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& state : stack_)
68 res.push_back(state->get_transition());
72 RecordTrace get_record_trace_of_stack(stack_t stack)
75 for (auto const& state : stack)
76 res.push_back(state->get_transition());
80 std::vector<std::string> DFSExplorer::get_textual_trace() // override
82 std::vector<std::string> trace;
83 for (auto const& state : stack_) {
84 const auto* t = state->get_transition();
85 trace.push_back(xbt::string_printf("%ld: %s", t->aid_, t->to_string().c_str()));
90 void DFSExplorer::log_state() // override
92 on_log_state_signal(get_remote_app());
93 XBT_INFO("DFS exploration ended. %ld unique states visited; %lu backtracks (%lu transition replays, %lu states "
95 State::get_expanded_states(), backtrack_count_, visited_states_count_,
96 Transition::get_replayed_transitions());
97 Exploration::log_state();
100 void DFSExplorer::add_to_opened_states(stack_t stack)
103 for (auto& state : stack)
104 tmp_stack.push_back(std::make_shared<State>(State(*state)));
105 opened_states_.emplace_back(tmp_stack);
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 State* state = stack_.back().get();
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
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("There remains %lu actors, but none to interleave (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());
164 if (_sg_mc_sleep_set && XBT_LOG_ISENABLED(mc_dfs, xbt_log_priority_verbose)) {
165 XBT_VERB("Sleep set actually containing:");
166 for (auto& [aid, transition] : state->get_sleep_set())
167 XBT_VERB(" <%ld,%s>", aid, transition.to_string().c_str());
170 // if (stack_.back()->count_todo_multiples() <= 1)
171 // add_to_opened_states(stack_);
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;
184 next_state = std::make_shared<State>(get_remote_app(), state);
185 on_state_creation_signal(next_state.get(), get_remote_app());
187 /* Sleep set procedure:
188 * adding the taken transition to the sleep set of the original state.
189 * <!> Since the parent sleep set is used to compute the child sleep set, this need to be
190 * done after next_state creation */
191 XBT_DEBUG("Marking Transition >>%s<< of process %ld done and adding it to the sleep set",
192 state->get_transition()->to_string().c_str(), state->get_transition()->aid_);
193 state->add_sleep_set(state->get_transition()); // Actors are marked done when they are considerd in ActorState
195 /* DPOR persistent set procedure:
196 * for each new transition considered, check if it depends on any other previous transition executed before it
197 * on another process. If there exists one, find the more recent, and add its process to the interleave set.
198 * If the process is not enabled at this point, then add every enabled process to the interleave */
199 if (reduction_mode_ == ReductionMode::dpor) {
200 aid_t issuer_id = state->get_transition()->aid_;
201 stack_t tmp_stack = std::list(stack_);
202 while (not tmp_stack.empty()) {
203 State* prev_state = tmp_stack.back().get();
204 if (state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
205 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
206 prev_state->get_transition()->to_string().c_str(), issuer_id);
207 tmp_stack.pop_back();
209 } else if (prev_state->get_transition()->depends(state->get_transition())) {
210 XBT_VERB("Dependent Transitions:");
211 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
212 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
214 if (prev_state->is_actor_enabled(issuer_id)) {
215 if (not prev_state->is_actor_done(issuer_id)) {
216 prev_state->consider_one(issuer_id);
217 add_to_opened_states(tmp_stack);
219 XBT_DEBUG("Actor %ld is already in done set: no need to explore it again", issuer_id);
221 XBT_DEBUG("Actor %ld is not enabled: DPOR may be failing. To stay sound, we are marking every enabled "
222 "transition as todo",
224 prev_state->consider_all();
225 add_to_opened_states(tmp_stack);
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 if (_sg_mc_termination)
238 this->check_non_termination(next_state.get());
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());
244 stack_.push_back(std::move(next_state));
246 /* If this is a new state (or if we don't care about state-equality reduction) */
247 if (visited_state_ == nullptr) {
248 /* Get an enabled process and insert it in the interleave set of the next state */
249 if (reduction_mode_ == ReductionMode::dpor)
250 stack_.back()->consider_best(); // Take only one transition if DPOR: others may be considered later if required
252 stack_.back()->consider_all();
254 if (stack_.back()->count_todo_multiples() > 1)
255 add_to_opened_states(stack_);
256 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(), stack_.back()->get_num(),
257 state->get_transition()->dot_string().c_str());
259 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(),
260 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_,
261 state->get_transition()->dot_string().c_str());
267 void DFSExplorer::backtrack()
270 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
271 XBT_DEBUG("%ld alternatives are yet to be explored:", opened_states_.size());
272 for (auto& stack : opened_states_)
273 XBT_DEBUG("--> %s", get_record_trace_of_stack(stack).to_string().c_str());
274 on_backtracking_signal(get_remote_app());
275 get_remote_app().check_deadlock();
277 // if no backtracking point, then set the stack_ to empty so we can end the exploration
278 if (opened_states_.size() == 0) {
279 stack_ = std::list<std::shared_ptr<State>>();
283 /* We may backtrack from somewhere either because it's leaf, or because every enabled process are in done/sleep set.
