From ecf1de6c6a5430bae210ae6e92835f0604a23749 Mon Sep 17 00:00:00 2001
From: Moritz Eigenauer <moritz.eigenauer@gmail.com>
Date: Tue, 18 Nov 2025 15:19:30 +0100
Subject: [PATCH] iterative deepening

---
 progress_tracking/progress.xlsx | Bin 5602 -> 5634 bytes
 src/bin/suite.rs                |   4 +--
 src/engine.rs                   |  51 +++++++++++++++++++++++++++++---
 src/search/alpha_beta.rs        |  29 ++++++++++++++++--
 src/uci.rs                      |   2 +-
 5 files changed, 77 insertions(+), 9 deletions(-)

diff --git a/progress_tracking/progress.xlsx b/progress_tracking/progress.xlsx
index f28baa38f3b110df809a50a12df7a99c854fffa1..b0b512623f44491a2afe94ddeda100aea3fa2093 100644
GIT binary patch
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diff --git a/src/bin/suite.rs b/src/bin/suite.rs
index cd7e569..5b4d8e5 100644
--- a/src/bin/suite.rs
+++ b/src/bin/suite.rs
@@ -29,7 +29,7 @@ fn main() {
     let mut engine = Engine::new("Yakari".to_string(), "EiSiMo".to_string());
 
     // Set the time limit to 1 second
-    let time_limit = Duration::from_secs(1);
+    let time_limit = Duration::from_millis(500);
 
     for test in &sts {
         let fen = &test[0];
@@ -40,7 +40,7 @@ fn main() {
         // Record start time
         let start_time = Instant::now();
 
-        let result = engine.search(5);
+        let result = engine.search(490_u64);
 
         // Calculate duration
         let duration = start_time.elapsed();
diff --git a/src/engine.rs b/src/engine.rs
index a3aa051..f51268c 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -1,7 +1,7 @@
-// ... (your use statements)
 use crate::board::Board;
 use crate::r#move::Move;
 use crate::search::alpha_beta::alpha_beta;
+use std::time::{Instant, Duration};
 
 pub struct Engine {
     pub name: String,
@@ -32,8 +32,51 @@ impl Engine {
         }
     }
 
-    pub fn search(&mut self, depth: u8) -> String {
-        let (opt_move, _score) = alpha_beta(&mut self.board, depth, 0, -i32::MAX, i32::MAX);
+    pub fn search(&mut self, time_limit_ms: u64) -> String {
+        let start_time = Instant::now();
+        let time_limit = Duration::from_millis(time_limit_ms);
+        
+        // We track nodes to limit how often we check the clock inside alpha_beta
+        let mut nodes = 0;
+
+        // Initial search at depth 1
+        let (mut opt_move, mut _score) = alpha_beta(
+            &mut self.board, 
+            1, 
+            0, 
+            -i32::MAX, 
+            i32::MAX, 
+            start_time, 
+            time_limit, 
+            &mut nodes
+        );
+        
+        let mut depth = 2;
+
+        // Iterative Deepening
+        while start_time.elapsed() < time_limit {
+            let (new_move, new_score) = alpha_beta(
+                &mut self.board, 
+                depth, 
+                0, 
+                -i32::MAX, 
+                i32::MAX, 
+                start_time, 
+                time_limit, 
+                &mut nodes
+            );
+
+            // If time ran out during the search, alpha_beta returns garbage (None, 0).
+            // We must verify we still have time before accepting the new result.
+            if start_time.elapsed() > time_limit {
+                break; // Discard new_move, keep the one from the previous depth
+            }
+
+            opt_move = new_move;
+            _score = new_score;
+            
+            depth += 1;
+        }
 
         if let Some(mv) = opt_move {
             mv.to_algebraic()
@@ -42,4 +85,4 @@ impl Engine {
             "null".to_string()
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/search/alpha_beta.rs b/src/search/alpha_beta.rs
index ea9e69a..7562d3a 100644
--- a/src/search/alpha_beta.rs
+++ b/src/search/alpha_beta.rs
@@ -1,8 +1,9 @@
-use crate::board::{Board, Color}; // <-- Assuming you have a Color enum (e.g., Color::White, Color::Black)
+use crate::board::{Board, Color};
 use crate::eval::basic::evaluate_board;
 use crate::movegen::generate_pseudo_legal_moves;
 use crate::movegen::legal_check::*;
 use crate::r#move::{Move, MoveList};
+use std::time::{Instant, Duration};
 
 // A score high enough to be > any material eval, but low enough to not overflow when adding ply
 const MATE_SCORE: i32 = 1_000_000;
@@ -21,7 +22,20 @@ pub fn alpha_beta(
     ply: u8,
     mut alpha: i32,
     beta: i32,
+    start_time: Instant,
+    time_limit: Duration,
+    nodes: &mut u64,
 ) -> (Option<Move>, i32) {
+    // Check for time usage every 4096 nodes to reduce system call overhead
+    if *nodes % 4096 == 0 {
+        if start_time.elapsed() > time_limit {
+            // Return immediately. The return value here effectively signals an abort,
+            // but the engine must discard this result.
+            return (None, 0); 
+        }
+    }
+    *nodes += 1;
+
     if depth == 0 {
         return (None, evaluate_board_relative(board));
     }
@@ -42,7 +56,18 @@ pub fn alpha_beta(
         legal_moves_found = true;
 
         // Recursive call with negated and swapped alpha/beta
-        let (_, score) = alpha_beta(board, depth - 1, ply + 1, -beta, -alpha);
+        // Pass time parameters and node counter down
+        let (_, score) = alpha_beta(board, depth - 1, ply + 1, -beta, -alpha, start_time, time_limit, nodes);
+        
+        // If we aborted deeper in the tree (returned 0 due to timeout), 
+        // we should technically propagate that up, but checking elapsed() 
+        // at the loop start (via recursion) handles it eventually.
+        // For a strict abort, we check here too:
+        if *nodes % 4096 == 0 && start_time.elapsed() > time_limit {
+             board.undo_move(undo_mv);
+             return (None, 0);
+        }
+
         let current_score = -score;
 
         if current_score > best_score {
diff --git a/src/uci.rs b/src/uci.rs
index 47ef0e4..53526ad 100644
--- a/src/uci.rs
+++ b/src/uci.rs
@@ -42,7 +42,7 @@ pub fn uci_mainloop(engine: &mut Engine) {
                 }
                 "go" => {
                     // TODO add a lot functionality
-                    println!("bestmove {}", engine.search(6));
+                    println!("bestmove {}", engine.search(1000_u64));
                 }
                 "stop" => {
                     // TODO stop search as soon as possible