source/libr2c2/trainrouteplanner.cpp

   1 #include <msp/core/maputils.h>
   2 #include <msp/time/utils.h>
   3 #include "catalogue.h"
   4 #include "layout.h"
   5 #include "route.h"
   6 #include "train.h"
   7 #include "trainroutemetric.h"
   8 #include "trainrouteplanner.h"
   9 #include "trainrouter.h"
  10 #include "vehicle.h"
  11
  12 using namespace std;
  13 using namespace Msp;
  14
  15 namespace R2C2 {
  16
  17 TrainRoutePlanner::TrainRoutePlanner(Layout &layout):
  18         goal(0),
  19         path_switch_bias(15*Time::sec),
  20         timeout(10*Time::sec),
  21         result(PENDING),
  22         thread(0)
  23 {
  24         const map<unsigned, Train *> &trains = layout.get_trains();
  25         for(map<unsigned, Train *>::const_iterator i=trains.begin(); i!=trains.end(); ++i)
  26         {
  27                 TrainRoutingInfo info(*i->second);
  28                 if(!info.waypoints.empty())
  29                         routed_trains.push_back(info);
  30         }
  31 }
  32
  33 TrainRoutePlanner::~TrainRoutePlanner()
  34 {
  35         if(thread)
  36         {
  37                 thread->join();
  38                 delete thread;
  39         }
  40 }
  41
  42 void TrainRoutePlanner::set_timeout(const Time::TimeDelta &t)
  43 {
  44         timeout = t;
  45 }
  46
  47 TrainRoutePlanner::Result TrainRoutePlanner::plan()
  48 {
  49         prepare_plan();
  50         create_plan();
  51         if(result==PENDING)
  52                 finalize_plan();
  53
  54         return result;
  55 }
  56
  57 void TrainRoutePlanner::plan_async()
  58 {
  59         if(thread)
  60                 throw logic_error("already planning");
  61
  62         prepare_plan();
  63         thread = new PlanningThread(*this);
  64 }
  65
  66 TrainRoutePlanner::Result TrainRoutePlanner::check()
  67 {
  68         if(result==PENDING && goal)
  69         {
  70                 if(thread)
  71                 {
  72                         thread->join();
  73                         delete thread;
  74                         thread = 0;
  75                 }
  76                 finalize_plan();
  77         }
  78
  79         return result;
  80 }
  81
  82 const list<Route *> &TrainRoutePlanner::get_routes_for(const Train &train) const
  83 {
  84         return get_train_info(train).routes;
  85 }
  86
  87 const list<TrainRouter::SequencePoint> &TrainRoutePlanner::get_sequence_for(const Train &train) const
  88 {
  89         return get_train_info(train).sequence;
  90 }
  91
  92 const TrainRoutePlanner::TrainRoutingInfo &TrainRoutePlanner::get_train_info(const Train &train) const
  93 {
  94         for(vector<TrainRoutingInfo>::const_iterator i=routed_trains.begin(); i!=routed_trains.end(); ++i)
  95                 if(i->train==&train)
  96                         return *i;
  97
  98         throw key_error(train.get_name());
  99 }
 100
 101 const TrainRoutePlanner::RoutingStep &TrainRoutePlanner::get_step()
 102 {
 103         steps.splice(steps.end(), queue, queue.begin());
 104         return steps.back();
 105 }
 106
 107 void TrainRoutePlanner::prepare_plan()
 108 {
 109         steps.clear();
 110         queue.clear();
 111         goal = 0;
 112         result = PENDING;
 113
 114         queue.push_back(RoutingStep());
 115         RoutingStep &start = queue.back();
 116         for(vector<TrainRoutingInfo>::iterator i=routed_trains.begin(); i!=routed_trains.end(); ++i)
 117                 start.trains.push_back(TrainRoutingState(*i));
 118         start.update_estimate();
 119 }
 120
 121 void TrainRoutePlanner::create_plan()
 122 {
 123         Time::TimeStamp timeout_stamp = Time::now()+timeout;
 124         unsigned count = 0;
 125         while(!queue.empty())
 126         {
 127                 const RoutingStep &step = get_step();
 128                 if(step.is_goal())
 129                 {
 130                         goal = &step;
 131                         return;
 132                 }
 133
 134                 add_steps(step);
 135
 136                 if(++count>=1000)
 137                 {
 138                         if(Time::now()>timeout_stamp)
