Transposition Table and Repetition Detection

CMakeLists.txt

@@ -7,8 +7,8 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 project(chess_engine VERSION 1.0 DESCRIPTION "Chess Engine")
 
 set(CMAKE_CXX_FLAGS "-Wall -Wpedantic -Wextra -Wconversion -Werror")
-set(CMAKE_CXX_FLAGS_DEBUG "-g")
 set(CMAKE_CXX_FLAGS_RELEASE "-O3")
+set(CMAKE_CXX_FLAGS_DEBUG "-g")
 
 if(NOT CMAKE_BUILD_TYPE)
   set(CMAKE_BUILD_TYPE Debug)

README.md

@@ -39,6 +39,7 @@ Features
 - [Null Move Pruning](https://www.chessprogramming.org/Null_Move_Pruning)
 - [Null Window Search](https://www.chessprogramming.org/Null_Window)
 - [Transposition Table](https://en.wikipedia.org/wiki/Transposition_table)
+- [Repetition Detection](https://www.chessprogramming.org/Repetitions)
 
 Building and Installation
 ===

src/engine/bitboard.cpp

@@ -19,16 +19,17 @@ namespace bitboard
         return (int)count;
     }
 
-    int bit_scan(u64 bb)
+    Square bit_scan(u64 bb)
     {
         if (bb)
         {
-            return bit_count((bb & -bb) - 1);
+            return (Square)bit_count((bb & -bb) - 1);
         }
-        return -1;
+
+        return EMPTY_SQUARE;
     }
 
-    int bit_scan_forward(u64 bb)
+    Square bit_scan_forward(u64 bb)
     {
         static const int index64[64] = {
             0, 47, 1, 56, 48, 27, 2, 60,
@@ -41,32 +42,33 @@ namespace bitboard
             13, 18, 8, 12, 7, 6, 5, 63};
 
         static const u64 debruijn64 = 0x03f79d71b4cb0a89;
-        return index64[((bb ^ (bb - 1)) * debruijn64) >> 58];
+        return (Square)index64[((bb ^ (bb - 1)) * debruijn64) >> 58];
     }
 
     u64 set_occupancy(int index, int bits_in_mask, u64 attack_mask)
     {
         u64 occupancy = ZERO;
         for (int bit = 0; bit < bits_in_mask; bit++)
         {
-            int lsb_sq = bit_scan_forward(attack_mask);
+            Square lsb_sq = bit_scan_forward(attack_mask);
             pop_bit(attack_mask, lsb_sq);
             if (index & (1 << bit))
             {
-                occupancy |= tables::SQUARE_BB[lsb_sq];
+                occupancy |= tables::square_to_bitboard((Square)lsb_sq);
             }
         }
+
         return occupancy;
     }
 
     void print(u64 bb)
     {
-        for (int i = 7; i >= 0; i--)
+        for (int i = RANK_8; i >= RANK_1; i--)
         {
             std::cout << i + 1 << "  ";
-            for (int n = 0; n < 8; n++)
+            for (int n = FILE_A; n < N_FILES; n++)
             {
-                std::cout << ((bb >> utils::get_square(i, n)) & ONE) << " ";
+                std::cout << ((bb >> utils::get_square((Rank)i, (File)n)) & ONE) << " ";
             }
             std::cout << "\n";
         }

src/engine/bitboard.hpp

@@ -1,14 +1,22 @@
 #pragma once
 
+#include <cstdint>
+
 #include <engine/constants.hpp>
 
+typedef std::uint64_t u64;
+
+constexpr u64 ONE = 1ULL;
+constexpr u64 ZERO = 0ULL;
+
 namespace bitboard
 {
+
     // Common Bitboard Operations
-    inline bool get_bit(u64 bb, int sq) { return ((bb >> sq) & 1ULL); }
-    inline void pop_bit(u64 &bn, int sq) { bn &= ~(1ULL << sq); }
+    inline bool get_bit(u64 bb, Square sq) { return ((bb >> sq) & 1ULL); }
+    inline void pop_bit(u64 &bn, Square sq) { bn &= ~(1ULL << sq); }
     inline void pop_last_bit(u64 &bb) { bb &= bb - 1; }
-    inline void set_bit(u64 &bb, int sq) { bb |= (1ULL << sq); }
+    inline void set_bit(u64 &bb, Square sq) { bb |= (1ULL << sq); }
 
     // Common Bitboard Shifts
     inline u64 sout_one(u64 bb) { return (bb >> 8); }
@@ -34,15 +42,15 @@ namespace bitboard
      * @param bb
      * @return unsigned int
      */
-    int bit_scan(u64 bb);
+    Square bit_scan(u64 bb);
 
     /**
      * @brief Returns index of LSB bit
      *
      * @param bb
      * @return unsigned int
      */
-    int bit_scan_forward(u64 bb);
+    Square bit_scan_forward(u64 bb);
 
     /**
      * @brief Sets the occupancy bits