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/VisitedState.hpp"
8 #include "src/mc/mc_config.hpp"
9 #include "src/mc/mc_exit.hpp"
10 #include "src/mc/mc_private.hpp"
11 #include "src/mc/mc_record.hpp"
12 #include "src/mc/transition/Transition.hpp"
14 #include "src/xbt/mmalloc/mmprivate.h"
16 #include "xbt/string.hpp"
17 #include "xbt/sysdep.h"
26 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_dfs, mc, "DFS exploration algorithm of the model-checker");
28 namespace simgrid::mc {
30 xbt::signal<void(RemoteApp&)> DFSExplorer::on_exploration_start_signal;
31 xbt::signal<void(RemoteApp&)> DFSExplorer::on_backtracking_signal;
33 xbt::signal<void(State*, RemoteApp&)> DFSExplorer::on_state_creation_signal;
35 xbt::signal<void(State*, RemoteApp&)> DFSExplorer::on_restore_system_state_signal;
36 xbt::signal<void(RemoteApp&)> DFSExplorer::on_restore_initial_state_signal;
37 xbt::signal<void(Transition*, RemoteApp&)> DFSExplorer::on_transition_replay_signal;
38 xbt::signal<void(Transition*, RemoteApp&)> DFSExplorer::on_transition_execute_signal;
40 xbt::signal<void(RemoteApp&)> DFSExplorer::on_log_state_signal;
42 void DFSExplorer::check_non_termination(const State* current_state)
44 for (auto const& state : stack_) {
45 if (state->get_system_state()->equals_to(*current_state->get_system_state(),
46 *get_remote_app().get_remote_process_memory())) {
47 XBT_INFO("Non-progressive cycle: state %ld -> state %ld", state->get_num(), current_state->get_num());
48 XBT_INFO("******************************************");
49 XBT_INFO("*** NON-PROGRESSIVE CYCLE DETECTED ***");
50 XBT_INFO("******************************************");
51 XBT_INFO("Counter-example execution trace:");
52 for (auto const& s : get_textual_trace())
53 XBT_INFO(" %s", s.c_str());
54 XBT_INFO("You can debug the problem (and see the whole details) by rerunning out of simgrid-mc with "
55 "--cfg=model-check/replay:'%s'",
56 get_record_trace().to_string().c_str());
59 throw TerminationError();
64 RecordTrace DFSExplorer::get_record_trace() // override
67 for (auto const& transition : stack_.back()->get_recipe())
68 res.push_back(transition);
69 res.push_back(stack_.back()->get_transition());
73 std::vector<std::string> DFSExplorer::get_textual_trace() // override
75 std::vector<std::string> trace;
76 for (auto const& transition : stack_.back()->get_recipe()) {
77 trace.push_back(xbt::string_printf("%ld: %s", transition->aid_, transition->to_string().c_str()));
79 trace.push_back(xbt::string_printf("%ld: %s", stack_.back()->get_transition()->aid_,
80 stack_.back()->get_transition()->to_string().c_str()));
84 void DFSExplorer::restore_stack(std::shared_ptr<State> state)
87 stack_ = std::list<std::shared_ptr<State>>();
88 std::shared_ptr<State> current_state(state);
89 stack_.push_front(std::shared_ptr<State>(current_state));
90 // condition corresponds to reaching initial state
91 while (current_state->get_parent_state() != nullptr) {
92 current_state = current_state->get_parent_state();
93 stack_.push_front(std::shared_ptr<State>(current_state));
95 XBT_DEBUG("Replaced stack by %s", get_record_trace().to_string().c_str());
98 void DFSExplorer::log_state() // override
100 on_log_state_signal(get_remote_app());
101 XBT_INFO("DFS exploration ended. %ld unique states visited; %lu backtracks (%lu transition replays, %lu states "
103 State::get_expanded_states(), backtrack_count_, visited_states_count_,
104 Transition::get_replayed_transitions());
105 Exploration::log_state();
108 void DFSExplorer::run()
110 on_exploration_start_signal(get_remote_app());
111 /* This function runs the DFS algorithm the state space.
112 * We do so iteratively instead of recursively, dealing with the call stack manually.
