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");
27 namespace simgrid::mc {
29 xbt::signal<void()> DFSExplorer::on_exploration_start_signal;
30 xbt::signal<void()> DFSExplorer::on_backtracking_signal;
32 xbt::signal<void(State*)> DFSExplorer::on_state_creation_signal;
34 xbt::signal<void(State*)> DFSExplorer::on_restore_system_state_signal;
35 xbt::signal<void()> DFSExplorer::on_restore_initial_state_signal;
36 xbt::signal<void(Transition*)> DFSExplorer::on_transition_replay_signal;
37 xbt::signal<void(Transition*)> DFSExplorer::on_transition_execute_signal;
39 xbt::signal<void()> DFSExplorer::on_log_state_signal;
41 void DFSExplorer::check_non_termination(const State* current_state)
43 for (auto state = stack_.rbegin(); state != stack_.rend(); ++state)
44 if (Api::get().snapshot_equal((*state)->get_system_state(), current_state->get_system_state())) {
45 XBT_INFO("Non-progressive cycle: state %ld -> state %ld", (*state)->get_num(), current_state->get_num());
46 XBT_INFO("******************************************");
47 XBT_INFO("*** NON-PROGRESSIVE CYCLE DETECTED ***");
48 XBT_INFO("******************************************");
49 XBT_INFO("Counter-example execution trace:");
50 for (auto const& s : get_textual_trace())
51 XBT_INFO(" %s", s.c_str());
52 XBT_INFO("Path = %s", get_record_trace().to_string().c_str());
55 throw TerminationError();
59 RecordTrace DFSExplorer::get_record_trace() // override
62 for (auto const& state : stack_)
63 res.push_back(state->get_transition());
67 std::vector<std::string> DFSExplorer::get_textual_trace() // override
69 std::vector<std::string> trace;
70 for (auto const& state : stack_) {
71 const auto* t = state->get_transition();
72 trace.push_back(xbt::string_printf("%ld: %s", t->aid_, t->to_string().c_str()));
77 void DFSExplorer::log_state() // override
79 on_log_state_signal();
80 XBT_INFO("DFS exploration ended. %ld unique states visited; %ld backtracks (%lu transition replays, %lu states "
82 State::get_expanded_states(), backtrack_count_, Api::get().mc_get_visited_states(),
83 Transition::get_replayed_transitions());
86 void DFSExplorer::run()
88 on_exploration_start_signal();
89 /* This function runs the DFS algorithm the state space.
90 * We do so iteratively instead of recursively, dealing with the call stack manually.
91 * This allows one to explore the call stack at will. */
93 while (not stack_.empty()) {
94 /* Get current state */
95 State* state = stack_.back().get();
97 XBT_DEBUG("**************************************************");
98 XBT_DEBUG("Exploration depth=%zu (state:%ld; %zu interleaves)", stack_.size(), state->get_num(),
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();
134 XBT_VERB("Execution came to an end at %s (state: %ld, depth: %zu)", get_record_trace().to_string().c_str(),
135 state->get_num(), stack_.size());
141 /* Actually answer the request: let's execute the selected request (MCed does one step) */
142 state->execute_next(next);
143 on_transition_execute_signal(state->get_transition());
145 // If there are processes to interleave and the maximum depth has not been
146 // reached then perform one step of the exploration algorithm.
147 XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition()->aid_,
148 state->get_transition()->to_string().c_str(), stack_.size(), state->get_num(), state->count_todo());
151 if (dot_output != nullptr)
152 req_str = state->get_transition()->dot_string();
154 /* Create the new expanded state (copy the state of MCed into our MCer data) */
155 auto next_state = std::make_unique<State>();
156 on_state_creation_signal(next_state.get());
158 if (_sg_mc_termination)
159 this->check_non_termination(next_state.get());
161 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
162 if (_sg_mc_max_visited_states > 0)
163 visited_state_ = visited_states_.addVisitedState(next_state->get_num(), next_state.get(), true);
165 /* If this is a new state (or if we don't care about state-equality reduction) */
166 if (visited_state_ == nullptr) {
167 /* Get an enabled process and insert it in the interleave set of the next state */
168 auto actors = mc_model_checker->get_remote_process().actors();
169 for (auto& remoteActor : actors) {
170 auto actor = remoteActor.copy.get_buffer();
171 if (get_session().actor_is_enabled(actor->get_pid())) {
172 next_state->mark_todo(actor->get_pid());
173 if (reductionMode_ == ReductionMode::dpor)
174 break; // With DPOR, we take the first enabled transition
178 if (dot_output != nullptr)
179 std::fprintf(dot_output, "\"%ld\" -> \"%ld\" [%s];\n", state->get_num(), next_state->get_num(),
182 } else if (dot_output != nullptr)
183 std::fprintf(dot_output, "\"%ld\" -> \"%ld\" [%s];\n", state->get_num(),
