postproc.cc

// -*- coding: utf-8 -*-
// Copyright (C) 2012, 2013, 2014, 2015 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 <spot/twaalgos/postproc.hh>
#include <spot/twaalgos/minimize.hh>
#include <spot/twaalgos/simulation.hh>
#include <spot/twaalgos/sccfilter.hh>
#include <spot/twaalgos/degen.hh>
#include <spot/twaalgos/stripacc.hh>
#include <cstdlib>
#include <spot/misc/optionmap.hh>
#include <spot/twaalgos/powerset.hh>
#include <spot/twaalgos/isdet.hh>
#include <spot/twaalgos/dtbasat.hh>
#include <spot/twaalgos/dtwasat.hh>
#include <spot/twaalgos/complete.hh>
#include <spot/twaalgos/totgba.hh>
#include <spot/twaalgos/sbacc.hh>
#include <spot/twaalgos/sepsets.hh>

namespace spot
{
  namespace
  {
    static twa_graph_ptr
    ensure_ba(twa_graph_ptr& a)
    {
      if (a->num_sets() == 0)
	{
	  auto m = a->set_buchi();
	  for (auto& t: a->edges())
	    t.acc = m;
	}
      return a;
    }
  }

  postprocessor::postprocessor(const option_map* opt)
    : type_(TGBA), pref_(Small), level_(High),
      degen_reset_(true), degen_order_(false), degen_cache_(true),
      degen_lskip_(true), degen_lowinit_(false), simul_(-1),
      scc_filter_(-1), ba_simul_(-1),
      tba_determinisation_(false), sat_minimize_(0), sat_acc_(0),
      sat_states_(0), state_based_(false), wdba_minimize_(true)
  {
    if (opt)
      {
	degen_order_ = opt->get("degen-order", 0);
	degen_reset_ = opt->get("degen-reset", 1);
	degen_cache_ = opt->get("degen-lcache", 1);
	degen_lskip_ = opt->get("degen-lskip", 1);
	degen_lowinit_ = opt->get("degen-lowinit", 0);
	simul_ = opt->get("simul", -1);
	scc_filter_ = opt->get("scc-filter", -1);
	ba_simul_ = opt->get("ba-simul", -1);
	tba_determinisation_ = opt->get("tba-det", 0);
	sat_minimize_ = opt->get("sat-minimize", 0);
	sat_acc_ = opt->get("sat-acc", 0);
	sat_states_ = opt->get("sat-states", 0);
	state_based_ = opt->get("state-based", 0);
	wdba_minimize_ = opt->get("wdba-minimize", 1);

	if (sat_acc_ && sat_minimize_ == 0)
	  sat_minimize_ = 1;	// 2?
	if (sat_states_ && sat_minimize_ == 0)
	  sat_minimize_ = 1;
	if (sat_minimize_)
	  {
	    tba_determinisation_ = 1;
	    if (sat_acc_ <= 0)
	      sat_acc_ = -1;
	    if (sat_states_ <= 0)
	      sat_states_ = -1;
	  }
      }
  }

  twa_graph_ptr
  postprocessor::do_simul(const twa_graph_ptr& a, int opt)
  {
    if (!has_separate_sets(a))
      return a;
    switch (opt)
      {
      case 0:
	return a;
      case 1:
	return simulation(a);
      case 2:
	return cosimulation(a);
      case 3:
      default:
	return iterated_simulations(a);
      }
  }

  twa_graph_ptr
  postprocessor::do_sba_simul(const twa_graph_ptr& a, int opt)
  {
    if (ba_simul_ <= 0)
      return a;
    switch (opt)
      {
      case 0:
	return a;
      case 1:
	return simulation_sba(a);
      case 2:
	return cosimulation_sba(a);
      case 3:
      default:
	return iterated_simulations_sba(a);
      }
  }

  twa_graph_ptr
  postprocessor::do_degen(const twa_graph_ptr& a)
  {
    auto d = degeneralize(a,
			  degen_reset_, degen_order_,
			  degen_cache_, degen_lskip_,
			  degen_lowinit_);
    return do_sba_simul(d, ba_simul_);
  }

  twa_graph_ptr
  postprocessor::do_scc_filter(const twa_graph_ptr& a, bool arg)
  {
    if (scc_filter_ == 0)
      return a;
    // If the automaton is weak, using transition-based acceptance
    // won't help, so let's preserve it.
    if ((state_based_ || a->prop_inherently_weak()) && a->prop_state_acc())
      return scc_filter_states(a, arg);
    else
      return scc_filter(a, arg);
  }

  twa_graph_ptr
  postprocessor::do_scc_filter(const twa_graph_ptr& a)
  {
    return do_scc_filter(a, scc_filter_ > 1);
  }

