#include <cassert>
#include <cstdio>
+#include <algorithm>
#include <memory>
#include <string>
+#include <unordered_set>
#include <vector>
XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_dfs, mc, "DFS exploration algorithm of the model-checker");
void DFSExplorer::restore_stack(std::shared_ptr<State> state)
{
stack_.clear();
+ execution_seq_ = odpor::Execution();
auto current_state = state;
stack_.emplace_front(current_state);
// condition corresponds to reaching initial state
stack_.emplace_front(current_state);
}
XBT_DEBUG("Replaced stack by %s", get_record_trace().to_string().c_str());
+ if (reduction_mode_ == ReductionMode::sdpor || reduction_mode_ == ReductionMode::odpor) {
+ // NOTE: The outgoing transition for the top-most
+ // state of the stack refers to that which was taken
+ // as part of the last trace explored by the algorithm.
+ // Thus, only the sequence of transitions leading up to,
+ // but not including, the last state must be included
+ // when reconstructing the Exploration for SDPOR.
+ for (auto iter = std::next(stack_.begin()); iter != stack_.end(); ++iter) {
+ execution_seq_.push_transition((*iter)->get_transition_in());
+ }
+ XBT_DEBUG("Replaced SDPOR/ODPOR execution to reflect the new stack");
+ }
}
void DFSExplorer::log_state() // override
XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
_sg_mc_max_depth.get());
XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
- } else
+ } else if (reduction_mode_ == ReductionMode::sdpor || reduction_mode_ == ReductionMode::odpor) {
+ XBT_ERROR("/!\\ Max depth of %d reached! THIS **WILL** BREAK the reduction, which is not sound "
+ "when stopping at a fixed depth /!\\",
+ _sg_mc_max_depth.get());
+ XBT_ERROR("/!\\ If bad things happen, disable the reduction with --cfg=model-check/reduction:none /!\\");
+ } else {
XBT_WARN("/!\\ Max depth reached ! /!\\ ");
+ }
this->backtrack();
continue;
}
}
#endif
+ if (reduction_mode_ == ReductionMode::odpor) {
+ // In the case of ODPOR, the wakeup tree for this
+ // state may be empty if we're exploring new territory
+ // (rather than following the partial execution of a
+ // wakeup tree). This corresponds to lines 9 to 13 of
+ // the ODPOR pseudocode
+ //
+ // INVARIANT: The execution sequence should be consistent
+ // with the state when seeding the tree. If the sequence
+ // gets out of sync with the state, selection will not
+ // work as we intend
+ state->seed_wakeup_tree_if_needed(execution_seq_);
+ }
+
// Search for the next transition
- // next_transition returns a pair<aid_t, int> in case we want to consider multiple state (eg. during backtrack)
- auto [next, _] = state->next_transition_guided();
+ // next_transition returns a pair<aid_t, int>
+ // in case we want to consider multiple states (eg. during backtrack)
+ const aid_t next = reduction_mode_ == ReductionMode::odpor ? state->next_odpor_transition()
+ : std::get<0>(state->next_transition_guided());
if (next < 0) { // If there is no more transition in the current state, backtrack.
XBT_VERB("%lu actors remain, but none of them need to be interleaved (depth %zu).", state->get_actor_count(),
if (_sg_mc_sleep_set && XBT_LOG_ISENABLED(mc_dfs, xbt_log_priority_verbose)) {
XBT_VERB("Sleep set actually containing:");
for (auto& [aid, transition] : state->get_sleep_set())
- XBT_VERB(" <%ld,%s>", aid, transition.to_string().c_str());
+ XBT_VERB(" <%ld,%s>", aid, transition->to_string().c_str());
}
/* Actually answer the request: let's execute the selected request (MCed does one step) */
- state->execute_next(next, get_remote_app());
+ const auto executed_transition = state->execute_next(next, get_remote_app());
on_transition_execute_signal(state->get_transition_out().get(), get_remote_app());
// If there are processes to interleave and the maximum depth has not been
auto next_state = std::make_shared<State>(get_remote_app(), state);
on_state_creation_signal(next_state.get(), get_remote_app());
- /* Sleep set procedure:
- * adding the taken transition to the sleep set of the original state.
- * <!> Since the parent sleep set is used to compute the child sleep set, this need to be
- * done after next_state creation */
- XBT_DEBUG("Marking Transition >>%s<< of process %ld done and adding it to the sleep set",
- state->get_transition_out()->to_string().c_str(), state->get_transition_out()->aid_);
- state->add_sleep_set(state->get_transition_out()); // Actors are marked done when they are considerd in ActorState
+ if (reduction_mode_ == ReductionMode::odpor) {
+ // With ODPOR, after taking a step forward, we must
+ // assign a copy of that subtree to the next state.
