first version of stickfosh, simply evaluates a

position based on the material (no AB-pruning)

cpp/src/board.cpp

@@ -182,7 +182,9 @@ Board Board::make_move(Move move) const {
     ret.squares[move.target_square] = this->squares[move.source_square];
 
     // -- Handle en passant target being eaten
-    if (move.en_passant)
+    if (en_passant_target != -1
+        && (squares[move.source_square] & 0b111) == Piece::Pawn
+        && squares[move.target_square] == Piece::None)
         ret.squares[move.target_square + (white_to_play ? -8 : 8)] =
             Piece::None;
 
@@ -203,23 +205,26 @@ Board Board::make_move(Move move) const {
 
     // -- Handle castling (just move the rook over)
     Coords c = Coords::from_index(move.source_square);
-    if (move.castle_side & KingSide) {
+    if ((squares[move.source_square] & 0b111) == Piece::King) {
-        Coords rook_source{7, c.y};
+        if (move.target_square - move.source_square == 2) { // king side castle
-        int8_t old_rook = ret.squares[rook_source.to_index()];
+            Coords rook_source{7, c.y};
-        ret.squares[rook_source.to_index()] = Piece::None;
+            int8_t old_rook = ret.squares[rook_source.to_index()];
-        Coords rook_dest{5, c.y};
+            ret.squares[rook_source.to_index()] = Piece::None;
-        ret.squares[rook_dest.to_index()] = old_rook;
+            Coords rook_dest{5, c.y};
-    } else if (move.castle_side & QueenSide) {
+            ret.squares[rook_dest.to_index()] = old_rook;
-        Coords rook_source{0, c.y};
+        } else if (move.target_square - move.source_square == -2) { // queen
-        int8_t old_rook = ret.squares[rook_source.to_index()];
+            Coords rook_source{0, c.y};
-        ret.squares[rook_source.to_index()] = Piece::None;
+            int8_t old_rook = ret.squares[rook_source.to_index()];
-        Coords rook_dest{3, c.y};
+            ret.squares[rook_source.to_index()] = Piece::None;
-        ret.squares[rook_dest.to_index()] = old_rook;
+            Coords rook_dest{3, c.y};
+            ret.squares[rook_dest.to_index()] = old_rook;
+        }
     }
 
     // -- Check for castling rights
     ret.w_castle_rights = w_castle_rights;
     ret.b_castle_rights = b_castle_rights;
+    bool is_capturing = squares[move.target_square] != Piece::None;
     if (white_to_play) {
         if ((squares[move.source_square] & 0b111) == King)
             ret.w_castle_rights = NeitherSide;
@@ -232,7 +237,7 @@ Board Board::make_move(Move move) const {
         }
 
         Coords target = Coords::from_index(move.target_square);
-        if (move.is_capturing && target.y == 7
+        if (is_capturing && target.y == 7
             && (squares[move.target_square] & 0b111) == Rook) {
             if (target.x == 0 && (ret.b_castle_rights & QueenSide))
                 ret.b_castle_rights &= ~(QueenSide);
@@ -251,7 +256,7 @@ Board Board::make_move(Move move) const {
         }
 
         Coords target = Coords::from_index(move.target_square);
-        if (move.is_capturing && target.y == 0
+        if (is_capturing && target.y == 0
             && (squares[move.target_square] & 0b111) == Rook) {
             if (target.x == 0 && (ret.w_castle_rights & QueenSide))
                 ret.w_castle_rights &= ~(QueenSide);

cpp/src/coords.hpp

@@ -1,6 +1,5 @@
 #pragma once
 
-#include <cstdint>
 #include <iostream>
 #include <stdexcept>
 #include <string>

cpp/src/main.cpp

@@ -1,12 +1,11 @@
-#include "board.hpp"
 #include "stickfosh.hpp"
 
 #include <iostream>
 
 int main(int argc, char* argv[]) {
     std::string pos =
-        "r2q1rk1/pP1p2pp/Q4n2/bbp1p3/Np6/1B3NBn/pPPP1PPP/R3K2R b KQ - 0 5";
+        "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
-    // Board b = Board::setup_fen_position(pos);
+    std::string move = search(pos, 4);
-    perft();
+    std::cout << move << std::endl;
     return 0;
 }

cpp/src/move.hpp

@@ -11,9 +11,6 @@ struct Move {
     int8_t source_square;
     int8_t target_square;
 