#define PREF_ (pref_ & (Small | Deterministic))
#define COMP_ (pref_ & Complete)
#define SBACC_ (pref_ & SBAcc)

  twa_graph_ptr
  postprocessor::run(twa_graph_ptr a, formula f)
  {
    if (simul_ < 0)
      simul_ = (level_ == Low) ? 1 : 3;
    if (ba_simul_ < 0)
      ba_simul_ = (level_ == High) ? 3 : 0;
    if (scc_filter_ < 0)
      scc_filter_ = 1;
    if (type_ == BA || SBACC_)
      state_based_ = true;

    bool tgb_used = false;
    if (type_ != Generic && !a->acc().is_generalized_buchi())
      {
	a = to_generalized_buchi(a);
	tgb_used = true;
      }

    if (PREF_ == Any && level_ == Low)
      if (type_ == Generic
	  || type_ == TGBA
	  || (type_ == BA && a->is_sba())
	  || (type_ == Monitor && a->num_sets() == 0))
	{
	  if (tgb_used)
	    a = do_scc_filter(a, true);
	  if (COMP_)
	    a = complete(a);
	  if (SBACC_)
	    a = sbacc(a);
	  return a;
	}

    int original_acc = a->num_sets();

    // Remove useless SCCs.
    if (type_ == Monitor)
      // Do not bother about acceptance conditions, they will be
      // ignored.
      a = scc_filter_states(a);
    else
      a = do_scc_filter(a, (PREF_ == Any));

    if (type_ == Monitor)
      {
	if (PREF_ == Deterministic)
	  a = minimize_monitor(a);
	else
	  strip_acceptance_here(a);

	if (PREF_ == Any)
	  return a;

	a = do_simul(a, simul_);

	// For Small,High we return the smallest between the output of
	// the simulation, and that of the deterministic minimization.
	if (PREF_ == Small && level_ == High && simul_)
	  {
	    auto m = minimize_monitor(a);
	    if (m->num_states() < a->num_states())
	      a = m;
	  }
	if (COMP_)
	  a = complete(a);
	return a;
      }

    if (PREF_ == Any)
      {
	if (type_ == BA)
	  a = do_degen(a);
	if (COMP_)
	  a = complete(a);
	if (SBACC_)
	  a = sbacc(a);
	return a;
      }

    bool dba_is_wdba = false;
    bool dba_is_minimal = false;
    twa_graph_ptr dba = nullptr;
    twa_graph_ptr sim = nullptr;

    // (Small,Low) is the only configuration where we do not run
    // WDBA-minimization.
    if ((PREF_ != Small || level_ != Low) && wdba_minimize_)
      {
	bool reject_bigger = (PREF_ == Small) && (level_ == Medium);
	dba = minimize_obligation(a, f, nullptr, reject_bigger);
	if (dba && dba->prop_inherently_weak() && dba->prop_deterministic())
	  {
	    // The WDBA is a BA, so no degeneralization is required.
	    // We just need to add an acceptance set if there is none.
	    dba_is_minimal = dba_is_wdba = true;
	    if (type_ == BA)
	      ensure_ba(dba);
	  }
	else
	  {
	    // Minimization failed.
	    dba = nullptr;
	  }
      }

    // Run a simulation when wdba failed (or was not run), or
    // at hard levels if we want a small output.
    if (!dba || (level_ == High && PREF_ == Small))
      {
	if (((SBACC_ && a->prop_state_acc())
	     || (type_ == BA && a->is_sba()))
	    && !tba_determinisation_)
	  {
	    sim = do_sba_simul(a, ba_simul_);
	  }
	else
	  {
	    sim = do_simul(a, simul_);
	    // Degeneralize the result of the simulation if needed.
	    // No need to do that if tba_determinisation_ will be used.
	    if (type_ == BA && !tba_determinisation_)
	      sim = do_degen(sim);
	    else if (SBACC_ && !tba_determinisation_)
	      sim = sbacc(sim);
	  }
      }

    // If WDBA failed, but the simulation returned a deterministic
    // automaton, use it as dba.
    assert(dba || sim);
    if (!dba && is_deterministic(sim))
      {
	std::swap(sim, dba);
	// We postponed degeneralization above i case we would need
	// to perform TBA-determinisation, but now it is clear
	// that we won't perform it.  So do degeneralize.
	if (tba_determinisation_)
	  {
	    if (type_ == BA)
	      {
		dba = do_degen(dba);
		assert(is_deterministic(dba));
	      }
	    else if (SBACC_)
	      {
		dba = sbacc(dba);
		assert(is_deterministic(dba));
	      }
	  }
      }

    // If we don't have a DBA, attempt tba-determinization if requested.
    if (tba_determinisation_ && !dba)
      {
	twa_graph_ptr tmpd = nullptr;
	if (PREF_ == Deterministic
	    && f
	    && f.is_syntactic_recurrence()
	    && sim->num_sets() > 1)
	  tmpd = degeneralize_tba(sim);

	auto in = tmpd ? tmpd : sim;