184 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num,
187 stack_.push_back(std::move(next_state));
193 void DFSExplorer::backtrack()
196 XBT_VERB("Backtracking from %s", get_record_trace().to_string().c_str());
197 on_backtracking_signal();
200 get_session().check_deadlock();
202 /* Traverse the stack backwards until a state with a non empty interleave set is found, deleting all the states that
203 * have it empty in the way. For each deleted state, check if the request that has generated it (from its
204 * predecessor state), depends on any other previous request executed before it. If it does then add it to the
205 * interleave set of the state that executed that previous request. */
207 while (not stack_.empty()) {
208 std::unique_ptr<State> state = std::move(stack_.back());
210 if (reductionMode_ == ReductionMode::dpor) {
211 aid_t issuer_id = state->get_transition()->aid_;
212 for (auto i = stack_.rbegin(); i != stack_.rend(); ++i) {
213 State* prev_state = i->get();
214 if (state->get_transition()->aid_ == prev_state->get_transition()->aid_) {
215 XBT_DEBUG("Simcall >>%s<< and >>%s<< with same issuer %ld", state->get_transition()->to_string().c_str(),
216 prev_state->get_transition()->to_string().c_str(), issuer_id);
218 } else if (prev_state->get_transition()->depends(state->get_transition())) {
219 XBT_VERB("Dependent Transitions:");
220 XBT_VERB(" %s (state=%ld)", prev_state->get_transition()->to_string().c_str(), prev_state->get_num());
221 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
223 if (not prev_state->is_done(issuer_id))
224 prev_state->mark_todo(issuer_id);
226 XBT_DEBUG("Actor %ld is in done set", issuer_id);
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());
236 if (state->count_todo() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
237 /* We found a back-tracking point, let's loop */
238 XBT_DEBUG("Back-tracking to state %ld at depth %zu", state->get_num(), stack_.size() + 1);
240 std::move(state)); // Put it back on the stack from which it was removed earlier in this while loop
241 this->restore_state();
242 XBT_DEBUG("Back-tracking to state %ld at depth %zu done", stack_.back()->get_num(), stack_.size());
245 XBT_DEBUG("Delete state %ld at depth %zu", state->get_num(), stack_.size() + 1);
250 void DFSExplorer::restore_state()
252 /* If asked to rollback on a state that has a snapshot, restore it */
253 State* last_state = stack_.back().get();
254 if (const auto* system_state = last_state->get_system_state()) {
255 Api::get().restore_state(system_state);
256 on_restore_system_state_signal(last_state);
260 /* if no snapshot, we need to restore the initial state and replay the transitions */
261 get_session().restore_initial_state();
262 on_restore_initial_state_signal();
264 /* Traverse the stack from the state at position start and re-execute the transitions */
265 for (std::unique_ptr<State> const& state : stack_) {
266 if (state == stack_.back()) /* If we are arrived on the target state, don't replay the outgoing transition */
268 state->get_transition()->replay();
269 on_transition_replay_signal(state->get_transition());
270 /* Update statistics */
271 Api::get().mc_inc_visited_states();
275 DFSExplorer::DFSExplorer(Session* session) : Exploration(session)
277 reductionMode_ = reduction_mode;
278 if (_sg_mc_termination)
279 reductionMode_ = ReductionMode::none;
280 else if (reductionMode_ == ReductionMode::unset)
281 reductionMode_ = ReductionMode::dpor;
283 if (_sg_mc_termination)
284 XBT_INFO("Check non progressive cycles");
286 XBT_INFO("Start a DFS exploration. Reduction is: %s.",
287 (reductionMode_ == ReductionMode::none ? "none"
288 : (reductionMode_ == ReductionMode::dpor ? "dpor" : "unknown")));
290 get_session().take_initial_snapshot();
292 XBT_DEBUG("Starting the DFS exploration");
294 auto initial_state = std::make_unique<State>();
296 XBT_DEBUG("**************************************************");
298 /* Get an enabled actor and insert it in the interleave set of the initial state */
299 auto actors = mc_model_checker->get_remote_process().actors();
300 XBT_DEBUG("Initial state. %zu actors to consider", actors.size());
301 for (auto& actor : actors) {
302 aid_t aid = actor.copy.get_buffer()->get_pid();
303 if (get_session().actor_is_enabled(aid)) {
304 initial_state->mark_todo(aid);
305 if (reductionMode_ == ReductionMode::dpor) {
306 XBT_DEBUG("Actor %ld is TODO, DPOR is ON so let's go for this one.", aid);
309 XBT_DEBUG("Actor %ld is TODO", aid);
313 stack_.push_back(std::move(initial_state));
316 Exploration* create_dfs_exploration(Session* session)
318 return new DFSExplorer(session);
321 } // namespace simgrid::mc