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 /* Usefull to show debug information */
70 RecordTrace DFSExplorer::get_record_trace_of_stack(stack_t stack)
73 for (auto const& state : stack)
74 res.push_back(state->get_transition());
78 std::vector<std::string> DFSExplorer::get_textual_trace() // override
80 std::vector<std::string> trace;
81 for (auto const& state : stack_) {
82 const auto* t = state->get_transition();
83 trace.push_back(xbt::string_printf("%ld: %s", t->aid_, t->to_string().c_str()));
88 void DFSExplorer::restore_stack(std::shared_ptr<State> state)
91 stack_ = std::list<std::shared_ptr<State>>();
92 std::shared_ptr<State> current_state(state);
93 stack_.push_front(std::shared_ptr<State>(current_state));
94 // condition corresponds to reaching initial state
95 while (current_state->get_parent_state() != nullptr) {
96 current_state = current_state->get_parent_state();
97 stack_.push_front(std::shared_ptr<State>(current_state));
99 XBT_DEBUG("Replaced stack by %s", get_record_trace().to_string().c_str());
102 void DFSExplorer::log_state() // override
104 on_log_state_signal(get_remote_app());
105 XBT_INFO("DFS exploration ended. %ld unique states visited; %lu backtracks (%lu transition replays, %lu states "
107 State::get_expanded_states(), backtrack_count_, visited_states_count_,
108 Transition::get_replayed_transitions());
109 Exploration::log_state();
112 void DFSExplorer::run()
114 on_exploration_start_signal(get_remote_app());
115 /* This function runs the DFS algorithm the state space.
116 * We do so iteratively instead of recursively, dealing with the call stack manually.
117 * This allows one to explore the call stack at will. */
119 while (not stack_.empty()) {
120 /* Get current state */
121 std::shared_ptr<State> state(stack_.back());
123 XBT_DEBUG("**************************************************");
124 XBT_DEBUG("Exploration depth=%zu (state:#%ld; %zu interleaves todo)", stack_.size(), state->get_num(),
125 state->count_todo());
127 visited_states_count_++;
129 // Backtrack if we reached the maximum depth
130 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
131 if (reduction_mode_ == ReductionMode::dpor) {
132 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
133 _sg_mc_max_depth.get());
134 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
136 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
141 // Backtrack if we are revisiting a state we saw previously while applying state-equality reduction
142 if (visited_state_ != nullptr) {
143 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
144 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_);
146 visited_state_ = nullptr;
151 // Search for the next transition
152 // next_transition returns a pair<aid_t, double> in case we want to consider multiple state (eg. during backtrack)
153 auto [next, _] = state->next_transition_guided();
155 if (next < 0) { // If there is no more transition in the current state, backtrack.
156 XBT_VERB("There remains %lu actors, but none to interleave (depth %zu).", state->get_actor_count(),
159 if (state->get_actor_count() == 0) {
160 get_remote_app().finalize_app();
161 XBT_VERB("Execution came to an end at %s (state: %ld, depth: %zu)", get_record_trace().to_string().c_str(),
162 state->get_num(), stack_.size());
169 if (_sg_mc_sleep_set && XBT_LOG_ISENABLED(mc_dfs, xbt_log_priority_verbose)) {
170 XBT_VERB("Sleep set actually containing:");
171 for (auto& [aid, transition] : state->get_sleep_set())
172 XBT_VERB(" <%ld,%s>", aid, transition.to_string().c_str());
175 /* Actually answer the request: let's execute the selected request (MCed does one step) */
176 state->execute_next(next, get_remote_app());
177 on_transition_execute_signal(state->get_transition(), get_remote_app());
179 // If there are processes to interleave and the maximum depth has not been
180 // reached then perform one step of the exploration algorithm.
181 XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition()->aid_,
182 state->get_transition()->to_string().c_str(), stack_.size(), state->get_num(), state->count_todo());
184 /* Create the new expanded state (copy the state of MCed into our MCer data) */
185 std::shared_ptr<State> next_state = std::make_shared<State>(get_remote_app(), state);
186 on_state_creation_signal(next_state.get(), get_remote_app());
188 /* Sleep set procedure:
189 * adding the taken transition to the sleep set of the original state.
190 * <!> Since the parent sleep set is used to compute the child sleep set, this need to be
191 * done after next_state creation */
192 XBT_DEBUG("Marking Transition >>%s<< of process %ld done and adding it to the sleep set",
193 state->get_transition()->to_string().c_str(), state->get_transition()->aid_);
194 state->add_sleep_set(state->get_transition()); // Actors are marked done when they are considerd in ActorState
196 /* DPOR persistent set procedure:
197 * for each new transition considered, check if it depends on any other previous transition executed before it
198 * on another process. If there exists one, find the more recent, and add its process to the interleave set.
