spot/src/tgbaalgos/tau03opt.hh

// -*- coding: utf-8 -*-
// Copyright (C) 2013, 2014 Laboratoire de Recherche et Développement de
// l'Epita (LRDE).
// Copyright (C) 2004, 2005  Laboratoire d'Informatique de Paris 6 (LIP6),
// département Systèmes Répartis Coopératifs (SRC), Université Pierre
// et Marie Curie.
//
// 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_TAU03OPT_HH
# define SPOT_TGBAALGOS_TAU03OPT_HH

# include "misc/optionmap.hh"
# include "tgba/fwd.hh"
# include "emptiness.hh"

namespace spot
{
  /// \addtogroup emptiness_check_algorithms
  /// @{

  /// \brief Returns an emptiness checker on the spot::tgba automaton \a a.
  ///
  /// \pre The automaton \a a must have at least one acceptance condition.
  ///
  /// During the visit of \a a, the returned checker stores explicitely all
  /// the traversed states. The implemented algorithm is the following:
  ///
  /** \verbatim
      procedure check ()
      begin
        weight = 0; // the null vector
        call dfs_blue(s0);
      end;

      procedure dfs_blue (s)
      begin
        s.color = cyan;
        s.acc = emptyset;
        s.weight = weight;
        for all t in post(s) do
          let (s, l, a, t) be the edge from s to t;
          if t.color == white then
            for all b in a do
              weight[b] = weight[b] + 1;
            end for;
            call dfs_blue(t);
            for all b in a do
              weight[b] = weight[b] - 1;
            end for;
          end if;
          Acc = s.acc U a;
          if t.color == cyan &&
                    (Acc U support(weight - t.weight) U t.acc) == all_acc then
            report a cycle;
          else if Acc not included in t.acc then
            t.acc := t.acc U Acc;
            call dfs_red(t, Acc);
          end if;
        end for;
        s.color = blue;
      end;

      procedure dfs_red(s, Acc)
      begin
        for all t in post(s) do
          let (s, l, a, t) be the edge from s to t;
          if t.color == cyan &&
                      (Acc U support(weight - t.weight) U t.acc) == all_acc then
            report a cycle;
          else if t.color != white and Acc not included in t.acc then
            t.acc := t.acc U Acc;
            call dfs_red(t, Acc);
          end if;
        end for;
      end;
      \endverbatim */
  ///
  /// This algorithm is a generalisation to TGBA of the one implemented in
  /// spot::explicit_se05_search. It is based on the acceptance set labelling
  /// of states used in spot::explicit_tau03_search. Moreover, it introduce
  /// a slight optimisation based on vectors of integers counting for each
  /// acceptance condition how many time the condition has been visited in
  /// the path stored in the blue stack. Such a vector is associated to each
  /// state of this stack.
  ///
  SPOT_API emptiness_check_ptr
  explicit_tau03_opt_search(const const_tgba_ptr& a,
			    option_map o = option_map());

  /// @}
}

#endif // SPOT_TGBAALGOS_TAU03OPT_HH