src/mc/checker/CommunicationDeterminismChecker.cpp

   1 /* Copyright (c) 2008-2017. The SimGrid Team. All rights reserved.          */
   2
   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. */
   5
   6 #include <cstdint>
   7
   8 #include <xbt/dynar.h>
   9 #include <xbt/dynar.hpp>
  10 #include <xbt/log.h>
  11 #include <xbt/sysdep.h>
  12
  13 #include "src/mc/Transition.hpp"
  14 #include "src/mc/VisitedState.hpp"
  15 #include "src/mc/checker/CommunicationDeterminismChecker.hpp"
  16 #include "src/mc/mc_exit.hpp"
  17 #include "src/mc/mc_private.hpp"
  18 #include "src/mc/mc_record.hpp"
  19 #include "src/mc/mc_request.hpp"
  20 #include "src/mc/mc_smx.hpp"
  21 #include "src/mc/mc_state.hpp"
  22 #include "src/mc/remote/Client.hpp"
  23
  24 #include "smpi_request.hpp"
  25
  26 using simgrid::mc::remote;
  27
  28 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_comm_determinism, mc, "Logging specific to MC communication determinism detection");
  29
  30 /********** Global variables **********/
  31
  32 xbt_dynar_t initial_communications_pattern;
  33 xbt_dynar_t incomplete_communications_pattern;
  34
  35 /********** Static functions ***********/
  36
  37 static e_mc_comm_pattern_difference_t compare_comm_pattern(simgrid::mc::PatternCommunication* comm1,
  38                                                            simgrid::mc::PatternCommunication* comm2)
  39 {
  40   if(comm1->type != comm2->type)
  41     return TYPE_DIFF;
  42   if (comm1->rdv != comm2->rdv)
  43     return RDV_DIFF;
  44   if (comm1->src_proc != comm2->src_proc)
  45     return SRC_PROC_DIFF;
  46   if (comm1->dst_proc != comm2->dst_proc)
  47     return DST_PROC_DIFF;
  48   if (comm1->tag != comm2->tag)
  49     return TAG_DIFF;
  50   if (comm1->data.size() != comm2->data.size())
  51     return DATA_SIZE_DIFF;
  52   if (comm1->data != comm2->data)
  53     return DATA_DIFF;
  54   return NONE_DIFF;
  55 }
  56
  57 static char* print_determinism_result(e_mc_comm_pattern_difference_t diff, int process,
  58                                       simgrid::mc::PatternCommunication* comm, unsigned int cursor)
  59 {
  60   char* type;
  61   char* res;
  62
  63   if (comm->type == simgrid::mc::PatternCommunicationType::send)
  64     type = bprintf("The send communications pattern of the process %d is different!", process - 1);
  65   else
  66     type = bprintf("The recv communications pattern of the process %d is different!", process - 1);
  67
  68   switch(diff) {
  69   case TYPE_DIFF:
  70     res = bprintf("%s Different type for communication #%u", type, cursor);
  71     break;
  72   case RDV_DIFF:
  73     res = bprintf("%s Different rdv for communication #%u", type, cursor);
  74     break;
  75   case TAG_DIFF:
  76     res = bprintf("%s Different tag for communication #%u", type, cursor);
  77     break;
  78   case SRC_PROC_DIFF:
  79     res = bprintf("%s Different source for communication #%u", type, cursor);
  80     break;
  81   case DST_PROC_DIFF:
  82     res = bprintf("%s Different destination for communication #%u", type, cursor);
  83     break;
  84   case DATA_SIZE_DIFF:
  85     res = bprintf("%s\n Different data size for communication #%u", type, cursor);
  86     break;
  87   case DATA_DIFF:
  88     res = bprintf("%s\n Different data for communication #%u", type, cursor);
  89     break;
  90   default:
  91     res = nullptr;
  92     break;
  93   }
  94
  95   return res;
  96 }
  97
  98 static void update_comm_pattern(simgrid::mc::PatternCommunication* comm_pattern,
  99                                 simgrid::mc::RemotePtr<simgrid::kernel::activity::CommImpl> comm_addr)
 100 {
 101   // HACK, type punning
 102   simgrid::mc::Remote<simgrid::kernel::activity::CommImpl> temp_comm;
