Introduce compositional suspension (SPIN'13)

* src/tgbaalgos/compsusp.cc, src/tgbaalgos/compsusp.hh: New files.
* src/tgbaalgos/Makefile.am: Add them.
* src/tgbaalgos/sccfilter.cc, src/tgbaalgos/sccfilter.hh: Add option
for suspended labels removal.
* src/tgbatest/ltl2tgba.cc, src/tgbatest/spotlbtt.test: Test it.

src/tgbaalgos/Makefile.am

@@ -29,6 +29,7 @@ tgbaalgosdir = $(pkgincludedir)/tgbaalgos
 
 tgbaalgos_HEADERS = \
   bfssteps.hh \
+  compsusp.hh \
   cutscc.hh \
   cycles.hh \
   degen.hh \
@@ -73,6 +74,7 @@ tgbaalgos_HEADERS = \
 noinst_LTLIBRARIES = libtgbaalgos.la
 libtgbaalgos_la_SOURCES = \
   bfssteps.cc \
+  compsusp.cc \
   cutscc.cc \
   cycles.cc \
   degen.cc \

src/tgbaalgos/compsusp.cc

+// -*- coding: utf-8 -*-
+// Copyright (C) 2012, 2013 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 3 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#include "compsusp.hh"
+#include "sccfilter.hh"
+#include "scc.hh"
+#include "tgba/tgbaexplicit.hh"
+#include "ltl2tgba_fm.hh"
+#include "minimize.hh"
+#include "simulation.hh"
+#include "safety.hh"
+#include "ltlast/allnodes.hh"
+#include "ltlvisit/tostring.hh"
+#include "ltlvisit/clone.hh"
+#include <queue>
+#include <sstream>
+#include "ltlenv/environment.hh"
+
+namespace spot
+{
+  namespace
+  {
+    typedef std::map<const ltl::formula*, bdd> formula_bdd_map;
+
+    // An environment to store atomic proposition associated to
+    // suspended variable.  (We don't use the default environment to
+    // avoid conflicts with user-defined atomic propositions that
+    // would share the same name.)
+    class suspended_environment: public ltl::environment
+    {
+    public:
+      const ltl::formula*
+      require(const std::string& s)
+      {
+	return ltl::atomic_prop::instance(s, *this);
+      }
+
+      const std::string&
+      name()
+      {
+	static std::string name("suspended environment");
+	return name;
+      }
+    };
+    static suspended_environment suspenv;
+
+    // Rewrite the suspendable subformulae "s" of an LTL formula in
+    // the form Gg where "g" is an atomic proposition representing
+    // "s".  At the same time, populate maps that associate "s" to "g"
+    // and vice-versa.
+    class ltl_suspender_visitor: public ltl::clone_visitor
+    {
+    public:
+      typedef std::map<const ltl::formula*, const ltl::formula*> fmap_t;
+      ltl_suspender_visitor(fmap_t& g2s, fmap_t& a2o, bool oblig)
+	: g2s_(g2s), a2o_(a2o), oblig_(oblig)
+      {
+      }
+
+      void
+      visit(const ltl::multop* mo)
+      {
+	ltl::multop::type op = mo->op();
+	switch (op)
+	  {
+	  case ltl::multop::Or:
+	  case ltl::multop::And:
+	    {
+	      ltl::multop::vec* res = new ltl::multop::vec;
+	      ltl::multop::vec* oblig = oblig_ ? new ltl::multop::vec : 0;
+	      ltl::multop::vec* susp = new ltl::multop::vec;
+	      unsigned mos = mo->size();
+	      for (unsigned i = 0; i < mos; ++i)
+		{
+		  const ltl::formula* c = mo->nth(i);
+		  if (c->is_boolean())
+		    res->push_back(c->clone());
+		  else if (oblig_ && c->is_syntactic_obligation())
+		    oblig->push_back(c->clone());
+		  else if (c->is_eventual() && c->is_universal())
+		    susp->push_back(c->clone());
+		  else
+		    res->push_back(recurse(c));
+		}
+	      if (!oblig_ || oblig->empty())
+		{
+		  delete oblig;
+		}
+	      else
+		{
+		  const ltl::formula* o = ltl::multop::instance(op, oblig);
+		  res->push_back(recurse(o));
+		  o->destroy();
+		}
+	      if (susp->empty())
+		{
+		  delete susp;
+		}
+	      else
+		{
+		  const ltl::formula* o = ltl::multop::instance(op, susp);
+		  // Rewrite 'o' as 'G"o"'
+		  const ltl::formula* g = recurse(o);
+		  o->destroy();
+		  if (op == ltl::multop::And)
+		    {
+		      res->push_back(g);
+		    }
+		  else
+		    {
+		      // res || susp -> (res && G![susp]) || G[susp])
+		      const ltl::formula* r = ltl::multop::instance(op, res);
+		      const ltl::unop* u =
+			down_cast<const ltl::unop*>(g);
+		      const ltl::formula* gn =
+			ltl::unop::instance
+			(ltl::unop::G, ltl::unop::instance
+			 (ltl::unop::Not, u->child()->clone()));
+		      result_ = ltl::multop::instance
