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)
45 for (auto const& state : stack_) {
46 if (state->get_system_state()->equals_to(*current_state->get_system_state(),
47 *get_remote_app().get_remote_process_memory())) {
48 XBT_INFO("Non-progressive cycle: state %ld -> state %ld", state->get_num(), current_state->get_num());
49 XBT_INFO("******************************************");
50 XBT_INFO("*** NON-PROGRESSIVE CYCLE DETECTED ***");
51 XBT_INFO("******************************************");
52 XBT_INFO("Counter-example execution trace:");
53 for (auto const& s : get_textual_trace())
54 XBT_INFO(" %s", s.c_str());
55 XBT_INFO("You can debug the problem (and see the whole details) by rerunning out of simgrid-mc with "
56 "--cfg=model-check/replay:'%s'",
57 get_record_trace().to_string().c_str());
60 throw TerminationError();
66 RecordTrace DFSExplorer::get_record_trace() // override
69 for (auto const& transition : stack_.back()->get_recipe())
70 res.push_back(transition);
71 res.push_back(stack_.back()->get_transition());
75 std::vector<std::string> DFSExplorer::get_textual_trace() // override
77 std::vector<std::string> trace;
78 for (auto const& transition : stack_.back()->get_recipe()) {
79 trace.push_back(xbt::string_printf("%ld: %s", transition->aid_, transition->to_string().c_str()));
81 trace.push_back(xbt::string_printf("%ld: %s", stack_.back()->get_transition()->aid_,
82 stack_.back()->get_transition()->to_string().c_str()));
86 void DFSExplorer::restore_stack(std::shared_ptr<State> state)
89 stack_ = std::list<std::shared_ptr<State>>();
90 std::shared_ptr<State> current_state(state);
91 stack_.push_front(std::shared_ptr<State>(current_state));
92 // condition corresponds to reaching initial state
93 while (current_state->get_parent_state() != nullptr) {
94 current_state = current_state->get_parent_state();
95 stack_.push_front(std::shared_ptr<State>(current_state));
97 XBT_DEBUG("Replaced stack by %s", get_record_trace().to_string().c_str());
100 void DFSExplorer::log_state() // override
102 on_log_state_signal(get_remote_app());
103 XBT_INFO("DFS exploration ended. %ld unique states visited; %lu backtracks (%lu transition replays, %lu states "
105 State::get_expanded_states(), backtrack_count_, visited_states_count_,
106 Transition::get_replayed_transitions());
107 Exploration::log_state();
110 void DFSExplorer::run()
112 on_exploration_start_signal(get_remote_app());
113 /* This function runs the DFS algorithm the state space.
114 * We do so iteratively instead of recursively, dealing with the call stack manually.
115 * This allows one to explore the call stack at will. */
117 while (not stack_.empty()) {
118 /* Get current state */
119 std::shared_ptr<State> state(stack_.back());
121 XBT_DEBUG("**************************************************");
122 XBT_DEBUG("Exploration depth=%zu (state:#%ld; %zu interleaves todo)", stack_.size(), state->get_num(),
123 state->count_todo());
125 visited_states_count_++;
127 // Backtrack if we reached the maximum depth
128 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
129 if (reduction_mode_ == ReductionMode::dpor) {
130 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
131 _sg_mc_max_depth.get());
132 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
134 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
139 // Backtrack if we are revisiting a state we saw previously while applying state-equality reduction
140 if (visited_state_ != nullptr) {
141 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
142 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_);
144 visited_state_ = nullptr;
149 // Search for the next transition
150 // next_transition returns a pair<aid_t, double> in case we want to consider multiple state (eg. during backtrack)
151 auto [next, _] = state->next_transition_guided();
153 if (next < 0) { // If there is no more transition in the current state, backtrack.
154 XBT_VERB("%lu actors remain, but none of them need to be interleaved (depth %zu).", state->get_actor_count(),
157 if (state->get_actor_count() == 0) {
158 get_remote_app().finalize_app();
159 XBT_VERB("Execution came to an end at %s (state: %ld, depth: %zu)", get_record_trace().to_string().c_str(),
160 state->get_num(), stack_.size());
167 if (_sg_mc_sleep_set && XBT_LOG_ISENABLED(mc_dfs, xbt_log_priority_verbose)) {
168 XBT_VERB("Sleep set actually containing:");
169 for (auto& [aid, transition] : state->get_sleep_set())
170 XBT_VERB(" <%ld,%s>", aid, transition.to_string().c_str());
173 /* Actually answer the request: let's execute the selected request (MCed does one step) */
174 state->execute_next(next, get_remote_app());
175 on_transition_execute_signal(state->get_transition(), get_remote_app());
177 // If there are processes to interleave and the maximum depth has not been
178 // reached then perform one step of the exploration algorithm.