 103   mc_model_checker->process().read(temp_comm, comm_addr);
 104   simgrid::kernel::activity::CommImpl* comm = temp_comm.getBuffer();
 105
 106   smx_actor_t src_proc   = mc_model_checker->process().resolveActor(simgrid::mc::remote(comm->src_proc));
 107   smx_actor_t dst_proc   = mc_model_checker->process().resolveActor(simgrid::mc::remote(comm->dst_proc));
 108   comm_pattern->src_proc = src_proc->pid;
 109   comm_pattern->dst_proc = dst_proc->pid;
 110   comm_pattern->src_host = MC_smx_actor_get_host_name(src_proc);
 111   comm_pattern->dst_host = MC_smx_actor_get_host_name(dst_proc);
 112   if (comm_pattern->data.size() == 0 && comm->src_buff != nullptr) {
 113     size_t buff_size;
 114     mc_model_checker->process().read(&buff_size, remote(comm->dst_buff_size));
 115     comm_pattern->data.resize(buff_size);
 116     mc_model_checker->process().read_bytes(comm_pattern->data.data(), comm_pattern->data.size(),
 117                                            remote(comm->src_buff));
 118   }
 119 }
 120
 121 namespace simgrid {
 122 namespace mc {
 123
 124 void CommunicationDeterminismChecker::deterministic_comm_pattern(int process, simgrid::mc::PatternCommunication* comm,
 125                                                                  int backtracking)
 126 {
 127   simgrid::mc::PatternCommunicationList* list =
 128     xbt_dynar_get_as(initial_communications_pattern, process, simgrid::mc::PatternCommunicationList*);
 129
 130   if (not backtracking) {
 131     e_mc_comm_pattern_difference_t diff = compare_comm_pattern(list->list[list->index_comm].get(), comm);
 132
 133     if (diff != NONE_DIFF) {
 134       if (comm->type == simgrid::mc::PatternCommunicationType::send) {
 135         this->send_deterministic = 0;
 136         if (this->send_diff != nullptr)
 137           xbt_free(this->send_diff);
 138         this->send_diff = print_determinism_result(diff, process, comm, list->index_comm + 1);
 139       } else {
 140         this->recv_deterministic = 0;
 141         if (this->recv_diff != nullptr)
 142           xbt_free(this->recv_diff);
 143         this->recv_diff = print_determinism_result(diff, process, comm, list->index_comm + 1);
 144       }
 145       if (_sg_mc_send_determinism && not this->send_deterministic) {
 146         XBT_INFO("*********************************************************");
 147         XBT_INFO("***** Non-send-deterministic communications pattern *****");
 148         XBT_INFO("*********************************************************");
 149         XBT_INFO("%s", this->send_diff);
 150         xbt_free(this->send_diff);
 151         this->send_diff = nullptr;
 152         simgrid::mc::session->logState();
 153         mc_model_checker->exit(SIMGRID_MC_EXIT_NON_DETERMINISM);
 154       } else if (_sg_mc_comms_determinism && (not this->send_deterministic && not this->recv_deterministic)) {
 155         XBT_INFO("****************************************************");
 156         XBT_INFO("***** Non-deterministic communications pattern *****");
 157         XBT_INFO("****************************************************");
 158         XBT_INFO("%s", this->send_diff);
 159         XBT_INFO("%s", this->recv_diff);
 160         xbt_free(this->send_diff);
 161         this->send_diff = nullptr;
 162         xbt_free(this->recv_diff);
 163         this->recv_diff = nullptr;
 164         simgrid::mc::session->logState();
 165         mc_model_checker->exit(SIMGRID_MC_EXIT_NON_DETERMINISM);
 166       }
 167     }
 168   }
 169 }
 170
 171 /********** Non Static functions ***********/
 172
 173 void CommunicationDeterminismChecker::get_comm_pattern(xbt_dynar_t list, smx_simcall_t request,
