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() == *current_state->get_system_state()) {
46 XBT_INFO("Non-progressive cycle: state %ld -> state %ld", state->get_num(), current_state->get_num());
47 XBT_INFO("******************************************");
48 XBT_INFO("*** NON-PROGRESSIVE CYCLE DETECTED ***");
49 XBT_INFO("******************************************");
50 XBT_INFO("Counter-example execution trace:");
51 for (auto const& s : get_textual_trace())
52 XBT_INFO(" %s", s.c_str());
53 XBT_INFO("You can debug the problem (and see the whole details) by rerunning out of simgrid-mc with "
54 "--cfg=model-check/replay:'%s'",
55 get_record_trace().to_string().c_str());
58 throw TerminationError();
63 RecordTrace DFSExplorer::get_record_trace() // override
66 for (auto const& state : stack_)
67 res.push_back(state->get_transition());
71 std::vector<std::string> DFSExplorer::get_textual_trace() // override
73 std::vector<std::string> trace;
74 for (auto const& state : stack_) {
75 const auto* t = state->get_transition();
76 trace.push_back(xbt::string_printf("%ld: %s", t->aid_, t->to_string().c_str()));
81 void DFSExplorer::log_state() // override
83 on_log_state_signal(get_remote_app());
84 XBT_INFO("DFS exploration ended. %ld unique states visited; %lu backtracks (%lu transition replays, %lu states "
86 State::get_expanded_states(), backtrack_count_, visited_states_count_,
87 Transition::get_replayed_transitions());
88 Exploration::log_state();
91 void DFSExplorer::run()
93 on_exploration_start_signal(get_remote_app());
94 /* This function runs the DFS algorithm the state space.
95 * We do so iteratively instead of recursively, dealing with the call stack manually.
96 * This allows one to explore the call stack at will. */
98 while (not stack_.empty()) {
99 /* Get current state */
100 State* state = stack_.back().get();
102 XBT_DEBUG("**************************************************");
103 XBT_DEBUG("Exploration depth=%zu (state:#%ld; %zu interleaves todo)", stack_.size(), state->get_num(),
104 state->count_todo());
106 visited_states_count_++;
108 // Backtrack if we reached the maximum depth
109 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
110 if (reduction_mode_ == ReductionMode::dpor) {
111 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
112 _sg_mc_max_depth.get());
113 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
115 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
120 // Backtrack if we are revisiting a state we saw previously while applying state-equality reduction
121 if (visited_state_ != nullptr) {
122 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
123 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_);
125 visited_state_ = nullptr;
130 // Search for the next transition
131 // next_transition returns a pair<aid_t, double> in case we want to consider multiple state
132 auto [next, _] = state->next_transition_guided();
134 if (next < 0) { // If there is no more transition in the current state, backtrack.
135 XBT_DEBUG("There remains %lu actors, but none to interleave (depth %zu).", state->get_actor_count(),
138 if (state->get_actor_count() == 0) {
139 get_remote_app().finalize_app();
140 XBT_VERB("Execution came to an end at %s (state: %ld, depth: %zu)", get_record_trace().to_string().c_str(),
141 state->get_num(), stack_.size());
148 if (_sg_mc_sleep_set && XBT_LOG_ISENABLED(mc_dfs, xbt_log_priority_verbose)) {
149 XBT_VERB("Sleep set actually containing:");
150 for (auto& [aid, transition] : state->get_sleep_set())
151 XBT_VERB(" <%ld,%s>", aid, transition.to_string().c_str());
154 /* Actually answer the request: let's execute the selected request (MCed does one step) */
155 state->execute_next(next, get_remote_app());
156 on_transition_execute_signal(state->get_transition(), get_remote_app());
158 // If there are processes to interleave and the maximum depth has not been
159 // reached then perform one step of the exploration algorithm.
160 XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition()->aid_,
161 state->get_transition()->to_string().c_str(), stack_.size(), state->get_num(), state->count_todo());
163 /* Create the new expanded state (copy the state of MCed into our MCer data) */
164 std::unique_ptr<State> next_state;
166 next_state = std::make_unique<State>(get_remote_app(), state);
167 on_state_creation_signal(next_state.get(), get_remote_app());
169 /* Sleep set procedure:
170 * adding the taken transition to the sleep set of the original state.
171 * <!> Since the parent sleep set is used to compute the child sleep set, this need to be
172 * done after next_state creation */
173 XBT_DEBUG("Marking Transition >>%s<< of process %ld done and adding it to the sleep set",
174 state->get_transition()->to_string().c_str(), state->get_transition()->aid_);
175 state->add_sleep_set(state->get_transition()); // Actors are marked done when they are considerd in ActorState
177 /* DPOR persistent set procedure:
178 * for each new transition considered, check if it depends on any other previous transition executed before it
179 * on another process. If there exists one, find the more recent, and add its process to the interleave set.
