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}
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}
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/// The main piece-square-table (PST) type that assigns scores to pieces on given squares.
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///
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/// This is the main source of positional knowledge, as well as the ability to count material.
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pub struct Pst([PstPiece; N_PIECES]);
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/// A PST for a specific piece.
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type PstPiece = [PstSide; N_COLORS];
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/// A PST for a given piece, of a given color.
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type PstSide = [EvalInt; N_SQUARES];
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impl Index<Piece> for Pst {
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type Output = PstPiece;
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fn index(&self, index: Piece) -> &Self::Output {
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&self.0[index as usize]
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}
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}
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impl Index<Color> for PstPiece {
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type Output = PstSide;
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fn index(&self, index: Color) -> &Self::Output {
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&self[index as usize]
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}
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}
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impl Index<Square> for PstSide {
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type Output = EvalInt;
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fn index(&self, index: Square) -> &Self::Output {
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&self[usize::from(index)]
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}
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}
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#[rustfmt::skip]
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const PERSPECTIVE_WHITE: [usize; N_SQUARES] = [
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56, 57, 58, 59, 60, 61, 62, 63,
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48, 49, 50, 51, 52, 53, 54, 55,
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40, 41, 42, 43, 44, 45, 46, 47,
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32, 33, 34, 35, 36, 37, 38, 39,
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24, 25, 26, 27, 28, 29, 30, 31,
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16, 17, 18, 19, 20, 21, 22, 23,
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8, 9, 10, 11, 12, 13, 14, 15,
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0, 1, 2, 3, 4, 5, 6, 7,
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];
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/// This perspective is also horizontally reversed so the king is on the right side.
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#[rustfmt::skip]
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const PERSPECTIVE_BLACK: [usize; N_SQUARES] = [
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0, 1, 2, 3, 4, 5, 6, 7,
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8, 9, 10, 11, 12, 13, 14, 15,
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16, 17, 18, 19, 20, 21, 22, 23,
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24, 25, 26, 27, 28, 29, 30, 31,
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32, 33, 34, 35, 36, 37, 38, 39,
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40, 41, 42, 43, 44, 45, 46, 47,
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48, 49, 50, 51, 52, 53, 54, 55,
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56, 57, 58, 59, 60, 61, 62, 63,
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];
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/// Helper to have the right board perspective in the source code.
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///
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/// In the source code, a1 will be at the bottom left, while h8 will be at the top right,
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/// corresponding to how humans usually see the board. This means that a8 is index 0, and h1 is
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/// index 63. This function shifts it so that a1 is 0, and h8 is 63, as in our implementation.
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///
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/// # Arguments
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/// * pst: Square values in centipawns.
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/// * base_val: The base value of the piece, which is added to every square.
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const fn pst_perspective(
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pst: PstSide,
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base_val: EvalInt,
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perspective: [usize; N_SQUARES],
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) -> PstSide {
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let mut ret = pst;
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let mut i = 0;
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while i < N_SQUARES {
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let j = perspective[i];
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ret[i] = pst[j] + base_val;
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i += 1;
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}
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ret
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}
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/// Construct PSTs for a single piece, from white's perspective.
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const fn make_pst(val: PstSide, base_val: EvalInt) -> PstPiece {
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[
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pst_perspective(val, base_val, PERSPECTIVE_WHITE),
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pst_perspective(val, base_val, PERSPECTIVE_BLACK),
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]
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}
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/// Middle-game PSTs.
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#[rustfmt::skip]
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pub const PST_MIDGAME: Pst = Pst([
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// rook
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make_pst([
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0, 0, 0, 0, 0, 0, 0, 0, // 8
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20, 20, 20, 20, 20, 20, 20, 20, // 7
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0, 0, 0, 0, 0, 0, 0, 0, // 6
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0, 0, 0, 0, 0, 0, 0, 0, // 5
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0, 0, 0, 0, 0, 0, 0, 0, // 4
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0, 0, 0, 0, 0, 0, 0, 0, // 3
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0, 0, 0, 0, 0, 0, 0, 0, // 2
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0, 0, 0, 10, 10, 5, 0, 0, // 1
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// a b c d e f g h
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], 500),
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// bishop
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make_pst([
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0, 0, 0, 0, 0, 0, 0, 0, // 8
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0, 0, 0, 0, 0, 0, 0, 0, // 7
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0, 0, 0, 0, 0, 0, 0, 0, // 6
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0, 0, 0, 0, 0, 0, 0, 0, // 5
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0, 0, 0, 0, 0, 0, 0, 0, // 4
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0, 0, 0, 0, 0, 0, 0, 0, // 3
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0, 0, 0, 0, 0, 0, 0, 0, // 2
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0, 0, -10, 0, 0, -10, 0, 0, // 1
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// a b c d e f g h
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], 300),
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// knight
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make_pst([
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0, 0, 0, 0, 0, 0, 0, 0, // 8
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0, 0, 0, 0, 0, 0, 0, 0, // 7
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0, 0, 0, 0, 0, 0, 0, 0, // 6
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0, 0, 0, 10, 10, 0, 0, 0, // 5
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0, 0, 0, 10, 10, 0, 0, 0, // 4
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0, 0, 10, 0, 0, 10, 0, 0, // 3
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0, 0, 0, 0, 0, 0, 0, 0, // 2
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0, 0, 0, 0, 0, 0, 0, 0, // 1
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// a b c d e f g h
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], 300),
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// king
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make_pst([
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0, 0, 0, 0, 0, 0, 0, 0, // 8