199 * If the process is not enabled at this point, then add every enabled process to the interleave */
200 if (reduction_mode_ == ReductionMode::dpor) {
201 aid_t issuer_id = state->get_transition()->aid_;
202 stack_t tmp_stack = std::list(stack_);
203 while (not tmp_stack.empty()) {
204 State* prev_state = tmp_stack.back().get();
205 if (state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
206 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
207 prev_state->get_transition()->to_string().c_str(), issuer_id);
208 tmp_stack.pop_back();
210 } else if (prev_state->get_transition()->depends(state->get_transition())) {
211 XBT_VERB("Dependent Transitions:");
212 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
213 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
215 if (prev_state->is_actor_enabled(issuer_id)) {
216 if (not prev_state->is_actor_done(issuer_id)) {
217 prev_state->consider_one(issuer_id);
218 opened_states_.push(std::shared_ptr<State>(tmp_stack.back()));
220 XBT_DEBUG("Actor %ld is already in done set: no need to explore it again", issuer_id);
222 XBT_DEBUG("Actor %ld is not enabled: DPOR may be failing. To stay sound, we are marking every enabled "
223 "transition as todo",
225 if (prev_state->consider_all() >
226 0) // If we ended up marking at least a transition, explore it at some point
227 opened_states_.push(std::shared_ptr<State>(tmp_stack.back()));
231 XBT_VERB("INDEPENDENT Transitions:");
232 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
233 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
235 tmp_stack.pop_back();
239 // Before leaving that state, if the transition we just took can be taken multiple times, we
240 // need to give it to the opened states
241 if (stack_.back()->count_todo_multiples() > 0)
242 opened_states_.push(std::shared_ptr<State>(stack_.back()));
244 if (_sg_mc_termination)
245 this->check_non_termination(next_state.get());
247 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
248 if (_sg_mc_max_visited_states > 0)
249 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. We may backtrack again");
297 // We found a real backtracking point, let's go to it
299 XBT_DEBUG("Backtracking to state#%ld", backtracking_point->get_num());
300 /* If asked to rollback on a state that has a snapshot, restore it */
301 if (const auto* system_state = backtracking_point->get_system_state()) {
302 system_state->restore(*get_remote_app().get_remote_process_memory());
303 on_restore_system_state_signal(backtracking_point.get(), get_remote_app());
304 this->restore_stack(backtracking_point);
308 /* if no snapshot, we need to restore the initial state and replay the transitions */
309 get_remote_app().restore_initial_state();
310 on_restore_initial_state_signal(get_remote_app());
311 /* Traverse the stack from the state at position start and re-execute the transitions */
312 for (auto& state : backtracking_point->get_recipe()) {
313 state->replay(get_remote_app());
314 on_transition_replay_signal(state, get_remote_app());
315 visited_states_count_++;
317 this->restore_stack(backtracking_point);
320 DFSExplorer::DFSExplorer(const std::vector<char*>& args, bool with_dpor, bool need_memory_info)
321 : Exploration(args, need_memory_info || _sg_mc_termination)
324 reduction_mode_ = ReductionMode::dpor;
326 reduction_mode_ = ReductionMode::none;
328 if (_sg_mc_termination) {
330 XBT_INFO("Check non progressive cycles (turning DPOR off)");
331 reduction_mode_ = ReductionMode::none;
333 XBT_INFO("Check non progressive cycles");
336 XBT_INFO("Start a DFS exploration. Reduction is: %s.", to_c_str(reduction_mode_));
338 auto initial_state = std::make_shared<State>(get_remote_app());
340 XBT_DEBUG("**************************************************");
342 stack_.push_back(std::move(initial_state));
344 /* Get an enabled actor and insert it in the interleave set of the initial state */
345 XBT_DEBUG("Initial state. %lu actors to consider", stack_.back()->get_actor_count());
346 if (reduction_mode_ == ReductionMode::dpor)
347 stack_.back()->consider_best();
349 stack_.back()->consider_all();
351 if (stack_.back()->count_todo_multiples() > 1)
352 opened_states_.push(std::shared_ptr<State>(stack_.back()));
355 Exploration* create_dfs_exploration(const std::vector<char*>& args, bool with_dpor)
357 return new DFSExplorer(args, with_dpor);
360 } // namespace simgrid::mc