Improve attack table init, add inline to fetch fns

src/movegen/attack_generator.rs

@@ -35,9 +35,8 @@ pub const BISHOP_RELEVANT_BITS: [usize; 64] = [
 static PAWN_ATTACKS: LazyLock<[[Bitboard; 2]; 64]> = LazyLock::new(init_pawn_attacks);
 static KNIGHT_ATTACKS: LazyLock<[Bitboard; 64]> = LazyLock::new(init_knight_attacks);
 static KING_ATTACKS: LazyLock<[Bitboard; 64]> = LazyLock::new(init_king_attacks);
-static BISHOP_ATTACKS: LazyLock<Box<[[Bitboard; 512]; 64]>> = LazyLock::new(init_bishop_attacks);
-static ROOK_ATTACKS: LazyLock<HashMap<usize, HashMap<usize, u64>>> =
-    LazyLock::new(init_rook_attacks);
+static BISHOP_ATTACKS: LazyLock<Vec<Vec<Bitboard>>> = LazyLock::new(init_bishop_attacks);
+static ROOK_ATTACKS: LazyLock<Vec<Vec<Bitboard>>> = LazyLock::new(init_rook_attacks);
 
 const fn pawn_attacks(bitboard: Bitboard, color: Color) -> Bitboard {
     let mut attacks = EMPTY;
@@ -86,7 +85,7 @@ const fn king_attacks(bitboard: Bitboard) -> Bitboard {
     attacks
 }
 
-pub fn mask_bishop_attacks(bitboard: Bitboard) -> Bitboard {
+fn mask_bishop_attacks(bitboard: Bitboard) -> Bitboard {
     let mut attacks = EMPTY;
     let (rank_dst, file_dst) = bitboard_to_coords(bitboard);
 
@@ -109,7 +108,7 @@ pub fn mask_bishop_attacks(bitboard: Bitboard) -> Bitboard {
     attacks
 }
 
-pub fn mask_rook_attacks(bitboard: Bitboard) -> Bitboard {
+fn mask_rook_attacks(bitboard: Bitboard) -> Bitboard {
     let mut attacks = EMPTY;
     let (rank_dst, file_dst) = bitboard_to_coords(bitboard);
 
@@ -135,7 +134,7 @@ pub fn mask_rook_attacks(bitboard: Bitboard) -> Bitboard {
     attacks
 }
 
-pub fn bishop_attacks_on_the_fly(bitboard: Bitboard, blocker: Bitboard) -> Bitboard {
+fn bishop_attacks_on_the_fly(bitboard: Bitboard, blocker: Bitboard) -> Bitboard {
     let mut attacks = EMPTY;
     let (rank_dst, file_dst) = bitboard_to_coords(bitboard);
 
@@ -164,7 +163,7 @@ pub fn bishop_attacks_on_the_fly(bitboard: Bitboard, blocker: Bitboard) -> Bitbo
     attacks
 }
 
-pub fn rook_attacks_on_the_fly(bitboard: Bitboard, blocker: Bitboard) -> Bitboard {
+fn rook_attacks_on_the_fly(bitboard: Bitboard, blocker: Bitboard) -> Bitboard {
     let mut attacks = EMPTY;
     let (rank_dst, file_dst) = bitboard_to_coords(bitboard);
 
@@ -194,7 +193,7 @@ pub fn rook_attacks_on_the_fly(bitboard: Bitboard, blocker: Bitboard) -> Bitboar
     attacks
 }
 
-pub fn set_occupancy(idx: u64, relevant_bits: usize, mut attack_mask: Bitboard) -> Bitboard {
+fn set_occupancy(idx: u64, relevant_bits: usize, mut attack_mask: Bitboard) -> Bitboard {
     let mut occupancy = EMPTY;
 
     for bit in 0..relevant_bits {
@@ -208,6 +207,7 @@ pub fn set_occupancy(idx: u64, relevant_bits: usize, mut attack_mask: Bitboard)
     occupancy
 }
 
+#[inline(always)]
 pub fn fetch_pawn_attacks(square: usize, color: Color) -> Bitboard {
     match color {
         Color::White => PAWN_ATTACKS[square][0],
@@ -215,16 +215,19 @@ pub fn fetch_pawn_attacks(square: usize, color: Color) -> Bitboard {
     }
 }
 
+#[inline(always)]
 pub fn fetch_knight_attacks(square: usize) -> Bitboard {
     KNIGHT_ATTACKS[square]
 }
 
+#[inline(always)]
 pub fn fetch_king_attacks(square: usize) -> Bitboard {
     KING_ATTACKS[square]
 }
 
 use crate::movegen::magic_bitboards::{BISHOP_MAGIC, ROOK_MAGIC};
 
+#[inline(always)]
 pub fn fetch_bishop_attacks(mut occupancy: Bitboard, square: usize) -> Bitboard {
     occupancy &= mask_bishop_attacks(square_to_bitboard_wrapping(square));
     occupancy = occupancy.wrapping_mul(BISHOP_MAGIC[square]);
@@ -232,18 +235,20 @@ pub fn fetch_bishop_attacks(mut occupancy: Bitboard, square: usize) -> Bitboard
     BISHOP_ATTACKS[square][occupancy as usize]
 }
 