 139                                 break;
 140                         count = 0;
 141                 }
 142         }
 143
 144         result = FAILED;
 145 }
 146
 147 void TrainRoutePlanner::add_steps(const RoutingStep &step)
 148 {
 149         list<RoutingStep> new_steps;
 150         step.create_successors(new_steps);
 151         if(new_steps.empty())
 152                 return;
 153
 154         new_steps.sort();
 155         if(!queue.empty() && new_steps.front().cost_estimate<queue.front().cost_estimate+path_switch_bias)
 156                 new_steps.front().preferred = true;
 157         queue.merge(new_steps);
 158 }
 159
 160 void TrainRoutePlanner::finalize_plan()
 161 {
 162         for(vector<TrainRoutingInfo>::iterator i=routed_trains.begin(); i!=routed_trains.end(); ++i)
 163         {
 164                 i->routes.clear();
 165                 i->sequence.clear();
 166                 for(unsigned j=0; j<2; ++j)
 167                         i->track_history[j] = 0;
 168         }
 169
 170         map<Track *, TrainRouter::SequencePoint *> sequenced_tracks;
 171         unsigned sequence = steps.size();
 172         for(const RoutingStep *i=goal; i; i=i->prev)
 173                 for(vector<TrainRoutingState>::const_iterator j=i->trains.begin(); j!=i->trains.end(); ++j)
 174                 {
 175                         Track **history = j->info->track_history;
 176                         // Don't process the same track again.
 177                         if(j->track.track()==history[0])
 178                                 continue;
 179
 180                         Route *route = 0;
 181                         bool start_new_route = true;
 182                         if(!j->info->routes.empty())
 183                         {
 184                                 /* If we already have a route and this track or any linked track is
 185                                 in it, start a new one to avoid loops. */
 186                                 route = j->info->routes.front();
 187                                 start_new_route = route->has_track(*j->track);
 188                                 if(!start_new_route)
 189                                 {
 190                                         unsigned nls = j->track->get_n_link_slots();
 191                                         for(unsigned k=0; (!start_new_route && k<nls); ++k)
 192                                         {
 193                                                 Track *link = j->track->get_link(k);
 194                                                 start_new_route = (link && link!=history[0] && route->has_track(*link));
 195                                         }
 196                                 }
 197                         }
 198
 199                         if(start_new_route)
 200                         {
 201                                 route = new Route(j->info->train->get_layout());
 202                                 route->set_name("Router");
 203                                 route->set_temporary(true);
 204                                 /* Have the routes overlap by two tracks to ensure that turnout
 205                                 paths can be deduced. */
 206                                 for(unsigned k=0; (k<2 && history[k]); ++k)
 207                                         route->add_track(*history[k]);
 208                                 j->info->routes.push_front(route);
 209                         }
 210
 211                         route->add_track(*j->track.track());
 212                         history[1] = history[0];
 213                         history[0] = j->track.track();
 214
 215                         bool waitable = j->track.endpoint().paths!=j->track->get_type().get_paths();
 216                         map<Track *, TrainRouter::SequencePoint *>::iterator k = sequenced_tracks.find(j->track.track());
 217                         if(k!=sequenced_tracks.end())
 218                         {
 219                                 // Add a sequence point if another train uses this track afterwards.
