minimize.cc 7.85 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
// Copyright (C) 2010 Laboratoire de Recherche et Développement
// de l'Epita (LRDE).
//
// 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
// the Free Software Foundation; either version 2 of the License, or
// (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
// along with Spot; see the file COPYING.  If not, write to the Free
// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
// 02111-1307, USA.

#include <queue>
#include "minimize.hh"
#include "ltlast/allnodes.hh"
#include "misc/hash.hh"
#include "tgbaalgos/powerset.hh"

namespace spot
{
  typedef Sgi::hash_set<const state*,
                        state_ptr_hash, state_ptr_equal> hash_set;
  typedef Sgi::hash_map<const state*, unsigned,
                        state_ptr_hash, state_ptr_equal> hash_map;

  // Given an automaton a, find all states that are not in "final" and add
  // them to the set "non_final".
  // "state_set_map" gives corresponding set for each state.
  void init_sets(const tgba_explicit* a,
                 hash_set& final,
                 hash_set& non_final,
                 hash_map& state_set_map)
  {
    hash_set seen;
Felix Abecassis's avatar
Felix Abecassis committed
43
    std::queue<const state*> tovisit;
44
    // Perform breadth-first traversal.
Felix Abecassis's avatar
Felix Abecassis committed
45
    const state* init = a->get_init_state();
46
47
48
49
    tovisit.push(init);
    seen.insert(init);
    while (!tovisit.empty())
    {
Felix Abecassis's avatar
Felix Abecassis committed
50
      const state* src = tovisit.front();
51
52
53
54
55
56
57
58
59
60
61
62
63
      tovisit.pop();
      // Is the state final ?
      if (final.find(src) == final.end())
      {
        // No, add it to the set non_final
        non_final.insert(src);
        state_set_map[src] = 0;
      }
      else
        state_set_map[src] = 1;
      tgba_succ_iterator* sit = a->succ_iter(src);
      for (sit->first(); !sit->done(); sit->next())
      {
Felix Abecassis's avatar
Felix Abecassis committed
64
        const state* dst = sit->current_state();
65
66
67
68
69
70
71
72
73
74
        // Is it a new state ?
        if (seen.find(dst) == seen.end())
        {
          // Register the successor for later processing.
          tovisit.push(dst);
          seen.insert(dst);
        }
        else
          delete dst;
      }
Felix Abecassis's avatar
Felix Abecassis committed
75
      delete sit;
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
    }
  }

  // From the base automaton and the list of sets, build the minimal
  // resulting automaton
  tgba_explicit_number* build_result(const tgba* a,
                                     std::list<hash_set*>& sets,
                                     hash_set* final)
  {
    // For each set, create a state in the resulting automaton.
    // For a state s, state_num[s] is the number of the state in the minimal
    // automaton.
    hash_map state_num;
    std::list<hash_set*>::iterator sit;
    unsigned num = 0;
    for (sit = sets.begin(); sit != sets.end(); ++sit)
    {
      hash_set::iterator hit;
      hash_set* h = *sit;
      for (hit = h->begin(); hit != h->end(); ++hit)
        state_num[*hit] = num;
      ++num;
    }
    typedef tgba_explicit_number::transition trs;
    tgba_explicit_number* res = new tgba_explicit_number(a->get_dict());
    // For each transition in the initial automaton, add the corresponding
    // transition in res.
    res->declare_acceptance_condition(ltl::constant::true_instance());
    for (sit = sets.begin(); sit != sets.end(); ++sit)
    {
      hash_set::iterator hit;
      hash_set* h = *sit;
      for (hit = h->begin(); hit != h->end(); ++hit)
      {
        const state* src = *hit;
        unsigned src_num = state_num[src];
        tgba_succ_iterator* succit = a->succ_iter(src);
Felix Abecassis's avatar
Felix Abecassis committed
113
        bool accepting = (final->find(src) != final->end());
114
115
        for (succit->first(); !succit->done(); succit->next())
        {
Felix Abecassis's avatar
Felix Abecassis committed
116
          const state* dst = succit->current_state();
117
          unsigned dst_num = state_num[dst];
Felix Abecassis's avatar
Felix Abecassis committed
118
          delete dst;
119
120
121
122
123
          trs* t = res->create_transition(src_num, dst_num);
          res->add_conditions(t, succit->current_condition());
          if (accepting)
            res->add_acceptance_condition(t, ltl::constant::true_instance());
        }
Felix Abecassis's avatar
Felix Abecassis committed
124
        delete succit;
125
126
127
128
129
      }
    }
    res->merge_transitions();
    const state* init_state = a->get_init_state();
    unsigned init_num = state_num[init_state];
Felix Abecassis's avatar
Felix Abecassis committed
130
    delete init_state;
131
132
133
134
135
136
137
138
139
    res->set_init_state(init_num);
    return res;
  }