+ //
+ // NOTE: We only add actions to the sleep set AFTER
+ // we've regenerated states. We must perform the search
+ // fully down a single path before we consider adding
+ // any elements to the sleep set according to the pseudocode
+ next_state->sprout_tree_from_parent_state();
+ } else {
+ /* Sleep set procedure:
+ * adding the taken transition to the sleep set of the original state.
+ * <!> Since the parent sleep set is used to compute the child sleep set, this need to be
+ * done after next_state creation */
+ XBT_DEBUG("Marking Transition >>%s<< of process %ld done and adding it to the sleep set",
+ state->get_transition_out()->to_string().c_str(), state->get_transition_out()->aid_);
+ state->add_sleep_set(
+ state->get_transition_out()); // Actors are marked done when they are considered in ActorState
+ }
/* DPOR persistent set procedure:
* for each new transition considered, check if it depends on any other previous transition executed before it
}
tmp_stack.pop_back();
}
+ } else if (reduction_mode_ == ReductionMode::sdpor) {
+ /**
+ * SDPOR Source Set Procedure:
+ *
+ * Find "reversible races" in the current execution `E` with respect
+ * to the latest action `p`. For each such race, determine one thread
+ * not contained in the backtrack set at the "race point" `r` which
+ * "represents" the trace formed by first executing everything after
+ * `r` that doesn't depend on it (`v := notdep(r, E)`) and then `p` to
+ * flip the race.
+ *
+ * The intuition is that some subsequence of `v` may enable `p`, so
+ * we want to be sure that search "in that direction"
+ */
+ execution_seq_.push_transition(std::move(executed_transition));
+ xbt_assert(execution_seq_.get_latest_event_handle().has_value(), "No events are contained in the SDPOR execution "
+ "even though one was just added");
+
+ const auto next_E_p = execution_seq_.get_latest_event_handle().value();
+ for (const auto e_race : execution_seq_.get_reversible_races_of(next_E_p)) {
+ State* prev_state = stack_[e_race].get();
+ const auto choices = execution_seq_.get_missing_source_set_actors_from(e_race, prev_state->get_backtrack_set());
+ if (!choices.empty()) {
+ // NOTE: To incorporate the idea of attempting to select the "best"
+ // backtrack point into SDPOR, instead of selecting the `first` initial,
+ // we should instead compute all choices and decide which is best
+ //
+ // Here, we choose the actor with the lowest ID to ensure
+ // we get deterministic results
+ const auto q =
+ std::min_element(choices.begin(), choices.end(), [](const aid_t a1, const aid_t a2) { return a1 < a2; });
+ prev_state->consider_one(*q);
+ opened_states_.emplace_back(std::move(prev_state));
+ }
+ }
+ } else if (reduction_mode_ == ReductionMode::odpor) {
+ // In the case of ODPOR, we simply observe the transition that was executed
+ // until we've reached a maximal trace
+ execution_seq_.push_transition(std::move(executed_transition));
}
// Before leaving that state, if the transition we just took can be taken multiple times, we
this->check_non_termination(next_state.get());
#if SIMGRID_HAVE_STATEFUL_MC
- /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
+ /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction)
+ */
if (_sg_mc_max_visited_states > 0)
visited_state_ = visited_states_.addVisitedState(next_state->get_num(), next_state.get(), get_remote_app());
#endif
return best_state;
}
+std::shared_ptr<State> DFSExplorer::next_odpor_state()
+{
+ for (auto iter = stack_.rbegin(); iter != stack_.rend(); ++iter) {
+ const auto& state = *iter;
+ state->do_odpor_unwind();
+ XBT_DEBUG("\tPerformed ODPOR 'clean-up'. Sleep set has:");
+ for (auto& [aid, transition] : state->get_sleep_set())
+ XBT_DEBUG("\t <%ld,%s>", aid, transition->to_string().c_str());
+ if (!state->has_empty_tree()) {
+ return state;
+ }
+ }
+ return nullptr;
+}
+
void DFSExplorer::backtrack()
{
+ if (const auto last_event = execution_seq_.get_latest_event_handle();