179 XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition()->aid_,
180 state->get_transition()->to_string().c_str(), stack_.size(), state->get_num(), state->count_todo());
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 opened_states_.push(std::shared_ptr<State>(tmp_stack.back()));
218 XBT_DEBUG("Actor %ld is already in done set: no need to explore it again", issuer_id);
220 XBT_DEBUG("Actor %ld is not enabled: DPOR may be failing. To stay sound, we are marking every enabled "
221 "transition as todo",
223 // If we ended up marking at least a transition, explore it at some point
224 if (prev_state->consider_all() > 0)
225 opened_states_.push(std::shared_ptr<State>(tmp_stack.back()));
229 XBT_VERB("INDEPENDENT Transitions:");
230 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
231 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
233 tmp_stack.pop_back();
237 // Before leaving that state, if the transition we just took can be taken multiple times, we
238 // need to give it to the opened states
239 if (stack_.back()->count_todo_multiples() > 0)
240 opened_states_.push(std::shared_ptr<State>(stack_.back()));
242 if (_sg_mc_termination)
243 this->check_non_termination(next_state.get());
246 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
247 if (_sg_mc_max_visited_states > 0)
248 visited_state_ = visited_states_.addVisitedState(next_state->get_num(), next_state.get(), get_remote_app());
251 stack_.push_back(std::move(next_state));
253 /* If this is a new state (or if we don't care about state-equality reduction) */
254 if (visited_state_ == nullptr) {
255 /* Get an enabled process and insert it in the interleave set of the next state */
256 if (reduction_mode_ == ReductionMode::dpor)
257 stack_.back()->consider_best(); // Take only one transition if DPOR: others may be considered later if required
259 stack_.back()->consider_all();
262 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(), stack_.back()->get_num(),
263 state->get_transition()->dot_string().c_str());
265 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(),
266 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_,
267 state->get_transition()->dot_string().c_str());
272 void DFSExplorer::backtrack()
274 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
275 XBT_DEBUG("%lu alternatives are yet to be explored:", opened_states_.size());
277 on_backtracking_signal(get_remote_app());
278 get_remote_app().check_deadlock();
280 // if no backtracking point, then set the stack_ to empty so we can end the exploration
281 if (opened_states_.empty()) {
282 XBT_DEBUG("No more opened point of exploration, the search will end");
283 stack_ = std::list<std::shared_ptr<State>>();
287 std::shared_ptr<State> backtracking_point = opened_states_.top(); // Take the point with smallest distance
288 opened_states_.pop();
290 // if the smallest distance corresponded to no enable actor, remove this and let the
291 // exploration ask again for a backtrack
292 if (backtracking_point->next_transition_guided().first == -1) {
293 XBT_DEBUG("Best backtracking candidates has already been explored. Let's backtrack again");
298 // We found a real backtracking point, let's go to it
300 XBT_DEBUG("Backtracking to state#%ld", backtracking_point->get_num());
303 /* If asked to rollback on a state that has a snapshot, restore it */
304 if (const auto* system_state = backtracking_point->get_system_state()) {
305 system_state->restore(*get_remote_app().get_remote_process_memory());
306 on_restore_system_state_signal(backtracking_point.get(), get_remote_app());
307 this->restore_stack(backtracking_point);
312 /* if no snapshot, we need to restore the initial state and replay the transitions */
313 get_remote_app().restore_initial_state();
314 on_restore_initial_state_signal(get_remote_app());
315 /* Traverse the stack from the state at position start and re-execute the transitions */
316 for (auto& state : backtracking_point->get_recipe()) {
317 state->replay(get_remote_app());
318 on_transition_replay_signal(state, get_remote_app());
319 visited_states_count_++;
321 this->restore_stack(backtracking_point);
324 DFSExplorer::DFSExplorer(const std::vector<char*>& args, bool with_dpor, bool need_memory_info)
325 : Exploration(args, need_memory_info || _sg_mc_termination)
328 reduction_mode_ = ReductionMode::dpor;
330 reduction_mode_ = ReductionMode::none;
332 if (_sg_mc_termination) {
334 XBT_INFO("Check non progressive cycles (turning DPOR off)");
335 reduction_mode_ = ReductionMode::none;
337 XBT_INFO("Check non progressive cycles");
340 XBT_INFO("Start a DFS exploration. Reduction is: %s.", to_c_str(reduction_mode_));
342 auto initial_state = std::make_shared<State>(get_remote_app());
344 XBT_DEBUG("**************************************************");
346 stack_.push_back(std::move(initial_state));
348 /* Get an enabled actor and insert it in the interleave set of the initial state */
349 XBT_DEBUG("Initial state. %lu actors to consider", stack_.back()->get_actor_count());
350 if (reduction_mode_ == ReductionMode::dpor)
351 stack_.back()->consider_best();
353 stack_.back()->consider_all();
355 if (stack_.back()->count_todo_multiples() > 1)
356 opened_states_.push(std::shared_ptr<State>(stack_.back()));
359 Exploration* create_dfs_exploration(const std::vector<char*>& args, bool with_dpor)
361 return new DFSExplorer(args, with_dpor);
364 } // namespace simgrid::mc