src/mc/checker/CommunicationDeterminismChecker.cpp

   1 /* Copyright (c) 2008-2018. 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 "src/mc/checker/CommunicationDeterminismChecker.hpp"
   7 #include "src/kernel/activity/MailboxImpl.hpp"
   8 #include "src/mc/VisitedState.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/mc_request.hpp"
  13 #include "src/mc/mc_smx.hpp"
  14 #include "src/mc/mc_state.hpp"
  15 #include "src/mc/remote/Client.hpp"
  16
  17 #include "smpi_request.hpp"
  18
  19 #include <cstdint>
  20
  21 using simgrid::mc::remote;
  22
  23 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_comm_determinism, mc, "Logging specific to MC communication determinism detection");
  24
  25 /********** Global variables **********/
  26
  27 xbt_dynar_t initial_communications_pattern;
  28 xbt_dynar_t incomplete_communications_pattern;
  29
  30 /********** Static functions ***********/
  31
  32 static e_mc_comm_pattern_difference_t compare_comm_pattern(simgrid::mc::PatternCommunication* comm1,
  33                                                            simgrid::mc::PatternCommunication* comm2)
  34 {
  35   if(comm1->type != comm2->type)
  36     return TYPE_DIFF;
  37   if (comm1->rdv != comm2->rdv)
  38     return RDV_DIFF;
  39   if (comm1->src_proc != comm2->src_proc)
  40     return SRC_PROC_DIFF;
  41   if (comm1->dst_proc != comm2->dst_proc)
  42     return DST_PROC_DIFF;
  43   if (comm1->tag != comm2->tag)
  44     return TAG_DIFF;
  45   if (comm1->data.size() != comm2->data.size())
  46     return DATA_SIZE_DIFF;
  47   if (comm1->data != comm2->data)
  48     return DATA_DIFF;
  49   return NONE_DIFF;
  50 }
  51
  52 static char* print_determinism_result(e_mc_comm_pattern_difference_t diff, int process,
  53                                       simgrid::mc::PatternCommunication* comm, unsigned int cursor)
  54 {
  55   char* type;
  56   char* res;
  57
  58   if (comm->type == simgrid::mc::PatternCommunicationType::send)
  59     type = bprintf("The send communications pattern of the process %d is different!", process - 1);
  60   else
  61     type = bprintf("The recv communications pattern of the process %d is different!", process - 1);
  62
  63   switch(diff) {
  64   case TYPE_DIFF:
  65     res = bprintf("%s Different type for communication #%u", type, cursor);
  66     break;
  67   case RDV_DIFF:
  68     res = bprintf("%s Different rdv for communication #%u", type, cursor);
  69     break;
  70   case TAG_DIFF:
  71     res = bprintf("%s Different tag for communication #%u", type, cursor);
  72     break;
  73   case SRC_PROC_DIFF:
  74     res = bprintf("%s Different source for communication #%u", type, cursor);
  75     break;
  76   case DST_PROC_DIFF:
  77     res = bprintf("%s Different destination for communication #%u", type, cursor);
  78     break;
  79   case DATA_SIZE_DIFF:
  80     res = bprintf("%s\n Different data size for communication #%u", type, cursor);
  81     break;
  82   case DATA_DIFF:
  83     res = bprintf("%s\n Different data for communication #%u", type, cursor);
  84     break;
  85   default:
  86     res = nullptr;
  87     break;
  88   }
  89
  90   return res;
  91 }
  92
  93 static void update_comm_pattern(simgrid::mc::PatternCommunication* comm_pattern,
  94                                 simgrid::mc::RemotePtr<simgrid::kernel::activity::CommImpl> comm_addr)
  95 {
  96   // HACK, type punning
  97   simgrid::mc::Remote<simgrid::kernel::activity::CommImpl> temp_comm;
  98   mc_model_checker->process().read(temp_comm, comm_addr);
  99   simgrid::kernel::activity::CommImpl* comm = temp_comm.getBuffer();
 100
 101   smx_actor_t src_proc   = mc_model_checker->process().resolveActor(simgrid::mc::remote(comm->src_proc));