-    bool is_capturing = false;
-    CastleSide castle_side = CastleSide::NeitherSide;
-    bool en_passant = false;
     int8_t promoting_to = Piece::None;
 
     std::string to_string() const {

cpp/src/perft.cpp

@@ -0,0 +1,187 @@
+#include "perft.hpp"
+
+#include "board.hpp"
+#include "move.hpp"
+#include "threadpool.hpp"
+
+#include <chrono>
+#include <map>
+#include <ostream>
+#include <sstream>
+#include <string>
+#include <vector>
+
+static std::string tick = "\033[92m✔️\033[0m";   // Green Tick;
+static std::string cross = "\033[91m❌\033[0m"; // Red Cross
+
+static std::map<std::string, std::map<int, int>> pos2expected{
+    // -- Position 1
+    {
+        "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
+        {
+            {1, 20},     // 0
+            {2, 400},    // 1
+            {3, 8902},   // 38
+            {4, 197281}, // 971
+            // {5, 4865609}, // 23032
+        },
+    },
+
+    // -- Position 2
+    {
+        "r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 0 2",
+        {
+            {1, 48},    // 0
+            {2, 2039},  // 16
+            {3, 97862}, // 602
+            // {4, 4085603}, // 26612
+        },
+    },
+
+    // -- Position 3
+    {
+        "8/2p5/3p4/KP5r/1R3p1k/8/4P1P1/8 w - - 0 3",
+        {
+            {1, 14},     // 0
+            {2, 191},    // 1
+            {3, 2812},   // 11
+            {4, 43238},  // 157
+            {5, 674624}, // 2199
+            // {6, 11030083},
+        },
+    },
+
+    // -- Position 4a
+    {
+        "r3k2r/Pppp1ppp/1b3nbN/nP6/BBP1P3/q4N2/Pp1P2PP/R2Q1RK1 w kq - 0 4",
+        {
+            {1, 6},      // 0
+            {2, 264},    // 1
+            {3, 9467},   // 69
+            {4, 422333}, // 3085
+            // {5, 15833292}, // 124452
+        },
+    },
+
+    // -- Position 4b
+    {
+        "r2q1rk1/pP1p2pp/Q4n2/bbp1p3/Np6/1B3NBn/pPPP1PPP/R3K2R b KQ - 0 5",
+        {
+            {1, 6},      // 0
+            {2, 264},    // 2
+            {3, 9467},   // 104
+            {4, 422333}, // 3742
+            // {5, 15833292}, // 136784
+        },
+    },
+
+    // -- Position 5
+    {
+        "rnbq1k1r/pp1Pbppp/2p5/8/2B5/8/PPP1NnPP/RNBQK2R w KQ - 1 6",
+        {
+            {1, 44},    // 0
+            {2, 1486},  // 12
+            {3, 62379}, // 357
+            // {4, 2103487}, // 13804
+            // {5, 89941194}, // 1230428
+        },
+    },
+
+    // -- Position 6
+    {
+        "r4rk1/1pp1qppp/p1np1n2/2b1p1B1/2B1P1b1/P1NP1N2/1PP1QPPP/R4RK1 w - - 0 "
+        "7",
+        {
+            {1, 46},    // 0
+            {2, 2079},  // 16
+            {3, 89890}, // 602
+            // {4, 3894594}, // 26612
+            // {5, 164075551}, // 1230428
+        },
+    },
+};
+
+static std::stringstream res;
+
+int move_generation_test(
+    const Board& b, int depth, int max_depth, ThreadPool& pool
+) {
+    if (depth == max_depth) {
+        res.str("");
+        res.clear();
+    }
+
+    if (b.is_terminal())
+        return 0;
+    if (depth == 0)
+        return 1;
+
+    std::vector<Move> moves = b.all_legal_moves();
+    if (depth == 1)
+        return moves.size();
+
+    int num_pos = 0;
+
+    if (depth == max_depth) {
+        // Parallel execution at the top level
+        std::vector<std::future<int>> futures;
+        for (const Move& move : moves) {
+            Board tmp_board = b.make_move(move);
+            futures.push_back(pool.enqueue(
+                move_generation_test,
+                tmp_board,
+                depth - 1,
+                max_depth,
+                std::ref(pool)
+            ));
+        }
+
+        for (auto& future : futures)
+            num_pos += future.get(); // Retrieve the result of each task
+    } else {
+        // Regular sequential execution
+        for (const Move& move : moves) {
+            Board tmp_board = b.make_move(move);
+            int n = move_generation_test(tmp_board, depth - 1, max_depth, pool);
+            if (depth == max_depth)
+                res << move << ": " << n << std::endl;
+            num_pos += n;
+        }
+    }
+
+    return num_pos;
+}
+
+void perft() {
+    for (auto& [key, value] : pos2expected)
+        perft(key);
+}
+
+void perft(std::string pos) {
+    std::cout << pos << std::endl;
+    std::map<int, int> expected = pos2expected[pos];
+    Board b = Board::setup_fen_position(pos);
+    ThreadPool pool(std::thread::hardware_concurrency());
+
+    for (const auto& [depth, expected_n_moves] : expected) {
+        std::cout << "Depth: " << depth << " " << std::flush;
+        auto start = std::chrono::steady_clock::now();
+        int moves = move_generation_test(b, depth, depth, pool);
+        auto end = std::chrono::steady_clock::now();
+        auto elapsed =
+            std::chrono::duration_cast<std::chrono::milliseconds>(end - start)
+                .count();
+
+        std::cout << "Results: " << moves << " ";
+        if (moves == expected_n_moves)
+            std::cout << tick << " ";
+        else
+            std::cout << cross << " (expected " << expected_n_moves << ") ";
+        std::cout << "positions Time: " << elapsed << " milliseconds"
+                  << std::endl;
+        if (moves != expected_n_moves) {
+            std::cout << std::endl << res.str();
+            exit(1);
+        }
+    }
+}

