From ef5cf6412cf451cdd49c9a09bdcac0f7e5cdb2f1 Mon Sep 17 00:00:00 2001
From: SzilBalazs <szilprogramming@gmail.com>
Date: Thu, 10 Aug 2023 20:38:47 +0200
Subject: [PATCH] Qsearch TT

Bench: 1997745
---
 src/search/search_thread.h | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/search/search_thread.h b/src/search/search_thread.h
index d6990a3..7a51658 100644
--- a/src/search/search_thread.h
+++ b/src/search/search_thread.h
@@ -434,11 +434,20 @@ namespace search {
 
         template<NodeType node_type>
         Score qsearch(Score alpha, Score beta) {
+            constexpr bool non_pv_node = node_type == NON_PV_NODE;
 
             if (!shared.is_searching) {
                 return UNKNOWN_SCORE;
             }
 
+            std::optional<TTEntry> entry = shared.tt.probe(board.get_hash());
+            chess::Move hash_move = entry ? entry->hash_move : chess::NULL_MOVE;
+
+            if (entry && non_pv_node &&
+                (entry->flag == TT_EXACT || (entry->flag == TT_ALPHA && entry->eval <= alpha) || (entry->flag == TT_BETA && entry->eval >= beta))) {
+                return entry->eval;
+            }
+
             Score static_eval = eval::evaluate(board, nnue);
 
             if (static_eval >= beta)
@@ -446,14 +455,16 @@ namespace search {
             if (static_eval > alpha)
                 alpha = static_eval;
 
-            MoveList<true> move_list(board, chess::NULL_MOVE, chess::NULL_MOVE, history, 0);
+            MoveList<true> move_list(board, hash_move, chess::NULL_MOVE, history, 0);
 
             while (!move_list.empty()) {
                 chess::Move move = move_list.next_move();
 
                 if (alpha > -WORST_MATE && !see(board, move, 0)) continue;
 
+                shared.tt.prefetch(board.hash_after_move(move));
                 shared.node_count[id]++;
+
                 board.make_move(move, &nnue);
                 Score score = -qsearch<node_type>(-beta, -alpha);
                 board.undo_move(move, &nnue);