 102   smx_actor_t dst_proc   = mc_model_checker->process().resolveActor(simgrid::mc::remote(comm->dst_proc));
 103   comm_pattern->src_proc = src_proc->pid_;
 104   comm_pattern->dst_proc = dst_proc->pid_;
 105   comm_pattern->src_host = MC_smx_actor_get_host_name(src_proc);
 106   comm_pattern->dst_host = MC_smx_actor_get_host_name(dst_proc);
 107   if (comm_pattern->data.size() == 0 && comm->src_buff != nullptr) {
 108     size_t buff_size;
 109     mc_model_checker->process().read(&buff_size, remote(comm->dst_buff_size));
 110     comm_pattern->data.resize(buff_size);
 111     mc_model_checker->process().read_bytes(comm_pattern->data.data(), comm_pattern->data.size(),
 112                                            remote(comm->src_buff));
 113   }
 114 }
 115
 116 namespace simgrid {
 117 namespace mc {
 118
 119 void CommunicationDeterminismChecker::deterministic_comm_pattern(int process, simgrid::mc::PatternCommunication* comm,
 120                                                                  int backtracking)
 121 {
 122   simgrid::mc::PatternCommunicationList* list =
 123     xbt_dynar_get_as(initial_communications_pattern, process, simgrid::mc::PatternCommunicationList*);
 124
 125   if (not backtracking) {
 126     e_mc_comm_pattern_difference_t diff = compare_comm_pattern(list->list[list->index_comm].get(), comm);
 127
 128     if (diff != NONE_DIFF) {
 129       if (comm->type == simgrid::mc::PatternCommunicationType::send) {
 130         this->send_deterministic = 0;
 131         if (this->send_diff != nullptr)
 132           xbt_free(this->send_diff);
 133         this->send_diff = print_determinism_result(diff, process, comm, list->index_comm + 1);
 134       } else {
 135         this->recv_deterministic = 0;
 136         if (this->recv_diff != nullptr)
 137           xbt_free(this->recv_diff);
 138         this->recv_diff = print_determinism_result(diff, process, comm, list->index_comm + 1);
 139       }
 140       if (_sg_mc_send_determinism && not this->send_deterministic) {
 141         XBT_INFO("*********************************************************");
 142         XBT_INFO("***** Non-send-deterministic communications pattern *****");
 143         XBT_INFO("*********************************************************");
 144         XBT_INFO("%s", this->send_diff);
 145         xbt_free(this->send_diff);
 146         this->send_diff = nullptr;
 147         simgrid::mc::session->logState();
 148         mc_model_checker->exit(SIMGRID_MC_EXIT_NON_DETERMINISM);
 149       } else if (_sg_mc_comms_determinism && (not this->send_deterministic && not this->recv_deterministic)) {
 150         XBT_INFO("****************************************************");
 151         XBT_INFO("***** Non-deterministic communications pattern *****");
 152         XBT_INFO("****************************************************");
 153         XBT_INFO("%s", this->send_diff);
 154         XBT_INFO("%s", this->recv_diff);
 155         xbt_free(this->send_diff);
 156         this->send_diff = nullptr;
 157         xbt_free(this->recv_diff);
 158         this->recv_diff = nullptr;
 159         simgrid::mc::session->logState();
 160         mc_model_checker->exit(SIMGRID_MC_EXIT_NON_DETERMINISM);
 161       }
 162     }
 163   }
 164 }
 165
 166 /********** Non Static functions ***********/
 167
 168 void CommunicationDeterminismChecker::get_comm_pattern(xbt_dynar_t list, smx_simcall_t request,
 169                                                        e_mc_call_type_t call_type, int backtracking)
 170 {
 171   const smx_actor_t issuer = MC_smx_simcall_get_issuer(request);
 172   simgrid::mc::PatternCommunicationList* initial_pattern =
