1 /* Copyright (c) 2016-2023. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #include "src/mc/explo/DFSExplorer.hpp"
7 #include "src/mc/mc_config.hpp"
8 #include "src/mc/mc_exit.hpp"
9 #include "src/mc/mc_private.hpp"
10 #include "src/mc/mc_record.hpp"
11 #include "src/mc/transition/Transition.hpp"
13 #if SIMGRID_HAVE_STATEFUL_MC
14 #include "src/mc/VisitedState.hpp"
17 #include "src/xbt/mmalloc/mmprivate.h"
19 #include "xbt/string.hpp"
20 #include "xbt/sysdep.h"
29 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_dfs, mc, "DFS exploration algorithm of the model-checker");
31 namespace simgrid::mc {
33 xbt::signal<void(RemoteApp&)> DFSExplorer::on_exploration_start_signal;
34 xbt::signal<void(RemoteApp&)> DFSExplorer::on_backtracking_signal;
36 xbt::signal<void(State*, RemoteApp&)> DFSExplorer::on_state_creation_signal;
38 xbt::signal<void(State*, RemoteApp&)> DFSExplorer::on_restore_system_state_signal;
39 xbt::signal<void(RemoteApp&)> DFSExplorer::on_restore_initial_state_signal;
40 xbt::signal<void(Transition*, RemoteApp&)> DFSExplorer::on_transition_replay_signal;
41 xbt::signal<void(Transition*, RemoteApp&)> DFSExplorer::on_transition_execute_signal;
43 xbt::signal<void(RemoteApp&)> DFSExplorer::on_log_state_signal;
45 void DFSExplorer::check_non_termination(const State* current_state)
47 #if SIMGRID_HAVE_STATEFUL_MC
48 for (auto const& state : stack_) {
49 if (state->get_system_state()->equals_to(*current_state->get_system_state(),
50 *get_remote_app().get_remote_process_memory())) {
51 XBT_INFO("Non-progressive cycle: state %ld -> state %ld", state->get_num(), current_state->get_num());
52 XBT_INFO("******************************************");
53 XBT_INFO("*** NON-PROGRESSIVE CYCLE DETECTED ***");
54 XBT_INFO("******************************************");
55 XBT_INFO("Counter-example execution trace:");
56 for (auto const& s : get_textual_trace())
57 XBT_INFO(" %s", s.c_str());
58 XBT_INFO("You can debug the problem (and see the whole details) by rerunning out of simgrid-mc with "
59 "--cfg=model-check/replay:'%s'",
60 get_record_trace().to_string().c_str());
63 throw McError(ExitStatus::NON_TERMINATION);
69 RecordTrace DFSExplorer::get_record_trace() // override
72 for (auto const& transition : stack_.back()->get_recipe())
73 res.push_back(transition);
74 if (const auto trans = stack_.back()->get_transition_out(); trans != nullptr)
75 res.push_back(stack_.back()->get_transition_out().get());
79 void DFSExplorer::restore_stack(std::shared_ptr<State> state)
82 auto current_state = state;
83 stack_.emplace_front(current_state);
84 // condition corresponds to reaching initial state
85 while (current_state->get_parent_state() != nullptr) {
86 current_state = current_state->get_parent_state();
87 stack_.emplace_front(current_state);
89 XBT_DEBUG("Replaced stack by %s", get_record_trace().to_string().c_str());
92 void DFSExplorer::log_state() // override
94 on_log_state_signal(get_remote_app());
95 XBT_INFO("DFS exploration ended. %ld unique states visited; %lu backtracks (%lu transition replays, %lu states "
97 State::get_expanded_states(), backtrack_count_, visited_states_count_,
98 Transition::get_replayed_transitions());
99 Exploration::log_state();
102 void DFSExplorer::run()
104 on_exploration_start_signal(get_remote_app());
105 /* This function runs the DFS algorithm the state space.
106 * We do so iteratively instead of recursively, dealing with the call stack manually.
107 * This allows one to explore the call stack at will. */
109 while (not stack_.empty()) {
110 /* Get current state */
111 auto state = stack_.back();
113 XBT_DEBUG("**************************************************");
114 XBT_DEBUG("Exploration depth=%zu (state:#%ld; %zu interleaves todo)", stack_.size(), state->get_num(),
115 state->count_todo());
117 visited_states_count_++;
119 // Backtrack if we reached the maximum depth
120 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
121 if (reduction_mode_ == ReductionMode::dpor) {
122 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
123 _sg_mc_max_depth.get());
124 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
126 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
131 #if SIMGRID_HAVE_STATEFUL_MC
132 // Backtrack if we are revisiting a state we saw previously while applying state-equality reduction
133 if (visited_state_ != nullptr) {
134 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
135 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_);
137 visited_state_ = nullptr;
143 // Search for the next transition
144 // next_transition returns a pair<aid_t, int> in case we want to consider multiple state (eg. during backtrack)
145 auto [next, _] = state->next_transition_guided();
147 if (next < 0) { // If there is no more transition in the current state, backtrack.
