// Follow the PV until we hit an illegal move.
std::stack<Move> pv;
+ std::set<Key> seen;
while (found && is_ok(entry->move())) {
FillMove(entry->move(), response->add_pv());
+ if (seen.count(pos->key())) break;
pv.push(entry->move());
+ seen.insert(pos->key());
setup_states->push(StateInfo());
pos->do_move(entry->move(), setup_states->top(), pos->gives_check(entry->move(), CheckInfo(*pos)));
entry = TT.probe(pos->key(), found);