 173       xbt_dynar_get_as(initial_communications_pattern, issuer->pid_, simgrid::mc::PatternCommunicationList*);
 174   xbt_dynar_t incomplete_pattern = xbt_dynar_get_as(incomplete_communications_pattern, issuer->pid_, xbt_dynar_t);
 175
 176   std::unique_ptr<simgrid::mc::PatternCommunication> pattern =
 177       std::unique_ptr<simgrid::mc::PatternCommunication>(new simgrid::mc::PatternCommunication());
 178   pattern->index = initial_pattern->index_comm + xbt_dynar_length(incomplete_pattern);
 179
 180   if (call_type == MC_CALL_TYPE_SEND) {
 181     /* Create comm pattern */
 182     pattern->type = simgrid::mc::PatternCommunicationType::send;
 183     pattern->comm_addr = static_cast<simgrid::kernel::activity::CommImpl*>(simcall_comm_isend__getraw__result(request));
 184
 185     simgrid::mc::Remote<simgrid::kernel::activity::CommImpl> temp_synchro;
 186     mc_model_checker->process().read(temp_synchro,
 187                                      remote(static_cast<simgrid::kernel::activity::CommImpl*>(pattern->comm_addr)));
 188     simgrid::kernel::activity::CommImpl* synchro =
 189         static_cast<simgrid::kernel::activity::CommImpl*>(temp_synchro.getBuffer());
 190
 191     char* remote_name = mc_model_checker->process().read<char*>(
 192         RemotePtr<char*>((uint64_t)(synchro->mbox ? &synchro->mbox->name_ : &synchro->mbox_cpy->name_)));
 193     pattern->rdv      = mc_model_checker->process().read_string(RemotePtr<char>(remote_name));
 194     pattern->src_proc = mc_model_checker->process().resolveActor(simgrid::mc::remote(synchro->src_proc))->pid_;
 195     pattern->src_host = MC_smx_actor_get_host_name(issuer);
 196
 197     simgrid::smpi::Request mpi_request = mc_model_checker->process().read<simgrid::smpi::Request>(
 198         RemotePtr<simgrid::smpi::Request>((std::uint64_t)simcall_comm_isend__get__data(request)));
 199     pattern->tag = mpi_request.tag();
 200
 201     if (synchro->src_buff != nullptr) {
 202       pattern->data.resize(synchro->src_buff_size);
 203       mc_model_checker->process().read_bytes(pattern->data.data(), pattern->data.size(), remote(synchro->src_buff));
 204     }
 205     if(mpi_request.detached()){
 206       if (not this->initial_communications_pattern_done) {
 207         /* Store comm pattern */
 208         simgrid::mc::PatternCommunicationList* list =
 209             xbt_dynar_get_as(initial_communications_pattern, pattern->src_proc, simgrid::mc::PatternCommunicationList*);
 210         list->list.push_back(std::move(pattern));
 211       } else {
 212         /* Evaluate comm determinism */
 213         this->deterministic_comm_pattern(pattern->src_proc, pattern.get(), backtracking);
 214         xbt_dynar_get_as(initial_communications_pattern, pattern->src_proc, simgrid::mc::PatternCommunicationList*)
 215             ->index_comm++;
 216       }
 217       return;
 218     }
 219   } else if (call_type == MC_CALL_TYPE_RECV) {
 220     pattern->type = simgrid::mc::PatternCommunicationType::receive;
 221     pattern->comm_addr = static_cast<simgrid::kernel::activity::CommImpl*>(simcall_comm_irecv__getraw__result(request));
 222
 223     simgrid::smpi::Request mpi_request;
 224     mc_model_checker->process().read(&mpi_request,
 225                                      remote((simgrid::smpi::Request*)simcall_comm_irecv__get__data(request)));
 226     pattern->tag = mpi_request.tag();
 227
 228     simgrid::mc::Remote<simgrid::kernel::activity::CommImpl> temp_comm;
 229     mc_model_checker->process().read(temp_comm,
 230                                      remote(static_cast<simgrid::kernel::activity::CommImpl*>(pattern->comm_addr)));
 231     simgrid::kernel::activity::CommImpl* comm = temp_comm.getBuffer();
