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
66 return get_record_trace_of_stack(stack_);
69 RecordTrace DFSExplorer::get_record_trace_of_stack(stack_t stack)
72 for (auto const& state : stack)
73 res.push_back(state->get_transition());
77 std::vector<std::string> DFSExplorer::get_textual_trace() // override
79 std::vector<std::string> trace;
80 for (auto const& state : stack_) {
81 const auto* t = state->get_transition();
82 trace.push_back(xbt::string_printf("%ld: %s", t->aid_, t->to_string().c_str()));
87 void DFSExplorer::log_state() // override
89 on_log_state_signal(get_remote_app());
90 XBT_INFO("DFS exploration ended. %ld unique states visited; %lu backtracks (%lu transition replays, %lu states "
92 State::get_expanded_states(), backtrack_count_, visited_states_count_,
93 Transition::get_replayed_transitions());
94 Exploration::log_state();
97 void DFSExplorer::add_to_opened_states(stack_t stack)
100 for (auto& state : stack)
101 tmp_stack.push_back(std::make_shared<State>(State(*state)));
102 opened_states_.emplace_back(tmp_stack);
105 void DFSExplorer::run()
107 on_exploration_start_signal(get_remote_app());
108 /* This function runs the DFS algorithm the state space.
109 * We do so iteratively instead of recursively, dealing with the call stack manually.
110 * This allows one to explore the call stack at will. */
112 while (not stack_.empty()) {
113 /* Get current state */
114 State* state = stack_.back().get();
116 XBT_DEBUG("**************************************************");
117 XBT_DEBUG("Exploration depth=%zu (state:#%ld; %zu interleaves todo)", stack_.size(), state->get_num(),
118 state->count_todo());
120 visited_states_count_++;
122 // Backtrack if we reached the maximum depth
123 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
124 if (reduction_mode_ == ReductionMode::dpor) {
125 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
126 _sg_mc_max_depth.get());
127 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
129 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
134 // Backtrack if we are revisiting a state we saw previously while applying state-equality reduction
135 if (visited_state_ != nullptr) {
136 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
137 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_);
139 visited_state_ = nullptr;
144 // Search for the next transition
145 // next_transition returns a pair<aid_t, double> in case we want to consider multiple state
146 auto [next, _] = state->next_transition_guided();
148 if (next < 0) { // If there is no more transition in the current state, backtrack.
149 XBT_VERB("There remains %lu actors, but none to interleave (depth %zu).", state->get_actor_count(),
152 if (state->get_actor_count() == 0) {
153 get_remote_app().finalize_app();
154 XBT_VERB("Execution came to an end at %s (state: %ld, depth: %zu)", get_record_trace().to_string().c_str(),
155 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 // if (stack_.back()->count_todo_multiples() <= 1)
168 // add_to_opened_states(stack_);
170 /* Actually answer the request: let's execute the selected request (MCed does one step) */
171 state->execute_next(next, get_remote_app());
172 on_transition_execute_signal(state->get_transition(), get_remote_app());
174 // If there are processes to interleave and the maximum depth has not been
175 // reached then perform one step of the exploration algorithm.
176 XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition()->aid_,
177 state->get_transition()->to_string().c_str(), stack_.size(), state->get_num(), state->count_todo());
179 /* Create the new expanded state (copy the state of MCed into our MCer data) */
180 std::shared_ptr<State> next_state;
181 next_state = std::make_shared<State>(get_remote_app(), state);
182 on_state_creation_signal(next_state.get(), get_remote_app());
184 /* Sleep set procedure:
185 * adding the taken transition to the sleep set of the original state.
186 * <!> Since the parent sleep set is used to compute the child sleep set, this need to be
187 * done after next_state creation */
188 XBT_DEBUG("Marking Transition >>%s<< of process %ld done and adding it to the sleep set",
189 state->get_transition()->to_string().c_str(), state->get_transition()->aid_);
190 state->add_sleep_set(state->get_transition()); // Actors are marked done when they are considerd in ActorState
192 /* DPOR persistent set procedure:
193 * for each new transition considered, check if it depends on any other previous transition executed before it
194 * on another process. If there exists one, find the more recent, and add its process to the interleave set.