 174                                                        e_mc_call_type_t call_type, int backtracking)
 175 {
 176   const smx_actor_t issuer = MC_smx_simcall_get_issuer(request);
 177   simgrid::mc::PatternCommunicationList* initial_pattern =
 178       xbt_dynar_get_as(initial_communications_pattern, issuer->pid, simgrid::mc::PatternCommunicationList*);
 179   xbt_dynar_t incomplete_pattern = xbt_dynar_get_as(incomplete_communications_pattern, issuer->pid, xbt_dynar_t);
 180
 181   std::unique_ptr<simgrid::mc::PatternCommunication> pattern =
 182       std::unique_ptr<simgrid::mc::PatternCommunication>(new simgrid::mc::PatternCommunication());
 183   pattern->index = initial_pattern->index_comm + xbt_dynar_length(incomplete_pattern);
 184
 185   if (call_type == MC_CALL_TYPE_SEND) {
 186     /* Create comm pattern */
 187     pattern->type = simgrid::mc::PatternCommunicationType::send;
 188     pattern->comm_addr = static_cast<simgrid::kernel::activity::CommImpl*>(simcall_comm_isend__getraw__result(request));
 189
 190     simgrid::mc::Remote<simgrid::kernel::activity::CommImpl> temp_synchro;
 191     mc_model_checker->process().read(temp_synchro,
 192                                      remote(static_cast<simgrid::kernel::activity::CommImpl*>(pattern->comm_addr)));
 193     simgrid::kernel::activity::CommImpl* synchro =
 194         static_cast<simgrid::kernel::activity::CommImpl*>(temp_synchro.getBuffer());
 195
 196     char* remote_name = mc_model_checker->process().read<char*>(
 197         (std::uint64_t)(synchro->mbox ? &synchro->mbox->name_ : &synchro->mbox_cpy->name_));
 198     pattern->rdv = mc_model_checker->process().read_string(remote_name);
 199     pattern->src_proc = mc_model_checker->process().resolveActor(simgrid::mc::remote(synchro->src_proc))->pid;
 200     pattern->src_host = MC_smx_actor_get_host_name(issuer);
 201
 202     simgrid::smpi::Request mpi_request =
 203         mc_model_checker->process().read<simgrid::smpi::Request>((std::uint64_t)simcall_comm_isend__get__data(request));
 204     pattern->tag = mpi_request.tag();
 205
 206     if (synchro->src_buff != nullptr) {
 207       pattern->data.resize(synchro->src_buff_size);
 208       mc_model_checker->process().read_bytes(pattern->data.data(), pattern->data.size(), remote(synchro->src_buff));
 209     }
 210     if(mpi_request.detached()){
 211       if (not this->initial_communications_pattern_done) {
 212         /* Store comm pattern */
 213         simgrid::mc::PatternCommunicationList* list =
 214             xbt_dynar_get_as(initial_communications_pattern, pattern->src_proc, simgrid::mc::PatternCommunicationList*);
 215         list->list.push_back(std::move(pattern));
 216       } else {
 217         /* Evaluate comm determinism */
 218         this->deterministic_comm_pattern(pattern->src_proc, pattern.get(), backtracking);
 219         xbt_dynar_get_as(initial_communications_pattern, pattern->src_proc, simgrid::mc::PatternCommunicationList*)
 220             ->index_comm++;
 221       }
 222       return;
 223     }
 224   } else if (call_type == MC_CALL_TYPE_RECV) {
 225     pattern->type = simgrid::mc::PatternCommunicationType::receive;
 226     pattern->comm_addr = static_cast<simgrid::kernel::activity::CommImpl*>(simcall_comm_irecv__getraw__result(request));
 227
 228     simgrid::smpi::Request mpi_request;
 229     mc_model_checker->process().read(&mpi_request,
 230                                      remote((simgrid::smpi::Request*)simcall_comm_irecv__get__data(request)));
 231     pattern->tag = mpi_request.tag();
 232
 233     simgrid::mc::Remote<simgrid::kernel::activity::CommImpl> temp_comm;
 234     mc_model_checker->process().read(temp_comm,
 235                                      remote(static_cast<simgrid::kernel::activity::CommImpl*>(pattern->comm_addr)));
