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ChessEngine: Don't throw away useful branches from last tree
Computation from last turn might have produced some nodes that are still accurate. Keeping them should make the engine a bit smarter.
This commit is contained in:
parent
351fc0cce2
commit
d5979516b4
Notes:
sideshowbarker
2024-07-17 08:03:29 +09:00
Author: https://github.com/LucasChollet Commit: https://github.com/SerenityOS/serenity/commit/d5979516b4 Pull-request: https://github.com/SerenityOS/serenity/pull/14855 Reviewed-by: https://github.com/linusg Reviewed-by: https://github.com/petelliott ✅
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@ -38,7 +38,14 @@ void ChessEngine::handle_go(GoCommand const& command)
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auto elapsed_time = Core::ElapsedTimer::start_new();
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MCTSTree mcts(m_board);
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auto mcts = [this]() -> MCTSTree {
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if (!m_last_tree.has_value())
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return { m_board };
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auto x = m_last_tree.value().child_with_move(m_board.last_move().value());
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if (x.has_value())
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return move(x.value());
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return { m_board };
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}();
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int rounds = 0;
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while (elapsed_time.elapsed() <= command.movetime.value()) {
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@ -47,7 +54,10 @@ void ChessEngine::handle_go(GoCommand const& command)
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}
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dbgln("MCTS finished {} rounds.", rounds);
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dbgln("MCTS evaluation {}", mcts.expected_value());
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auto best_move = mcts.best_move();
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auto& best_node = mcts.best_node();
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auto const& best_move = best_node.last_move();
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dbgln("MCTS best move {}", best_move.to_long_algebraic());
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send_command(BestMoveCommand(best_move));
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m_last_tree = move(best_node);
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}
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@ -6,6 +6,7 @@
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#pragma once
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#include "MCTSTree.h"
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#include <LibChess/Chess.h>
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#include <LibChess/UCIEndpoint.h>
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@ -26,4 +27,5 @@ private:
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}
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Chess::Board m_board;
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Optional<MCTSTree> m_last_tree;
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};
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@ -16,6 +16,19 @@ MCTSTree::MCTSTree(Chess::Board const& board, MCTSTree* parent)
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{
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}
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MCTSTree::MCTSTree(MCTSTree&& other)
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: m_children(move(other.m_children))
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, m_parent(other.m_parent)
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, m_white_points(other.m_white_points)
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, m_simulations(other.m_simulations)
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, m_board(move(other.m_board))
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, m_last_move(move(other.m_last_move))
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, m_turn(other.m_turn)
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, m_moves_generated(other.m_moves_generated)
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{
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other.m_parent = nullptr;
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}
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MCTSTree& MCTSTree::select_leaf()
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{
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if (!expanded() || m_children.size() == 0)
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@ -117,22 +130,37 @@ void MCTSTree::do_round()
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node.apply_result(result);
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}
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Chess::Move MCTSTree::best_move() const
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Optional<MCTSTree&> MCTSTree::child_with_move(Chess::Move chess_move)
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{
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for (auto& node : m_children) {
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if (node.last_move() == chess_move)
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return node;
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}
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return {};
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}
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MCTSTree& MCTSTree::best_node()
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{
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int score_multiplier = (m_turn == Chess::Color::White) ? 1 : -1;
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Chess::Move best_move = { { 0, 0 }, { 0, 0 } };
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MCTSTree* best_node_ptr = nullptr;
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double best_score = -double(INFINITY);
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VERIFY(m_children.size());
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for (auto& node : m_children) {
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double node_score = node.expected_value() * score_multiplier;
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if (node_score >= best_score) {
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best_move = node.m_last_move.value();
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best_node_ptr = &node;
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best_score = node_score;
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}
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}
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VERIFY(best_node_ptr);
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return best_move;
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return *best_node_ptr;
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}
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Chess::Move MCTSTree::last_move() const
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{
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return m_last_move.value();
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}
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double MCTSTree::expected_value() const
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@ -20,6 +20,7 @@ public:
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};
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MCTSTree(Chess::Board const& board, MCTSTree* parent = nullptr);
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MCTSTree(MCTSTree&&);
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MCTSTree& select_leaf();
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MCTSTree& expand();
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@ -28,7 +29,11 @@ public:
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void apply_result(int game_score);
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void do_round();
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Chess::Move best_move() const;
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Optional<MCTSTree&> child_with_move(Chess::Move);
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MCTSTree& best_node();
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Chess::Move last_move() const;
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double expected_value() const;
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double uct(Chess::Color color) const;
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bool expanded() const;
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