+			(ltl::multop::Or, ltl::multop::instance
+			 (ltl::multop::And, r, gn),
+			 g);
+		      return;
+		    }
+		}
+	      result_ = ltl::multop::instance(op, res);
+	    }
+	    break;
+	  case ltl::multop::OrRat:
+	  case ltl::multop::AndRat:
+	  case ltl::multop::AndNLM:
+	  case ltl::multop::Concat:
+	  case ltl::multop::Fusion:
+	    this->ltl::clone_visitor::visit(mo);
+	    break;
+	  }
+      }
+
+
+      const ltl::formula*
+      recurse(const ltl::formula* f)
+      {
+	const ltl::formula* res;
+	if (f->is_boolean())
+	  return f->clone();
+	if (oblig_ && f->is_syntactic_obligation())
+	  {
+	    fmap_t::const_iterator i = assoc_.find(f);
+	    if (i != assoc_.end())
+	      return i->second->clone();
+
+	    std::ostringstream s;
+	    s << "〈";
+	    to_string(f, s);
+	    s << "〉";
+	    res = suspenv.require(s.str());
+	    // We have to clone f, because it is not always a sub-tree
+	    // of the original formula.  (Think n-ary operators.)
+	    a2o_[res] = f->clone();
+	    assoc_[f] = res;
+	    return res;
+	  }
+	if (f->is_eventual() && f->is_universal())
+	  {
+	    fmap_t::const_iterator i = assoc_.find(f);
+	    if (i != assoc_.end())
+	      return ltl::unop::instance(ltl::unop::G, i->second->clone());
+
+	    std::ostringstream s;
+	    s << "[";
+	    to_string(f, s);
+	    s << "]";
+	    res = suspenv.require(s.str());
+	    // We have to clone f, because it is not always a sub-tree
+	    // of the original formula.  (Think n-ary operators.)
+	    g2s_[res] = f->clone();
+	    assoc_[f] = res;
+	    return ltl::unop::instance(ltl::unop::G, res);
+	  }
+	f->accept(*this);
+	return result_;
+      }
+
+    private:
+      fmap_t& g2s_;
+      fmap_t assoc_;		// This one is only needed by the visitor.
+      fmap_t& a2o_;
+      bool oblig_;
+    };
+
+
+    typedef std::pair<const state*, const state*> state_pair;
+
+    typedef std::map<state_pair, int> pair_map;
+    typedef std::deque<state_pair> pair_queue;
+
+    static
+    tgba*
+    susp_prod(tgba* left, const ltl::formula* f, bdd v)
+    {
+      bdd_dict* dict = left->get_dict();
+      const tgba* a1 = ltl_to_tgba_fm(f, dict, true, true);
+
+      const tgba* a2 = scc_filter(a1, false);
+      delete a1;
+      const tgba* right = iterated_simulations(a2);
+      delete a2;
+
+      tgba_explicit_number* res = new tgba_explicit_number(dict);
+      dict->register_all_variables_of(left, res);
+      dict->register_all_variables_of(right, res);
+      dict->unregister_variable(bdd_var(v), res);
+
+      // The left and right automata might have acceptance marker in
+      // common.
+      // For the example, assume left has acceptance conditions A,B,C,D
+      // while right has acceptance condition C,D,E,F.
+
+      // Negative acceptance variables...
+      // !A&!B&!C&!D
+      bdd lna = left->neg_acceptance_conditions();
+      // !C&!D&!E&!F
+      bdd rna = right->neg_acceptance_conditions();
+
+      // Missing acceptance variables...
+      // !E&!F
+      bdd lma = bdd_exist(rna, bdd_support(lna));
+      // !A&!B
+      bdd rma = bdd_exist(lna, bdd_support(rna));
+
+      // (A&!B&!C&!D + ... + !A&!B&!C&D) & !E&!F
+      bdd lac = left->all_acceptance_conditions() & lma;
+      // (C&!D&!E&!F + ... + !C&!D&!E&F) & !A&!B
+      bdd rac = right->all_acceptance_conditions() & rma;
+      bdd allacc = lac | rac;
+      res->set_acceptance_conditions(allacc);
+
+      // Acceptance condition to add to all transitions
+      // of the left automaton.
+      // !A&!B&!C&!D&E&!F | !A&!B&!C&!D&!E&F
+      bdd ladd = rac - lma;
+      bdd radd = lac - rma;
+
+      pair_map seen;
+      pair_queue todo;
+
+      state_pair p(left->get_init_state(), 0);
+      state* ris = right->get_init_state();
+      p.second = ris;
+      seen[p] = 0;
+      todo.push_back(p);
+      res->set_init_state(0);
+
+      typedef state_explicit_number::transition trans;
+
+      while (!todo.empty())
+	{
+	  p = todo.front();
+	  todo.pop_front();
+	  const state* ls = p.first;
+	  const state* rs = p.second;
+	  int src = seen[p];
+
+	  tgba_succ_iterator* li = left->succ_iter(ls);
+	  for (li->first(); !li->done(); li->next())