 220                                 if(!k->second->preceding_train)
 221                                 {
 222                                         k->second->preceding_train = j->info->train;
 223                                         k->second->sequence_in = sequence;
 224                                 }
 225                                 j->info->sequence.push_front(TrainRouter::SequencePoint(j->track->get_block(), sequence));
 226                                 if(waitable)
 227                                         k->second = &j->info->sequence.front();
 228                                 --sequence;
 229                         }
 230                         else if(waitable)
 231                         {
 232                                 /* Create a sequence point if it's possible to wait and let another
 233                                 train past. */
 234                                 j->info->sequence.push_front(TrainRouter::SequencePoint(j->track->get_block(), sequence));
 235                                 sequenced_tracks[j->track.track()] = &j->info->sequence.front();
 236                                 --sequence;
 237                         }
 238                 }
 239
 240         result = COMPLETE;
 241 }
 242
 243
 244 TrainRoutePlanner::TrainRoutingInfo::TrainRoutingInfo(Train &t):
 245         train(&t),
 246         length(0),
 247         speed(train->get_maximum_speed()),
 248         first_noncritical(train->get_last_critical_block().next().block()),
 249         router(train->get_ai_of_type<TrainRouter>()),
 250         has_duration(false)
 251 {
 252         if(unsigned n_wps = router->get_n_waypoints())
 253         {
 254                 waypoints.reserve(n_wps),
 255                 metrics.reserve(n_wps);
 256                 for(unsigned i=0; i<n_wps; ++i)
 257                 {
 258                         waypoints.push_back(router->get_waypoint(i));
 259                         metrics.push_back(&router->get_metric(i));
 260                 }
 261                 has_duration = router->get_trip_duration();
 262         }
 263
 264         unsigned n_vehs = train->get_n_vehicles();
 265         for(unsigned i=0; i<n_vehs; ++i)
 266                 length += train->get_vehicle(i).get_type().get_length();
 267
 268         // If no maximum speed is specified, use a sensible default
 269         if(!speed)
 270                 speed = 20*train->get_layout().get_catalogue().get_scale();
 271 }
 272
 273
 274 TrainRoutePlanner::OccupiedTrack::OccupiedTrack(Track &t, unsigned p, OccupiedTrack *n):
 275         track(&t),
 276         path_length(track->get_type().get_path_length(p)),
 277         next(n),
 278         n_tracks(next ? next->n_tracks+1 : 1),
 279         refcount(1)
 280 {
 281         if(next)
 282                 ++next->refcount;
 283 }
 284
 285 TrainRoutePlanner::OccupiedTrack::OccupiedTrack(const OccupiedTrack &other):
 286         track(other.track),
 287         path_length(other.path_length),
 288         next(other.next),
 289         n_tracks(other.n_tracks),
 290         refcount(1)
 291 {
 292         if(next)
 293                 ++next->refcount;
 294 }
 295
 296 TrainRoutePlanner::OccupiedTrack::~OccupiedTrack()
 297 {
 298         if(next && !--next->refcount)
 299                 delete next;
 300 }
 301
 302
 303 TrainRoutePlanner::TrainRoutingState::TrainRoutingState(TrainRoutingInfo &inf):
 304         info(&inf),
 305         critical(true),
 306         occupied_tracks(0),
 307         state(MOVING),
 308         delay(info->router->get_departure_delay()),
 309         duration(info->router->get_trip_duration()),
 310         waypoint(0),
 311         distance_traveled(0),
 312         blocked_by(-1)
 313 {
 314         const Vehicle *veh = &info->train->get_vehicle(0);
 315         // TODO margins
 316         TrackOffsetIter track_and_offs = veh->get_placement().get_position(VehiclePlacement::FRONT_BUFFER);
 317         track = track_and_offs.track_iter();
 318         offset = track_and_offs.offset();
 319         path = track->get_active_path();
 320
 321         while(Vehicle *next = veh->get_link(1))
 322                 veh = next;
 323         track_and_offs = veh->get_placement().get_position(VehiclePlacement::BACK_BUFFER);
 324         back_offset = track_and_offs.offset();
 325
 326         TrackIter iter = track_and_offs.track_iter();
 327         while(1)
 328         {
 329                 occupied_tracks = new OccupiedTrack(*iter, iter->get_active_path(), occupied_tracks);
 330                 if(iter.track()==track.track())
 331                         break;
 332                 iter = iter.next();
 333         }
 334
 335         travel_multiplier = info->metrics[waypoint]->get_travel_multiplier(*track, track.reverse(path).entry());
 336
