postproc.cc

// -*- coding: utf-8 -*-
// Copyright (C) 2012, 2013, 2014, 2015, 2016 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>
#include <spot/twaalgos/determinize.hh>
#include <spot/twaalgos/alternation.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)
  {
    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);
        det_scc_ = opt->get("det-scc", 1);
        det_simul_ = opt->get("det-simul", 1);
        det_stutter_ = opt->get("det-stutter", 1);
        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);
        param_ = opt->get("param", 0);
        dicho_langmap_ = opt->get("langmap", 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().is_true())
        && a->prop_state_acc().is_true())
      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;

    if (a->is_alternating() &&
        // We will probably have to revisit this condition later.
        // Currently, the intent is that postprocessor should never
        // return an alternating automaton, unless it is called with
        // its laxest settings.
        !(type_ == Generic && PREF_ == Any && level_ == Low))
      a = remove_alternation(a);

    if (type_ != Generic && !a->acc().is_generalized_buchi())
      {
        a = to_generalized_buchi(a);
        if (PREF_ == Any && level_ == Low)
          a = do_scc_filter(a, true);
      }

    if (PREF_ == Any && level_ == Low
        && (type_ == Generic
            || type_ == TGBA
            || (type_ == BA && a->is_sba())
            || (type_ == Monitor && a->num_sets() == 0)))
      {
        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;
          }
        a->remove_unused_ap();
        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().is_true()
            && dba->prop_deterministic().is_true())
          {
            // 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().is_true())
             || (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);
          }
      }

    if (PREF_ == Deterministic && type_ == Generic && !dba)
      {
        dba = tgba_determinize(to_generalized_buchi(sim),
                               false, det_scc_, det_simul_, det_stutter_);
        if (level_ != Low)
          dba = simulation(dba);
        sim = nullptr;
      }

    // 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), or a
    // parity automaton coming from tgba_determinize().  If the dba is
    // a WDBA, we do not have to run SAT-minimization.  A negative
    // value in sat_minimize_ can force its use for debugging.
    if (sat_minimize_ && dba && (!dba_is_wdba || sat_minimize_ < 0))
      {
        if (type_ == Generic)
          throw std::runtime_error
            ("postproc() not yet updated to mix sat-minimize and Generic");
        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
              in = degeneralize_tba(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 if (sat_minimize_ == 2)
              res = dtba_sat_minimize_dichotomy
                (res, state_based_, dicho_langmap_);
            else if (sat_minimize_ == 3)
              res = dtba_sat_minimize_incr(res, state_based_, -1, param_);
            else // if (sat_minimize == 4)
              res = dtba_sat_minimize_assume(res, state_based_, -1, param_);
          }
        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 if (sat_minimize_ == 2)
              res = dtwa_sat_minimize_dichotomy
                (res, target_acc,
                 acc_cond::acc_code::generalized_buchi(target_acc),
                 state_based_, dicho_langmap_);
            else if (sat_minimize_ == 3)
              res = dtwa_sat_minimize_incr
                (res, target_acc,
                 acc_cond::acc_code::generalized_buchi(target_acc),
                 state_based_, -1, false, param_);
            else // if (sat_minimize_ == 4)
              res = dtwa_sat_minimize_assume
                (res, target_acc,
                 acc_cond::acc_code::generalized_buchi(target_acc),
                 state_based_, -1, false, param_);
          }

        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;

    sim->remove_unused_ap();

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

    return sim;
  }
}