 236     simgrid::kernel::activity::CommImpl* comm = temp_comm.getBuffer();
 237
 238     char* remote_name;
 239     mc_model_checker->process().read(
 240         &remote_name, remote(comm->mbox ? &simgrid::xbt::string::to_string_data(comm->mbox->name_).data
 241                                         : &simgrid::xbt::string::to_string_data(comm->mbox_cpy->name_).data));
 242     pattern->rdv = mc_model_checker->process().read_string(remote_name);
 243     pattern->dst_proc = mc_model_checker->process().resolveActor(simgrid::mc::remote(comm->dst_proc))->pid;
 244     pattern->dst_host = MC_smx_actor_get_host_name(issuer);
 245   } else
 246     xbt_die("Unexpected call_type %i", (int) call_type);
 247
 248   XBT_DEBUG("Insert incomplete comm pattern %p for process %lu", pattern.get(), issuer->pid);
 249   xbt_dynar_t dynar = xbt_dynar_get_as(incomplete_communications_pattern, issuer->pid, xbt_dynar_t);
 250   simgrid::mc::PatternCommunication* pattern2 = pattern.release();
 251   xbt_dynar_push(dynar, &pattern2);
 252 }
 253
 254 void CommunicationDeterminismChecker::complete_comm_pattern(
 255     xbt_dynar_t list, simgrid::mc::RemotePtr<simgrid::kernel::activity::CommImpl> comm_addr, unsigned int issuer,
 256     int backtracking)
 257 {
 258   simgrid::mc::PatternCommunication* current_comm_pattern;
 259   unsigned int cursor = 0;
 260   std::unique_ptr<simgrid::mc::PatternCommunication> comm_pattern;
 261   int completed = 0;
 262
 263   /* Complete comm pattern */
 264   xbt_dynar_foreach(xbt_dynar_get_as(incomplete_communications_pattern, issuer, xbt_dynar_t), cursor, current_comm_pattern)
 265     if (remote(current_comm_pattern->comm_addr) == comm_addr) {
 266       update_comm_pattern(current_comm_pattern, comm_addr);
 267       completed = 1;
 268       simgrid::mc::PatternCommunication* temp;
 269       xbt_dynar_remove_at(xbt_dynar_get_as(incomplete_communications_pattern, issuer, xbt_dynar_t), cursor, &temp);
 270       comm_pattern = std::unique_ptr<simgrid::mc::PatternCommunication>(temp);
 271       XBT_DEBUG("Remove incomplete comm pattern for process %u at cursor %u", issuer, cursor);
 272       break;
 273     }
 274
 275   if (not completed)
 276     xbt_die("Corresponding communication not found!");
 277
 278   simgrid::mc::PatternCommunicationList* pattern =
 279       xbt_dynar_get_as(initial_communications_pattern, issuer, simgrid::mc::PatternCommunicationList*);
 280
 281   if (not this->initial_communications_pattern_done)
 282     /* Store comm pattern */
 283     pattern->list.push_back(std::move(comm_pattern));
 284   else {
 285     /* Evaluate comm determinism */
 286     this->deterministic_comm_pattern(issuer, comm_pattern.get(), backtracking);
 287     pattern->index_comm++;
 288   }
 289 }
 290
 291 CommunicationDeterminismChecker::CommunicationDeterminismChecker(Session& session) : Checker(session)
 292 {
 293 }
 294
 295 CommunicationDeterminismChecker::~CommunicationDeterminismChecker() = default;
 296
 297 RecordTrace CommunicationDeterminismChecker::getRecordTrace() // override
 298 {
 299   RecordTrace res;
 300   for (auto const& state : stack_)
 301     res.push_back(state->getTransition());
 302   return res;
 303 }
 304
 305 std::vector<std::string> CommunicationDeterminismChecker::getTextualTrace() // override
 306 {
 307   std::vector<std::string> trace;
 308   for (auto const& state : stack_) {
 309     smx_simcall_t req = &state->executed_req;
 310     if (req)
 311       trace.push_back(
 312           simgrid::mc::request_to_string(req, state->transition.argument, simgrid::mc::RequestType::executed));
 313   }
 314   return trace;
 315 }
 316
 317 void CommunicationDeterminismChecker::logState() // override