cpp/src/perft.hpp

@@ -0,0 +1,6 @@
+#pragma once
+
+#include <string>
+
+void perft(std::string pos);
+void perft();

cpp/src/pieces/king.cpp

@@ -60,7 +60,6 @@ std::vector<Move> king_moves(const Board& b, const Coords xy) {
         ret.push_back(Move{
             xy.to_index(),
             Coords{6, xy.y}.to_index(),
-            .castle_side = CastleSide::KingSide
         });
     }
 
@@ -68,7 +67,6 @@ std::vector<Move> king_moves(const Board& b, const Coords xy) {
         ret.push_back(Move{
             xy.to_index(),
             Coords{2, xy.y}.to_index(),
-            .castle_side = CastleSide::QueenSide
         });
     }
 

cpp/src/pieces/pawn.cpp

@@ -21,7 +21,6 @@ std::vector<Move> pawn_moves(const Board& b, const Coords xy) {
                         ret.push_back(Move{
                             xy.to_index(),
                             left.to_index(),
-                            .is_capturing = true,
                             .promoting_to = (int8_t) (my_colour | piece)
                         });
                 else
@@ -43,7 +42,6 @@ std::vector<Move> pawn_moves(const Board& b, const Coords xy) {
                         ret.push_back(Move{
                             xy.to_index(),
                             right.to_index(),
-                            .is_capturing = true,
                             .promoting_to = (int8_t) (my_colour | piece)
                         });
                 else
@@ -55,14 +53,8 @@ std::vector<Move> pawn_moves(const Board& b, const Coords xy) {
     if (b.en_passant_target != -1) {
         Coords c = Coords::from_index(b.en_passant_target);
         int dy = my_colour == Colour::White ? 1 : -1;
-        if (c.y == xy.y + dy && (c.x == xy.x - 1 || c.x == xy.x + 1)) {
+        if (c.y == xy.y + dy && (c.x == xy.x - 1 || c.x == xy.x + 1))
-            ret.push_back(Move{
+            ret.push_back(Move{xy.to_index(), c.to_index()});
-                xy.to_index(),
-                c.to_index(),
-                .is_capturing = true,
-                .en_passant = true
-            });
-        }
     }
 
     // -- Normal move + promotion

cpp/src/pieces/piece.cpp

@@ -53,18 +53,11 @@ legal_moves(int8_t p, const Board& b, const Coords xy, bool looking_for_check) {
 
 std::optional<Move>
 move_for_position(const Board& board, const Coords source, const Coords dest) {
-    if (!dest.is_within_bounds())
+    if (!dest.is_within_bounds()
+        || board.colour_at(source) == board.colour_at(dest))
         return {};
 
-    int8_t piece = board.squares[dest.to_index()];
+    return Move{source.to_index(), dest.to_index()};
-    if (piece == Piece::None)
-        return Move{source.to_index(), dest.to_index()};
-
-    int8_t source_colour = board.colour_at(source);
-    int8_t dest_colour = board.colour_at(dest);
-    if (source_colour != dest_colour)
-        return Move{source.to_index(), dest.to_index(), true};
-    return {};
 }
 
 std::vector<Move>
@@ -74,11 +67,11 @@ look_direction(const Board& board, const Coords xy, int mult_dx, int mult_dy) {
         int dx = mult_dx * d;
         int dy = mult_dy * d;
 