 337         update_estimate();
 338 }
 339
 340 TrainRoutePlanner::TrainRoutingState::TrainRoutingState(const TrainRoutingState &other):
 341         info(other.info),
 342         track(other.track),
 343         path(other.path),
 344         critical(other.critical),
 345         occupied_tracks(other.occupied_tracks),
 346         offset(other.offset),
 347         back_offset(other.back_offset),
 348         state(other.state),
 349         delay(other.delay),
 350         duration(other.duration),
 351         waypoint(other.waypoint),
 352         travel_multiplier(other.travel_multiplier),
 353         distance_traveled(other.distance_traveled),
 354         remaining_estimate(other.remaining_estimate),
 355         wait_time(other.wait_time),
 356         estimated_wait(other.estimated_wait),
 357         blocked_by(other.blocked_by)
 358 {
 359         ++occupied_tracks->refcount;
 360 }
 361
 362 TrainRoutePlanner::TrainRoutingState::~TrainRoutingState()
 363 {
 364         if(occupied_tracks && !--occupied_tracks->refcount)
 365                 delete occupied_tracks;
 366 }
 367
 368 Time::TimeDelta TrainRoutePlanner::TrainRoutingState::get_time_to_next_track() const
 369 {
 370         return ((occupied_tracks->path_length-offset)/info->speed)*Time::sec+delay;
 371 }
 372
 373 Time::TimeDelta TrainRoutePlanner::TrainRoutingState::get_time_to_pass(Track &trk) const
 374 {
 375         if(is_occupying(trk))
 376         {
 377                 float passed_length = 0;
 378                 for(const OccupiedTrack *occ=occupied_tracks; (occ && occ->track!=&trk); occ=occ->next)
 379                         passed_length += occ->path_length;
 380                 return (max(info->length-passed_length, 0.0f)/info->speed)*Time::sec+delay;
 381         }
 382
 383         for(unsigned wp=waypoint; wp<info->waypoints.size(); ++wp)
 384         {
 385                 float distance = info->metrics[wp]->get_distance_from(trk);
 386                 if(distance>=0 && distance<remaining_estimate)
 387                         return ((remaining_estimate-distance+info->length)/info->speed)*Time::sec+delay;
 388         }
 389
 390         return Time::day;
 391 }
 392
 393 bool TrainRoutePlanner::TrainRoutingState::is_occupying(Track &trk) const
 394 {
 395         if(state==ARRIVED && !duration && info->has_duration)
 396                 return false;
 397
 398         OccupiedTrack *occ = occupied_tracks;
 399         for(unsigned n=occ->n_tracks; n>0; --n, occ=occ->next)
 400                 if(occ->track==&trk)
 401                         return true;
 402         return false;
 403 }
 404
 405 bool TrainRoutePlanner::TrainRoutingState::check_arrival()
 406 {
 407         TrackIter next_track = track.next(path);
 408
 409         // Check if we're about the exit the current waypoint's tracks.
 410         const TrainRouter::Waypoint &wp = info->waypoints[waypoint];
 411         if(wp.chain->has_track(*track) && !wp.chain->has_track(*next_track))
 412                 if(wp.direction==TrackChain::UNSPECIFIED || track==wp.chain->iter_for(*track, wp.direction))
 413                 {
 414                         if(waypoint+1<info->waypoints.size())
 415                                 ++waypoint;
 416                         else
 417                         {
 418                                 state = ARRIVED;
 419                                 return true;
 420                         }
 421                 }
 422
 423         // If we're entering the first non-critical block, clear the critical flag.
 424         if(info->first_noncritical->has_track(*next_track))
 425                 critical = false;
 426
 427         return false;
 428 }
 429
 430 void TrainRoutePlanner::TrainRoutingState::advance(float distance)
 431 {
 432         offset += distance;
 433         back_offset += distance;
 434
 435         // See if the tail end of the train has passed any sensors.
 436         unsigned count_to_free = 0;
 437         unsigned last_sensor_addr = 0;
 438         float distance_after_sensor = 0;
 439         OccupiedTrack *occ = occupied_tracks;
 440         for(unsigned n=occupied_tracks->n_tracks; n>0; --n)
 441         {
 442                 if(unsigned saddr = occ->track->get_sensor_address())
 443                 {
 444                         if(saddr!=last_sensor_addr)
 445                         {
 446                                 count_to_free = 0;
 447                                 distance_after_sensor = 0;
 448                         }
 449                         last_sensor_addr = saddr;
 450                 }
 451
 452                 ++count_to_free;
 453                 distance_after_sensor += occ->path_length;
 454
 455                 occ = occ->next;
 456         }
 457
 458         // Free the last passed sensor and any tracks behind it.