 318 {
 319   if (_sg_mc_comms_determinism && not this->recv_deterministic && this->send_deterministic) {
 320     XBT_INFO("******************************************************");
 321     XBT_INFO("**** Only-send-deterministic communication pattern ****");
 322     XBT_INFO("******************************************************");
 323     XBT_INFO("%s", this->recv_diff);
 324   } else if (_sg_mc_comms_determinism && not this->send_deterministic && this->recv_deterministic) {
 325     XBT_INFO("******************************************************");
 326     XBT_INFO("**** Only-recv-deterministic communication pattern ****");
 327     XBT_INFO("******************************************************");
 328     XBT_INFO("%s", this->send_diff);
 329   }
 330   XBT_INFO("Expanded states = %lu", expandedStatesCount_);
 331   XBT_INFO("Visited states = %lu", mc_model_checker->visited_states);
 332   XBT_INFO("Executed transitions = %lu", mc_model_checker->executed_transitions);
 333   XBT_INFO("Send-deterministic : %s", not this->send_deterministic ? "No" : "Yes");
 334   if (_sg_mc_comms_determinism)
 335     XBT_INFO("Recv-deterministic : %s", not this->recv_deterministic ? "No" : "Yes");
 336 }
 337
 338 void CommunicationDeterminismChecker::prepare()
 339 {
 340   const int maxpid = MC_smx_get_maxpid();
 341
 342   // Create initial_communications_pattern elements:
 343   initial_communications_pattern = simgrid::xbt::newDeleteDynar<simgrid::mc::PatternCommunicationList*>();
 344   for (int i = 0; i < maxpid; i++) {
 345     simgrid::mc::PatternCommunicationList* process_list_pattern = new simgrid::mc::PatternCommunicationList();
 346     xbt_dynar_insert_at(initial_communications_pattern, i, &process_list_pattern);
 347   }
 348
 349   // Create incomplete_communications_pattern elements:
 350   incomplete_communications_pattern = xbt_dynar_new(sizeof(xbt_dynar_t), xbt_dynar_free_voidp);
 351   for (int i = 0; i < maxpid; i++) {
 352     xbt_dynar_t process_pattern = xbt_dynar_new(sizeof(simgrid::mc::PatternCommunication*), nullptr);
 353     xbt_dynar_insert_at(incomplete_communications_pattern, i, &process_pattern);
 354   }
 355
 356   std::unique_ptr<simgrid::mc::State> initial_state =
 357       std::unique_ptr<simgrid::mc::State>(new simgrid::mc::State(++expandedStatesCount_));
 358
 359   XBT_DEBUG("********* Start communication determinism verification *********");
 360
 361   /* Get an enabled actor and insert it in the interleave set of the initial state */
 362   for (auto& actor : mc_model_checker->process().actors())
 363     if (simgrid::mc::actor_is_enabled(actor.copy.getBuffer()))
 364       initial_state->addInterleavingSet(actor.copy.getBuffer());
 365
 366   stack_.push_back(std::move(initial_state));
 367 }
 368
 369 static inline bool all_communications_are_finished()
 370 {
 371   for (size_t current_actor = 1; current_actor < MC_smx_get_maxpid(); current_actor++) {
 372     xbt_dynar_t pattern = xbt_dynar_get_as(incomplete_communications_pattern, current_actor, xbt_dynar_t);
 373     if (not xbt_dynar_is_empty(pattern)) {
 374       XBT_DEBUG("Some communications are not finished, cannot stop the exploration! State not visited.");
 375       return false;
 376     }
 377   }
 378   return true;
 379 }
 380
 381 void CommunicationDeterminismChecker::restoreState()
 382 {
 383   /* Intermediate backtracking */
 384   simgrid::mc::State* state = stack_.back().get();
 385   if (state->system_state) {
 386     simgrid::mc::restore_snapshot(state->system_state);
 387     MC_restore_communications_pattern(state);
 388     return;
 389   }
 390
 391   /* Restore the initial state */
 392   simgrid::mc::session->restoreInitialState();
 393