 232
 233     char* remote_name;
 234     mc_model_checker->process().read(
 235         &remote_name, remote(comm->mbox ? &simgrid::xbt::string::to_string_data(comm->mbox->name_).data
 236                                         : &simgrid::xbt::string::to_string_data(comm->mbox_cpy->name_).data));
 237     pattern->rdv      = mc_model_checker->process().read_string(RemotePtr<char>(remote_name));
 238     pattern->dst_proc = mc_model_checker->process().resolveActor(simgrid::mc::remote(comm->dst_proc))->pid_;
 239     pattern->dst_host = MC_smx_actor_get_host_name(issuer);
 240   } else
 241     xbt_die("Unexpected call_type %i", (int) call_type);
 242
 243   XBT_DEBUG("Insert incomplete comm pattern %p for process %ld", pattern.get(), issuer->pid_);
 244   xbt_dynar_t dynar = xbt_dynar_get_as(incomplete_communications_pattern, issuer->pid_, xbt_dynar_t);
 245   simgrid::mc::PatternCommunication* pattern2 = pattern.release();
 246   xbt_dynar_push(dynar, &pattern2);
 247 }
 248
 249 void CommunicationDeterminismChecker::complete_comm_pattern(
 250     xbt_dynar_t list, simgrid::mc::RemotePtr<simgrid::kernel::activity::CommImpl> comm_addr, unsigned int issuer,
 251     int backtracking)
 252 {
 253   simgrid::mc::PatternCommunication* current_comm_pattern;
 254   unsigned int cursor = 0;
 255   std::unique_ptr<simgrid::mc::PatternCommunication> comm_pattern;
 256   int completed = 0;
 257
 258   /* Complete comm pattern */
 259   xbt_dynar_foreach(xbt_dynar_get_as(incomplete_communications_pattern, issuer, xbt_dynar_t), cursor, current_comm_pattern)
 260     if (remote(current_comm_pattern->comm_addr) == comm_addr) {
 261       update_comm_pattern(current_comm_pattern, comm_addr);
 262       completed = 1;
 263       simgrid::mc::PatternCommunication* temp;
 264       xbt_dynar_remove_at(xbt_dynar_get_as(incomplete_communications_pattern, issuer, xbt_dynar_t), cursor, &temp);
 265       comm_pattern = std::unique_ptr<simgrid::mc::PatternCommunication>(temp);
 266       XBT_DEBUG("Remove incomplete comm pattern for process %u at cursor %u", issuer, cursor);
 267       break;
 268     }
 269
 270   if (not completed)
 271     xbt_die("Corresponding communication not found!");
 272
 273   simgrid::mc::PatternCommunicationList* pattern =
 274       xbt_dynar_get_as(initial_communications_pattern, issuer, simgrid::mc::PatternCommunicationList*);
 275
 276   if (not this->initial_communications_pattern_done)
 277     /* Store comm pattern */
 278     pattern->list.push_back(std::move(comm_pattern));
 279   else {
 280     /* Evaluate comm determinism */
 281     this->deterministic_comm_pattern(issuer, comm_pattern.get(), backtracking);
 282     pattern->index_comm++;
 283   }
 284 }
 285
 286 CommunicationDeterminismChecker::CommunicationDeterminismChecker(Session& session) : Checker(session)
 287 {
 288 }
 289
 290 CommunicationDeterminismChecker::~CommunicationDeterminismChecker() = default;
 291
 292 RecordTrace CommunicationDeterminismChecker::getRecordTrace() // override
 293 {
 294   RecordTrace res;
 295   for (auto const& state : stack_)
 296     res.push_back(state->getTransition());
 297   return res;
 298 }
 299
 300 std::vector<std::string> CommunicationDeterminismChecker::getTextualTrace() // override
 301 {
 302   std::vector<std::string> trace;
 303   for (auto const& state : stack_) {
 304     smx_simcall_t req = &state->executed_req;
 305     if (req)
 306       trace.push_back(
 307           simgrid::mc::request_to_string(req, state->transition.argument, simgrid::mc::RequestType::executed));
 308   }
 309   return trace;
 310 }
 311
 312 void CommunicationDeterminismChecker::logState() // override
 313 {
