Offline version of the degeneralization.
* src/tgbaalgos/degen.cc, src/tgbaalgos/degen.hh: New files, with most of the logic extracted from src/tgba/tgbatba.cc (SBA version). * src/tgbaalgos/Makefile.am: Distribute these. * src/tgbatest/ltl2tgba.cc: Use the new degeneralization instead of the on-the-fly version.
This commit is contained in:
Alexandre Duret-Lutz
parent
b68d9d189c
commit
5dbee4faab
4 changed files with 405 additions and 3 deletions
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@ -32,6 +32,7 @@ tgbaalgosdir = $(pkgincludedir)/tgbaalgos
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tgbaalgos_HEADERS = \
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bfssteps.hh \
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cutscc.hh \
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degen.hh \
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dotty.hh \
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dottydec.hh \
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dupexp.hh \
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@ -69,6 +70,7 @@ noinst_LTLIBRARIES = libtgbaalgos.la
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libtgbaalgos_la_SOURCES = \
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bfssteps.cc \
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cutscc.cc \
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degen.cc \
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dotty.cc \
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dottydec.cc \
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dupexp.cc \
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355
src/tgbaalgos/degen.cc
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355
src/tgbaalgos/degen.cc
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@ -0,0 +1,355 @@
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// Copyright (C) 2012 Laboratoire de Recherche et
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// Développement de l'Epita.
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//
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// This file is part of Spot, a model checking library.
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//
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// Spot is free software; you can redistribute it and/or modify it
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// under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// Spot is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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// or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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// License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Spot; see the file COPYING. If not, write to the Free
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// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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// 02111-1307, USA.
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#include "degen.hh"
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#include "tgba/tgbaexplicit.hh"
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#include "misc/hash.hh"
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#include "misc/hashfunc.hh"
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#include "ltlast/constant.hh"
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#include <deque>
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#include <vector>
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namespace spot
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{
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namespace
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{
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// A state in the degenalized automaton corresponds to a state in
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// the TGBA associated to a level. The level is just an index in
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// the list of acceptance sets.
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typedef std::pair<const state*, unsigned> degen_state;
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struct degen_state_hash
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{
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size_t
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operator()(const degen_state& s) const
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{
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return s.first->hash() & wang32_hash(s.second);
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}
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};
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struct degen_state_equal
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{
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bool
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operator()(const degen_state& left,
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const degen_state& right) const
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{
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if (left.second != right.second)
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return false;
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return left.first->compare(right.first) == 0;
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}
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};
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// Associate the degeneralized state to its number.
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typedef Sgi::hash_map<degen_state, int,
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degen_state_hash, degen_state_equal> ds2num_map;
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// Queue of state to be processed.
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typedef std::deque<degen_state> queue_t;
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// Memory management for the input states.
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class unicity_table
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{
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typedef Sgi::hash_set<const state*,
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state_ptr_hash, state_ptr_equal> uniq_set;
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uniq_set m;
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public:
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const state* operator()(const state* s)
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{
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uniq_set::const_iterator i = m.find(s);
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if (i == m.end())
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{
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m.insert(s);
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return s;
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}
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else
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{
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s->destroy();
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return *i;
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}
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}
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~unicity_table()
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{
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for (uniq_set::iterator i = m.begin(); i != m.end(); ++i)
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(*i)->destroy();
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}
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};
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// Acceptance set common to all outgoing transitions of some state.
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class outgoing_acc
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{
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const tgba* a_;
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typedef Sgi::hash_map<const state*, bdd,
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state_ptr_hash, state_ptr_equal> accmap_t;
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mutable accmap_t accmap_;
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mutable accmap_t accmapu_;
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public:
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outgoing_acc(const tgba* a): a_(a)
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{
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}
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bdd common_acc(const state* s)
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{
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// Lookup cache
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accmap_t::const_iterator i = accmap_.find(s);
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if (i != accmap_.end())
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return i->second;
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bdd common = a_->all_acceptance_conditions();
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tgba_succ_iterator* it = a_->succ_iter(s);
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for (it->first(); !it->done() && common != bddfalse; it->next())
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common &= it->current_acceptance_conditions();
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delete it;
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// Populate cache
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accmap_[s->clone()] = common;
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return common;
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}
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bdd union_acc(const state* s)
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{
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// Lookup cache
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accmap_t::const_iterator i = accmapu_.find(s);
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if (i != accmapu_.end())
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return i->second;
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bdd common = bddfalse;
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tgba_succ_iterator* it = a_->succ_iter(s);
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for (it->first(); !it->done(); it->next())
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common |= it->current_acceptance_conditions();
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delete it;
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// Populate cache
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accmapu_[s->clone()] = common;
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return common;
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}
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};
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}
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sba*
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degeneralize(const tgba* a)
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{
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bdd_dict* dict = a->get_dict();
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// The result (degeneralized) automaton uses numbered state.