180 * If the process is not enabled at this point, then add every enabled process to the interleave */
181 if (reduction_mode_ == ReductionMode::dpor) {
182 aid_t issuer_id = state->get_transition()->aid_;
183 for (auto i = stack_.rbegin(); i != stack_.rend(); ++i) {
184 State* prev_state = i->get();
185 if (state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
186 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
187 prev_state->get_transition()->to_string().c_str(), issuer_id);
189 } else if (prev_state->get_transition()->depends(state->get_transition())) {
190 XBT_VERB("Dependent Transitions:");
191 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
192 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
194 if (prev_state->is_actor_enabled(issuer_id)) {
195 if (not prev_state->is_actor_done(issuer_id))
196 prev_state->consider_one(issuer_id);
198 XBT_DEBUG("Actor %ld is already in done set: no need to explore it again", issuer_id);
200 XBT_DEBUG("Actor %ld is not enabled: DPOR may be failing. To stay sound, we are marking every enabled "
201 "transition as todo",
203 prev_state->consider_all();
207 XBT_VERB("INDEPENDENT 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());
214 if (_sg_mc_termination)
215 this->check_non_termination(next_state.get());
217 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
218 if (_sg_mc_max_visited_states > 0)
219 visited_state_ = visited_states_.addVisitedState(next_state->get_num(), next_state.get(), get_remote_app());
221 /* If this is a new state (or if we don't care about state-equality reduction) */
222 if (visited_state_ == nullptr) {
223 /* Get an enabled process and insert it in the interleave set of the next state */
224 if (reduction_mode_ == ReductionMode::dpor)
225 next_state->consider_best(); // Take only one transition if DPOR: others may be considered later if required
227 next_state->consider_all();
229 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(), next_state->get_num(),
230 state->get_transition()->dot_string().c_str());
232 dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(),
233 visited_state_->original_num_ == -1 ? visited_state_->num_ : visited_state_->original_num_,
234 state->get_transition()->dot_string().c_str());
236 stack_.push_back(std::move(next_state));
242 void DFSExplorer::backtrack()
245 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
246 on_backtracking_signal(get_remote_app());
247 get_remote_app().check_deadlock();
249 /* We may backtrack from somewhere either because it's leaf, or because every enabled process are in done/sleep set.
250 * In the first case, we need to remove the last transition corresponding to the Finalize */
251 if (stack_.back()->get_transition()->aid_ == 0)
254 /* Traverse the stack backwards until a state with a non empty interleave set is found, deleting all the states that
255 * have it empty in the way. */
256 bool found_backtracking_point = false;
257 while (not stack_.empty() && not found_backtracking_point) {
258 std::unique_ptr<State> state = std::move(stack_.back());
263 if (state->count_todo() == 0) { // Empty interleaving set: exploration at this level is over
264 XBT_DEBUG("Delete state %ld at depth %zu", state->get_num(), stack_.size() + 1);
267 XBT_DEBUG("Back-tracking to state %ld at depth %zu: %lu transitions left to be explored", state->get_num(),
268 stack_.size() + 1, state->count_todo());
270 std::move(state)); // Put it back on the stack so we can explore the next transition of the interleave
271 found_backtracking_point = true;
275 if (found_backtracking_point) {
276 /* If asked to rollback on a state that has a snapshot, restore it */
277 State* last_state = stack_.back().get();
278 if (const auto* system_state = last_state->get_system_state()) {
279 system_state->restore(get_remote_app().get_remote_process_memory());
280 on_restore_system_state_signal(last_state, get_remote_app());
284 /* if no snapshot, we need to restore the initial state and replay the transitions */
285 get_remote_app().restore_initial_state();
286 on_restore_initial_state_signal(get_remote_app());
288 /* Traverse the stack from the state at position start and re-execute the transitions */
289 for (std::unique_ptr<State> const& state : stack_) {
290 if (state == stack_.back()) /* If we are arrived on the target state, don't replay the outgoing transition */
292 state->get_transition()->replay();
293 on_transition_replay_signal(state->get_transition(), get_remote_app());
294 visited_states_count_++;
296 } // If no backtracing point, then the stack is empty and the exploration is over
299 DFSExplorer::DFSExplorer(const std::vector<char*>& args, bool with_dpor) : Exploration(args)
302 reduction_mode_ = ReductionMode::dpor;
304 reduction_mode_ = ReductionMode::none;
306 if (_sg_mc_termination) {
308 XBT_INFO("Check non progressive cycles (turning DPOR off)");
309 reduction_mode_ = ReductionMode::none;
311 XBT_INFO("Check non progressive cycles");
314 XBT_INFO("Start a DFS exploration. Reduction is: %s.", to_c_str(reduction_mode_));
316 auto initial_state = std::make_unique<State>(get_remote_app());
318 XBT_DEBUG("**************************************************");
320 /* Get an enabled actor and insert it in the interleave set of the initial state */
321 XBT_DEBUG("Initial state. %lu actors to consider", initial_state->get_actor_count());
322 if (reduction_mode_ == ReductionMode::dpor)
323 initial_state->consider_best();
325 initial_state->consider_all();
327 stack_.push_back(std::move(initial_state));
330 Exploration* create_dfs_exploration(const std::vector<char*>& args, bool with_dpor)
332 return new DFSExplorer(args, with_dpor);
335 } // namespace simgrid::mc