implemented v4 that resolves all the captures

after looking at the next two moves (all of them)

cpp/src/main.cpp

@@ -11,15 +11,16 @@
 #include <chrono>
 
 int main(int argc, char* argv[]) {
-    // std::string pos =
-    //     "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
+    std::string pos =
+        "r2qkb1r/2p1pppp/p1n1b3/1p6/B2P4/2P1P3/P4PPP/R1BQK1NR w KQkq - 0 9 ";
     // std::string pos =
     //     "r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 4 3
     //     ";
 
     // pos for ai timing<
-    std::string pos =
-        "r3k2r/p1ppqpb1/Bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPB1PPP/R3K2R b KQkq - 0 3 ";
+    // std::string pos =
+    //     "r3k2r/p1ppqpb1/Bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPB1PPP/R3K2R b KQkq -
+    //     0 3 ";
 
     Board b = Board::setup_fen_position(pos);
 
@@ -28,9 +29,9 @@ int main(int argc, char* argv[]) {
     // ai::v2_alpha_beta p2(false, std::chrono::milliseconds(20000));
     ai::v3_AB_ordering p2(false, std::chrono::milliseconds(20000));
 
-    NoOpView gui;
-    AIvsAIController manual(b, gui, p1, p2);
-    // HumanVsAIController manual(b, gui, p2);
+    GUI gui;
+    // AIvsAIController manual(b, gui, p1, p2);
+    HumanVsAIController manual(b, gui, p2);
 
     Controller& controller = manual;
 

cpp/src/model/ais/ai.hpp

@@ -57,7 +57,7 @@ namespace ai {
 
     class v3_AB_ordering : public AI {
         // looks two moves ahead, with alpha-beta pruning, with move ordering
-        int _search(const Board&, int, int, int);
+        virtual int _search(const Board&, int, int, int);
 
       public:
         v3_AB_ordering(bool w, std::chrono::milliseconds tt): AI(w, tt) {}
@@ -65,4 +65,15 @@ namespace ai {
         Move _search(const Board&) override;
         int eval(const Board&) override;
     };
+
+    class v4_search_captures : public v3_AB_ordering {
+        // same as v3, but looking at only at captures when leaf is reached,
+        // until no captures are left
+        int _search(const Board&, int, int, int) override;
+        int _search_captures(const Board&, int, int);
+
+      public:
+        v4_search_captures(bool w, std::chrono::milliseconds tt)
+            : v3_AB_ordering(w, tt) {}
+    };
 } // namespace ai

cpp/src/model/ais/v4_search_captures.cpp

@@ -0,0 +1,61 @@
+#include "../pieces/piece.hpp"
+#include "../utils/utils.hpp"
+#include "ai.hpp"
+
+#include <algorithm>
+
+#define MULTITHREADED 1
+
+
+static int position_counter;
+
+int ai::v4_search_captures::_search(
+    const Board& b, int depth, int alpha, int beta
+) {
+    if (depth == 0 || stop_computation)
+        return _search_captures(b, alpha, beta);
+
+    if (b.no_legal_moves()) {
+        if (b.is_check())
+            return -INFINITY;
+        return 0;
+    }
+
+    std::vector<Move> moves = b.all_legal_moves();
+    std::sort(moves.begin(), moves.end(), [&](Move& m1, Move& m2) {
+        return m1.score_guess(b) > m2.score_guess(b);
+    });
+
+    Move best_move;
+    for (const Move& move : moves) {
+        Board tmp_board = b.make_move(move);
+        int tmp_eval = -_search(tmp_board, depth - 1, -beta, -alpha);
+        if (tmp_eval >= beta)
+            return beta;
+        alpha = std::max(alpha, tmp_eval);
+    }
+    return alpha;
+}
+
+int ai::v4_search_captures::_search_captures(
+    const Board& b, int alpha, int beta
+) {
+    int evaluation = eval(b);
+    if (evaluation >= beta)
+        return beta;
+    alpha = std::max(evaluation, alpha);
+
+    std::vector<Move> moves = b.all_capturing_moves();
+    std::sort(moves.begin(), moves.end(), [&](Move& m1, Move& m2) {
+        return m1.score_guess(b) > m2.score_guess(b);
+    });
+
+    for (const Move& move : moves) {
+        Board tmp_board = b.make_move(move);
+        int tmp_eval = -_search_captures(tmp_board, -beta, -alpha);
+        if (tmp_eval >= beta)
+            return beta;
+        alpha = std::max(alpha, tmp_eval);
+    }
+    return alpha;
+}

cpp/src/model/board/board.cpp

@@ -410,3 +410,14 @@ std::vector<Move> Board::all_legal_moves() const {
     }
     return ret;
 }
+
+std::vector<Move> Board::all_capturing_moves() const {
+    std::vector<Move> moves = all_legal_moves();
+    std::vector<Move> ret;
+    ret.reserve(moves.size());
+    for (const Move& move : moves)
+        if (piece_at(move.target_square) != Piece::None)
+            ret.push_back(move);
+
+    return ret;
+}

cpp/src/model/board/board.hpp

@@ -38,6 +38,7 @@ struct Board {
     };
 
     std::vector<Move> all_legal_moves() const;
+    std::vector<Move> all_capturing_moves() const;
 
     bool is_checkmate() const;