 314   if (_sg_mc_comms_determinism && not this->recv_deterministic && this->send_deterministic) {
 315     XBT_INFO("******************************************************");
 316     XBT_INFO("**** Only-send-deterministic communication pattern ****");
 317     XBT_INFO("******************************************************");
 318     XBT_INFO("%s", this->recv_diff);
 319   } else if (_sg_mc_comms_determinism && not this->send_deterministic && this->recv_deterministic) {
 320     XBT_INFO("******************************************************");
 321     XBT_INFO("**** Only-recv-deterministic communication pattern ****");
 322     XBT_INFO("******************************************************");
 323     XBT_INFO("%s", this->send_diff);
 324   }
 325   XBT_INFO("Expanded states = %lu", expandedStatesCount_);
 326   XBT_INFO("Visited states = %lu", mc_model_checker->visited_states);
 327   XBT_INFO("Executed transitions = %lu", mc_model_checker->executed_transitions);
 328   XBT_INFO("Send-deterministic : %s", not this->send_deterministic ? "No" : "Yes");
 329   if (_sg_mc_comms_determinism)
 330     XBT_INFO("Recv-deterministic : %s", not this->recv_deterministic ? "No" : "Yes");
 331 }
 332
 333 void CommunicationDeterminismChecker::prepare()
 334 {
 335   const int maxpid = MC_smx_get_maxpid();
 336
 337   // Create initial_communications_pattern elements:
 338   initial_communications_pattern = simgrid::xbt::newDeleteDynar<simgrid::mc::PatternCommunicationList*>();
 339   for (int i = 0; i < maxpid; i++) {
 340     simgrid::mc::PatternCommunicationList* process_list_pattern = new simgrid::mc::PatternCommunicationList();
 341     xbt_dynar_insert_at(initial_communications_pattern, i, &process_list_pattern);
 342   }
 343
 344   // Create incomplete_communications_pattern elements:
 345   incomplete_communications_pattern = xbt_dynar_new(sizeof(xbt_dynar_t), xbt_dynar_free_voidp);
 346   for (int i = 0; i < maxpid; i++) {
 347     xbt_dynar_t process_pattern = xbt_dynar_new(sizeof(simgrid::mc::PatternCommunication*), nullptr);
 348     xbt_dynar_insert_at(incomplete_communications_pattern, i, &process_pattern);
 349   }
 350
 351   std::unique_ptr<simgrid::mc::State> initial_state =
 352       std::unique_ptr<simgrid::mc::State>(new simgrid::mc::State(++expandedStatesCount_));
 353
 354   XBT_DEBUG("********* Start communication determinism verification *********");
 355
 356   /* Get an enabled actor and insert it in the interleave set of the initial state */
 357   for (auto& actor : mc_model_checker->process().actors())
 358     if (simgrid::mc::actor_is_enabled(actor.copy.getBuffer()))
 359       initial_state->addInterleavingSet(actor.copy.getBuffer());
 360
 361   stack_.push_back(std::move(initial_state));
 362 }
 363
 364 static inline bool all_communications_are_finished()
 365 {
 366   for (size_t current_actor = 1; current_actor < MC_smx_get_maxpid(); current_actor++) {
 367     xbt_dynar_t pattern = xbt_dynar_get_as(incomplete_communications_pattern, current_actor, xbt_dynar_t);
 368     if (not xbt_dynar_is_empty(pattern)) {
 369       XBT_DEBUG("Some communications are not finished, cannot stop the exploration! State not visited.");
 370       return false;
 371     }
 372   }
 373   return true;
 374 }
 375
 376 void CommunicationDeterminismChecker::restoreState()
 377 {
 378   /* Intermediate backtracking */
 379   simgrid::mc::State* state = stack_.back().get();
 380   if (state->system_state) {
 381     simgrid::mc::restore_snapshot(state->system_state);
 382     MC_restore_communications_pattern(state);
 383     return;
 384   }
 385
 386   /* Restore the initial state */
 387   simgrid::mc::session->restoreInitialState();
 388
 389   unsigned n = MC_smx_get_maxpid();