284 * In the first case, we need to remove the last transition corresponding to the Finalize */
285 if (stack_.back()->get_transition()->aid_ == 0)
289 double min_dist = std::numeric_limits<double>::infinity();
291 for (auto iter = opened_states_.begin(); iter != opened_states_.end();) {
292 auto [aid, dist] = (*iter).back()->next_transition_guided();
293 if (aid == -1) { // happens if no actors are todo anymore in this transition
294 iter = opened_states_.erase(iter);
297 if (dist < min_dist) {
306 stack_ = std::list<std::shared_ptr<State>>();
310 if (backtrack.back()->count_todo_multiples() <= 1)
311 opened_states_.remove(backtrack);
313 /* If asked to rollback on a state that has a snapshot, restore it */
314 State* last_state = backtrack.back().get();
315 if (const auto* system_state = last_state->get_system_state()) {
316 system_state->restore(*get_remote_app().get_remote_process_memory());
317 on_restore_system_state_signal(last_state, get_remote_app());
322 /* if no snapshot, we need to restore the initial state and replay the transitions */
323 get_remote_app().restore_initial_state();
324 on_restore_initial_state_signal(get_remote_app());
325 /* Traverse the stack from the state at position start and re-execute the transitions */
326 for (std::shared_ptr<State> const& state : backtrack) {
327 if (state == backtrack.back()) /* If we are arrived on the target state, don't replay the outgoing transition */
329 state->get_transition()->replay(get_remote_app());
330 on_transition_replay_signal(state->get_transition(), get_remote_app());
331 visited_states_count_++;
334 XBT_DEBUG(">> Backtracked to %s", get_record_trace().to_string().c_str());
337 DFSExplorer::DFSExplorer(const std::vector<char*>& args, bool with_dpor, bool need_memory_info)
338 : Exploration(args, need_memory_info || _sg_mc_termination)
341 reduction_mode_ = ReductionMode::dpor;
343 reduction_mode_ = ReductionMode::none;
345 if (_sg_mc_termination) {
347 XBT_INFO("Check non progressive cycles (turning DPOR off)");
348 reduction_mode_ = ReductionMode::none;
350 XBT_INFO("Check non progressive cycles");
353 XBT_INFO("Start a DFS exploration. Reduction is: %s.", to_c_str(reduction_mode_));
355 auto initial_state = std::make_unique<State>(get_remote_app());
357 XBT_DEBUG("**************************************************");
359 stack_.push_back(std::move(initial_state));
361 /* Get an enabled actor and insert it in the interleave set of the initial state */
362 XBT_DEBUG("Initial state. %lu actors to consider", initial_state->get_actor_count());
363 if (reduction_mode_ == ReductionMode::dpor)
364 stack_.back()->consider_best();
366 stack_.back()->consider_all();
368 if (stack_.back()->count_todo_multiples() > 1)
369 add_to_opened_states(stack_);
372 Exploration* create_dfs_exploration(const std::vector<char*>& args, bool with_dpor)
374 return new DFSExplorer(args, with_dpor);
377 } // namespace simgrid::mc