 394   unsigned n = MC_smx_get_maxpid();
 395   assert(n == xbt_dynar_length(incomplete_communications_pattern));
 396   assert(n == xbt_dynar_length(initial_communications_pattern));
 397   for (unsigned j=0; j < n ; j++) {
 398     xbt_dynar_reset((xbt_dynar_t)xbt_dynar_get_as(incomplete_communications_pattern, j, xbt_dynar_t));
 399     xbt_dynar_get_as(initial_communications_pattern, j, simgrid::mc::PatternCommunicationList*)->index_comm = 0;
 400   }
 401
 402   /* Traverse the stack from the state at position start and re-execute the transitions */
 403   for (std::unique_ptr<simgrid::mc::State> const& state : stack_) {
 404     if (state == stack_.back())
 405       break;
 406
 407     int req_num = state->transition.argument;
 408     smx_simcall_t saved_req = &state->executed_req;
 409     xbt_assert(saved_req);
 410
 411     /* because we got a copy of the executed request, we have to fetch the
 412        real one, pointed by the request field of the issuer process */
 413
 414     const smx_actor_t issuer = MC_smx_simcall_get_issuer(saved_req);
 415     smx_simcall_t req = &issuer->simcall;
 416
 417     /* TODO : handle test and testany simcalls */
 418     e_mc_call_type_t call = MC_get_call_type(req);
 419     mc_model_checker->handle_simcall(state->transition);
 420     MC_handle_comm_pattern(call, req, req_num, nullptr, 1);
 421     mc_model_checker->wait_for_requests();
 422
 423     /* Update statistics */
 424     mc_model_checker->visited_states++;
 425     mc_model_checker->executed_transitions++;
 426   }
 427 }
 428
 429 void CommunicationDeterminismChecker::main()
 430 {
 431   std::unique_ptr<simgrid::mc::VisitedState> visited_state = nullptr;
 432   smx_simcall_t req = nullptr;
 433
 434   while (not stack_.empty()) {
 435     /* Get current state */
 436     simgrid::mc::State* state = stack_.back().get();
 437
 438     XBT_DEBUG("**************************************************");
 439     XBT_DEBUG("Exploration depth = %zu (state = %d, interleaved processes = %zu)", stack_.size(), state->num,
 440               state->interleaveSize());
 441
 442     /* Update statistics */
 443     mc_model_checker->visited_states++;
 444
 445     if (stack_.size() <= (std::size_t)_sg_mc_max_depth)
 446       req = MC_state_get_request(state);
 447     else
 448       req = nullptr;
 449
 450     if (req != nullptr && visited_state == nullptr) {
 451
 452       int req_num = state->transition.argument;
 453
 454       XBT_DEBUG("Execute: %s", simgrid::mc::request_to_string(req, req_num, simgrid::mc::RequestType::simix).c_str());
 455
 456       std::string req_str;
 457       if (dot_output != nullptr)
 458         req_str = simgrid::mc::request_get_dot_output(req, req_num);
 459
 460       mc_model_checker->executed_transitions++;
 461
 462       /* TODO : handle test and testany simcalls */
 463       e_mc_call_type_t call = MC_CALL_TYPE_NONE;
 464       if (_sg_mc_comms_determinism || _sg_mc_send_determinism)
 465         call = MC_get_call_type(req);
 466
 467       /* Answer the request */
 468       mc_model_checker->handle_simcall(state->transition);
 469       /* After this call req is no longer useful */
 470
 471       if (not this->initial_communications_pattern_done)
 472         MC_handle_comm_pattern(call, req, req_num, initial_communications_pattern, 0);
 473       else
 474         MC_handle_comm_pattern(call, req, req_num, nullptr, 0);
 475
 476       /* Wait for requests (schedules processes) */
 477       mc_model_checker->wait_for_requests();
 478
 479       /* Create the new expanded state */
 480       std::unique_ptr<simgrid::mc::State> next_state =
 481           std::unique_ptr<simgrid::mc::State>(new simgrid::mc::State(++expandedStatesCount_));
 482
