tgba2ta.cc 23.4 KB
Newer Older
1
// -*- coding: utf-8 -*-
2
// Copyright (C) 2010-2018 Laboratoire de Recherche et Développement de
3
// l'Epita (LRDE).
4
5
6
7
8
//
// This file is part of Spot, a model checking library.
//
// Spot is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
9
// the Free Software Foundation; either version 3 of the License, or
10
11
12
13
14
15
16
17
// (at your option) any later version.
//
// Spot is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
// License for more details.
//
// You should have received a copy of the GNU General Public License
18
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
19

20
//#define TRACE
21

22
#include "config.h"
23
24
25
26
27
28
29
#include <iostream>
#ifdef TRACE
#define trace std::clog
#else
#define trace while (0) std::clog
#endif

30
#include <spot/twa/formula2bdd.hh>
31
32
#include <cassert>
#include <iostream>
33
#include <spot/twa/bddprint.hh>
34
#include <stack>
35
36
37
#include <spot/taalgos/tgba2ta.hh>
#include <spot/taalgos/statessetbuilder.hh>
#include <spot/ta/tgtaexplicit.hh>
38
39
40
41
42
43

using namespace std;

namespace spot
{

44
45
  namespace
  {
46
    typedef std::pair<const spot::state*, twa_succ_iterator*> pair_state_iter;
47

48
49
    static void
    transform_to_single_pass_automaton
50
    (const ta_explicit_ptr& testing_automata,
51
     state_ta_explicit* artificial_livelock_acc_state = nullptr)
52
    {
53

54
      if (artificial_livelock_acc_state)
55
56
        {
          auto artificial_livelock_acc_state_added =
57
            testing_automata->add_state(artificial_livelock_acc_state);
58

59
60
61
62
63
64
65
          // unique artificial_livelock_acc_state
          assert(artificial_livelock_acc_state_added
                 == artificial_livelock_acc_state);
          (void)artificial_livelock_acc_state_added;
          artificial_livelock_acc_state->set_livelock_accepting_state(true);
          artificial_livelock_acc_state->free_transitions();
        }
66

67
68
      ta::states_set_t states_set = testing_automata->get_states_set();
      ta::states_set_t::iterator it;
69

70
      state_ta_explicit::transitions* transitions_to_livelock_states =
71
72
        new state_ta_explicit::transitions;

73
      for (it = states_set.begin(); it != states_set.end(); ++it)
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
        {
          auto source = const_cast<state_ta_explicit*>
            (static_cast<const state_ta_explicit*>(*it));

          transitions_to_livelock_states->clear();

          state_ta_explicit::transitions* trans = source->get_transitions();
          state_ta_explicit::transitions::iterator it_trans;

          if (trans)
            for (it_trans = trans->begin(); it_trans != trans->end();)
              {
                auto dest = const_cast<state_ta_explicit*>((*it_trans)->dest);

                state_ta_explicit::transitions* dest_trans =
                  dest->get_transitions();
                bool dest_trans_empty = !dest_trans || dest_trans->empty();

                //select transitions where a destination is a livelock state
                // which isn't a Buchi accepting state and has successors
                if (dest->is_livelock_accepting_state()
                    && (!dest->is_accepting_state()) && (!dest_trans_empty))
                  transitions_to_livelock_states->push_front(*it_trans);

Alexandre Duret-Lutz's avatar
Alexandre Duret-Lutz committed
98
                // optimization to have, after minimization, a unique
99
100
101
102
103
104
105
                // livelock state which has no successors
                if (dest->is_livelock_accepting_state() && (dest_trans_empty))
                  dest->set_accepting_state(false);

                ++it_trans;
              }

106
107
108
109
110
111
112
          for (auto* trans: *transitions_to_livelock_states)
            testing_automata->create_transition
              (source, trans->condition,
               trans->acceptance_conditions,
               artificial_livelock_acc_state ?
               artificial_livelock_acc_state :
               trans->dest->stuttering_reachable_livelock, true);
113
        }
114
115
116
      delete transitions_to_livelock_states;

      for (it = states_set.begin(); it != states_set.end(); ++it)
117
118
119
        {
          state_ta_explicit* state = static_cast<state_ta_explicit*> (*it);
          state_ta_explicit::transitions* state_trans =
120
            (state)->get_transitions();
121
          bool state_trans_empty = !state_trans || state_trans->empty();
122