+#[inline(always)]
 pub fn fetch_rook_attacks(mut occupancy: Bitboard, square: usize) -> Bitboard {
     occupancy &= mask_rook_attacks(square_to_bitboard_wrapping(square));
     occupancy = occupancy.wrapping_mul(ROOK_MAGIC[square]);
     occupancy >>= 64 - ROOK_RELEVANT_BITS[square];
-    ROOK_ATTACKS[&square][&(occupancy as usize)]
+    ROOK_ATTACKS[square][occupancy as usize]
 }
 
+#[inline(always)]
 pub fn fetch_queen_attacks(occupancy: Bitboard, square: usize) -> Bitboard {
     fetch_rook_attacks(occupancy, square) | fetch_bishop_attacks(occupancy, square)
 }
 
-pub fn init_pawn_attacks() -> [[Bitboard; 2]; 64] {
+fn init_pawn_attacks() -> [[Bitboard; 2]; 64] {
     array::from_fn(|square| {
         [
             pawn_attacks(square_to_bitboard(square), Color::White),
@@ -252,74 +257,68 @@ pub fn init_pawn_attacks() -> [[Bitboard; 2]; 64] {
     })
 }
 
-pub fn init_knight_attacks() -> [Bitboard; 64] {
+fn init_knight_attacks() -> [Bitboard; 64] {
     array::from_fn(|square| knight_attacks(square_to_bitboard(square)))
 }
 
-pub fn init_king_attacks() -> [Bitboard; 64] {
+fn init_king_attacks() -> [Bitboard; 64] {
     array::from_fn(|square| king_attacks(square_to_bitboard(square)))
 }
 
-pub fn init_bishop_attacks() -> Box<[[Bitboard; 512]; 64]> {
+fn init_bishop_attacks() -> Vec<Vec<Bitboard>> {
     let mut bishop_masks = [0; 64];
-    let mut bishop_atks: Box<[[Bitboard; 512]; 64]> = Box::new([[0; 512]; 64]);
+    let mut bishop_atks: Vec<Vec<Bitboard>> = Vec::with_capacity(64);
 
     for square in 0..64 {
         bishop_masks[square] = mask_bishop_attacks(square_to_bitboard(square));
         let attack_mask = bishop_masks[square];
         let occupancy_indices = square_to_bitboard(BISHOP_RELEVANT_BITS[square]);
+        let mut square_attacks = vec![0; occupancy_indices as usize];
 
         for idx in 0..occupancy_indices {
             let occupancy = set_occupancy(idx, BISHOP_RELEVANT_BITS[square], attack_mask);
-            let magic_idx = (occupancy.wrapping_mul(BISHOP_MAGIC[square])
-                >> (64 - BISHOP_RELEVANT_BITS[square])) as usize;
+            let magic_idx =
+                occupancy.wrapping_mul(BISHOP_MAGIC[square]) >> (64 - BISHOP_RELEVANT_BITS[square]);
 
-            bishop_atks[square][magic_idx] =
+            square_attacks[magic_idx as usize] =
                 bishop_attacks_on_the_fly(square_to_bitboard(square), occupancy);
         }
+        bishop_atks.push(square_attacks);
     }
     bishop_atks
 }
 
-use std::collections::HashMap;
-
-#[allow(clippy::large_stack_frames)]
-pub fn init_rook_attacks() -> HashMap<usize, HashMap<usize, Bitboard>> {
+fn init_rook_attacks() -> Vec<Vec<Bitboard>> {
     let mut rook_masks: Vec<Bitboard> = vec![0; 64];
-    let mut rook_atks: HashMap<usize, HashMap<usize, Bitboard>> = HashMap::new();
+    let mut rook_atks: Vec<Vec<Bitboard>> = Vec::with_capacity(64);
 
     for square in 0..64 {
         rook_masks[square] = mask_rook_attacks(square_to_bitboard(square));
         let attack_mask = rook_masks[square];
         let occupancy_indices = square_to_bitboard(ROOK_RELEVANT_BITS[square]);
-
-        let mut square_map: HashMap<usize, Bitboard> = HashMap::new();
+        let mut square_attacks = vec![0; occupancy_indices as usize];
 
         for idx in 0..occupancy_indices {
-            let occupancy = set_occupancy(idx, ROOK_RELEVANT_BITS[square], attack_mask);
-            let magic_idx = (occupancy.wrapping_mul(ROOK_MAGIC[square])
-                >> (64 - ROOK_RELEVANT_BITS[square])) as usize;
+            let occupancy = set_occupancy(idx as u64, ROOK_RELEVANT_BITS[square], attack_mask);
+            let magic_idx =
+                occupancy.wrapping_mul(ROOK_MAGIC[square]) >> (64 - ROOK_RELEVANT_BITS[square]);
 
-            square_map.insert(
-                magic_idx,
-                rook_attacks_on_the_fly(square_to_bitboard(square), occupancy),
-            );
+            square_attacks[magic_idx as usize] =
+                rook_attacks_on_the_fly(square_to_bitboard(square), occupancy);
         }
-
-        rook_atks.insert(square, square_map);
+        rook_atks.push(square_attacks);
     }
-
     rook_atks
 }
 
 use std::{array, sync::LazyLock};
 
 pub fn init_attacks() {
-    init_pawn_attacks();
-    init_knight_attacks();
-    init_king_attacks();
-    init_bishop_attacks();
-    init_rook_attacks();
+    let _ = &*PAWN_ATTACKS;
+    let _ = &*KNIGHT_ATTACKS;
+    let _ = &*KING_ATTACKS;
+    let _ = &*BISHOP_ATTACKS;
+    let _ = &*ROOK_ATTACKS;
 }
 
 #[cfg(test)]