#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");
RecordTrace DFSExplorer::get_record_trace() // override
{
RecordTrace res;
- for (auto const& transition : stack_.back()->get_recipe())
- res.push_back(transition);
- res.push_back(stack_.back()->get_transition());
- return res;
-}
-std::vector<std::string> DFSExplorer::get_textual_trace() // override
-{
- std::vector<std::string> trace;
- for (auto const& transition : stack_.back()->get_recipe()) {
- trace.push_back(xbt::string_printf("%ld: %s", transition->aid_, transition->to_string().c_str()));
- }
- if (const auto* trans = stack_.back()->get_transition(); trans != nullptr)
- trace.push_back(xbt::string_printf("%ld: %s", trans->aid_, trans->to_string().c_str()));
- return trace;
+ if (const auto trans = stack_.back()->get_transition_out(); trans != nullptr)
+ res.push_back(trans.get());
+ for (const auto* state = stack_.back().get(); state != nullptr; state = state->get_parent_state().get())
+ if (state->get_transition_in() != nullptr)
+ res.push_front(state->get_transition_in().get());
+
+ return res;
}
void DFSExplorer::restore_stack(std::shared_ptr<State> 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) {
+ execution_seq_ = odpor::Execution();
+
+ // 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 = stack_.begin(); iter != stack_.end() - 1 and iter != stack_.end(); ++iter) {
+ const auto& state = *(iter);
+ execution_seq_.push_transition(state->get_transition_out());
+ }
+ }
+ XBT_DEBUG("Additionally replaced corresponding SDPOR execution 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 dpor 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
+ state->seed_wakeup_tree_if_needed(execution_seq_);
+ }
+
// Search for the next transition
- // next_transition returns a pair<aid_t, double> 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(),
}
/* Actually answer the request: let's execute the selected request (MCed does one step) */
- state->execute_next(next, get_remote_app());
- on_transition_execute_signal(state->get_transition(), 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
// reached then perform one step of the exploration algorithm.
- XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition()->aid_,
- state->get_transition()->to_string().c_str(), stack_.size(), state->get_num(), state->count_todo());
+ XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition_out()->aid_,
+ state->get_transition_out()->to_string().c_str(), stack_.size(), state->get_num(), state->count_todo());
/* Create the new expanded state (copy the state of MCed into our MCer data) */
auto next_state = std::make_shared<State>(get_remote_app(), 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()->to_string().c_str(), state->get_transition()->aid_);
- state->add_sleep_set(state->get_transition()); // Actors are marked done when they are considerd in ActorState
+ 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
+
+ if (reduction_mode_ == ReductionMode::odpor) {
+ // With ODPOR, after taking a step forward, we must:
+ // 1. remove the subtree whose root is a single-process
+ // node of actor `next` (viz. the action we took) from
+ // the wakeup tree of `state`
+ //
+ // 2. assign a copy of that subtree to the next state
+ //
+ // The latter evidently must be done BEFORE the former
+ next_state->sprout_tree_from_parent_state();
+ state->remove_subtree_starting_with(next);
+
+ // TODO: Consider what we have to do to handle transitions
+ // with multiple possible executions. We probably have to re-insert
+ // something into `state` and make note of that for later (opened_states_)
+ }
/* DPOR persistent set procedure:
* for each new transition considered, check if it depends on any other previous transition executed before it
* on another process. If there exists one, find the more recent, and add its process to the interleave set.
* If the process is not enabled at this point, then add every enabled process to the interleave */
if (reduction_mode_ == ReductionMode::dpor) {
- aid_t issuer_id = state->get_transition()->aid_;
+ aid_t issuer_id = state->get_transition_out()->aid_;
stack_t tmp_stack = stack_;
while (not tmp_stack.empty()) {
if (const State* prev_state = tmp_stack.back().get();
- state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
- XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
- prev_state->get_transition()->to_string().c_str(), issuer_id);
+ state->get_transition_out()->aid_ == prev_state->get_transition_out()->aid_) {
+ XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition_out()->to_string().c_str(),
+ prev_state->get_transition_out()->to_string().c_str(), issuer_id);
tmp_stack.pop_back();
continue;
- } else if (prev_state->get_transition()->depends(state->get_transition())) {
+ } else if (prev_state->get_transition_out()->depends(state->get_transition_out().get())) {
XBT_VERB("Dependent Transitions:");
- XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
- XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
+ XBT_VERB(" %s (state=%ld)", prev_state->get_transition_out()->to_string().c_str(), prev_state->get_num());
+ XBT_VERB(" %s (state=%ld)", state->get_transition_out()->to_string().c_str(), state->get_num());
if (prev_state->is_actor_enabled(issuer_id)) {
if (not prev_state->is_actor_done(issuer_id)) {
break;
} else {
XBT_VERB("INDEPENDENT Transitions:");
- XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
- XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
+ XBT_VERB(" %s (state=%ld)", prev_state->get_transition_out()->to_string().c_str(), prev_state->get_num());
+ XBT_VERB(" %s (state=%ld)", state->get_transition_out()->to_string().c_str(), state->get_num());
}
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"
+ */
+ const aid_t p = executed_transition->aid_;
+ 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/OPDPOR execution "
+ "even though one was just added");
+
+ const auto next_E_p = execution_seq_.get_latest_event_handle().value();
+ for (const auto racing_event_handle : execution_seq_.get_racing_events_of(next_E_p)) {
+ // To determine if the race is reversible, we have to ensure
+ // that actor `p` running `next_E_p` (viz. the event such that
+ // `racing_event -> (E_p) next_E_p` and no other event
+ // "happens-between" the two) is enabled in any equivalent
+ // execution where `racing_event` happens before `next_E_p`.