 459         if(count_to_free && back_offset>distance_after_sensor)
 460         {
 461                 back_offset -= distance_after_sensor;
 462                 if(occupied_tracks->refcount>1)
 463                 {
 464                         --occupied_tracks->refcount;
 465                         occupied_tracks = new OccupiedTrack(*occupied_tracks);
 466                 }
 467                 occupied_tracks->n_tracks -= count_to_free;
 468         }
 469
 470         distance_traveled += distance*travel_multiplier;
 471         remaining_estimate -= distance*travel_multiplier;
 472 }
 473
 474 void TrainRoutePlanner::TrainRoutingState::advance(const Time::TimeDelta &dt)
 475 {
 476         if(delay>=dt)
 477         {
 478                 delay -= dt;
 479                 return;
 480         }
 481
 482         float secs = dt/Time::sec;
 483         // There may be some delay remaining.
 484         if(delay)
 485         {
 486                 secs -= delay/Time::sec;
 487                 delay = Time::zero;
 488         }
 489
 490         if(duration)
 491                 duration = max(duration-secs*Time::sec, Time::zero);
 492
 493         if(estimated_wait)
 494                 estimated_wait = max(estimated_wait-secs*Time::sec, Time::zero);
 495
 496         if(state==MOVING)
 497                 advance(info->speed*secs);
 498         else if(state!=ARRIVED)
 499         {
 500                 float remaining_distance = occupied_tracks->path_length-offset;
 501                 if(remaining_distance>0)
 502                 {
 503                         advance(remaining_distance);
 504                         wait_time += (secs-remaining_distance/info->speed)*Time::sec;
 505                 }
 506                 else
 507                         wait_time += secs*Time::sec;
 508         }
 509 }
 510
 511 void TrainRoutePlanner::TrainRoutingState::advance_track(unsigned next_path)
 512 {
 513         float distance = occupied_tracks->path_length-offset;
 514
 515         track = track.next(path);
 516         path = next_path;
 517         occupied_tracks = new OccupiedTrack(*track, path, occupied_tracks);
 518
 519         advance(distance);
 520         offset = 0;
 521         travel_multiplier = info->metrics[waypoint]->get_travel_multiplier(*track, track.reverse(path).entry());
 522 }
 523
 524 void TrainRoutePlanner::TrainRoutingState::set_path(unsigned p)
 525 {
 526         path = p;
 527         OccupiedTrack *next_occ = occupied_tracks->next;
 528         if(!--occupied_tracks->refcount)
 529                 delete occupied_tracks;
 530         occupied_tracks = new OccupiedTrack(*track, path, next_occ);
 531         update_estimate();
 532 }
 533
 534 void TrainRoutePlanner::TrainRoutingState::update_estimate()
 535 {
 536         TrackIter iter = track.reverse(path);
 537         const TrainRouteMetric *metric = info->metrics[waypoint];
 538         remaining_estimate = metric->get_distance_from(*iter, iter.entry());
 539         travel_multiplier = metric->get_travel_multiplier(*iter, iter.entry());
 540         if(remaining_estimate>=0)
 541                 remaining_estimate += (occupied_tracks->path_length-offset)*travel_multiplier;
 542 }
 543
 544 bool TrainRoutePlanner::TrainRoutingState::is_viable() const
 545 {
 546         if(remaining_estimate<0)
 547                 return false;
 548         if(critical && state==BLOCKED)
 549                 return false;
 550         return true;
 551 }
 552
 553
 554 TrainRoutePlanner::RoutingStep::RoutingStep():
 555         preferred(false),
 556         prev(0)
 557 { }
 558
 559 TrainRoutePlanner::RoutingStep::RoutingStep(const RoutingStep *p):
 560         time(p->time),
 561         cost_estimate(p->cost_estimate),
 562         preferred(false),
 563         trains(p->trains),
 564         prev(p)
 565 { }
 566
 567 void TrainRoutePlanner::RoutingStep::create_successors(list<RoutingStep> &new_steps) const
 568 {
 569         RoutingStep next(this);
 570         if(next.update_states() && next.check_deadlocks())
 571                 return;
 572
 573         int train_index = next.find_next_train();
 574         if(train_index<0)
 575                 return;
 576
 577         TrainRoutingState &train = next.trains[train_index];
 578
 579         Time::TimeDelta dt = train.get_time_to_next_track();
 580         next.advance(dt);
 581
 582         /* Check arrival after the train has advanced to the end of its current track
 583         so travel time and occupied tracks will be correct. */
 584         if(train.check_arrival())
 585         {
 586                 new_steps.push_back(next);
 587                 return;
 588         }
 589
 590         if(train.state==MOVING)
 591                 train.advance_track(0);
 592         else
 593         {
 594                 new_steps.push_back(next);
 595                 return;
 596         }
 597
 598         const TrackType::Endpoint &entry_ep = train.track.endpoint();
 599         if(train.critical)
 600         {
 601                 /* Only create a successor step matching the currently set path for a
 602                 critical track. */
 603                 unsigned critical_path = train.track->get_type().coerce_path(train.track.entry(), train.track->get_active_path());
 604                 create_successor(next, train_index, critical_path, new_steps);
 605         }
 606         else
 607         {
 608                 // Create successor steps for all possible paths through the new track.