123
124
125
126
          if (state->is_livelock_accepting_state()
              && (!state->is_accepting_state()) && (!state_trans_empty))
            state->set_livelock_accepting_state(false);
        }
127
128
    }

129
    static void
130
    compute_livelock_acceptance_states(const ta_explicit_ptr& testing_aut,
131
132
133
                                       bool single_pass_emptiness_check,
                                       state_ta_explicit*
                                       artificial_livelock_acc_state)
134
    {
135
136
137
138
139
      // We use five main data in this algorithm:
      // * sscc: a stack of strongly stuttering-connected components (SSCC)
      scc_stack_ta sscc;

      // * arc, a stack of acceptance conditions between each of these SCC,
140
      std::stack<acc_cond::mark_t> arc;
141
142
143

      // * h: a hash of all visited nodes, with their order,
      //   (it is called "Hash" in Couvreur's paper)
144
      state_map<int> h; ///< Heap of visited states.
145
146
147
148
149
150

      // * num: the number of visited nodes.  Used to set the order of each
      //   visited node,
      int num = 0;

      // * todo: the depth-first search stack.  This holds pairs of the
151
      //   form (STATE, ITERATOR) where ITERATOR is a twa_succ_iterator
152
153
154
155
156
157
      //   over the successors of STATE.  In our use, ITERATOR should
      //   always be freed when TODO is popped, but STATE should not because
      //   it is also used as a key in H.
      std::stack<pair_state_iter> todo;

      // * init: the set of the depth-first search initial states
158
      std::stack<const state*> init_set;
159

160
      for (auto s: testing_aut->get_initial_states_set())
161
        init_set.push(s);
162
163

      while (!init_set.empty())
164
165
166
167
168
169
170
171
172
173
174
175
176
177
        {
          // Setup depth-first search from initial states.

          {
            auto init = down_cast<const state_ta_explicit*> (init_set.top());
            init_set.pop();

            if (!h.emplace(init, num + 1).second)
              {
                init->destroy();
                continue;
              }

            sscc.push(++num);
178
            arc.push({});
179
            sscc.top().is_accepting
180
              = testing_aut->is_accepting_state(init);
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
            twa_succ_iterator* iter = testing_aut->succ_iter(init);
            iter->first();
            todo.emplace(init, iter);
          }

          while (!todo.empty())
            {
              auto curr = todo.top().first;

              auto i = h.find(curr);
              // If we have reached a dead component, ignore it.
              if (i != h.end() && i->second == -1)
                {
                  todo.pop();
                  continue;
                }

              // We are looking at the next successor in SUCC.
              twa_succ_iterator* succ = todo.top().second;

              // If there is no more successor, backtrack.
              if (succ->done())
                {
                  // We have explored all successors of state CURR.

                  // Backtrack TODO.
                  todo.pop();

                  // fill rem with any component removed,
                  assert(i != h.end());
                  sscc.rem().push_front(curr);

                  // When backtracking the root of an SSCC, we must also
                  // remove that SSCC from the ROOT stacks.  We must
                  // discard from H all reachable states from this SSCC.
                  assert(!sscc.empty());
                  if (sscc.top().index == i->second)
                    {
                      // removing states
                      bool is_livelock_accepting_sscc = (sscc.rem().size() > 1)
                        && ((sscc.top().is_accepting) ||
                            (testing_aut->acc().
                             accepting(sscc.top().condition)));
                      trace << "*** sscc.size()  = ***" <<  sscc.size() << '\n';
                      for (auto j: sscc.rem())
                        {
                          h[j] = -1;

                          if (is_livelock_accepting_sscc)
                            {
                              // if it is an accepting sscc add the state to
                              // G (=the livelock-accepting states set)
                              trace << "*** sscc.size() > 1: states: ***"
                                    << testing_aut->format_state(j)
                                    << '\n';
                              auto livelock_accepting_state =
                                const_cast<state_ta_explicit*>
                                (down_cast<const state_ta_explicit*>(j));

                              livelock_accepting_state->
                                set_livelock_accepting_state(true);

                              if (single_pass_emptiness_check)
                                {
                                  livelock_accepting_state
                                    ->set_accepting_state(true);
                                  livelock_accepting_state
                                    ->stuttering_reachable_livelock
                                    = livelock_accepting_state;
                                }
                            }
                        }

                      assert(!arc.empty());
                      sscc.pop();
                      arc.pop();
                    }

                  // automata reduction
                  testing_aut->delete_stuttering_and_hole_successors(curr);

                  delete succ;
                  // Do not delete CURR: it is a key in H.
                  continue;
                }

              // Fetch the values destination state we are interested in...
              auto dest = succ->dst();

              auto acc_cond = succ->acc();
              // ... and point the iterator to the next successor, for
              // the next iteration.
              succ->next();
              // We do not need SUCC from now on.

