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Fix bug where pv might not update for best move change. #1286

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Merged
merged 2 commits into from
May 10, 2020
Merged

Fix bug where pv might not update for best move change. #1286

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3543013
Fix bug where pv might not update.
Tilps May 10, 2020
cb87e0a
Fix...
Tilps May 10, 2020
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12 changes: 11 additions & 1 deletion src/mcts/search.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1524,6 +1524,8 @@ void SearchWorker::DoBackupUpdateSingleNode(
// Nothing left to do without ancestors to update.
if (!p) break;

bool old_update_parent_bounds = update_parent_bounds;

// Try setting parent bounds except the root or those already terminal.
update_parent_bounds = update_parent_bounds && p != search_->root_node_ &&
!p->IsTerminal() && MaybeSetBounds(p, m);
Expand All @@ -1535,8 +1537,16 @@ void SearchWorker::DoBackupUpdateSingleNode(

// Update the stats.
// Best move.
// If update_parent_bounds was set, we just adjusted bounds on the
// previous loop or there was no previous loop, so if n is a terminal, it
// just became that way and could be a candidate for changing the current
// best edge. Otherwise a visit can only change best edge if its to an edge
// that isn't already the best and the new n is equal or greater to the old
// n.
if (p == search_->root_node_ &&
search_->current_best_edge_.GetN() <= n->GetN()) {
(old_update_parent_bounds && n->IsTerminal() ||
n != search_->current_best_edge_.node() &&
search_->current_best_edge_.GetN() <= n->GetN())) {
search_->current_best_edge_ =
search_->GetBestChildNoTemperature(search_->root_node_, 0);
}
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