Prefetch tt cluster for the new zobrist key after makemove

CMakeLists.txt

@@ -146,7 +146,7 @@ set(srcs
     src/util/bit.hpp
     src/util/parse.hpp
     src/util/pretty.hpp
-    src/util/large_pages.hpp
+    src/util/mem.hpp
     src/util/static_vector.hpp
     src/util/types.hpp
     src/util/vec/sse2.hpp

src/position.cpp

@@ -4,6 +4,7 @@
 #include "common.hpp"
 #include "geometry.hpp"
 #include "psqt_state.hpp"
+#include "util/mem.hpp"
 #include "util/parse.hpp"
 #include "util/types.hpp"
 #include "zobrist.hpp"
@@ -366,7 +367,7 @@ void Position::add_attacks(bool color, PieceId id, Square sq, PieceType ptype, m
 }
 
 template<bool UPDATE_PSQT>
-Position Position::move(Move m, PsqtState* psqtState) const {
+Position Position::move(Move m, PsqtState* psqtState, const TT* tt) const {
     Position    new_pos = *this;
     PsqtUpdates updates{};
 
@@ -514,6 +515,11 @@ Position Position::move(Move m, PsqtState* psqtState) const {
       new_pos.m_rook_info[0].as_index() | (new_pos.m_rook_info[1].as_index() << 2);
     new_pos.m_hash_key ^= Zobrist::castling_zobrist[new_castle_index];
 
+    // Prefetch hash key tt entry
+    if (tt != nullptr) {
+        prefetch(tt->addr_key(new_pos.m_hash_key));
+    }
+
     new_pos.m_active_color = invert(m_active_color);
     new_pos.m_ply++;
 
@@ -524,8 +530,8 @@ Position Position::move(Move m, PsqtState* psqtState) const {
     return new_pos;
 }
 
-template Position Position::move<true>(Move m, PsqtState* psqtState) const;
-template Position Position::move<false>(Move m, PsqtState* psqtState) const;
+template Position Position::move<true>(Move m, PsqtState* psqtState, const TT* tt = nullptr) const;
+template Position Position::move<false>(Move m, PsqtState* psqtState, const TT* tt = nullptr) const;
 
 Position Position::null_move() const {
     Position new_pos = *this;

src/position.hpp

@@ -3,6 +3,7 @@
 #include "board.hpp"
 #include "move.hpp"
 #include "square.hpp"
+#include "tt.hpp"
 #include "util/types.hpp"
 #include <array>
 #include <bit>
@@ -12,6 +13,8 @@
 
 namespace Clockwork {
 
+class TT;
+
 struct PsqtState;
 struct PsqtUpdates;
 
@@ -259,15 +262,18 @@ struct Position {
     }
 
     template<bool UPDATE_PSQT>
-    [[nodiscard]] Position move(Move m, PsqtState* psqt_state) const;
-    [[nodiscard]] Position null_move() const;
-
-    [[nodiscard]] Position move(Move m) const {
-        return move<false>(m, nullptr);
+    [[nodiscard]] Position move(Move m, PsqtState* psqt_state, const TT* tt = nullptr) const;
+    [[nodiscard]] Position move(Move m, PsqtState& psqt_state, const TT* tt = nullptr) const {
+        return move<true>(m, &psqt_state, tt);
     }
     [[nodiscard]] Position move(Move m, PsqtState& psqt_state) const {
         return move<true>(m, &psqt_state);
     }
+    [[nodiscard]] Position move(Move m) const {
+        return move<false>(m, nullptr);
+    }
+
+    [[nodiscard]] Position null_move() const;
 
     [[nodiscard]] std::tuple<Wordboard, Bitboard> calc_pin_mask() const;
 

src/search.cpp

@@ -10,8 +10,8 @@
 #include "tm.hpp"
 #include "tuned.hpp"
 #include "uci.hpp"
-#include "util/large_pages.hpp"
 #include "util/log2.hpp"
+#include "util/mem.hpp"
 #include "util/types.hpp"
 #include <algorithm>
 #include <array>
@@ -555,7 +555,7 @@ Value Worker::search(
             for (Move m = moves.next(); m != Move::none(); m = moves.next()) {
 
                 ss->cont_hist_entry = &m_td.history.get_cont_hist_entry(pos, m);
-                Position pos_after  = pos.move(m, m_td.push_psqt_state());
+                Position pos_after  = pos.move(m, m_td.push_psqt_state(), &m_searcher.tt);
                 repetition_info.push(pos_after.get_hash_key(), pos_after.is_reversible(m));
 
                 Value probcut_value =
@@ -708,7 +708,7 @@ Value Worker::search(
         // Do move
         ss->cont_hist_entry = &m_td.history.get_cont_hist_entry(pos, m);
 
-        Position pos_after = pos.move(m, m_td.push_psqt_state());
+        Position pos_after = pos.move(m, m_td.push_psqt_state(), &m_searcher.tt);
         moves_played++;
 
         // Put hash into repetition table. TODO: encapsulate this and any other future adjustment to do "on move" into a proper function
@@ -988,7 +988,7 @@ Value Worker::quiesce(const Position& pos, Stack* ss, Value alpha, Value beta, i
 
         // Do move
         ss->cont_hist_entry = &m_td.history.get_cont_hist_entry(pos, m);
-        Position pos_after  = pos.move(m, m_td.push_psqt_state());
+        Position pos_after  = pos.move(m, m_td.push_psqt_state(), &m_searcher.tt);
         moves_searched++;
 
         // If we've found a legal move, then we can begin skipping quiet moves.

src/tt.cpp

@@ -85,6 +85,11 @@ std::optional<TTData> TT::probe(const Position& pos, i32 ply) const {
     return {};
 }
 
+TTClusterMemory* TT::addr_key(const u64 key) const {
+    size_t idx = mulhi64(key, m_size);
+    return &this->m_clusters[idx];
+}
+
 void TT::store(const Position& pos,
                i32             ply,
                Value           eval,

src/tt.hpp

@@ -1,7 +1,7 @@
 #pragma once
 
 #include "position.hpp"
-#include "util/large_pages.hpp"
+#include "util/mem.hpp"
 #include <array>
 #include <atomic>
 #include <bit>
@@ -105,6 +105,8 @@ class TT {
     void                  clear();
     void                  increment_age();
     i32                   hashfull() const;
+    TTClusterMemory*      addr_key(const u64 key) const;
+
 
 private:
     unique_ptr_huge_page<TTClusterMemory[]> m_clusters;

src/util/large_pages.hpp → src/util/mem.hpp

@@ -13,6 +13,8 @@
     #include <windows.h>
 #endif
 
+// Large page allocation utilities
+
 template<typename T>
 using unique_ptr_huge_page =
   std::conditional_t<std::is_array_v<T>,
@@ -154,3 +156,9 @@ unique_ptr_huge_page<T> make_unique_for_overwrite_huge_page(std::size_t n) {
 template<class T, class... Args>
     requires std::is_bounded_array_v<T>
 void make_unique_for_overwrite_huge_page(Args&&...) = delete;
+
+
+// Prefetching utilities
+inline void prefetch(const void* ptr) {
+    __builtin_prefetch(ptr);
+}