feat: add initial implementation of killers table

Author: DeveloperPaul123

engine/src/defs.rs

@@ -14,11 +14,11 @@
 
 #[rustfmt::skip]
 const BANNER: &str = r#"
- _         _           _        _      _   _   
-| |__ _  _| |_ ___ ___| |___ _ (_)__ _| |_| |_ 
+ _         _           _        _      _   _
+| |__ _  _| |_ ___ ___| |___ _ (_)__ _| |_| |_
 | '_ \ || |  _/ -_)___| / / ' \| / _` | ' \  _|
 |_.__/\_, |\__\___|   |_\_\_||_|_\__, |_||_\__|
-      |__/                       |___/         
+      |__/                       |___/
 "#;
 
 pub struct About;
@@ -32,3 +32,4 @@ impl About {
 }
 
 pub(crate) const MAX_DEPTH: u8 = 128;
+pub(crate) const MAX_KILLERS_PER_PLY: usize = 2;

engine/src/killer_moves_table.rs

@@ -0,0 +1,68 @@
+use chess::moves::Move;
+
+use crate::defs::{MAX_DEPTH, MAX_KILLERS_PER_PLY};
+
+pub struct KillerMovesTable {
+    table: [[Option<Move>; MAX_KILLERS_PER_PLY]; MAX_DEPTH as usize],
+}
+
+impl KillerMovesTable {
+    pub(crate) fn new() -> Self {
+        let table = [[None; MAX_KILLERS_PER_PLY]; MAX_DEPTH as usize];
+
+        Self { table }
+    }
+
+    pub(crate) fn get(&self, ply: u8) -> &[Option<Move>] {
+        assert!(ply < MAX_DEPTH, "Depth is out of bounds");
+
+        &self.table[ply as usize][..]
+    }
+
+    fn get_mut(&mut self, ply: u8) -> &mut [Option<Move>] {
+        assert!(ply < MAX_DEPTH, "Depth is out of bounds");
+
+        &mut self.table[ply as usize][..]
+    }
+
+    pub(crate) fn update(&mut self, ply: u8, mv: Move) {
+        assert!(ply < MAX_DEPTH, "Depth is out of bounds");
+
+        let current_killers = self.get_mut(ply);
+        if !current_killers[0].is_some_and(|killer_mv| killer_mv == mv) {
+            current_killers.swap(0, 1);
+            current_killers[0] = Some(mv);
+        }
+    }
+
+    pub(crate) fn clear(&mut self) {
+        for item in self.table.as_flattened_mut() {
+            *item = None;
+        }
+    }
+}
+
+impl Default for KillerMovesTable {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use crate::defs::{MAX_DEPTH, MAX_KILLERS_PER_PLY};
+
+    use super::KillerMovesTable;
+
+    #[test]
+
+    fn initialize_killers_table() {
+        let killers_table: KillerMovesTable = Default::default();
+        for i in 0..MAX_DEPTH {
+            let killers = killers_table.get(i);
+            assert_eq!(killers, &[None, None]);
+            assert_eq!(killers.len(), MAX_KILLERS_PER_PLY);
+        }
+    }
+}

engine/src/lib.rs

@@ -10,6 +10,7 @@ pub mod hce_values;
 pub mod history_table;
 mod inplace_incremental_sort;
 pub mod input_handler;
+pub mod killer_moves_table;
 mod lmr;
 pub mod log_level;
 mod move_order;