	// These thresholds are arbitrary.
	//
	// For producing Small automata, we assume that a
	// deterministic automaton that is twice the size of the
	// original will never get reduced to a smaller one.  We also
	// do not want more than 2^13 cycles in an SCC.
	//
	// For Deterministic automata, we accept automata that
	// are 8 times bigger, with no more that 2^15 cycle per SCC.
	// The cycle threshold is the most important limit here.  You
	// may up it if you want to try producing larger automata.
	auto tmp =
	  tba_determinize_check(in,
				(PREF_ == Small) ? 2 : 8,
				1 << ((PREF_ == Small) ? 13 : 15),
				f);
	if (tmp && tmp != in)
	  {
	    // There is no point in running the reverse simulation on
	    // a deterministic automaton, since all prefixes are
	    // unique.
	    dba = simulation(tmp);
	  }
	if (dba && PREF_ == Deterministic)
	  {
	    // disregard the result of the simulation.
	    sim = nullptr;
	  }
	else
	  {
	    // degeneralize sim, because we did not do it earlier
	    if (type_ == BA)
	      sim = do_degen(sim);
	  }
      }

    // Now dba contains either the result of WDBA-minimization (in
    // that case dba_is_wdba=true), or some deterministic automaton
    // that is either the result of the simulation or of the
    // TBA-determinization (dba_is_wdba=false in both cases).  If the
    // dba is a WDBA, we do not have to run SAT-minimization.  A
    // negative value in sat_minimize_ can for its use for debugging.
    if (sat_minimize_ && dba && (!dba_is_wdba || sat_minimize_ < 0))
      {
	unsigned target_acc;
	if (type_ == BA)
	  target_acc = 1;
	else if (sat_acc_ != -1)
	  target_acc = sat_acc_;
	else
	  // Take the number of acceptance conditions from the input
	  // automaton, not from dba, because dba often has been
	  // degeneralized by tba_determinize_check().  Make sure it
	  // is at least 1.
	  target_acc = original_acc > 0 ? original_acc : 1;

	const_twa_graph_ptr in = nullptr;
	if (target_acc == 1)
	  {
	    // If we are seeking a minimal DBA with unknown number of
	    // states, then we should start from the degeneralized,
	    // because the input TBA might be smaller.
	    if (state_based_)
	      in = degeneralize(dba);
	    else if (dba->num_sets() != 1)
	      in = degeneralize_tba(dba);
	    else
	      in = dba;
	  }
	else
	  {
	    in = dba;
	  }

	twa_graph_ptr res = complete(in);
	if (target_acc == 1)
	  {
	    if (sat_states_ != -1)
	      res = dtba_sat_synthetize(res, sat_states_, state_based_);
	    else if (sat_minimize_ == 1 || sat_minimize_ == -1)
	      res = dtba_sat_minimize(res, state_based_);
	    else  // sat_minimize_ == 2
	      res = dtba_sat_minimize_dichotomy(res, state_based_);
	  }
	else
	  {
	    if (sat_states_ != -1)
	      res = dtwa_sat_synthetize
		(res, target_acc,
		 acc_cond::acc_code::generalized_buchi(target_acc),
		 sat_states_, state_based_);
	    else if (sat_minimize_ == 1 || sat_minimize_ == -1)
	      res = dtwa_sat_minimize
		(res, target_acc,
		 acc_cond::acc_code::generalized_buchi(target_acc),
		 state_based_);
	    else  // sat_minimize_ == 2
	      res = dtwa_sat_minimize_dichotomy
		(res, target_acc,
		 acc_cond::acc_code::generalized_buchi(target_acc),
		 state_based_);
	  }

	if (res)
	  {
	    dba = do_scc_filter(res, true);
	    dba_is_minimal = true;
	  }
      }

    // Degeneralize the dba resulting from tba-determinization or
    // sat-minimization (which is a TBA) if requested and needed.
    if (dba && !dba_is_wdba && type_ == BA
	&& !(dba_is_minimal && state_based_ && dba->num_sets() == 1))
      dba = degeneralize(dba);

    if (dba && sim)
      {
	if (dba->num_states() > sim->num_states())
	  dba = nullptr;
	else
	  sim = nullptr;
      }

    if (level_ == High && scc_filter_ != 0)
      {
	if (dba)
	  {
	    // Do that even for WDBA, to remove marks from transitions
	    // leaving trivial SCCs.
	    dba = do_scc_filter(dba, true);
	    assert(!sim);
	  }
	else if (sim)
	  {
	    sim = do_scc_filter(sim, true);
	    assert(!dba);
	  }
      }

    sim = dba ? dba : sim;

    if (COMP_)
      sim = complete(sim);
    if (SBACC_)
      sim = sbacc(sim);

    return sim;
  }
}