-        std::optional<Move> move =
+        Coords target{xy.x + dx, xy.y + dy};
-            move_for_position(board, xy, Coords{xy.x + dx, xy.y + dy});
+        std::optional<Move> move = move_for_position(board, xy, target);
         if (move.has_value()) {
             ret.push_back(move.value());
-            if (move.value().is_capturing)
+            if (board.squares[target.to_index()] != Piece::None)
                 break;
         } else {
             break;

cpp/src/stickfosh.cpp

@@ -1,187 +1,96 @@
 #include "stickfosh.hpp"
 
-#include "board.hpp"
+#include "pieces/piece.hpp"
-#include "move.hpp"
 #include "threadpool.hpp"
 
-#include <chrono>
+#include <future>
 #include <map>
-#include <ostream>
-#include <sstream>
-#include <string>
-#include <vector>
 
-static std::string tick = "\033[92m✔️\033[0m";   // Green Tick;
+static int INFINITY = std::numeric_limits<int>::max();
-static std::string cross = "\033[91m❌\033[0m"; // Red Cross
 
-static std::map<std::string, std::map<int, int>> pos2expected{
+std::string search(std::string pos, int depth) {
-    // -- Position 1
-    {
-        "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
-        {
-            {1, 20},     // 0
-            {2, 400},    // 1
-            {3, 8902},   // 38
-            {4, 197281}, // 971
-            // {5, 4865609}, // 23032
-        },
-    },
-
-    // -- Position 2
-    {
-        "r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 0 2",
-        {
-            {1, 48},    // 0
-            {2, 2039},  // 16
-            {3, 97862}, // 602
-            // {4, 4085603}, // 26612
-        },
-    },
-
-    // -- Position 3
-    {
-        "8/2p5/3p4/KP5r/1R3p1k/8/4P1P1/8 w - - 0 3",
-        {
-            {1, 14},     // 0
-            {2, 191},    // 1
-            {3, 2812},   // 11
-            {4, 43238},  // 157
-            {5, 674624}, // 2199
-            // {6, 11030083},
-        },
-    },
-
-    // -- Position 4a
-    {
-        "r3k2r/Pppp1ppp/1b3nbN/nP6/BBP1P3/q4N2/Pp1P2PP/R2Q1RK1 w kq - 0 4",
-        {
-            {1, 6},      // 0
-            {2, 264},    // 1
-            {3, 9467},   // 69
-            {4, 422333}, // 3085
-            // {5, 15833292}, // 124452
-        },
-    },
-
-    // -- Position 4b
-    {
-        "r2q1rk1/pP1p2pp/Q4n2/bbp1p3/Np6/1B3NBn/pPPP1PPP/R3K2R b KQ - 0 5",
-        {
-            {1, 6},      // 0
-            {2, 264},    // 2
-            {3, 9467},   // 104
-            {4, 422333}, // 3742
-            // {5, 15833292}, // 136784
-        },
-    },
-
-    // -- Position 5
-    {
-        "rnbq1k1r/pp1Pbppp/2p5/8/2B5/8/PPP1NnPP/RNBQK2R w KQ - 1 6",
-        {
-            {1, 44},    // 0
-            {2, 1486},  // 12
-            {3, 62379}, // 357
-            // {4, 2103487}, // 13804
-            // {5, 89941194}, // 1230428
-        },
-    },
-
-    // -- Position 6
-    {
-        "r4rk1/1pp1qppp/p1np1n2/2b1p1B1/2B1P1b1/P1NP1N2/1PP1QPPP/R4RK1 w - - 0 "
-        "7",
-        {
-            {1, 46},    // 0
-            {2, 2079},  // 16
-            {3, 89890}, // 602
-            // {4, 3894594}, // 26612
-            // {5, 164075551}, // 1230428
-        },
-    },
-};
-
-static std::stringstream res;
-
-int move_generation_test(
-    const Board& b, int depth, int max_depth, ThreadPool& pool
-) {
-    if (depth == max_depth) {
-        res.str("");
-        res.clear();
-    }
-
-    if (b.is_terminal())
-        return 0;
-    if (depth == 0)
-        return 1;
-
-    std::vector<Move> moves = b.all_legal_moves();
-    if (depth == 1)
-        return moves.size();
-
-    int num_pos = 0;
-
-    if (depth == max_depth) {
-        // Parallel execution at the top level
-        std::vector<std::future<int>> futures;
-        for (const Move& move : moves) {
-            Board tmp_board = b.make_move(move);
-            futures.push_back(pool.enqueue(
-                move_generation_test,
-                tmp_board,
-                depth - 1,
-                max_depth,
-                std::ref(pool)
-            ));
-        }
-
-        for (auto& future : futures)
-            num_pos += future.get(); // Retrieve the result of each task
-    } else {
-        // Regular sequential execution
-        for (const Move& move : moves) {
-            Board tmp_board = b.make_move(move);
-            int n = move_generation_test(tmp_board, depth - 1, max_depth, pool);
-            if (depth == max_depth)
-                res << move << ": " << n << std::endl;
-            num_pos += n;
-        }
-    }
-
-    return num_pos;
-}
-
-void perft() {
-    for (auto& [key, value] : pos2expected)
-        perft(key);
-}
-
-void perft(std::string pos) {
-    std::cout << pos << std::endl;
-    std::map<int, int> expected = pos2expected[pos];
     Board b = Board::setup_fen_position(pos);
+
     ThreadPool pool(std::thread::hardware_concurrency());
 
