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ChessEngine: Don't throw away useful branches from last tree

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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:
Lucas CHOLLET 2022-08-14 16:39:32 +02:00 • committed by Andreas Kling
parent 351fc0cce2
commit d5979516b4
4 changed files with 52 additions and 7 deletions
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36
Userland/Services/ChessEngine/MCTSTree.cpp
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@ -16,6 +16,19 @@ MCTSTree::MCTSTree(Chess::Board const& board, MCTSTree* parent)
{
}
MCTSTree::MCTSTree(MCTSTree&& other)
: m_children(move(other.m_children))
, m_parent(other.m_parent)
, m_white_points(other.m_white_points)
, m_simulations(other.m_simulations)
, m_board(move(other.m_board))
, m_last_move(move(other.m_last_move))
, m_turn(other.m_turn)
, m_moves_generated(other.m_moves_generated)
{
other.m_parent = nullptr;
}
MCTSTree& MCTSTree::select_leaf()
{
if (!expanded() || m_children.size() == 0)
@ -117,22 +130,37 @@ void MCTSTree::do_round()
node.apply_result(result);
}
Chess::Move MCTSTree::best_move() const
Optional<MCTSTree&> MCTSTree::child_with_move(Chess::Move chess_move)
{
for (auto& node : m_children) {
if (node.last_move() == chess_move)
return node;
}
return {};
}
MCTSTree& MCTSTree::best_node()
{
int score_multiplier = (m_turn == Chess::Color::White) ? 1 : -1;
Chess::Move best_move = { { 0, 0 }, { 0, 0 } };
MCTSTree* best_node_ptr = nullptr;
double best_score = -double(INFINITY);
VERIFY(m_children.size());
for (auto& node : m_children) {
double node_score = node.expected_value() * score_multiplier;
if (node_score >= best_score) {
best_move = node.m_last_move.value();
best_node_ptr = &node;
best_score = node_score;
}
}
VERIFY(best_node_ptr);
return best_move;
return *best_node_ptr;
}
Chess::Move MCTSTree::last_move() const
{
return m_last_move.value();
}
double MCTSTree::expected_value() const