195 * If the process is not enabled at this point, then add every enabled process to the interleave */
196 if (reduction_mode_ == ReductionMode::dpor) {
197 aid_t issuer_id = state->get_transition()->aid_;
198 stack_t tmp_stack = std::list(stack_);
199 while (not tmp_stack.empty()) {
200 State* prev_state = tmp_stack.back().get();
201 if (state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
202 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
203 prev_state->get_transition()->to_string().c_str(), issuer_id);
204 tmp_stack.pop_back();
206 } else if (prev_state->get_transition()->depends(state->get_transition())) {
207 XBT_VERB("Dependent Transitions:");
208 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
209 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
211 if (prev_state->is_actor_enabled(issuer_id)) {
212 if (not prev_state->is_actor_done(issuer_id)) {
213 prev_state->consider_one(issuer_id);
214 add_to_opened_states(tmp_stack);
216 XBT_DEBUG("Actor %ld is already in done set: no need to explore it again", issuer_id);
218 XBT_DEBUG("Actor %ld is not enabled: DPOR may be failing. To stay sound, we are marking every enabled "
219 "transition as todo",
221 prev_state->consider_all();
222 add_to_opened_states(tmp_stack);
226 XBT_VERB("INDEPENDENT Transitions:");
227 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
228 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
230 tmp_stack.pop_back();
234 if (_sg_mc_termination)
235 this->check_non_termination(next_state.get());
237 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
238 if (_sg_mc_max_visited_states > 0)
239 visited_state_ = visited_states_.addVisitedState(next_state->get_num(), next_state.get(), get_remote_app());
241 stack_.push_back(std::move(next_state));
243 /* If this is a new state (or if we don't care about state-equality reduction) */
244 if (visited_state_ == nullptr) {
245 /* Get an enabled process and insert it in the interleave set of the next state */
246 if (reduction_mode_ == ReductionMode::dpor)
247 stack_.back()->consider_best(); // Take only one transition if DPOR: others may be considered later if required
249 stack_.back()->consider_all();
251 if (stack_.back()->count_todo_multiples() > 1)
252 add_to_opened_states(stack_);
253 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(), stack_.back()->get_num(),
254 state->get_transition()->dot_string().c_str());
256 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(),
257 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_,
258 state->get_transition()->dot_string().c_str());
264 void DFSExplorer::backtrack()
267 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
268 XBT_DEBUG("%lu alternatives are yet to be explored:", opened_states_.size());
269 for (auto& stack : opened_states_)
270 XBT_DEBUG("--> %s", get_record_trace_of_stack(stack).to_string().c_str());
271 on_backtracking_signal(get_remote_app());
272 get_remote_app().check_deadlock();
274 // if no backtracking point, then set the stack_ to empty so we can end the exploration
275 if (opened_states_.size() == 0) {
276 stack_ = std::list<std::shared_ptr<State>>();
280 /* We may backtrack from somewhere either because it's leaf, or because every enabled process are in done/sleep set.
281 * In the first case, we need to remove the last transition corresponding to the Finalize */
282 if (stack_.back()->get_transition()->aid_ == 0)
286 double min_dist = std::numeric_limits<double>::infinity();
288 for (auto iter = opened_states_.begin(); iter != opened_states_.end();) {
289 auto [aid, dist] = (*iter).back()->next_transition_guided();
290 if (aid == -1) { // happens if no actors are todo anymore in this transition
291 iter = opened_states_.erase(iter);
294 if (dist < min_dist) {
303 stack_ = std::list<std::shared_ptr<State>>();
307 if (backtrack.back()->count_todo_multiples() <= 1)
308 opened_states_.remove(backtrack);
310 /* If asked to rollback on a state that has a snapshot, restore it */
311 State* last_state = backtrack.back().get();
312 if (const auto* system_state = last_state->get_system_state()) {
313 system_state->restore(*get_remote_app().get_remote_process_memory());
314 on_restore_system_state_signal(last_state, get_remote_app());
319 /* if no snapshot, we need to restore the initial state and replay the transitions */
320 get_remote_app().restore_initial_state();
321 on_restore_initial_state_signal(get_remote_app());
322 /* Traverse the stack from the state at position start and re-execute the transitions */
323 for (std::shared_ptr<State> const& state : backtrack) {
324 if (state == backtrack.back()) /* If we are arrived on the target state, don't replay the outgoing transition */
326 state->get_transition()->replay(get_remote_app());
327 on_transition_replay_signal(state->get_transition(), get_remote_app());
328 visited_states_count_++;
331 XBT_DEBUG(">> Backtracked to %s", get_record_trace().to_string().c_str());
334 DFSExplorer::DFSExplorer(const std::vector<char*>& args, bool with_dpor, bool need_memory_info)
335 : Exploration(args, need_memory_info || _sg_mc_termination)
338 reduction_mode_ = ReductionMode::dpor;
340 reduction_mode_ = ReductionMode::none;
342 if (_sg_mc_termination) {
344 XBT_INFO("Check non progressive cycles (turning DPOR off)");
345 reduction_mode_ = ReductionMode::none;
347 XBT_INFO("Check non progressive cycles");
350 XBT_INFO("Start a DFS exploration. Reduction is: %s.", to_c_str(reduction_mode_));
352 auto initial_state = std::make_unique<State>(get_remote_app());
354 XBT_DEBUG("**************************************************");
356 stack_.push_back(std::move(initial_state));
358 /* Get an enabled actor and insert it in the interleave set of the initial state */
359 XBT_DEBUG("Initial state. %lu actors to consider", initial_state->get_actor_count());
360 if (reduction_mode_ == ReductionMode::dpor)
361 stack_.back()->consider_best();
363 stack_.back()->consider_all();
365 if (stack_.back()->count_todo_multiples() > 1)
366 add_to_opened_states(stack_);
369 Exploration* create_dfs_exploration(const std::vector<char*>& args, bool with_dpor)
371 return new DFSExplorer(args, with_dpor);
374 } // namespace simgrid::mc