148 XBT_VERB("%lu actors remain, but none of them need to be interleaved (depth %zu).", state->get_actor_count(),
151 if (state->get_actor_count() == 0) {
152 get_remote_app().finalize_app();
153 XBT_VERB("Execution came to an end at %s (state: %ld, depth: %zu)", get_record_trace().to_string().c_str(),
154 state->get_num(), stack_.size());
161 if (_sg_mc_sleep_set && XBT_LOG_ISENABLED(mc_dfs, xbt_log_priority_verbose)) {
162 XBT_VERB("Sleep set actually containing:");
163 for (auto& [aid, transition] : state->get_sleep_set())
164 XBT_VERB(" <%ld,%s>", aid, transition.to_string().c_str());
167 /* Actually answer the request: let's execute the selected request (MCed does one step) */
168 state->execute_next(next, get_remote_app());
169 on_transition_execute_signal(state->get_transition_out().get(), get_remote_app());
171 // If there are processes to interleave and the maximum depth has not been
172 // reached then perform one step of the exploration algorithm.
173 XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition_out()->aid_,
174 state->get_transition_out()->to_string().c_str(), stack_.size(), state->get_num(), state->count_todo());
176 /* Create the new expanded state (copy the state of MCed into our MCer data) */
177 auto next_state = std::make_shared<State>(get_remote_app(), state);
178 on_state_creation_signal(next_state.get(), get_remote_app());
180 /* Sleep set procedure:
181 * adding the taken transition to the sleep set of the original state.
182 * <!> Since the parent sleep set is used to compute the child sleep set, this need to be
183 * done after next_state creation */
184 XBT_DEBUG("Marking Transition >>%s<< of process %ld done and adding it to the sleep set",
185 state->get_transition_out()->to_string().c_str(), state->get_transition_out()->aid_);
186 state->add_sleep_set(state->get_transition_out()); // Actors are marked done when they are considerd in ActorState
188 /* DPOR persistent set procedure:
189 * for each new transition considered, check if it depends on any other previous transition executed before it
190 * on another process. If there exists one, find the more recent, and add its process to the interleave set.
191 * If the process is not enabled at this point, then add every enabled process to the interleave */
192 if (reduction_mode_ == ReductionMode::dpor) {
193 aid_t issuer_id = state->get_transition_out()->aid_;
194 stack_t tmp_stack = stack_;
195 while (not tmp_stack.empty()) {
196 if (const State* prev_state = tmp_stack.back().get();
197 state->get_transition_out()->aid_ == prev_state->get_transition_out()->aid_) {
198 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition_out()->to_string().c_str(),
199 prev_state->get_transition_out()->to_string().c_str(), issuer_id);
200 tmp_stack.pop_back();
202 } else if (prev_state->get_transition_out()->depends(state->get_transition_out().get())) {
203 XBT_VERB("Dependent Transitions:");
204 XBT_VERB(" %s (state=%ld)", prev_state->get_transition_out()->to_string().c_str(), prev_state->get_num());
205 XBT_VERB(" %s (state=%ld)", state->get_transition_out()->to_string().c_str(), state->get_num());
207 if (prev_state->is_actor_enabled(issuer_id)) {
208 if (not prev_state->is_actor_done(issuer_id)) {
209 prev_state->consider_one(issuer_id);
210 opened_states_.emplace_back(tmp_stack.back());
212 XBT_DEBUG("Actor %ld is already in done set: no need to explore it again", issuer_id);
214 XBT_DEBUG("Actor %ld is not enabled: DPOR may be failing. To stay sound, we are marking every enabled "
215 "transition as todo",
217 // If we ended up marking at least a transition, explore it at some point
218 if (prev_state->consider_all() > 0)
219 opened_states_.emplace_back(tmp_stack.back());
223 XBT_VERB("INDEPENDENT Transitions:");
224 XBT_VERB(" %s (state=%ld)", prev_state->get_transition_out()->to_string().c_str(), prev_state->get_num());
225 XBT_VERB(" %s (state=%ld)", state->get_transition_out()->to_string().c_str(), state->get_num());
227 tmp_stack.pop_back();
231 // Before leaving that state, if the transition we just took can be taken multiple times, we
232 // need to give it to the opened states
233 if (stack_.back()->count_todo_multiples() > 0)
234 opened_states_.emplace_back(stack_.back());
236 if (_sg_mc_termination)
237 this->check_non_termination(next_state.get());
239 #if SIMGRID_HAVE_STATEFUL_MC
240 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
241 if (_sg_mc_max_visited_states > 0)
242 visited_state_ = visited_states_.addVisitedState(next_state->get_num(), next_state.get(), get_remote_app());
245 stack_.emplace_back(std::move(next_state));
247 /* If this is a new state (or if we don't care about state-equality reduction) */
248 if (visited_state_ == nullptr) {
249 /* Get an enabled process and insert it in the interleave set of the next state */
250 if (reduction_mode_ == ReductionMode::dpor)
251 stack_.back()->consider_best(); // Take only one transition if DPOR: others may be considered later if required
253 stack_.back()->consider_all();
256 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(), stack_.back()->get_num(),
257 state->get_transition_out()->dot_string().c_str());
258 #if SIMGRID_HAVE_STATEFUL_MC
260 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(),
261 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_,
262 state->get_transition_out()->dot_string().c_str());
269 std::shared_ptr<State> DFSExplorer::best_opened_state()
271 int best_prio = 0; // cache the value for the best priority found so far (initialized to silence gcc)
272 auto best = end(opened_states_); // iterator to the state to explore having the best priority
273 auto valid = begin(opened_states_); // iterator marking the limit between states still to explore, and already
276 // Keep only still non-explored states (aid != -1), and record the one with the best (greater) priority.