              // Are we going to a new state through a stuttering transition?
              bool is_stuttering_transition =
                testing_aut->get_state_condition(curr)
                == testing_aut->get_state_condition(dest);
              auto id = h.find(dest);

              // Is this a new state?
              if (id == h.end())
                {
                  if (!is_stuttering_transition)
                    {
                      init_set.push(dest);
                      dest->destroy();
                      continue;
                    }

                  // Number it, stack it, and register its successors
                  // for later processing.
                  h[dest] = ++num;
                  sscc.push(num);
                  arc.push(acc_cond);
                  sscc.top().is_accepting =
                    testing_aut->is_accepting_state(dest);

                  twa_succ_iterator* iter = testing_aut->succ_iter(dest);
                  iter->first();
                  todo.emplace(dest, iter);
                  continue;
                }
              dest->destroy();

              // If we have reached a dead component, ignore it.
              if (id->second == -1)
                continue;

              trace << "***compute_livelock_acceptance_states: CYCLE***\n";

              if (!curr->compare(id->first))
                {
                  auto self_loop_state = const_cast<state_ta_explicit*>
                    (down_cast<const state_ta_explicit*>(curr));

                  if (testing_aut->is_accepting_state(self_loop_state)
                      || (testing_aut->acc().accepting(acc_cond)))
                    {
                      self_loop_state->set_livelock_accepting_state(true);
                      if (single_pass_emptiness_check)
                        {
                          self_loop_state->set_accepting_state(true);
                          self_loop_state->stuttering_reachable_livelock
                            = self_loop_state;
                        }
                    }

                  trace
                    << "***compute_livelock_acceptance_states: CYCLE: "
                    << "self_loop_state***\n";
                }

              // Now this is the most interesting case.  We have reached a
              // state S1 which is already part of a non-dead SSCC.  Any such
              // non-dead SSCC has necessarily been crossed by our path to
              // this state: there is a state S2 in our path which belongs
              // to this SSCC too.  We are going to merge all states between
              // this S1 and S2 into this SSCC.
              //
              // This merge is easy to do because the order of the SSCC in
              // ROOT is ascending: we just have to merge all SSCCs from the
              // top of ROOT that have an index greater to the one of
              // the SSCC of S2 (called the "threshold").
              int threshold = id->second;
              std::list<const state*> rem;
              bool acc = false;

              while (threshold < sscc.top().index)
                {
                  assert(!sscc.empty());
                  assert(!arc.empty());
                  acc |= sscc.top().is_accepting;
                  acc_cond |= sscc.top().condition;
                  acc_cond |= arc.top();
                  rem.splice(rem.end(), sscc.rem());
                  sscc.pop();
                  arc.pop();
                }

              // Note that we do not always have
              //  threshold == sscc.top().index
              // after this loop, the SSCC whose index is threshold might have
              // been merged with a lower SSCC.

              // Accumulate all acceptance conditions into the merged SSCC.
              sscc.top().is_accepting |= acc;
              sscc.top().condition |= acc_cond;

              sscc.rem().splice(sscc.rem().end(), rem);

            }

        }
376

377
      if (artificial_livelock_acc_state || single_pass_emptiness_check)
378
379
        transform_to_single_pass_automaton(testing_aut,
                                           artificial_livelock_acc_state);
380
    }
381

382
383
    ta_explicit_ptr
    build_ta(const ta_explicit_ptr& ta, bdd atomic_propositions_set_,
384
385
386
387
             bool degeneralized,
             bool single_pass_emptiness_check,
             bool artificial_livelock_state_mode,
             bool no_livelock)
388
    {
389

390
      std::stack<state_ta_explicit*> todo;
391
      const_twa_ptr tgba_ = ta->get_tgba();
392
393

      // build Initial states set:
394
      auto tgba_init_state = tgba_->get_init_state();
395

396
      bdd tgba_condition = [&]()
397
398
399
400
401
402
        {
          bdd cond = bddfalse;
          for (auto i: tgba_->succ(tgba_init_state))
            cond |= i->cond();
          return cond;
        }();
403

