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LibChess: Only save hash of board state for repetition checking
This more than doubles the number of nodes that MCTS can search for a given time limit, and greatly reduces memory usage.
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675b8ba995
commit
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2 changed files with 9 additions and 10 deletions
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@ -579,14 +579,12 @@ bool Board::apply_move(const Move& move, Color color)
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bool Board::apply_illegal_move(const Move& move, Color color)
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{
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Board clone = *this;
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clone.m_previous_states = {};
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clone.m_moves = {};
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auto state = Traits<Board>::hash(*this);
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auto state_count = 0;
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if (m_previous_states.contains(clone))
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state_count = m_previous_states.get(clone).value();
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if (m_previous_states.contains(state))
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state_count = m_previous_states.get(state).value();
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m_previous_states.set(clone, state_count + 1);
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m_previous_states.set(state, state_count + 1);
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m_moves.append(move);
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m_turn = opposing_color(color);
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@ -758,7 +756,7 @@ Board::Result Board::game_result() const
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if (m_moves_since_capture == 50 * 2)
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return Result::FiftyMoveRule;
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auto repeats = m_previous_states.get(*this);
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auto repeats = m_previous_states.get(Traits<Board>::hash(*this));
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if (repeats.has_value()) {
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if (repeats.value() == 3)
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return Result::ThreeFoldRepetition;
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