+	    {
+	      state_pair d(li->current_state(), ris);
+	      bdd lc = li->current_condition();
+
+	      tgba_succ_iterator* ri = 0;
+	      // Should we reset the right automaton?
+	      if ((lc & v) == lc)
+		{
+		  // No.
+		  ri = right->succ_iter(rs);
+		  ri->first();
+		}
+	      // Yes.  Reset the right automaton.
+	      else
+		{
+		  p.second = ris;
+		}
+
+	      // This loops over all the right transitions
+	      // if RI is defined.  Otherwise this just makes
+	      // one iteration as if the right automaton was
+	      // looping in state 0 with "true".
+	      while (!ri || !ri->done())
+		{
+		  bdd cond = lc;
+		  bdd ra = allacc;
+		  if (ri)
+		    {
+		      cond = lc & ri->current_condition();
+		      // Skip incompatible transitions.
+		      if (cond == bddfalse)
+			{
+			  ri->next();
+			  continue;
+			}
+		      d.second = ri->current_state();
+		      ra = (ri->current_acceptance_conditions() & rma) | radd;
+		    }
+
+		  int dest = seen.size();
+		  pair_map::const_iterator i = seen.find(d);
+		  if (i != seen.end())
+		    {
+		      dest = i->second;
+		    }
+		  else
+		    {
+		      seen[d] = dest;
+		      todo.push_back(d);
+		    }
+
+		  trans* t = res->create_transition(src, dest);
+		  t->condition = bdd_exist(cond, v);
+		  bdd la = (li->current_acceptance_conditions() & lma) | ladd;
+		  t->acceptance_conditions = ra & la;
+
+		  if (ri)
+		    ri->next();
+		  else
+		    break;
+		}
+	      delete ri;
+	    }
+	}
+      delete left;
+      delete right;
+
+      return res;
+    }
+  }
+
+  tgba*
+  compsusp(const ltl::formula* f, bdd_dict* dict,
+	   bool no_wdba, bool no_simulation,
+	   bool early_susp, bool no_susp_product, bool wdba_smaller,
+	   bool oblig)
+  {
+    ltl_suspender_visitor::fmap_t g2s;
+    ltl_suspender_visitor::fmap_t a2o;
+    ltl_suspender_visitor v(g2s, a2o, oblig);
+    const ltl::formula* g = v.recurse(f);
+
+    tgba* res;
+    {
+      // Translate the patched formula, and remove useless SCCs.
+      tgba* aut = spot::ltl_to_tgba_fm(g, dict, true, true, false, false, 0, 0);
+      res = scc_filter(aut, false);
+      delete aut;
+    }
+
+    if (!no_wdba)
+      {
+	tgba* min = minimize_obligation(res, g, 0, wdba_smaller);
+	if (min != res)
+	  {
+	    delete res;
+	    res = min;
+	    no_simulation = true;
+	  }
+      }
+
+    if (!no_simulation)
+      {
+	tgba* sim = spot::iterated_simulations(res);
+	delete res;
+	res = sim;
+      }
+
+    spot::formula_bdd_map susp;
+    ltl_suspender_visitor::fmap_t::const_iterator it;
+    for (it = g2s.begin(); it != g2s.end(); ++it)
+      {
+	bdd_dict::fv_map::const_iterator j = dict->var_map.find(it->first);
+	assert(j != dict->var_map.end());
+	susp[it->second] = bdd_ithvar(j->second);
+      }
+
+    // Remove suspendable formulae from non-accepting SCCs.
+    bdd suspvars = bddtrue;
+    for (formula_bdd_map::const_iterator i = susp.begin();
+	 i != susp.end(); ++i)
+      suspvars &= i->second;
+
+    bdd allaccap = bddtrue; // set of atomic prop used in accepting SCCs.
+    tgba* aut = res;
+    {
+      scc_map sm(aut);
+      sm.build_map();
+
+      // Restrict suspvars to the set of suspension labels that occur
+      // in accepting SCC.
+      unsigned sn = sm.scc_count();
+      for (unsigned n = 0; n < sn; n++)
+	if (sm.accepting(n))
+	  allaccap &= sm.ap_set_of(n);
+
+      bdd ignored = bdd_exist(suspvars, allaccap);
+      suspvars = bdd_existcomp(suspvars, allaccap);
+      res = scc_filter(aut, false, &sm, suspvars, early_susp, ignored);
+    }
+    delete aut;
+
+    // Do we need to synchronize any suspended formula?
+    if (!susp.empty() && !no_susp_product)
+      for (formula_bdd_map::const_iterator i = susp.begin();
+	   i != susp.end(); ++i)
+	if ((allaccap & i->second) == allaccap)
+	  res = susp_prod(res, i->first, i->second);
+
+    g->destroy();
+
+    for (ltl_suspender_visitor::fmap_t::iterator i = g2s.begin();
+	 i != g2s.end(); ++i)
+      i->second->destroy();
+    for (ltl_suspender_visitor::fmap_t::iterator i = a2o.begin();
+	 i != a2o.end(); ++i)
+      i->second->destroy();
+    return res;
+  }
+}

