+namespace simgrid::mc::udpor {
+
+UdporChecker::UdporChecker(const std::vector<char*>& args) : Exploration(args, true) {}
+
+void UdporChecker::run()
+{
+ XBT_INFO("Starting a UDPOR exploration");
+ state_stack.clear();
+ state_stack.push_back(get_current_state());
+ explore(Configuration(), EventSet(), EventSet(), EventSet());
+ XBT_INFO("UDPOR exploration terminated -- model checking completed");
+}
+
+void UdporChecker::explore(const Configuration& C, EventSet D, EventSet A, EventSet prev_exC)
+{
+ auto& stateC = *state_stack.back();
+ auto exC = compute_exC(C, stateC, prev_exC);
+ const auto enC = compute_enC(C, exC);
+ XBT_DEBUG("explore(C, D, A) with:\n"
+ "C\t := %s \n"
+ "D\t := %s \n"
+ "A\t := %s \n"
+ "ex(C)\t := %s \n"
+ "en(C)\t := %s \n",
+ C.to_string().c_str(), D.to_string().c_str(), A.to_string().c_str(), exC.to_string().c_str(),
+ enC.to_string().c_str());
+ XBT_DEBUG("ex(C) has %zu elements, of which %zu are in en(C)", exC.size(), enC.size());
+
+ // If enC is a subset of D, intuitively
+ // there aren't any enabled transitions
+ // which are "worth" exploring since their
+ // exploration would lead to a so-called
+ // "sleep-set blocked" trace.
+ if (enC.is_subset_of(D)) {
+ XBT_DEBUG("en(C) is a subset of the sleep set D (size %zu); if we "
+ "kept exploring, we'd hit a sleep-set blocked trace",
+ D.size());
+ XBT_DEBUG("The current configuration has %zu elements", C.get_events().size());
+
+ // When `en(C)` is empty, intuitively this means that there
+ // are no enabled transitions that can be executed from the
+ // state reached by `C` (denoted `state(C)`), i.e. by some
+ // execution of the transitions in C obeying the causality
+ // relation. Here, then, we may be in a deadlock (the other
+ // possibility is that we've finished running everything, and
+ // we wouldn't be in deadlock then)
+ if (enC.empty()) {
+ XBT_VERB("**************************");
+ XBT_VERB("*** TRACE INVESTIGATED ***");
+ XBT_VERB("**************************");
+ XBT_VERB("Execution sequence:");
+ for (auto const& s : get_textual_trace())
+ XBT_VERB(" %s", s.c_str());
+ get_remote_app().check_deadlock();
+ }
+
+ return;
+ }
+ UnfoldingEvent* e = select_next_unfolding_event(A, enC);
+ xbt_assert(e != nullptr, "\n\n****** INVARIANT VIOLATION ******\n"
+ "UDPOR guarantees that an event will be chosen at each point in\n"
+ "the search, yet no events were actually chosen\n"
+ "*********************************\n\n");
+ XBT_DEBUG("Selected event `%s` (%zu dependencies) to extend the configuration", e->to_string().c_str(),
+ e->get_immediate_causes().size());
+
+ // Ce := C + {e}
+ Configuration Ce = C;
+ Ce.add_event(e);
+
+ A.remove(e);
+ exC.remove(e);
+
+ // Explore(C + {e}, D, A \ {e})
+
+ // Move the application into stateCe (i.e. `state(C + {e})`) and make note of that state
+ move_to_stateCe(&stateC, e);
+ state_stack.push_back(record_current_state());
+
+ explore(Ce, D, std::move(A), std::move(exC));
+
+ // Prepare to move the application back one state.
+ // We need only remove the state from the stack here: if we perform
+ // another `Explore()` after computing an alternative, at that
+ // point we'll actually create a fresh RemoteProcess
+ state_stack.pop_back();
+
+ // D <-- D + {e}
+ D.insert(e);
+
+ XBT_DEBUG("Checking for the existence of an alternative...");
+ if (auto J = C.compute_alternative_to(D, this->unfolding); J.has_value()) {
+ // Before searching the "right half", we need to make
+ // sure the program actually reflects the fact
+ // that we are searching again from `state(C)`. While the
+ // stack of states is properly adjusted to represent
+ // `state(C)` all together, the RemoteApp is currently sitting
+ // at some *future* state with respect to `state(C)` since the
+ // recursive calls had moved it there.
+ restore_program_state_with_current_stack();
+
+ // Explore(C, D + {e}, J \ C)
+ auto J_minus_C = J.value().get_events().subtracting(C.get_events());
+
+ XBT_DEBUG("Alternative detected! The alternative is:\n"
+ "J\t := %s \n"
+ "J / C := %s\n"
+ "UDPOR is going to explore it...",
+ J.value().to_string().c_str(), J_minus_C.to_string().c_str());
+ explore(C, D, std::move(J_minus_C), std::move(prev_exC));
+ } else {
+ XBT_DEBUG("No alternative detected with:\n"
+ "C\t := %s \n"
+ "D\t := %s \n"
+ "A\t := %s \n",
+ C.to_string().c_str(), D.to_string().c_str(), A.to_string().c_str());
+ }
+
+ // D <-- D - {e}
+ D.remove(e);
+
+ // Remove(e, C, D)
+ clean_up_explore(e, C, D);
+}
+
+EventSet UdporChecker::compute_exC(const Configuration& C, const State& stateC, const EventSet& prev_exC)
+{
+ // See eqs. 5.7 of section 5.2 of [3]
+ // C = C' + {e_cur}, i.e. C' = C - {e_cur}
+ //
+ // Then
+ //
+ // ex(C) = ex(C' + {e_cur}) = ex(C') / {e_cur} +
+ // U{<a, K> : K is maximal, `a` depends on all of K, `a` enabled at config(K) }
+ const UnfoldingEvent* e_cur = C.get_latest_event();
+ EventSet exC = prev_exC;
+ exC.remove(e_cur);
+
+ // IMPORTANT NOTE: In order to have deterministic results, we need to process
+ // the actors in a deterministic manner so that events are discovered by
+ // UDPOR in a deterministic order. The processing done here always processes
+ // actors in a consistent order since `std::map` is by-default ordered using
+ // `std::less<Key>` (see the return type of `State::get_actors_list()`)
+ for (const auto& [aid, actor_state] : stateC.get_actors_list()) {
+ const auto& enabled_transitions = actor_state.get_enabled_transitions();
+ if (enabled_transitions.empty()) {
+ XBT_DEBUG("\t Actor `%ld` is disabled: no partial extensions need to be considered", aid);
+ } else {
+ XBT_DEBUG("\t Actor `%ld` is enabled", aid);
+ for (const auto& transition : enabled_transitions) {
+ XBT_DEBUG("\t Considering partial extension for %s", transition->to_string().c_str());
+ EventSet extension = ExtensionSetCalculator::partially_extend(C, &unfolding, transition);
+ exC.form_union(extension);
+ }
+ }
+ }
+ return exC;
+}
+
+EventSet UdporChecker::compute_enC(const Configuration& C, const EventSet& exC) const
+{
+ EventSet enC;
+ for (const auto* e : exC) {
+ if (C.is_compatible_with(e)) {
+ enC.insert(e);
+ }
+ }
+ return enC;
+}