1 /* Copyright (c) 2016-2022. 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/sysdep.h"
25 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_dfs, mc, "DFS exploration algorithm of the model-checker");
30 xbt::signal<void()> DFSExplorer::on_exploration_start_signal;
31 xbt::signal<void()> DFSExplorer::on_backtracking_signal;
33 xbt::signal<void(State*)> DFSExplorer::on_state_creation_signal;
35 xbt::signal<void(State*)> DFSExplorer::on_restore_system_state_signal;
36 xbt::signal<void()> DFSExplorer::on_restore_initial_state_signal;
37 xbt::signal<void(Transition*)> DFSExplorer::on_transition_replay_signal;
38 xbt::signal<void(Transition*)> DFSExplorer::on_transition_execute_signal;
40 xbt::signal<void()> DFSExplorer::on_log_state_signal;
42 void DFSExplorer::check_non_termination(const State* current_state)
44 for (auto state = stack_.rbegin(); state != stack_.rend(); ++state)
45 if (Api::get().snapshot_equal((*state)->system_state_.get(), current_state->system_state_.get())) {
46 XBT_INFO("Non-progressive cycle: state %ld -> state %ld", (*state)->num_, current_state->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("Path = %s", get_record_trace().to_string().c_str());
56 throw TerminationError();
60 RecordTrace DFSExplorer::get_record_trace() // override
63 for (auto const& state : stack_)
64 res.push_back(state->get_transition());
68 std::vector<std::string> DFSExplorer::get_textual_trace() // override
70 std::vector<std::string> trace;
71 for (auto const& state : stack_) {
72 const auto* t = state->get_transition();
73 trace.push_back(xbt::string_printf("%ld: %s", t->aid_, t->to_string().c_str()));
78 void DFSExplorer::log_state() // override
80 on_log_state_signal();
81 XBT_INFO("DFS exploration ended. %ld unique states visited; %ld backtracks (%lu transition replays, %lu states "
83 State::get_expanded_states(), backtrack_count_, Api::get().mc_get_visited_states(),
84 Transition::get_replayed_transitions());
87 void DFSExplorer::run()
89 on_exploration_start_signal();
90 /* This function runs the DFS algorithm the state space.
91 * We do so iteratively instead of recursively, dealing with the call stack manually.
92 * This allows one to explore the call stack at will. */
94 while (not stack_.empty()) {
95 /* Get current state */
96 State* state = stack_.back().get();
98 XBT_DEBUG("**************************************************");
99 XBT_DEBUG("Exploration depth=%zu (state:%ld; %zu interleaves)", stack_.size(), state->num_, state->count_todo());
101 Api::get().mc_inc_visited_states();
103 // Backtrack if we reached the maximum depth
104 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
105 if (reductionMode_ == ReductionMode::dpor) {
106 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
107 _sg_mc_max_depth.get());
108 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
110 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
115 // Backtrack if we are revisiting a state we saw previously
116 if (visited_state_ != nullptr) {
117 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
118 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num);
120 visited_state_ = nullptr;
125 // Search for the next transition
126 int next = state->next_transition();
128 if (next < 0) { // If there is no more transition in the current state, backtrack.
129 XBT_DEBUG("There remains %zu actors, but none to interleave (depth %zu).",
130 mc_model_checker->get_remote_process().actors().size(), stack_.size() + 1);
132 if (mc_model_checker->get_remote_process().actors().empty())
133 mc_model_checker->finalize_app();
138 /* Actually answer the request: let's execute the selected request (MCed does one step) */
139 state->execute_next(next);
140 on_transition_execute_signal(state->get_transition());
142 // If there are processes to interleave and the maximum depth has not been
143 // reached then perform one step of the exploration algorithm.