113 * This allows one to explore the call stack at will. */
115 while (not stack_.empty()) {
116 /* Get current state */
117 std::shared_ptr<State> state(stack_.back());
119 XBT_DEBUG("**************************************************");
120 XBT_DEBUG("Exploration depth=%zu (state:#%ld; %zu interleaves todo)", stack_.size(), state->get_num(),
121 state->count_todo());
123 visited_states_count_++;
125 // Backtrack if we reached the maximum depth
126 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
127 if (reduction_mode_ == ReductionMode::dpor) {
128 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
129 _sg_mc_max_depth.get());
130 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
132 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
137 // Backtrack if we are revisiting a state we saw previously while applying state-equality reduction
138 if (visited_state_ != nullptr) {
139 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
140 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_);
142 visited_state_ = nullptr;
147 // Search for the next transition
148 // next_transition returns a pair<aid_t, double> in case we want to consider multiple state (eg. during backtrack)
149 auto [next, _] = state->next_transition_guided();
151 if (next < 0) { // If there is no more transition in the current state, backtrack.
152 XBT_VERB("%lu actors remain, but none of them need to be interleaved (depth %zu).", state->get_actor_count(),
155 if (state->get_actor_count() == 0) {
156 get_remote_app().finalize_app();
157 XBT_VERB("Execution came to an end at %s (state: %ld, depth: %zu)", get_record_trace().to_string().c_str(),
158 state->get_num(), stack_.size());
165 if (_sg_mc_sleep_set && XBT_LOG_ISENABLED(mc_dfs, xbt_log_priority_verbose)) {
166 XBT_VERB("Sleep set actually containing:");
167 for (auto& [aid, transition] : state->get_sleep_set())
168 XBT_VERB(" <%ld,%s>", aid, transition.to_string().c_str());
171 /* Actually answer the request: let's execute the selected request (MCed does one step) */
172 state->execute_next(next, get_remote_app());
173 on_transition_execute_signal(state->get_transition(), get_remote_app());
175 // If there are processes to interleave and the maximum depth has not been
176 // reached then perform one step of the exploration algorithm.
177 XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves out of %zu enabled, %zu alternatives "
179 state->get_transition()->aid_, state->get_transition()->to_string().c_str(), stack_.size(),
180 state->get_num(), state->count_todo(), state->get_actor_count(), opened_states_.size());
182 /* Create the new expanded state (copy the state of MCed into our MCer data) */
183 std::shared_ptr<State> next_state = std::make_shared<State>(get_remote_app(), state);
184 on_state_creation_signal(next_state.get(), get_remote_app());
186 /* Sleep set procedure:
187 * adding the taken transition to the sleep set of the original state.
188 * <!> Since the parent sleep set is used to compute the child sleep set, this need to be
189 * done after next_state creation */
190 XBT_DEBUG("Marking Transition >>%s<< of process %ld done and adding it to the sleep set",
191 state->get_transition()->to_string().c_str(), state->get_transition()->aid_);
192 state->add_sleep_set(state->get_transition()); // Actors are marked done when they are considerd in ActorState
194 /* DPOR persistent set procedure:
195 * for each new transition considered, check if it depends on any other previous transition executed before it
196 * on another process. If there exists one, find the more recent, and add its process to the interleave set.
197 * If the process is not enabled at this point, then add every enabled process to the interleave */
198 if (reduction_mode_ == ReductionMode::dpor) {
199 aid_t issuer_id = state->get_transition()->aid_;
200 stack_t tmp_stack = std::list(stack_);
201 while (not tmp_stack.empty()) {
202 State* prev_state = tmp_stack.back().get();
203 if (state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
204 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
205 prev_state->get_transition()->to_string().c_str(), issuer_id);
206 tmp_stack.pop_back();
208 } else if (prev_state->get_transition()->depends(state->get_transition())) {
209 XBT_VERB("Dependent Transitions:");
210 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
211 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
213 if (prev_state->is_actor_enabled(issuer_id)) {
214 if (not prev_state->is_actor_done(issuer_id)) {
215 prev_state->consider_one(issuer_id);
216 if (not tmp_stack.back()->is_opened) {
217 opened_states_.push(std::shared_ptr<State>(tmp_stack.back()));
218 tmp_stack.back()->is_opened = true;
221 XBT_DEBUG("Actor %ld is already in done set: no need to explore it again", issuer_id);
223 XBT_DEBUG("Actor %ld is not enabled: DPOR may be failing. To stay sound, we are marking every enabled "
224 "transition as todo",
226 // If we ended up marking at least a transition, explore it at some point
