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 state = stack_.rbegin(); state != stack_.rend(); ++state)
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();
62 RecordTrace DFSExplorer::get_record_trace() // override
65 for (auto const& state : stack_)
66 res.push_back(state->get_transition());
70 std::vector<std::string> DFSExplorer::get_textual_trace() // override
72 std::vector<std::string> trace;
73 for (auto const& state : stack_) {
74 const auto* t = state->get_transition();
75 trace.push_back(xbt::string_printf("%ld: %s", t->aid_, t->to_string().c_str()));
80 void DFSExplorer::log_state() // override
82 on_log_state_signal(get_remote_app());
83 XBT_INFO("DFS exploration ended. %ld unique states visited; %ld backtracks (%lu transition replays, %lu states "
85 State::get_expanded_states(), backtrack_count_, mc_model_checker->get_visited_states(),
86 Transition::get_replayed_transitions());
89 void DFSExplorer::run()
91 on_exploration_start_signal(get_remote_app());
92 /* This function runs the DFS algorithm the state space.
93 * We do so iteratively instead of recursively, dealing with the call stack manually.
94 * This allows one to explore the call stack at will. */
96 while (not stack_.empty()) {
97 /* Get current state */
98 State* state = stack_.back().get();
100 XBT_DEBUG("**************************************************");
101 XBT_DEBUG("Exploration depth=%zu (state:#%ld; %zu interleaves todo)", stack_.size(), state->get_num(),
102 state->count_todo());
104 mc_model_checker->inc_visited_states();
106 // Backtrack if we reached the maximum depth
107 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
108 if (reduction_mode_ == ReductionMode::dpor) {
109 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
110 _sg_mc_max_depth.get());
111 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
113 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
118 // Backtrack if we are revisiting a state we saw previously
119 if (visited_state_ != nullptr) {
120 XBT_DEBUG("State already visited (equal to state %ld), exploration stopped on this path.",
121 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num);
123 visited_state_ = nullptr;
128 // Search for the next transition
129 aid_t next = state->next_transition();
131 if (next < 0) { // If there is no more transition in the current state, backtrack.
132 XBT_DEBUG("There remains %lu actors, but none to interleave (depth %zu).", state->get_actor_count(),
135 if (state->get_actor_count() == 0) {
136 mc_model_checker->finalize_app();
137 XBT_VERB("Execution came to an end at %s (state: %ld, depth: %zu)", get_record_trace().to_string().c_str(),
138 state->get_num(), stack_.size());
144 /* Actually answer the request: let's execute the selected request (MCed does one step) */
145 state->execute_next(next);
146 on_transition_execute_signal(state->get_transition(), get_remote_app());
148 // If there are processes to interleave and the maximum depth has not been
149 // reached then perform one step of the exploration algorithm.
150 XBT_VERB("Execute %ld: %.60s (stack depth: %zu, state: %ld, %zu interleaves)", state->get_transition()->aid_,
151 state->get_transition()->to_string().c_str(), stack_.size(), state->get_num(), state->count_todo());
153 /* Create the new expanded state (copy the state of MCed into our MCer data) */
154 auto next_state = std::make_unique<State>(get_remote_app());
155 on_state_creation_signal(next_state.get(), get_remote_app());
157 if (_sg_mc_termination)
158 this->check_non_termination(next_state.get());
160 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
161 if (_sg_mc_max_visited_states > 0)
162 visited_state_ = visited_states_.addVisitedState(next_state->get_num(), next_state.get());
164 /* If this is a new state (or if we don't care about state-equality reduction) */
165 if (visited_state_ == nullptr) {
166 /* Get an enabled process and insert it in the interleave set of the next state */
167 for (auto const& [aid, _] : next_state->get_actors_list()) {
168 if (next_state->is_actor_enabled(aid)) {
169 next_state->mark_todo(aid);
170 if (reduction_mode_ == ReductionMode::dpor)
171 break; // With DPOR, we take the first enabled transition
175 mc_model_checker->dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(), next_state->get_num(),
176 state->get_transition()->dot_string().c_str());
178 mc_model_checker->dot_output("\"%ld\" -> \"%ld\" [%s];\n", state->get_num(),
179 visited_state_->original_num == -1 ? visited_state_->num
180 : visited_state_->original_num,
181 state->get_transition()->dot_string().c_str());
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(get_remote_app());
196 get_remote_app().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. */
202 bool found_backtracking_point = false;
203 while (not stack_.empty() && not found_backtracking_point) {
204 std::unique_ptr<State> state = std::move(stack_.back());
206 if (reduction_mode_ == 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->get_num());
217 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
219 if (not prev_state->is_done(issuer_id))
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->get_num());
227 XBT_VERB(" %s (state=%ld)", state->get_transition()->to_string().c_str(), state->get_num());
232 if (state->count_todo() == 0) { // Empty interleaving set
233 XBT_DEBUG("Delete state %ld at depth %zu", state->get_num(), stack_.size() + 1);
236 XBT_DEBUG("Back-tracking to state %ld at depth %zu", state->get_num(), stack_.size() + 1);
237 stack_.push_back(std::move(state)); // Put it back on the stack
238 found_backtracking_point = true;
242 if (found_backtracking_point) {
243 /* If asked to rollback on a state that has a snapshot, restore it */
244 State* last_state = stack_.back().get();
245 if (const auto* system_state = last_state->get_system_state()) {
246 system_state->restore(&get_remote_app().get_remote_process());
247 on_restore_system_state_signal(last_state, get_remote_app());
251 /* if no snapshot, we need to restore the initial state and replay the transitions */
252 get_remote_app().restore_initial_state();
253 on_restore_initial_state_signal(get_remote_app());
255 /* Traverse the stack from the state at position start and re-execute the transitions */
256 for (std::unique_ptr<State> const& state : stack_) {
257 if (state == stack_.back()) /* If we are arrived on the target state, don't replay the outgoing transition */
259 state->get_transition()->replay();
260 on_transition_replay_signal(state->get_transition(), get_remote_app());
261 /* Update statistics */
262 mc_model_checker->inc_visited_states();
264 } // If no backtracing point, then the stack is empty and the exploration is over
267 DFSExplorer::DFSExplorer(const std::vector<char*>& args, bool with_dpor) : Exploration(args)
270 reduction_mode_ = ReductionMode::dpor;
272 reduction_mode_ = ReductionMode::none;
274 if (_sg_mc_termination) {
276 XBT_INFO("Check non progressive cycles (turning DPOR off)");
277 reduction_mode_ = ReductionMode::none;
279 XBT_INFO("Check non progressive cycles");
282 XBT_INFO("Start a DFS exploration. Reduction is: %s.", to_c_str(reduction_mode_));
284 auto initial_state = std::make_unique<State>(get_remote_app());
286 XBT_DEBUG("**************************************************");
288 /* Get an enabled actor and insert it in the interleave set of the initial state */
289 XBT_DEBUG("Initial state. %lu actors to consider", initial_state->get_actor_count());
290 for (auto const& [aid, _] : initial_state->get_actors_list()) {
291 if (initial_state->is_actor_enabled(aid)) {
292 initial_state->mark_todo(aid);
293 if (reduction_mode_ == ReductionMode::dpor) {
294 XBT_DEBUG("Actor %ld is TODO, DPOR is ON so let's go for this one.", aid);
297 XBT_DEBUG("Actor %ld is TODO", aid);
301 stack_.push_back(std::move(initial_state));
304 Exploration* create_dfs_exploration(const std::vector<char*>& args, bool with_dpor)
306 return new DFSExplorer(args, with_dpor);
309 } // namespace simgrid::mc