404
405
      bool is_acc = false;
      if (degeneralized)
406
407
408
409
        {
          twa_succ_iterator* it = tgba_->succ_iter(tgba_init_state);
          it->first();
          if (!it->done())
410
            is_acc = !!it->acc();
411
412
          delete it;
        }
413

414
415
      bdd satone_tgba_condition;
      while ((satone_tgba_condition = bdd_satoneset(tgba_condition,
416
417
418
419
420
421
422
423
424
425
426
427
428
                                                    atomic_propositions_set_,
                                                    bddtrue)) != bddfalse)
        {
          tgba_condition -= satone_tgba_condition;
          state_ta_explicit* init_state = new
            state_ta_explicit(tgba_init_state->clone(),
                              satone_tgba_condition, true, is_acc);
          state_ta_explicit* s = ta->add_state(init_state);
          assert(s == init_state);
          ta->add_to_initial_states_set(s);

          todo.push(init_state);
        }
429
      tgba_init_state->destroy();
430

431
      while (!todo.empty())
432
433
434
435
436
437
438
439
440
441
442
443
        {
          state_ta_explicit* source = todo.top();
          todo.pop();

          twa_succ_iterator* twa_succ_it =
            tgba_->succ_iter(source->get_tgba_state());
          for (twa_succ_it->first(); !twa_succ_it->done();
               twa_succ_it->next())
            {
              const state* tgba_state = twa_succ_it->dst();
              bdd tgba_condition = twa_succ_it->cond();
              acc_cond::mark_t tgba_acceptance_conditions =
444
                twa_succ_it->acc();
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
              bdd satone_tgba_condition;
              while ((satone_tgba_condition =
                      bdd_satoneset(tgba_condition,
                                    atomic_propositions_set_, bddtrue))
                     != bddfalse)
                {
                  tgba_condition -= satone_tgba_condition;

                  bdd all_props = bddtrue;
                  bdd dest_condition;

                  bool is_acc = false;
                  if (degeneralized)
                  {
                    twa_succ_iterator* it = tgba_->succ_iter(tgba_state);
                    it->first();
                    if (!it->done())
462
                      is_acc = !!it->acc();
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
                    delete it;
                  }

                  if (satone_tgba_condition == source->get_tgba_condition())
                    while ((dest_condition =
                            bdd_satoneset(all_props,
                                          atomic_propositions_set_, bddtrue))
                           != bddfalse)
                      {
                        all_props -= dest_condition;
                        state_ta_explicit* new_dest =
                          new state_ta_explicit(tgba_state->clone(),
                                                dest_condition, false, is_acc);
                        state_ta_explicit* dest = ta->add_state(new_dest);

                        if (dest != new_dest)
                          {
                            // the state dest already exists in the automaton
                            new_dest->get_tgba_state()->destroy();
                            delete new_dest;
                          }
                        else
                          {
                            todo.push(dest);
                          }

                        bdd cs = bdd_setxor(source->get_tgba_condition(),
                                            dest->get_tgba_condition());
                        ta->create_transition(source, cs,
                                              tgba_acceptance_conditions, dest);
                      }
                }
              tgba_state->destroy();
            }
          delete twa_succ_it;
        }
499

500
      if (no_livelock)
501
        return ta;
502

503
      state_ta_explicit* artificial_livelock_acc_state = nullptr;
504
505

      trace << "*** build_ta: artificial_livelock_acc_state_mode = ***"
506
            << artificial_livelock_state_mode << std::endl;
507
508

      if (artificial_livelock_state_mode)
509
510
511
512
513
514
515
516
517
        {
          single_pass_emptiness_check = true;
          artificial_livelock_acc_state =
            new state_ta_explicit(ta->get_tgba()->get_init_state(), bddtrue,
                                  false, false, true, nullptr);
          trace
            << "*** build_ta: artificial_livelock_acc_state = ***"
            << artificial_livelock_acc_state << std::endl;
        }
518
519

      compute_livelock_acceptance_states(ta, single_pass_emptiness_check,
520
                                         artificial_livelock_acc_state);
521
522
      return ta;
    }
523
524
  }

525
  ta_explicit_ptr
526
  tgba_to_ta(const const_twa_ptr& tgba_, bdd atomic_propositions_set_,
527
528
529
530
             bool degeneralized, bool artificial_initial_state_mode,
             bool single_pass_emptiness_check,
             bool artificial_livelock_state_mode,
             bool no_livelock)
531
  {
532
    ta_explicit_ptr ta;
533