 609                 for(unsigned i=0; entry_ep.paths>>i; ++i)
 610                         if(entry_ep.has_path(i))
 611                                 create_successor(next, train_index, i, new_steps);
 612         }
 613
 614         if(entry_ep.paths!=train.track->get_type().get_paths() && !train.critical)
 615         {
 616                 /* Create a waiting state before the track if there's at least one path
 617                 that doesn't pass through the entry endpoint. */
 618                 RoutingStep wait(this);
 619                 wait.advance(dt);
 620                 wait.trains[train_index].state = WAITING;
 621
 622                 Time::TimeDelta estimated_wait = Time::day;
 623                 for(unsigned i=0; i<wait.trains.size(); ++i)
 624                         if(i!=static_cast<unsigned>(train_index) && wait.trains[i].state!=ARRIVED)
 625                         {
 626                                 Time::TimeDelta ttp = wait.trains[i].get_time_to_pass(*train.track);
 627                                 estimated_wait = min(estimated_wait, ttp);
 628                         }
 629                 wait.trains[train_index].estimated_wait = estimated_wait;
 630
 631                 wait.update_estimate();
 632                 if(wait.is_viable())
 633                         new_steps.push_back(wait);
 634         }
 635 }
 636
 637 void TrainRoutePlanner::RoutingStep::create_successor(RoutingStep &next, unsigned train_index, unsigned path, list<RoutingStep> &new_steps)
 638 {
 639         TrainRoutingState &train = next.trains[train_index];
 640
 641         train.set_path(path);
 642         next.update_estimate();
 643         if(next.is_viable())
 644                 new_steps.push_back(next);
 645 }
 646
 647 bool TrainRoutePlanner::RoutingStep::update_states()
 648 {
 649         bool changes = false;
 650         for(vector<TrainRoutingState>::iterator i=trains.begin(); i!=trains.end(); ++i)
 651         {
 652                 if(i->state==ARRIVED)
 653                         continue;
 654
 655                 TrainState old_state = i->state;
 656
 657                 TrackIter next_track = i->track.next(i->path);
 658                 if(next_track)
 659                 {
 660                         i->blocked_by = get_occupant(*next_track);
 661                         if(i->blocked_by>=0)
 662                         {
 663                                 /* If the train is still traversing its last critical track, the
 664                                 flag needs to be cleared here to pass viability test. */
 665                                 if(i->info->first_noncritical->has_track(*next_track))
 666                                         i->critical = false;
 667
 668                                 if(i->state!=BLOCKED)
 669                                         i->estimated_wait = trains[i->blocked_by].get_time_to_pass(*next_track);
 670
 671                                 /* Trains in the WAITING state will also transition to BLOCKED and
 672                                 then to MOVING when the other train has passed. */
 673                                 i->state = BLOCKED;
 674                         }
 675                         else if(i->state==BLOCKED)
 676                         {
 677                                 i->estimated_wait = Time::zero;
 678                                 i->state = MOVING;
 679                         }
 680                 }
 681                 else
 682                         i->state = BLOCKED;
 683
 684                 if(i->state!=old_state)
 685                         changes = true;
 686         }
 687
 688         return changes;
 689 }
 690
 691 bool TrainRoutePlanner::RoutingStep::check_deadlocks() const
 692 {
 693         for(vector<TrainRoutingState>::const_iterator i=trains.begin(); i!=trains.end(); ++i)
 694         {
 695                 if(i->state!=BLOCKED)
 696                         continue;
 697
 698                 // A train blocked by end of track is always considered a deadlock.