227 if (prev_state->consider_all() > 0 and not tmp_stack.back()->is_opened) {
228 opened_states_.push(std::shared_ptr<State>(tmp_stack.back()));
229 tmp_stack.back()->is_opened = true;
234 XBT_VERB("INDEPENDENT Transitions:");
235 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
236 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
238 tmp_stack.pop_back();
242 // Before leaving that state, if the transition we just took can be taken multiple times, we
243 // need to give it to the opened states
244 if (stack_.back()->count_todo_multiples() > 0 and not stack_.back()->is_opened) {
245 opened_states_.push(std::shared_ptr<State>(stack_.back()));
246 stack_.back()->is_opened = true;
249 if (_sg_mc_termination)
250 this->check_non_termination(next_state.get());
252 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
253 if (_sg_mc_max_visited_states > 0)
254 visited_state_ = visited_states_.addVisitedState(next_state->get_num(), next_state.get(), get_remote_app());
256 stack_.push_back(std::move(next_state));
258 /* If this is a new state (or if we don't care about state-equality reduction) */
259 if (visited_state_ == nullptr) {
260 /* Get an enabled process and insert it in the interleave set of the next state */
261 if (reduction_mode_ == ReductionMode::dpor)
262 stack_.back()->consider_best(); // Take only one transition if DPOR: others may be considered later if required
264 stack_.back()->consider_all();
267 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(), stack_.back()->get_num(),
268 state->get_transition()->dot_string().c_str());
270 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(),
271 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_,
272 state->get_transition()->dot_string().c_str());
277 void DFSExplorer::backtrack()
279 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
280 XBT_DEBUG("%lu alternatives are yet to be explored:", opened_states_.size());
282 on_backtracking_signal(get_remote_app());
283 get_remote_app().check_deadlock();
285 // if no backtracking point, then set the stack_ to empty so we can end the exploration
286 if (opened_states_.empty()) {
287 XBT_DEBUG("No more opened point of exploration, the search will end");
288 stack_ = std::list<std::shared_ptr<State>>();
292 std::shared_ptr<State> backtracking_point = opened_states_.top(); // Take the point with smallest distance
293 opened_states_.pop();
295 // if the smallest distance corresponded to no enable actor, remove this and let the
296 // exploration ask again for a backtrack
297 if (backtracking_point->next_transition_guided().first == -1) {
298 XBT_DEBUG("Best backtracking candidates has already been explored. Let's backtrack again");
303 // We found a real backtracking point, let's go to it
305 XBT_DEBUG("Backtracking to state#%ld", backtracking_point->get_num());
306 /* If asked to rollback on a state that has a snapshot, restore it */
307 if (const auto* system_state = backtracking_point->get_system_state()) {
308 system_state->restore(*get_remote_app().get_remote_process_memory());
309 on_restore_system_state_signal(backtracking_point.get(), get_remote_app());
310 this->restore_stack(backtracking_point);
314 /* if no snapshot, we need to restore the initial state and replay the transitions */
315 get_remote_app().restore_initial_state();
316 on_restore_initial_state_signal(get_remote_app());
317 /* Traverse the stack from the state at position start and re-execute the transitions */
319 for (auto& transition : backtracking_point->get_recipe()) {
320 transition->replay(get_remote_app());
321 on_transition_replay_signal(transition, get_remote_app());
322 XBT_DEBUG("[Backtracking in progress] executing state #%ld/#%ld", i, backtracking_point->get_num());
323 visited_states_count_++;
326 this->restore_stack(backtracking_point);
329 DFSExplorer::DFSExplorer(const std::vector<char*>& args, bool with_dpor, bool need_memory_info)
330 : Exploration(args, need_memory_info || _sg_mc_termination)
333 reduction_mode_ = ReductionMode::dpor;
335 reduction_mode_ = ReductionMode::none;
337 if (_sg_mc_termination) {
339 XBT_INFO("Check non progressive cycles (turning DPOR off)");
340 reduction_mode_ = ReductionMode::none;
342 XBT_INFO("Check non progressive cycles");
345 XBT_INFO("Start a DFS exploration. Reduction is: %s.", to_c_str(reduction_mode_));
347 auto initial_state = std::make_shared<State>(get_remote_app());
349 XBT_DEBUG("**************************************************");
351 stack_.push_back(std::move(initial_state));
353 /* Get an enabled actor and insert it in the interleave set of the initial state */
354 XBT_DEBUG("Initial state. %lu actors to consider", stack_.back()->get_actor_count());
355 if (reduction_mode_ == ReductionMode::dpor)
356 stack_.back()->consider_best();
358 stack_.back()->consider_all();
360 if (stack_.back()->count_todo_multiples() > 1)
361 opened_states_.push(std::shared_ptr<State>(stack_.back()));
364 Exploration* create_dfs_exploration(const std::vector<char*>& args, bool with_dpor)
366 return new DFSExplorer(args, with_dpor);
369 } // namespace simgrid::mc