144 XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition()->aid_,
145 state->get_transition()->to_string().c_str(), stack_.size(), state->num_, state->count_todo());
148 if (dot_output != nullptr)
149 req_str = state->get_transition()->dot_string();
151 /* Create the new expanded state (copy the state of MCed into our MCer data) */
152 auto next_state = std::make_unique<State>();
153 on_state_creation_signal(next_state.get());
155 if (_sg_mc_termination)
156 this->check_non_termination(next_state.get());
158 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
159 if (_sg_mc_max_visited_states > 0)
160 visited_state_ = visited_states_.addVisitedState(next_state->num_, next_state.get(), true);
162 /* If this is a new state (or if we don't care about state-equality reduction) */
163 if (visited_state_ == nullptr) {
164 /* Get an enabled process and insert it in the interleave set of the next state */
165 auto actors = Api::get().get_actors();
166 for (auto& remoteActor : actors) {
167 auto actor = remoteActor.copy.get_buffer();
168 if (get_session().actor_is_enabled(actor->get_pid())) {
169 next_state->mark_todo(actor->get_pid());
170 if (reductionMode_ == ReductionMode::dpor)
171 break; // With DPOR, we take the first enabled transition
175 if (dot_output != nullptr)
176 std::fprintf(dot_output, "\"%ld\" -> \"%ld\" [%s];\n", state->num_, next_state->num_, req_str.c_str());
178 } else if (dot_output != nullptr)
179 std::fprintf(dot_output, "\"%ld\" -> \"%ld\" [%s];\n", state->num_,
180 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num,
183 stack_.push_back(std::move(next_state));
189 void DFSExplorer::backtrack()
192 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
193 on_backtracking_signal();
196 get_session().check_deadlock();
198 /* Traverse the stack backwards until a state with a non empty interleave set is found, deleting all the states that
199 * have it empty in the way. For each deleted state, check if the request that has generated it (from its
200 * predecessor state), depends on any other previous request executed before it. If it does then add it to the
201 * interleave set of the state that executed that previous request. */
203 while (not stack_.empty()) {
204 std::unique_ptr<State> state = std::move(stack_.back());
206 if (reductionMode_ == ReductionMode::dpor) {
207 aid_t issuer_id = state->get_transition()->aid_;
208 for (auto i = stack_.rbegin(); i != stack_.rend(); ++i) {
209 State* prev_state = i->get();
210 if (state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
211 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
212 prev_state->get_transition()->to_string().c_str(), issuer_id);
214 } else if (prev_state->get_transition()->depends(state->get_transition())) {
215 XBT_VERB("Dependent Transitions:");
216 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->num_);
217 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->num_);
219 if (not prev_state->actor_states_[issuer_id].is_done())
220 prev_state->mark_todo(issuer_id);
222 XBT_DEBUG("Actor %ld is in done set", issuer_id);
225 XBT_VERB("INDEPENDENT Transitions:");
226 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->num_);
227 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->num_);
232 if (state->count_todo() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
233 /* We found a back-tracking point, let's loop */
234 XBT_DEBUG("Back-tracking to state %ld at depth %zu", state->num_, stack_.size() + 1);
236 std::move(state)); // Put it back on the stack from which it was removed earlier in this while loop
237 this->restore_state();
238 XBT_DEBUG("Back-tracking to state %ld at depth %zu done", stack_.back()->num_, stack_.size());
241 XBT_DEBUG("Delete state %ld at depth %zu", state->num_, stack_.size() + 1);
246 void DFSExplorer::restore_state()
248 /* If asked to rollback on a state that has a snapshot, restore it */
249 State* last_state = stack_.back().get();
250 if (last_state->system_state_) {
251 Api::get().restore_state(last_state->system_state_);
252 on_restore_system_state_signal(last_state);
256 /* if no snapshot, we need to restore the initial state and replay the transitions */
257 get_session().restore_initial_state();
258 on_restore_initial_state_signal();
260 /* Traverse the stack from the state at position start and re-execute the transitions */
261 for (std::unique_ptr<State> const& state : stack_) {
262 if (state == stack_.back()) /* If we are arrived on the target state, don't replay the outgoing transition */
264 state->get_transition()->replay();
265 on_transition_replay_signal(state->get_transition());
266 /* Update statistics */
267 Api::get().mc_inc_visited_states();
271 DFSExplorer::DFSExplorer(Session* session) : Exploration(session)
273 reductionMode_ = reduction_mode;
274 if (_sg_mc_termination)
275 reductionMode_ = ReductionMode::none;
276 else if (reductionMode_ == ReductionMode::unset)
277 reductionMode_ = ReductionMode::dpor;
279 if (_sg_mc_termination)
280 XBT_INFO("Check non progressive cycles");
282 XBT_INFO("Start a DFS exploration. Reduction is: %s.",
283 (reductionMode_ == ReductionMode::none ? "none"
284 : (reductionMode_ == ReductionMode::dpor ? "dpor" : "unknown")));
286 get_session().take_initial_snapshot();
288 XBT_DEBUG("Starting the DFS exploration");
290 auto initial_state = std::make_unique<State>();
292 XBT_DEBUG("**************************************************");
294 /* Get an enabled actor and insert it in the interleave set of the initial state */
295 auto actors = Api::get().get_actors();
296 XBT_DEBUG("Initial state. %zu actors to consider", actors.size());
297 for (auto& actor : actors) {
298 aid_t aid = actor.copy.get_buffer()->get_pid();
299 if (get_session().actor_is_enabled(aid)) {
300 initial_state->mark_todo(aid);
301 if (reductionMode_ == ReductionMode::dpor) {
302 XBT_DEBUG("Actor %ld is TODO, DPOR is ON so let's go for this one.", aid);
305 XBT_DEBUG("Actor %ld is TODO", aid);
309 stack_.push_back(std::move(initial_state));
312 Exploration* create_dfs_exploration(Session* session)
314 return new DFSExplorer(session);
318 } // namespace simgrid