From 20dd36d4b39654c4d8d2f5d28817fa308eb4c624 Mon Sep 17 00:00:00 2001
From: eug-vs <eugene@eug-vs.xyz>
Date: Mon, 4 Sep 2023 12:22:54 +0300
Subject: feat: use plain negamax instead of MTD(f)

TODO: figure out MTD(f) with TTable
---
 src/grossmeister/search.rs | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

(limited to 'src/grossmeister')

diff --git a/src/grossmeister/search.rs b/src/grossmeister/search.rs
index 23bcdfa..09c8bc1 100644
--- a/src/grossmeister/search.rs
+++ b/src/grossmeister/search.rs
@@ -48,7 +48,7 @@ impl Grossmeister {
         }
 
         if let Some(transposition) = self.transposition() {
-            if transposition.depth == depth_left {
+            if transposition.depth >= depth_left {
                 match transposition.node_type {
                     NodeType::PV => { // PV-nodes have exact score
                         return transposition.score
@@ -57,11 +57,17 @@ impl Grossmeister {
                         if transposition.score >= beta {
                             return beta
                         }
+                        if transposition.score > alpha {
+                            alpha = transposition.score
+                        }
                     }
                     NodeType::All => {
                         if transposition.score <= alpha {
                             return alpha
                         }
+                        if transposition.score < beta {
+                            beta = transposition.score
+                        }
                     }
                 }
             }
@@ -229,7 +235,6 @@ impl Grossmeister {
         let mut pv = Vec::with_capacity(depth as usize);
 
         if let Some(transposition) = self.transposition() {
-            debug_assert!(transposition.node_type == NodeType::PV);
             let mov = transposition.mov;
             let ep_target_before = self.board.ep_target;
             let castling_rights_before = self.board.castling_rights;
@@ -248,7 +253,9 @@ impl Grossmeister {
 
     /// Memory-enhanced Test Driver
     /// Given a guess score (from previous iteration), use it for series of small-window searches
+    #[allow(unused)]
     fn mtdf(&mut self, score_guess: Score, depth: u8) -> Score {
+        todo!("In order to use, (NodeType::PV ? NodeType::Cut) must be Ordering::Equal, try your luck with mate_in_3 test");
         let window_size = 1.00;
         let mut score = score_guess;
         let mut lowerbound = -INFINITY;
@@ -279,7 +286,7 @@ impl Grossmeister {
         let mut depth = 0;
 
         while depth <= max_depth {
-            let score = self.mtdf(best_score, depth);
+            let score = self.negamax_search(-INFINITY, INFINITY, depth, 0);
 
             if self.should_halt.load(std::sync::atomic::Ordering::SeqCst) {
                 println!("info string halting search");
-- 
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