feat: tune evaluation parameters

1 files changed, 13 insertions, 20 deletions

diff --git a/src/grossmeister/evaluation.rs b/src/grossmeister/evaluation.rs
index dafc33a..6669545 100644
--- a/src/grossmeister/evaluation.rs
+++ b/src/grossmeister/evaluation.rs
@@ -1,9 +1,7 @@
-use crate::{board::{piece::Piece, color::Color, CastlingSide}, bitboard::{BitboardFns, Bitboard}, square::Square};
+use crate::{board::{piece::Piece, color::Color, CastlingSide}, bitboard::{Bitboard, BitboardFns}, square::Square};
 
 use super::Grossmeister;
 
-static A_FILE: Bitboard = 0x0101010101010101;
-
 const PAWN_BONUS: [f32; 64] = [
   //  A      B      C      D      E      F      G      H
      0.00,  0.00,  0.00,  0.00,  0.00,  0.00,  0.00,  0.00,
@@ -16,7 +14,7 @@ const PAWN_BONUS: [f32; 64] = [
      0.00,  0.00,  0.00,  0.00,  0.00,  0.00,  0.00,  0.00
 ];
 
-const PAWN_BONUS_ENDGAME: [f32; 64] = [
+const PAWN_BONUS_PASSER_ENDGAME: [f32; 64] = [
   //  A      B      C      D      E      F      G      H
      0.00,  0.00,  0.00,  0.00,  0.00,  0.00,  0.00,  0.00,
      2.00,  2.00,  2.00,  2.00,  2.00,  2.00,  2.00,  2.00,
@@ -101,11 +99,11 @@ const KING_BONUS_ENGAME: [f32; 64] = [
 ];
 
 impl Grossmeister {
-    pub fn passer_count(&self, color: Color) -> f32 {
+    pub fn passer_mask(&self, color: Color) -> Bitboard {
         let black_pawns = self.board.piece_sets[Piece::PawnBlack as usize];
         let white_pawns = self.board.piece_sets[Piece::Pawn as usize];
 
-        let mask = match color {
+        match color {
             Color::Black => {
                 let mut front_fill = white_pawns.nort_fill().nort_one();
                 front_fill |= front_fill.east_one() | front_fill.west_one();
@@ -116,12 +114,7 @@ impl Grossmeister {
                 front_fill |= front_fill.east_one() | front_fill.west_one();
                 white_pawns & !front_fill
             }
-        };
-
-        (mask & match color {
-            Color::White => white_pawns,
-            Color::Black => black_pawns,
-        }).pop_count() as f32
+        }
     }
 
     pub fn is_dead_position(&self) -> bool {
@@ -173,7 +166,7 @@ impl Grossmeister {
         let fileset = pawns.nort_fill().sout_fill();
         // Does not matter west/east, each island has both sides
         let islands_west_files = fileset & !fileset.east_one();
-        islands_west_files.pop_count() as f32
+        (islands_west_files.pop_count() / 8) as f32
     }
 
     /// Compute total bonus for well-positioned pieces
@@ -181,8 +174,8 @@ impl Grossmeister {
     pub fn pst_bonus(&self, color: Color, is_endgame: bool) -> f32 {
         self.board.pieces_by_color(color).iter().enumerate().fold(0., |total, (piece_index, bitboard)| {
             let pst = match Piece::from(piece_index).without_color() {
-                Piece::Pawn => if is_endgame {
-                    PAWN_BONUS_ENDGAME
+                Piece::Pawn => if is_endgame && (bitboard & self.passer_mask(color) > 0) {
+                    PAWN_BONUS_PASSER_ENDGAME
                 } else {
                     PAWN_BONUS
                 }
@@ -252,23 +245,23 @@ impl Grossmeister {
         let material_advantage = self.material(color) - self.material(opponent_color);
         let mobility_advantage = self.mobility(color) - self.mobility(opponent_color);
         let pawn_shield_advantage = self.pawn_shield(color) - self.pawn_shield(opponent_color);
-        let passer_advantage = self.passer_count(color) - self.passer_count(opponent_color);
         let pawn_islands_advantage = self.pawn_islands(opponent_color) - self.pawn_islands(color);
 
+        // Middlegame eval, assumming all pieces are on the Board
         let middlegame_eval =
             mobility_advantage * 0.05 +
-            pawn_shield_advantage * 0.15 +
+            pawn_shield_advantage * 0.20 +
             pawn_islands_advantage * 0.10 +
-            passer_advantage * 0.05 +
             (self.pst_bonus(color, false) - self.pst_bonus(opponent_color, false));
 
+        // Engame eval, assuming no pieces are left on the Board (only kings and pawns)
         let endgame_eval =
             mobility_advantage * 0.03 +
-            pawn_shield_advantage * 0.20 +
+            pawn_shield_advantage * 0.05 +
             pawn_islands_advantage * 0.15 +
-            passer_advantage * 0.10 +
             (self.pst_bonus(color, true) - self.pst_bonus(opponent_color, true));
 
+        // Interpolate evalutaion based on amount of pieces to remove discontinuity
         let phase = self.phase();
         let tapered_eval = (middlegame_eval * phase as f32 + endgame_eval * (240 - phase) as f32) / 240.;