  tgba_explicit* minimize(const tgba* a)
  {
    // The list of accepting states of a.
    std::list<const state*> acc_list;
    std::queue<hash_set*> todo;
Felix Abecassis's avatar
Felix Abecassis committed
140
    // The list of equivalent states.
141
142
    std::list<hash_set*> done;
    tgba_explicit* det_a = tgba_powerset(a, &acc_list);
Felix Abecassis's avatar
Felix Abecassis committed
143
144
    hash_set* final = new hash_set;
    hash_set* non_final = new hash_set;
145
146
147
    hash_map state_set_map;
    std::list<const state*>::iterator li;
    for (li = acc_list.begin(); li != acc_list.end(); ++li)
Felix Abecassis's avatar
Felix Abecassis committed
148
149
150
151
152
153
154
155
156
157
158
      final->insert(*li);
    init_sets(det_a, *final, *non_final, state_set_map);
    hash_set* final_copy = new hash_set(*final);
    if (final->size() > 1)
      todo.push(final);
    else if (!final->empty())
      done.push_back(final);
    if (non_final->size() > 1)
      todo.push(non_final);
    else if (!non_final->empty())
      done.push_back(non_final);
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
    unsigned set_num = 1;
    // A bdd_states_map is a list of formulae (in a BDD form) associated with a
    // destination set of states.
    typedef std::list<std::pair<bdd, hash_set*> > bdd_states_map;
    // While we have unprocessed sets.
    while (!todo.empty())
    {
      // Get a set to process.
      hash_set* cur = todo.front();
      todo.pop();
      hash_set::iterator hi;
      bdd_states_map bdd_map;
      for (hi = cur->begin(); hi != cur->end(); ++hi)
      {
        const state* src = *hi;
        bdd f = bddfalse;
        tgba_succ_iterator* si = a->succ_iter(src);
        for (si->first(); !si->done(); si->next())
        {
          const state* dst = si->current_state();
          unsigned dst_set = state_set_map[dst];
Felix Abecassis's avatar
Felix Abecassis committed
180
          delete dst;
181
182
          f |= (bdd_ithvar(dst_set) & si->current_condition());
        }
Felix Abecassis's avatar
Felix Abecassis committed
183
        delete si;
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
        bdd_states_map::iterator bsi;
        // Have we already seen this formula ?
        for (bsi = bdd_map.begin(); bsi != bdd_map.end() && bsi->first != f;
             ++bsi)
          continue;
        if (bsi == bdd_map.end())
        {
          // No, create a new set.
          hash_set* new_set = new hash_set;
          new_set->insert(src);
          bdd_map.push_back(std::make_pair<bdd, hash_set*>(f, new_set));
        }
        else
        {
          // Yes, add the current state to the set.
          hash_set* set = bsi->second;
          set->insert(src);
        }
      }
      bdd_states_map::iterator bsi = bdd_map.begin();
      // The set is minimal.
      if (bdd_map.size() == 1)
        done.push_back(bsi->second);
      else
      {
        for (; bsi != bdd_map.end(); ++bsi)
        {
          hash_set* set = bsi->second;
          // Give a new number for new states.
          ++set_num;
          hash_set::iterator hit;
          for (hit = set->begin(); hit != set->end(); ++hit)
            state_set_map[*hit] = set_num;
          // Trivial sets can't be splitted any further.
          if (set->size() == 1)
            done.push_back(set);
          else
            todo.push(set);
        }
      }
Felix Abecassis's avatar
Felix Abecassis committed
224
      delete cur;
225
    }
Felix Abecassis's avatar
Felix Abecassis committed
226
227
228
229
230
231
232
233
234
235
236
237
238
239

    // Build the result.
    tgba_explicit_number* res = build_result(det_a, done, final_copy);

    // Free all the allocated memory.
    delete final_copy;
    hash_map::iterator hit;
    for (hit = state_set_map.begin(); hit != state_set_map.end(); ++hit)
      delete hit->first;
    std::list<hash_set*>::iterator it;
    for (it = done.begin(); it != done.end(); ++it)
      delete *it;
    delete det_a;

240
241
242
    return res;
  }
}