-    for (const auto& [depth, expected_n_moves] : expected) {
+    std::vector<Move> moves = b.all_legal_moves();
-        std::cout << "Depth: " << depth << " " << std::flush;
+    std::map<std::string, std::future<int>> futures;
-        auto start = std::chrono::steady_clock::now();
+    for (const Move& move : moves) {
-        int moves = move_generation_test(b, depth, depth, pool);
+        Board tmp_board = b.make_move(move);
-        auto end = std::chrono::steady_clock::now();
+        futures.insert(
-        auto elapsed =
+            {move.to_string(), pool.enqueue(minimax, tmp_board, depth - 1)}
-            std::chrono::duration_cast<std::chrono::milliseconds>(end - start)
+        );
-                .count();
+    }
 
-        std::cout << "Results: " << moves << " ";
+    std::string best_move;
-        if (moves == expected_n_moves)
+    int best_eval = -INFINITY;
-            std::cout << tick << " ";
+    for (auto& [move, future] : futures) {
-        else
+        int eval = future.get();
-            std::cout << cross << " (expected " << expected_n_moves << ") ";
+        if (eval > best_eval) {
-        std::cout << "positions Time: " << elapsed << " milliseconds"
+            best_eval = eval;
-                  << std::endl;
+            best_move = move;
-        if (moves != expected_n_moves) {
-            std::cout << std::endl << res.str();
-            exit(1);
         }
     }
+
+    return best_move;
+}
+
+int minimax(const Board& b, int depth) {
+    if (b.is_checkmate_for(b.white_to_play ? White : Black))
+        return -INFINITY;
+
+    if (depth == 0)
+        return eval(b);
+
+    std::vector<Move> moves = b.all_legal_moves();
+    int best_evaluation = 0;
+    Move best_move;
+    for (const Move& move : moves) {
+        Board tmp_board = b.make_move(move);
+        int tmp_eval = -minimax(tmp_board, depth - 1);
+        best_evaluation = std::max(best_evaluation, tmp_eval);
+    }
+    return best_evaluation;
+}
+
+static int PawnValue = 100;
+static int KnightValue = 300;
+static int BishopValue = 320;
+static int RookValue = 500;
+static int QueenValue = 900;
+
+int count_material(const Board& b, int8_t colour) {
+    int ret = 0;
+    for (int i = 0; i < 64; i++) {
+        if (b.colour_at(i) == colour)
+            switch (b.squares[i] & 0b111) {
+            case Piece::Pawn:
+                ret += PawnValue;
+                break;
+            case Piece::Knigt:
+                ret += KnightValue;
+                break;
+            case Piece::Bishop:
+                ret += BishopValue;
+                break;
+            case Piece::Rook:
+                ret += RookValue;
+                break;
+            case Piece::Queen:
+                ret += QueenValue;
+                break;
+            }
+    }
+    return ret;
+}
+
+int eval(const Board& b) {
+    int white_eval = count_material(b, Colour::White);
+    int black_eval = count_material(b, Colour::Black);
+
+    int evaluation = white_eval - black_eval;
+
+    int perspective = b.white_to_play ? 1 : -1;
+
+    return perspective * evaluation;
 }

cpp/src/stickfosh.hpp

@@ -1,6 +1,9 @@
 #pragma once
 
+#include "board.hpp"
+
 #include <string>
 
-void perft(std::string pos);
+std::string search(std::string, int);
-void perft();
+int minimax(const Board&, int);
+int eval(const Board&);