From 1c7100f510a4830acdc1d1979000eaa408ca6948 Mon Sep 17 00:00:00 2001
From: stefiosif <stef8iosif@gmail.com>
Date: Sat, 18 Jan 2025 17:44:27 +0200
Subject: [PATCH] Use TT to store best move after each ID iteration

---
 src/search/iterative_deepening.rs | 21 ++++++---------------
 src/search/mod.rs                 | 16 ----------------
 src/search/negamax.rs             | 29 ++++++++++++-----------------
 src/search/transposition_table.rs |  4 +---
 4 files changed, 19 insertions(+), 51 deletions(-)

diff --git a/src/search/iterative_deepening.rs b/src/search/iterative_deepening.rs
index 0c80c76..599c516 100644
--- a/src/search/iterative_deepening.rs
+++ b/src/search/iterative_deepening.rs
@@ -22,7 +22,7 @@ pub fn iterative_deepening(
             return Ok(best_move);
         }
 
-        let search_result = negamax::negamax(
+        let score = negamax::negamax(
             game,
             MIN_SCORE,
             MAX_SCORE,
@@ -31,22 +31,13 @@ pub fn iterative_deepening(
             &TimeInfo::new(time, remaining_time),
         );
 
-        if let Ok(search_result) = search_result {
-            if search_result.best_move.is_some() {
-                best_move = search_result.best_move;
-            }
-            best_score = search_result.best_score;
-        } else {
-            return Ok(best_move);
+        if score.is_err() {
+            break;
         }
+
+        best_score = score?;
+        best_move = game.tt.lookup(game.hash).and_then(|entry| entry.mv);
     }
-
-    // tt.lookup(game.hash).map(|entry| {
-    //     if entry.mv.is_some() {
-    //         best_move = entry.mv;
-    //     }
-    // });
-
     Ok(best_move)
 }
 
diff --git a/src/search/mod.rs b/src/search/mod.rs
index 6462ac2..7afda13 100644
--- a/src/search/mod.rs
+++ b/src/search/mod.rs
@@ -1,5 +1,3 @@
-use crate::movegen::r#move::Move;
-
 pub mod iterative_deepening;
 pub mod move_ordering;
 pub mod negamax;
@@ -14,17 +12,3 @@ pub const HARD_LIMIT_DIVISION: u128 = 10; // % of the remaining time
 pub const SOFT_LIMIT_DIVISION: u128 = HARD_LIMIT_DIVISION / 2;
 pub const SOFT_EVAL_THRESHOLD: i32 = 500;
 pub const MAX_TT_SIZE: u64 = 1000000;
-
-pub struct SearchResult {
-    pub best_move: Option<Move>,
-    pub best_score: i32,
-}
-
-impl SearchResult {
-    pub const fn new(best_move: Option<Move>, best_score: i32) -> Self {
-        Self {
-            best_move,
-            best_score,
-        }
-    }
-}
diff --git a/src/search/negamax.rs b/src/search/negamax.rs
index 9cb5499..f57c9a8 100644
--- a/src/search/negamax.rs
+++ b/src/search/negamax.rs
@@ -10,7 +10,6 @@ use super::{
     quiescence::quiescence,
     time::{hard_limit, TimeInfo},
     transposition_table::TTEntry,
-    SearchResult,
 };
 
 pub fn negamax(
@@ -20,14 +19,14 @@ pub fn negamax(
     depth: u8,
     plies: u8,
     time_info: &TimeInfo,
-) -> Result<SearchResult> {
+) -> Result<i32> {
     if hard_limit(&time_info.time, time_info.remaining_time_in_ms) {
         bail!("Time is up! In Negamax");
     }
 
     if depth == 0 {
         let q_score = quiescence(game, alpha, beta, time_info).map_err(|e| anyhow!("{e}"))?;
-        return Ok(SearchResult::new(None, q_score));
+        return Ok(q_score);
     }
 
     let color = game.current_player();
@@ -49,7 +48,7 @@ pub fn negamax(
         }
 
         legal_moves += 1;
-        let score = -negamax(game, -beta, -alpha, depth - 1, plies + 1, time_info)?.best_score;
+        let score = -negamax(game, -beta, -alpha, depth - 1, plies + 1, time_info)?;
         game.unmake_move();
 
         if score > best_score {
@@ -70,13 +69,13 @@ pub fn negamax(
 
     if legal_moves == 0 {
         if game.board.king_under_check(color) {
-            return Ok(SearchResult::new(None, mate_score));
+            return Ok(mate_score);
         }
-        return Ok(SearchResult::new(None, 0));
+        return Ok(0);
     }
 
     game.tt.insert(TTEntry::new(game.hash, best_move));
-    Ok(SearchResult::new(best_move, best_score))
+    Ok(best_score)
 }
 
 #[cfg(test)]
@@ -100,22 +99,18 @@ mod tests {
 
         let e3f2 = Move::new(Square::E3, Square::F2);
         let time_info = TimeInfo::new(std::time::Instant::now(), 1000);
-        let anointed_move = negamax(&mut game, MIN_SCORE, MAX_SCORE, 2, 0, &time_info)
-            .expect("Expected a search result")
-            .best_move
-            .expect("Expected a move");
+        negamax(&mut game, MIN_SCORE, MAX_SCORE, 2, 0, &time_info)
+            .expect("Expected a search result");
 
-        assert_eq!(e3f2, anointed_move);
+        assert_eq!(e3f2, game.tt.lookup(game.hash).unwrap().mv.unwrap());
 
         let mut game = from_fen(FEN_MATE_IN_1[1]).unwrap();
 
         let e3f2 = Move::new(Square::E3, Square::F2);
-        let anointed_move = negamax(&mut game, MIN_SCORE, MAX_SCORE, 2, 0, &time_info)
-            .expect("Expected a search result")
-            .best_move
-            .expect("Expected a move");
+        negamax(&mut game, MIN_SCORE, MAX_SCORE, 2, 0, &time_info)
+            .expect("Expected a search result");
 
-        assert_eq!(e3f2, anointed_move);
+        assert_eq!(e3f2, game.tt.lookup(game.hash).unwrap().mv.unwrap());
 
         Ok(())
     }
diff --git a/src/search/transposition_table.rs b/src/search/transposition_table.rs
index d7b3962..c60725f 100644
--- a/src/search/transposition_table.rs
+++ b/src/search/transposition_table.rs
@@ -61,9 +61,7 @@ mod tests {
         let time_info = TimeInfo::new(std::time::Instant::now(), 30000);
 
         negamax(&mut game, MIN_SCORE, MAX_SCORE, 2, 0, &time_info)
-            .expect("Expected a search result")
-            .best_move
-            .expect("Expected a move");
+            .expect("Expected a search result");
 
         dbg!(time_info.time.elapsed());