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