src/tgbaalgos/compsusp.hh

+// -*- coding: utf-8 -*-
+// Copyright (C) 2012, 2013 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 3 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#ifndef SPOT_TGBAALGOS_COMPSUSP_HH
+# define SPOT_TGBAALGOS_COMPSUSP_HH
+
+#include "ltlast/formula.hh"
+
+namespace spot
+{
+  class tgba;
+  class bdd_dict;
+
+  /// \brief Compositional translation algorithm with resetable
+  /// suspension.
+  ///
+  /// Described in "Compositional Approach to Suspension and Other
+  /// Improvements to LTL Translation", Tomáš Babiak, Thomas Badie,
+  /// Alexandre Duret-Lutz, Mojmír Křetínský, Jan Strejček (SPIN'13).
+  ///
+  /// If \a no_wdba or \a no_simulation is true, the corresponding
+  /// operation is not performed on the skeleton automaton.  If \a
+  /// early_susp is true, then composition starts on the transition
+  /// that enters the accepting SCC, not just in the SCC itself.  If
+  /// \a no_susp_product is true, then the composition is not
+  /// performed and the skeleton automaton is returned for debugging.
+  /// If \a wdba_smaller is true, then the WDBA-minimization of the
+  /// skeleton is used only if it produces a smaller automaton.
+  ///
+  /// Finally the \a oblig flag is a work in progress and should not
+  /// be set to true.
+  ///
+  /// This interface is subject to change, and clients aiming for
+  /// long-term stability should better use the services of the
+  /// spot::translator class instead.
+  tgba* compsusp(const ltl::formula* f, bdd_dict* dict,
+		 bool no_wdba = false, bool no_simulation = false,
+		 bool early_susp = false, bool no_susp_product = false,
+		 bool wdba_smaller = false, bool oblig = false);
+}
+
+#endif // SPOT_TGBAALGOS_COMPSUSP_HH