+ reduction_mode_ == ReductionMode::odpor and last_event.has_value()) {
+ /**
+ * ODPOR Race Detection Procedure:
+ *
+ * For each reversible race in the current execution, we
+ * note if there are any continuations `C` equivalent to that which
+ * would reverse the race that have already either a) been searched by ODPOR or
+ * b) been *noted* to be searched by the wakeup tree at the
+ * appropriate reversal point, either as `C` directly or
+ * an as equivalent to `C` ("eventually looks like C", viz. the `~_E`
+ * relation)
+ */
+ for (auto e_prime = static_cast<odpor::Execution::EventHandle>(0); e_prime <= last_event.value(); ++e_prime) {
+ for (const auto e : execution_seq_.get_reversible_races_of(e_prime)) {
+ XBT_DEBUG("ODPOR: Reversible race detected between events `%u` and `%u`", e, e_prime);
+ State& prev_state = *stack_[e];
+ if (const auto v = execution_seq_.get_odpor_extension_from(e, e_prime, prev_state); v.has_value()) {
+ const auto result = prev_state.insert_into_wakeup_tree(v.value(), execution_seq_.get_prefix_before(e));
+ switch (result) {
+ case odpor::WakeupTree::InsertionResult::root: {
+ XBT_DEBUG("ODPOR: Reversible race with `%u` unaccounted for in the wakeup tree for "
+ "the execution prior to event `%u`:",
+ e_prime, e);
+ break;
+ }
+ case odpor::WakeupTree::InsertionResult::interior_node: {
+ XBT_DEBUG("ODPOR: Reversible race with `%u` partially accounted for in the wakeup tree for "
+ "the execution prior to event `%u`:",
+ e_prime, e);
+ break;
+ }
+ case odpor::WakeupTree::InsertionResult::leaf: {
+ XBT_DEBUG("ODPOR: Reversible race with `%u` accounted for in the wakeup tree for "
+ "the execution prior to event `%u`:",
+ e_prime, e);
+ break;
+ }
+ }
+ for (const auto& seq : simgrid::mc::odpor::get_textual_trace(v.value())) {
+ XBT_DEBUG(" %s", seq.c_str());
+ }
+ } else {
+ XBT_DEBUG("ODPOR: Ignoring race: `sleep(E')` intersects `WI_[E'](v := notdep(%u, E))`", e);
+ XBT_DEBUG("Sleep set contains:");
+ for (auto& [aid, transition] : prev_state.get_sleep_set())
+ XBT_DEBUG(" <%ld,%s>", aid, transition->to_string().c_str());
+ }
+ }
+ }
+ }
+
XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
XBT_DEBUG("%lu alternatives are yet to be explored:", opened_states_.size());
get_remote_app().check_deadlock();
// Take the point with smallest distance
- auto backtracking_point = best_opened_state();
+ auto backtracking_point = reduction_mode_ == ReductionMode::odpor ? next_odpor_state() : best_opened_state();
// if no backtracking point, then set the stack_ to empty so we can end the exploration
if (not backtracking_point) {
this->restore_stack(backtracking_point);
}
-DFSExplorer::DFSExplorer(const std::vector<char*>& args, bool with_dpor, bool need_memory_info)
+DFSExplorer::DFSExplorer(const std::vector<char*>& args, ReductionMode mode, bool need_memory_info)
: Exploration(args, need_memory_info || _sg_mc_termination
#if SIMGRID_HAVE_STATEFUL_MC
|| _sg_mc_checkpoint > 0
#endif
- )
+ )
+ , reduction_mode_(mode)
{
- if (with_dpor)
- reduction_mode_ = ReductionMode::dpor;
- else
- reduction_mode_ = ReductionMode::none;
-
if (_sg_mc_termination) {
- if (with_dpor) {
+ if (mode != ReductionMode::none) {
XBT_INFO("Check non progressive cycles (turning DPOR off)");
reduction_mode_ = ReductionMode::none;
} else {
}
if (stack_.back()->count_todo_multiples() > 1)
opened_states_.emplace_back(stack_.back());
+
+ if (mode == ReductionMode::odpor && !_sg_mc_sleep_set) {
+ // ODPOR requires the use of sleep sets; SDPOR
+ // "likes" using sleep sets but it is not strictly
+ // required
+ XBT_INFO("Forcing the use of sleep sets for use with ODPOR");
+ _sg_mc_sleep_set = true;
+ }
}
-Exploration* create_dfs_exploration(const std::vector<char*>& args, bool with_dpor)
+Exploration* create_dfs_exploration(const std::vector<char*>& args, ReductionMode mode)
{
- return new DFSExplorer(args, with_dpor);
+ return new DFSExplorer(args, mode);
}
} // namespace simgrid::mc