 699                 if(i->blocked_by<0)
 700                         return true;
 701
 702                 /* Use the tortoise and hare algorithm to check if trains are blocked
 703                 cyclically (A blocks B, which blocks ..., which blocks A). */
 704                 int slow = i->blocked_by;
 705                 int fast = trains[slow].blocked_by;
 706                 while(fast>=0 && trains[fast].blocked_by>=0)
 707                 {
 708                         if(fast==slow)
 709                                 return true;
 710
 711                         slow = trains[slow].blocked_by;
 712                         fast = trains[trains[fast].blocked_by].blocked_by;
 713                 }
 714         }
 715
 716         return false;
 717 }
 718
 719 int TrainRoutePlanner::RoutingStep::get_occupant(Track &track) const
 720 {
 721         for(unsigned i=0; i<trains.size(); ++i)
 722                 if(trains[i].is_occupying(track))
 723                         return i;
 724
 725         return -1;
 726 }
 727
 728 int TrainRoutePlanner::RoutingStep::find_next_train() const
 729 {
 730         /* Pick a moving train with the lowest time to next track.  A train that
 731         just became blocked can still travel until the end of its current track,
 732         so consider those too. */
 733         Time::TimeDelta min_dt;
 734         int next_train = -1;
 735         for(unsigned i=0; i<trains.size(); ++i)
 736                 if(trains[i].state==MOVING || (trains[i].state==BLOCKED && prev && prev->trains[i].state==MOVING))
 737                 {
 738                         Time::TimeDelta dt = trains[i].get_time_to_next_track();
 739                         if(dt<min_dt || next_train<0)
 740                         {
 741                                 min_dt = dt;
 742                                 next_train = i;
 743                         }
 744                 }
 745
 746         return next_train;
 747 }
 748
 749 void TrainRoutePlanner::RoutingStep::advance(const Time::TimeDelta &dt)
 750 {
 751         time += dt;
 752         for(vector<TrainRoutingState>::iterator i=trains.begin(); i!=trains.end(); ++i)
 753                 i->advance(dt);
 754 }
 755
 756 void TrainRoutePlanner::RoutingStep::update_estimate()
 757 {
 758         cost_estimate = Time::zero;
 759         for(vector<TrainRoutingState>::const_iterator i=trains.begin(); i!=trains.end(); ++i)
 760                 if(i->remaining_estimate>=0)
 761                         cost_estimate += i->wait_time+i->estimated_wait+((i->distance_traveled+i->remaining_estimate)/i->info->speed)*Time::sec;
 762 }
 763
 764 bool TrainRoutePlanner::RoutingStep::is_viable() const
 765 {
 766         for(vector<TrainRoutingState>::const_iterator i=trains.begin(); i!=trains.end(); ++i)
 767                 if(!i->is_viable())
 768                         return false;
 769
 770         for(vector<TrainRoutingState>::const_iterator i=trains.begin(); i!=trains.end(); ++i)
 771                 if(i->state==MOVING)
 772                         return true;
 773
 774         return false;
 775 }
 776
 777 bool TrainRoutePlanner::RoutingStep::is_goal() const
 778 {
 779         for(vector<TrainRoutingState>::const_iterator i=trains.begin(); i!=trains.end(); ++i)
 780                 if(i->state!=ARRIVED)
 781                         return false;
 782         return true;
 783 }
 784
 785 bool TrainRoutePlanner::RoutingStep::operator<(const RoutingStep &other) const
 786 {
 787         if(preferred!=other.preferred)
 788                 return preferred>other.preferred;
 789         return cost_estimate<other.cost_estimate;
 790 }
 791
 792
 793 TrainRoutePlanner::PlanningThread::PlanningThread(TrainRoutePlanner &p):
 794         planner(p)
 795 {
 796         launch();
 797 }
 798
 799 void TrainRoutePlanner::PlanningThread::main()
 800 {
 801         planner.create_plan();
 802 }
 803
 804 } // namespace R2C2