src/tgbaalgos/sccfilter.cc

@@ -195,7 +195,7 @@ namespace spot
 	  }
       }
 
-    private:
+    protected:
       T* out_;
       const scc_map& sm_;
       const std::vector<bool>& useless_;
@@ -205,14 +205,81 @@ namespace spot
       remap_t remap_;
     };
 
+    template<class T>
+    class filter_iter_susp: public filter_iter<T>
+    {
+    public:
+      typedef filter_iter<T> super;
+      filter_iter_susp(const tgba* a,
+		       const scc_map& sm,
+		       const std::vector<bool>& useless,
+		       remap_table_t& remap_table,
+		       unsigned max_num,
+		       const std::vector<unsigned>& max_table,
+		       bool remove_all_useless,
+		       bdd susp_pos, bool early_susp, bdd ignored)
+	: super(a, sm, useless, remap_table, max_num, max_table,
+		remove_all_useless),
+	  susp_pos(susp_pos), early_susp(early_susp), ignored(ignored)
+      {
+      }
+
+
+      void
+      process_link(const state* in_s, int in,
+		   const state* out_s, int out,
+		   const tgba_succ_iterator* si)
+      {
+	unsigned u = this->sm_.scc_of_state(out_s);
+	unsigned v = this->sm_.scc_of_state(in_s);
+	bool destacc = this->sm_.accepting(u);
+
+	typename super::output_t::state::transition* t =
+	  create_transition(this->aut_, this->out_, in_s, in, out_s, out);
+
+	bdd cond = bdd_exist(si->current_condition(), ignored);
+	// Remove suspended variables on transitions going to
+	// non-accepting SCC, or on transition between SCC unless
+	// early_susp is set.
+	if (!destacc || (!early_susp && (u != this->sm_.scc_of_state(in_s))))
+	  cond = bdd_exist(cond, susp_pos);
+
+	this->out_->add_conditions(t, cond);
+
+	// Regardless of all_, do not output any acceptance condition
+	// if the destination is not in an accepting SCC.
+	//
+	// If all_ is set, do not output any acceptance condition if the
+	// source is not in the same SCC as dest.
+	//
+	// (See the documentation of scc_filter() for a rational.)
+	if (destacc && (!this->all_ || u == v))
+	  {
+	    bdd acc = si->current_acceptance_conditions();
+	    if (acc == bddfalse)
+	      return;
+	    t->acceptance_conditions = this->remap_[u][acc.id()];
+	  }
+      }
+    protected:
+      bdd susp_pos;
+      bool early_susp;
+      bdd ignored;
+    };
+
   } // anonymous
 
 
-  tgba* scc_filter(const tgba* aut, bool remove_all_useless)
+  tgba* scc_filter(const tgba* aut, bool remove_all_useless,
+		   scc_map* given_sm, bdd susp, bool early_susp, bdd ignored)
   {
-    scc_map sm(aut);
-    sm.build_map();
-    scc_stats ss = build_scc_stats(sm);
+    scc_map* sm = given_sm;
+    if (!sm)
+      {
+	sm = new scc_map(aut);
+	sm->build_map();
+      }
+    scc_stats ss = build_scc_stats(*sm);
 
     remap_table_t remap_table(ss.scc_total);
     std::vector<unsigned> max_table(ss.scc_total);
@@ -220,9 +287,9 @@ namespace spot
 
     for (unsigned n = 0; n < ss.scc_total; ++n)
       {
-	if (!sm.accepting(n))