+ //
+ // Importantly, it is equivalent to checking if in ANY
+ // such equivalent execution sequence where `racing_event`
+ // happens-before `next_E_p` that `p` is enabled in `pre(racing_event, E.p)`.
+ // Thus it suffices to check THIS execution
+ //
+ // If the actor `p` is not enabled at s_[E'], it is not a *reversible* race
+ const std::shared_ptr<State> prev_state = stack_[racing_event_handle];
+ if (prev_state->is_actor_enabled(p)) {
+ // 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
+ const std::optional<aid_t> q =
+ execution_seq_.get_first_sdpor_initial_from(racing_event_handle, prev_state->get_backtrack_set());
+ if (q.has_value()) {
+ prev_state->consider_one(q.value());
+ 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
}
dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(), stack_.back()->get_num(),
- state->get_transition()->dot_string().c_str());
+ state->get_transition_out()->dot_string().c_str());
#if SIMGRID_HAVE_STATEFUL_MC
} else {
dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(),
visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_,
- state->get_transition()->dot_string().c_str());
+ state->get_transition_out()->dot_string().c_str());
#endif
}
}
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; e_prime++) {
+ for (const auto e : execution_seq_.get_racing_events_of(e_prime)) {
+ // To determine if the race is reversible, we have to ensure
+ // that actor `p` running `e_i` (viz. the event such that
+ // `racing_event -> (E_p) e_i` and no other event
+ // "happens-between" the two) is enabled in any equivalent
+ // execution where `racing_event` happens before `e_i`.
+ //
+ // Importantly, it is equivalent to checking if in ANY
+ // such equivalent execution sequence where `racing_event`
+ // happens-before `next_E_p` that `p` is enabled in `pre(racing_event, E.p)`.
+ // Thus it suffices to check THIS execution
+ //
+ // If the actor `p` is not enabled at s_[E'], it is not a *reversible* race
+ const aid_t p = execution_seq_.get_actor_with_handle(e_prime);
+ const std::shared_ptr<State> prev_state = stack_[e];
+ if (prev_state->is_actor_enabled(p)) {
+ const std::optional<odpor::PartialExecution> v = execution_seq_.get_odpor_extension_from(
+ e, e_prime, prev_state->get_sleeping_set(), prev_state->get_enabled_actors());
+ if (v.has_value()) {
+ prev_state->mark_path_interesting_for_odpor(v.value(), execution_seq_.get_prefix_before(e));
+ }
+ }
+ }
+ }
+ }
+
XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
XBT_DEBUG("%lu alternatives are yet to be explored:", opened_states_.size());
}
#endif
+ // Search how to restore the backtracking point
+ State* init_state = nullptr;
+ std::deque<Transition*> replay_recipe;
+ for (auto* s = backtracking_point.get(); s != nullptr; s = s->get_parent_state().get()) {
+#if SIMGRID_HAVE_STATEFUL_MC
+ if (s->get_system_state() != nullptr) { // Found a state that I can restore
+ init_state = s;
+ break;
+ }
+#endif
+ if (s->get_transition_in() != nullptr) // The root has no transition_in
+ replay_recipe.push_front(s->get_transition_in().get());
+ }
+
+ // Restore the init_state, if any
+ if (init_state != nullptr) {
+#if SIMGRID_HAVE_STATEFUL_MC
+ const auto* system_state = init_state->get_system_state();
+ system_state->restore(*get_remote_app().get_remote_process_memory());
+ on_restore_system_state_signal(init_state, get_remote_app());
+#endif
+ } else { // Restore the initial state if no intermediate state was found
+ get_remote_app().restore_initial_state();
+ on_restore_initial_state_signal(get_remote_app());
+ }
+
/* if no snapshot, we need to restore the initial state and replay the transitions */
- get_remote_app().restore_initial_state();
- on_restore_initial_state_signal(get_remote_app());
/* Traverse the stack from the state at position start and re-execute the transitions */
- for (auto& state : backtracking_point->get_recipe()) {
- state->replay(get_remote_app());
- on_transition_replay_signal(state, get_remote_app());
+ for (auto& transition : replay_recipe) {
+ transition->replay(get_remote_app());
+ on_transition_replay_signal(transition, get_remote_app());
visited_states_count_++;
}
this->restore_stack(backtracking_point);
}
-DFSExplorer::DFSExplorer(const std::vector<char*>& args, bool with_dpor, bool need_memory_info)
- : Exploration(args, need_memory_info || _sg_mc_termination)
+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 {
opened_states_.emplace_back(stack_.back());
}
-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