 390   assert(n == xbt_dynar_length(incomplete_communications_pattern));
 391   assert(n == xbt_dynar_length(initial_communications_pattern));
 392   for (unsigned j=0; j < n ; j++) {
 393     xbt_dynar_reset((xbt_dynar_t)xbt_dynar_get_as(incomplete_communications_pattern, j, xbt_dynar_t));
 394     xbt_dynar_get_as(initial_communications_pattern, j, simgrid::mc::PatternCommunicationList*)->index_comm = 0;
 395   }
 396
 397   /* Traverse the stack from the state at position start and re-execute the transitions */
 398   for (std::unique_ptr<simgrid::mc::State> const& state : stack_) {
 399     if (state == stack_.back())
 400       break;
 401
 402     int req_num = state->transition.argument;
 403     smx_simcall_t saved_req = &state->executed_req;
 404     xbt_assert(saved_req);
 405
 406     /* because we got a copy of the executed request, we have to fetch the
 407        real one, pointed by the request field of the issuer process */
 408
 409     const smx_actor_t issuer = MC_smx_simcall_get_issuer(saved_req);
 410     smx_simcall_t req = &issuer->simcall;
 411
 412     /* TODO : handle test and testany simcalls */
 413     e_mc_call_type_t call = MC_get_call_type(req);
 414     mc_model_checker->handle_simcall(state->transition);
 415     MC_handle_comm_pattern(call, req, req_num, nullptr, 1);
 416     mc_model_checker->wait_for_requests();
 417
 418     /* Update statistics */
 419     mc_model_checker->visited_states++;
 420     mc_model_checker->executed_transitions++;
 421   }
 422 }
 423
 424 void CommunicationDeterminismChecker::main()
 425 {
 426   std::unique_ptr<simgrid::mc::VisitedState> visited_state = nullptr;
 427   smx_simcall_t req = nullptr;
 428
 429   while (not stack_.empty()) {
 430     /* Get current state */
 431     simgrid::mc::State* state = stack_.back().get();
 432
 433     XBT_DEBUG("**************************************************");
 434     XBT_DEBUG("Exploration depth = %zu (state = %d, interleaved processes = %zu)", stack_.size(), state->num,
 435               state->interleaveSize());
 436
 437     /* Update statistics */
 438     mc_model_checker->visited_states++;
 439
 440     if (stack_.size() <= (std::size_t)_sg_mc_max_depth)
 441       req = MC_state_get_request(state);
 442     else
 443       req = nullptr;
 444
 445     if (req != nullptr && visited_state == nullptr) {
 446
 447       int req_num = state->transition.argument;
 448
 449       XBT_DEBUG("Execute: %s", simgrid::mc::request_to_string(req, req_num, simgrid::mc::RequestType::simix).c_str());
 450
 451       std::string req_str;
 452       if (dot_output != nullptr)
 453         req_str = simgrid::mc::request_get_dot_output(req, req_num);
 454
 455       mc_model_checker->executed_transitions++;
 456
 457       /* TODO : handle test and testany simcalls */
 458       e_mc_call_type_t call = MC_CALL_TYPE_NONE;
 459       if (_sg_mc_comms_determinism || _sg_mc_send_determinism)
 460         call = MC_get_call_type(req);
 461
 462       /* Answer the request */
 463       mc_model_checker->handle_simcall(state->transition);
 464       /* After this call req is no longer useful */
 465
 466       if (not this->initial_communications_pattern_done)
 467         MC_handle_comm_pattern(call, req, req_num, initial_communications_pattern, 0);
 468       else
 469         MC_handle_comm_pattern(call, req, req_num, nullptr, 0);
 470
 471       /* Wait for requests (schedules processes) */
 472       mc_model_checker->wait_for_requests();
 473
 474       /* Create the new expanded state */
 475       std::unique_ptr<simgrid::mc::State> next_state =
 476           std::unique_ptr<simgrid::mc::State>(new simgrid::mc::State(++expandedStatesCount_));
 477