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0, 0, 0, 0, 0, 0, 0, 0, // 7
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0, 0, 0, 0, 0, 0, 0, 0, // 6
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0, 0, 0, 0, 0, 0, 0, 0, // 5
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0, 0, 0, 0, 0, 0, 0, 0, // 4
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0, 0, 0, 0, 0, 0, 0, 0, // 3
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0, 0, 0, 0, 0, 0, 0, 0, // 2
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0, 0, 10, 0, 0, 0, 20, 0, // 1
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// a b c d e f g h
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], 20_000),
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// queen
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make_pst([
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0, 0, 0, 0, 0, 0, 0, 0, // 8
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0, 0, 0, 0, 0, 0, 0, 0, // 7
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0, 0, 0, 0, 0, 0, 0, 0, // 6
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0, 0, 0, 0, 0, 0, 0, 0, // 5
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0, 0, 0, 0, 0, 0, 0, 0, // 4
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0, 0, 0, 0, 0, 0, 0, 0, // 3
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0, 0, 0, 0, 0, 0, 0, 0, // 2
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0, 0, 0, 0, 0, 0, 0, 0, // 1
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// a b c d e f g h
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], 900),
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// pawn
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make_pst([
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10, 10, 10, 10, 10, 10, 10, 10, // 8
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9, 9, 9, 9, 9, 9, 9, 9, // 7
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8, 8, 8, 8, 8, 8, 8, 8, // 6
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7, 7, 7, 8, 8, 7, 7, 7, // 5
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6, 6, 6, 6, 6, 6, 6, 6, // 4
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2, 2, 2, 4, 4, 0, 2, 0, // 3
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0, 0, 0, 0, 0, 0, 0, 0, // 2
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0, 0, 0, 0, 0, 0, 0, 0, // 1
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// a b c d e f g h
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], 100),
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]);
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impl Eval for Board {
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fn eval(&self) -> EvalInt {
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self.eval.midgame.score
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}
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}
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30
src/lib.rs
30
src/lib.rs
@ -23,6 +23,8 @@ pub mod movegen;
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pub mod search;
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use crate::fen::{FromFen, ToFen, START_POSITION};
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use eval::eval_score::EvalScores;
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use eval::PST_MIDGAME;
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const BOARD_WIDTH: usize = 8;
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const BOARD_HEIGHT: usize = 8;
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@ -44,6 +46,12 @@ impl Color {
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Color::Black => Color::White,
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}
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}
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pub fn sign(&self) -> i8 {
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match self {
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Color::White => 1,
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Color::Black => -1,
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}
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}
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}
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impl From<Color> for char {
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@ -439,6 +447,9 @@ pub struct Board {
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/// Whose turn it is
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turn: Color,
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/// Counters for evaluation.
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eval: EvalScores,
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}
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impl Board {
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@ -453,11 +464,12 @@ impl Board {
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}
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/// Create a new piece in a location, and pop any existing piece in the destination.
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pub fn set_piece(&mut self, idx: Square, pc: ColPiece) -> Option<ColPiece> {
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let dest_pc = self.del_piece(idx);
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pub fn set_piece(&mut self, sq: Square, pc: ColPiece) -> Option<ColPiece> {
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let dest_pc = self.del_piece(sq);
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let pl = &mut self[pc.col];
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pl[pc.into()].on_sq(idx);
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*self.mail.sq_mut(idx) = Some(pc);
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pl[pc.into()].on_sq(sq);
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*self.mail.sq_mut(sq) = Some(pc);
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self.eval.midgame.add_piece(pc, sq, &PST_MIDGAME);
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dest_pc
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}
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@ -470,11 +482,12 @@ impl Board {
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}
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/// Delete the piece in a location, and return ("pop") that piece.
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pub fn del_piece(&mut self, idx: Square) -> Option<ColPiece> {
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if let Some(pc) = *self.mail.sq_mut(idx) {
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pub fn del_piece(&mut self, sq: Square) -> Option<ColPiece> {
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if let Some(pc) = *self.mail.sq_mut(sq) {
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let pl = &mut self[pc.col];
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pl[pc.into()].off_sq(idx);
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*self.mail.sq_mut(idx) = None;
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pl[pc.into()].off_sq(sq);
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*self.mail.sq_mut(sq) = None;
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self.eval.midgame.del_piece(pc, sq, &PST_MIDGAME);
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Some(pc)
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} else {
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None
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@ -508,6 +521,7 @@ impl Board {
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mail: Default::default(),
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ep_square: self.ep_square.map(|sq| sq.mirror_vert()),
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castle: CastleRights(self.castle.0),
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eval: Default::default(),
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};
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new_board.castle.0.reverse();
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@ -672,11 +672,7 @@ impl MoveGenInternal for Board {
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Color::Black => 0,
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};
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let nr = (r)
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+ match self.turn {
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Color::White => 1,
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Color::Black => -1,
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};
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let nr = r + isize::from(self.turn.sign());
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let is_promotion = nr == last_row;
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macro_rules! push_moves {
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@ -1093,7 +1089,10 @@ mod tests {
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let all_cases = [augmented_test_cases, test_cases].concat();
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for (mut board, expected_moves) in all_cases {
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let mut moves: Vec<Move> = board.gen_moves_general(MoveGenType::Pseudo).into_iter().collect();
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let mut moves: Vec<Move> = board
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.gen_moves_general(MoveGenType::Pseudo)
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.into_iter()
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.collect();
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moves.sort_unstable();
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let moves = moves;
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