277 for (auto current = begin(opened_states_); current != end(opened_states_); ++current) {
278 auto [aid, prio] = (*current)->next_transition_guided();
281 if (valid != current)
282 *valid = std::move(*current);
283 if (best == end(opened_states_) || prio > best_prio) {
290 std::shared_ptr<State> best_state;
292 // There are non-explored states, and one of them has the best priority. Remove it from opened_states_ before
294 best_state = std::move(*best);
297 *best = std::move(*valid);
299 opened_states_.erase(valid, end(opened_states_));
304 void DFSExplorer::backtrack()
306 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
307 XBT_DEBUG("%lu alternatives are yet to be explored:", opened_states_.size());
309 on_backtracking_signal(get_remote_app());
310 get_remote_app().check_deadlock();
312 // Take the point with smallest distance
313 auto backtracking_point = best_opened_state();
315 // if no backtracking point, then set the stack_ to empty so we can end the exploration
316 if (not backtracking_point) {
317 XBT_DEBUG("No more opened point of exploration, the search will end");
322 // We found a backtracking point, let's go to it
324 XBT_DEBUG("Backtracking to state#%ld", backtracking_point->get_num());
326 #if SIMGRID_HAVE_STATEFUL_MC
327 /* If asked to rollback on a state that has a snapshot, restore it */
328 if (const auto* system_state = backtracking_point->get_system_state()) {
329 system_state->restore(*get_remote_app().get_remote_process_memory());
330 on_restore_system_state_signal(backtracking_point.get(), get_remote_app());
331 this->restore_stack(backtracking_point);
336 /* if no snapshot, we need to restore the initial state and replay the transitions */
337 get_remote_app().restore_initial_state();
338 on_restore_initial_state_signal(get_remote_app());
339 /* Traverse the stack from the state at position start and re-execute the transitions */
340 for (auto& state : backtracking_point->get_recipe()) {
341 state->replay(get_remote_app());
342 on_transition_replay_signal(state, get_remote_app());
343 visited_states_count_++;
345 this->restore_stack(backtracking_point);
348 DFSExplorer::DFSExplorer(const std::vector<char*>& args, bool with_dpor, bool need_memory_info)
349 : Exploration(args, need_memory_info || _sg_mc_termination)
352 reduction_mode_ = ReductionMode::dpor;
354 reduction_mode_ = ReductionMode::none;
356 if (_sg_mc_termination) {
358 XBT_INFO("Check non progressive cycles (turning DPOR off)");
359 reduction_mode_ = ReductionMode::none;
361 XBT_INFO("Check non progressive cycles");
364 XBT_INFO("Start a DFS exploration. Reduction is: %s.", to_c_str(reduction_mode_));
366 auto initial_state = std::make_shared<State>(get_remote_app());
368 XBT_DEBUG("**************************************************");
370 stack_.emplace_back(std::move(initial_state));
372 /* Get an enabled actor and insert it in the interleave set of the initial state */
373 XBT_DEBUG("Initial state. %lu actors to consider", stack_.back()->get_actor_count());
374 if (reduction_mode_ == ReductionMode::dpor)
375 stack_.back()->consider_best();
377 stack_.back()->consider_all();
379 if (stack_.back()->count_todo_multiples() > 1)
380 opened_states_.emplace_back(stack_.back());
383 Exploration* create_dfs_exploration(const std::vector<char*>& args, bool with_dpor)
385 return new DFSExplorer(args, with_dpor);
388 } // namespace simgrid::mc