534
    auto tgba_init_state = tgba_->get_init_state();
535
536
    if (artificial_initial_state_mode)
      {
Alexandre Duret-Lutz's avatar
Alexandre Duret-Lutz committed
537
        state_ta_explicit* artificial_init_state =
538
          new state_ta_explicit(tgba_init_state->clone(), bddfalse, true);
539

540
        ta = make_ta_explicit(tgba_, tgba_->acc().num_sets(),
541
                              artificial_init_state);
542
543
544
      }
    else
      {
545
        ta = make_ta_explicit(tgba_, tgba_->acc().num_sets());
546
547
548
      }
    tgba_init_state->destroy();

549
    // build ta automaton
550
    build_ta(ta, atomic_propositions_set_, degeneralized,
551
552
             single_pass_emptiness_check, artificial_livelock_state_mode,
             no_livelock);
553
554
555
556
557
558
559
560
561

    // (degeneralized=true) => TA
    if (degeneralized)
      return ta;

    // (degeneralized=false) => GTA
    // adapt a GTA to remove acceptance conditions from states
    ta::states_set_t states_set = ta->get_states_set();
    ta::states_set_t::iterator it;
562
    for (it = states_set.begin(); it != states_set.end(); ++it)
563
564
565
566
567
568
569
570
      {
        state_ta_explicit* state = static_cast<state_ta_explicit*> (*it);

        if (state->is_accepting_state())
          {
            state_ta_explicit::transitions* trans = state->get_transitions();
            state_ta_explicit::transitions::iterator it_trans;

Alexandre Duret-Lutz's avatar
Alexandre Duret-Lutz committed
571
            for (it_trans = trans->begin(); it_trans != trans->end();
572
573
                 ++it_trans)
              (*it_trans)->acceptance_conditions = ta->acc().all_sets();
574
575
576
577
578

            state->set_accepting_state(false);
          }
      }

579
580
581
    return ta;
  }

582
  tgta_explicit_ptr
583
  tgba_to_tgta(const const_twa_ptr& tgba_, bdd atomic_propositions_set_)
584
  {
585
    auto tgba_init_state = tgba_->get_init_state();
586
    auto artificial_init_state = new state_ta_explicit(tgba_init_state->clone(),
587
                                                       bddfalse, true);
588
589
    tgba_init_state->destroy();

590
    auto tgta = make_tgta_explicit(tgba_, tgba_->acc().num_sets(),
591
                                   artificial_init_state);
592

593
594
    // build a Generalized TA automaton involving a single_pass_emptiness_check
    // (without an artificial livelock state):
595
    auto ta = tgta->get_ta();
596
    build_ta(ta, atomic_propositions_set_, false, true, false, false);
597

598
    trace << "***tgba_to_tgbta: POST build_ta***" << std::endl;
599

600
    // adapt a ta automata to build tgta automata :
601
    ta::states_set_t states_set = ta->get_states_set();
602
    ta::states_set_t::iterator it;
603
    twa_succ_iterator* initial_states_iter =
604
      ta->succ_iter(ta->get_artificial_initial_state());
605
606
    initial_states_iter->first();
    if (initial_states_iter->done())
607
      {
608
609
        delete initial_states_iter;
        return tgta;
610
      }
611
    bdd first_state_condition = initial_states_iter->cond();
612
613
614
    delete initial_states_iter;

    bdd bdd_stutering_transition = bdd_setxor(first_state_condition,
615
                                              first_state_condition);
616

617
    for (it = states_set.begin(); it != states_set.end(); ++it)
618
619
620
621
622
623
      {
        state_ta_explicit* state = static_cast<state_ta_explicit*> (*it);

        state_ta_explicit::transitions* trans = state->get_transitions();
        if (state->is_livelock_accepting_state())
          {
624
            bool trans_empty = !trans || trans->empty();
625
            if (trans_empty || state->is_accepting_state())
626
              {
627
                ta->create_transition(state, bdd_stutering_transition,
628
                                      ta->acc().all_sets(), state);
629
630
631
              }
          }

632
        if (state->compare(ta->get_artificial_initial_state()))
Alexandre Duret-Lutz's avatar
Alexandre Duret-Lutz committed
633
          ta->create_transition(state, bdd_stutering_transition,
634
                                {}, state);
635

636
637
        state->set_livelock_accepting_state(false);
        state->set_accepting_state(false);
638
        trace << "***tgba_to_tgbta: POST create_transition ***" << std::endl;
639
640
      }

641
    return tgta;
642
  }
643
}