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sba_explicit_number* res = new sba_explicit_number(dict);
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dict->register_all_variables_of(a, res);
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// FIXME: unregister acceptance conditions.
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// Invent a new acceptance set for the degeneralized automaton.
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int accvar =
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dict->register_acceptance_variable(ltl::constant::true_instance(), res);
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bdd degen_acc = bdd_ithvar(accvar);
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res->set_acceptance_conditions(degen_acc);
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// Create an order of acceptance conditions. Each entry in this
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// vector correspond to an acceptance set. Each index can
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// be used as a level in degen_state to indicate the next expected
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// acceptance set. Level order.size() is a special level used to
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// denote accepting states.
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std::vector<bdd> order;
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{
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// The order is arbitrary, but it turns out that using push_back
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// instead of push_front often gives better results because
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// acceptance sets at the beginning if the cycle are more often
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// used in the automaton. (This surprising fact is probably
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// related to the order in which we declare the BDD variables
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// during the translation.)
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bdd all = a->all_acceptance_conditions();
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while (all != bddfalse)
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{
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bdd next = bdd_satone(all);
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all -= next;
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order.push_back(next);
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}
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}
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outgoing_acc outgoing(a);
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// Make sure we always use the same pointer for identical states
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// from the input automaton.
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unicity_table uniq;
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// These maps make it possible to convert degen_state to number
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// and vice-versa.
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ds2num_map ds2num;
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queue_t todo;
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const state* s0 = uniq(a->get_init_state());
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degen_state s(s0, 0);
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// As an heuristic, if the initial state has accepting self-loops,
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// start the degeneralization on the accepting level.
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{
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bdd all = a->all_acceptance_conditions();
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tgba_succ_iterator* it = a->succ_iter(s0);
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for (it->first(); !it->done(); it->next())
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{
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// Look only for transitions that are accepting.
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if (all != it->current_acceptance_conditions())
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continue;
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// Look only for self-loops.
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const state* dest = uniq(it->current_state());
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if (dest == s0)
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{
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// The initial state has an accepting self-loop.
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s.second = order.size();
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break;
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}
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}
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delete it;
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}
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ds2num[s] = 0;
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todo.push_back(s);
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while (!todo.empty())
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{
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s = todo.front();
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todo.pop_front();
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int src = ds2num[s];
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unsigned slevel = s.second;
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// If we have a state on the last level, it should be accepting.
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bool is_acc = slevel == order.size();
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// On the accepting level, start again from level 0.
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if (is_acc)
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slevel = 0;
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tgba_succ_iterator* i = a->succ_iter(s.first);
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for (i->first(); !i->done(); i->next())
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{
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degen_state d(uniq(i->current_state()), 0);
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// The old level is slevel. What should be the new one?
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bdd acc = i->current_acceptance_conditions();
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bdd otheracc = outgoing.common_acc(d.first);
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if (is_acc)
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{
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// Ignore the last expected acceptance set (the value of
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// *prev below) if it is common to all other outgoing
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// transitions (of the current state) AND if it is not
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// used by any outgoing transition of the destination
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// state.
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//
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// 1) It's correct to do that, because this acceptance
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// set is common to other outgoing transitions.
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// Therefore if we make a cycle to this state we
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// will eventually see that acceptance set thanks
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// to the "pulling" of the common acceptance sets
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// of the destination state (d.first).
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//
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// 2) It's also desirable because it makes the
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// degeneralization idempotent (up to a renaming of
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// states). Consider the following automaton where
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// 1 is initial and => marks accepting transitions:
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// 1=>1, 1=>2, 2->2, 2->1 This is already an SBA,
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// with 1 as accepting state. However if you try
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// degeralize it without ignoring *prev, you'll get
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// two copies of states 2, depending on whether we
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// reach it using 1=>2 or from 2->2. If this
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// example was not clear, uncomment this following
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// "if" block, and play with the "degenid.test"
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// test case.
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//
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// 3) Ignoring all common acceptance sets would also
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// be correct, but it would make the
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// degeneralization produce larger automata in some
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// cases. The current condition to ignore only one
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// acceptance set if is this not used by the next
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// state is a heuristic that is compatible with
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// point 2) above while not causing more states to
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// be generated in our benchmark of 188 formulae
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// from the literature.