 478       /* If comm determinism verification, we cannot stop the exploration if some communications are not finished (at
 479        * least, data are transferred). These communications  are incomplete and they cannot be analyzed and compared
 480        * with the initial pattern. */
 481       bool compare_snapshots = all_communications_are_finished() && this->initial_communications_pattern_done;
 482
 483       if (_sg_mc_max_visited_states != 0)
 484         visited_state = visitedStates_.addVisitedState(expandedStatesCount_, next_state.get(), compare_snapshots);
 485       else
 486         visited_state = nullptr;
 487
 488       if (visited_state == nullptr) {
 489
 490         /* Get enabled actors and insert them in the interleave set of the next state */
 491         for (auto& actor : mc_model_checker->process().actors())
 492           if (simgrid::mc::actor_is_enabled(actor.copy.getBuffer()))
 493             next_state->addInterleavingSet(actor.copy.getBuffer());
 494
 495         if (dot_output != nullptr)
 496           fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n",
 497             state->num,  next_state->num, req_str.c_str());
 498
 499       } else if (dot_output != nullptr)
 500         fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num,
 501                 visited_state->original_num == -1 ? visited_state->num : visited_state->original_num, req_str.c_str());
 502
 503       stack_.push_back(std::move(next_state));
 504
 505     } else {
 506
 507       if (stack_.size() > (std::size_t) _sg_mc_max_depth)
 508         XBT_WARN("/!\\ Max depth reached! /!\\ ");
 509       else if (visited_state != nullptr)
 510         XBT_DEBUG("State already visited (equal to state %d), exploration stopped on this path.",
 511             visited_state->original_num == -1 ? visited_state->num : visited_state->original_num);
 512       else
 513         XBT_DEBUG("There are no more processes to interleave. (depth %zu)", stack_.size());
 514
 515       if (not this->initial_communications_pattern_done)
 516         this->initial_communications_pattern_done = 1;
 517
 518       /* Trash the current state, no longer needed */
 519       XBT_DEBUG("Delete state %d at depth %zu", state->num, stack_.size());
 520       stack_.pop_back();
 521
 522       visited_state = nullptr;
 523
 524       /* Check for deadlocks */
 525       if (mc_model_checker->checkDeadlock()) {
 526         MC_show_deadlock();
 527         throw simgrid::mc::DeadlockError();
 528       }
 529
 530       while (not stack_.empty()) {
 531         std::unique_ptr<simgrid::mc::State> state = std::move(stack_.back());
 532         stack_.pop_back();
 533         if (state->interleaveSize() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
 534           /* We found a back-tracking point, let's loop */
 535           XBT_DEBUG("Back-tracking to state %d at depth %zu", state->num, stack_.size() + 1);
 536           stack_.push_back(std::move(state));
 537
 538           this->restoreState();
 539
 540           XBT_DEBUG("Back-tracking to state %d at depth %zu done", stack_.back()->num, stack_.size());
 541
 542           break;
 543         } else {
 544           XBT_DEBUG("Delete state %d at depth %zu", state->num, stack_.size() + 1);
 545         }
 546       }
 547     }
 548   }
 549
 550   simgrid::mc::session->logState();
 551 }
 552
 553 void CommunicationDeterminismChecker::run()
 554 {
 555   XBT_INFO("Check communication determinism");
 556   simgrid::mc::session->initialize();
 557
 558   this->prepare();
 559
 560   this->main();
 561 }
 562
 563 Checker* createCommunicationDeterminismChecker(Session& session)
 564 {
 565   return new CommunicationDeterminismChecker(session);
 566 }
 567
 568 }
 569 }