 483       /* If comm determinism verification, we cannot stop the exploration if some communications are not finished (at
 484        * least, data are transferred). These communications  are incomplete and they cannot be analyzed and compared
 485        * with the initial pattern. */
 486       bool compare_snapshots = all_communications_are_finished() && this->initial_communications_pattern_done;
 487
 488       if (_sg_mc_max_visited_states != 0)
 489         visited_state = visitedStates_.addVisitedState(expandedStatesCount_, next_state.get(), compare_snapshots);
 490       else
 491         visited_state = nullptr;
 492
 493       if (visited_state == nullptr) {
 494
 495         /* Get enabled actors and insert them in the interleave set of the next state */
 496         for (auto& actor : mc_model_checker->process().actors())
 497           if (simgrid::mc::actor_is_enabled(actor.copy.getBuffer()))
 498             next_state->addInterleavingSet(actor.copy.getBuffer());
 499
 500         if (dot_output != nullptr)
 501           fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n",
 502             state->num,  next_state->num, req_str.c_str());
 503
 504       } else if (dot_output != nullptr)
 505         fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num,
 506                 visited_state->original_num == -1 ? visited_state->num : visited_state->original_num, req_str.c_str());
 507
 508       stack_.push_back(std::move(next_state));
 509
 510     } else {
 511
 512       if (stack_.size() > (std::size_t) _sg_mc_max_depth)
 513         XBT_WARN("/!\\ Max depth reached! /!\\ ");
 514       else if (visited_state != nullptr)
 515         XBT_DEBUG("State already visited (equal to state %d), exploration stopped on this path.",
 516             visited_state->original_num == -1 ? visited_state->num : visited_state->original_num);
 517       else
 518         XBT_DEBUG("There are no more processes to interleave. (depth %zu)", stack_.size());
 519
 520       if (not this->initial_communications_pattern_done)
 521         this->initial_communications_pattern_done = 1;
 522
 523       /* Trash the current state, no longer needed */
 524       XBT_DEBUG("Delete state %d at depth %zu", state->num, stack_.size());
 525       stack_.pop_back();
 526
 527       visited_state = nullptr;
 528
 529       /* Check for deadlocks */
 530       if (mc_model_checker->checkDeadlock()) {
 531         MC_show_deadlock();
 532         throw simgrid::mc::DeadlockError();
 533       }
 534
 535       while (not stack_.empty()) {
 536         std::unique_ptr<simgrid::mc::State> state = std::move(stack_.back());
 537         stack_.pop_back();
 538         if (state->interleaveSize() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
 539           /* We found a back-tracking point, let's loop */
 540           XBT_DEBUG("Back-tracking to state %d at depth %zu", state->num, stack_.size() + 1);
 541           stack_.push_back(std::move(state));
 542
 543           this->restoreState();
 544
 545           XBT_DEBUG("Back-tracking to state %d at depth %zu done", stack_.back()->num, stack_.size());
 546
 547           break;
 548         } else {
 549           XBT_DEBUG("Delete state %d at depth %zu", state->num, stack_.size() + 1);
 550         }
 551       }
 552     }
 553   }
 554
 555   simgrid::mc::session->logState();
 556 }
 557
 558 void CommunicationDeterminismChecker::run()
 559 {
 560   XBT_INFO("Check communication determinism");
 561   simgrid::mc::session->initialize();
 562
 563   this->prepare();
 564
 565   this->main();
 566 }
 567
 568 Checker* createCommunicationDeterminismChecker(Session& session)
 569 {
 570   return new CommunicationDeterminismChecker(session);
 571 }
 572
 573 }
 574 }