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if (!order.empty())
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{
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unsigned prev = order.size() - 1;
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bdd common = outgoing.common_acc(s.first);
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if ((common & order[prev]) == order[prev])
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{
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bdd u = outgoing.union_acc(d.first);
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if ((u & order[prev]) != order[prev])
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acc -= order[prev];
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}
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}
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}
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// A transition in the SLEVEL acceptance set should
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// be directed to the next acceptance set. If the
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// current transition is also in the next acceptance
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// set, then go to the one after, etc.
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//
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// See Denis Oddoux's PhD thesis for a nice
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// explanation (in French).
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// @PhDThesis{ oddoux.03.phd,
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// author = {Denis Oddoux},
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// title = {Utilisation des automates alternants pour un
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// model-checking efficace des logiques
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// temporelles lin{\'e}aires.},
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// school = {Universit{\'e}e Paris 7},
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// year = {2003},
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// address= {Paris, France},
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// month = {December}
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// }
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unsigned next = slevel;
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// Consider both the current acceptance sets, and the
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// acceptance sets common to the outgoing transitions of
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// the destination state.
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acc |= otheracc;
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while (next < order.size()
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&& (acc & order[next]) == order[next])
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++next;
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d.second = next;
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// Have we already seen this destination?
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int dest;
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ds2num_map::const_iterator di = ds2num.find(d);
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if (di != ds2num.end())
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{
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dest = di->second;
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}
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else
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{
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dest = ds2num.size();
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ds2num[d] = dest;
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todo.push_back(d);
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}
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// Actually create the transition.
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state_explicit_number::transition* t
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= res->create_transition(src, dest);
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t->condition = i->current_condition();
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// If the source state is accepting, we have to put
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// degen_acc on all outgoing transitions. (We are still
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// building a TGBA; we only assure that it can be used as
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// an SBA.)
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t->acceptance_conditions = is_acc ? degen_acc : bddfalse;
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}
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delete i;
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}
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res->merge_transitions();
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return res;
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}
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}
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44
src/tgbaalgos/degen.hh
Normal file
44
src/tgbaalgos/degen.hh
Normal file
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@ -0,0 +1,44 @@
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// Copyright (C) 2012 Laboratoire de Recherche et
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// Développement de l'Epita.
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//
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// This file is part of Spot, a model checking library.
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//
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// Spot is free software; you can redistribute it and/or modify it
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// 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.
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//
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// 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.
|
||||
//
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||||
// 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
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// 02111-1307, USA.
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#ifndef SPOT_TGBAALGOS_DEGEN_HH
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# define SPOT_TGBAALGOS_DEGEN_HH
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namespace spot
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{
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class sba;
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class tgba;
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/// \brief Degeneralize a spot::tgba into an equivalent sba with
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/// only one acceptance condition.
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///
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/// This algorithms will build a new explicit automaton that has
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/// at most (N+1) times the number of states of the original automaton.
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///
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/// If you want to build a degeneralized automaton on-the-fly, see
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/// spot::tgba_sba_proxy or spot::tgba_tba_proxy.
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///
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/// \see tgba_sba_proxy, tgba_tba_proxy
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/// \ingroup tgba_misc
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sba* degeneralize(const tgba* a);
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}
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#endif
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@ -41,6 +41,7 @@
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#include "tgbaalgos/lbtt.hh"
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#include "tgba/tgbatba.hh"
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#include "tgba/tgbasgba.hh"
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#include "tgbaalgos/degen.hh"
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#include "tgba/tgbaproduct.hh"
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#include "tgba/futurecondcol.hh"
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#include "tgbaalgos/reducerun.hh"
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@ -1012,7 +1013,7 @@ main(int argc, char** argv)
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}
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else if (degeneralize_opt == DegenSBA)
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{
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degeneralized = a = new spot::tgba_sba_proxy(a);
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degeneralized = a = spot::degeneralize(a);
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assume_sba = true;
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}
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else if (labeling_opt == StateLabeled)
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@ -1066,7 +1067,7 @@ main(int argc, char** argv)
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else if (degeneralize_opt == DegenSBA)
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{
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product = product_degeneralized = a =
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new spot::tgba_sba_proxy(product);
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spot::degeneralize(product);
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assume_sba = true;
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}
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}
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@ -1148,7 +1149,7 @@ main(int argc, char** argv)
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// It is possible that we have applied other
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// operations to the automaton since its initial
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// degeneralization. Let's degeneralize again!
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spot::tgba_sba_proxy* s = new spot::tgba_sba_proxy(a);
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spot::tgba* s = spot::degeneralize(a);
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spot::never_claim_reachable(std::cout, s, f, spin_comments);
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delete s;
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}
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