730c6bbca2
Fixes #347. * spot/twaalgos/minimize.cc, spot/twaalgos/minimize.hh: An SCC of the determinized automaton is marked as accepting if it intersects any accepting SCC of the original automaton. This can be checked by making a product. As a consequence the output of minimize_wdba() now always includes the original language, and minimize_obligation() only needs a single containment check. * NEWS: Mention this.
158 lines
7 KiB
C++
158 lines
7 KiB
C++
// -*- coding: utf-8 -*-
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// Copyright (C) 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2018
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// Laboratoire de Recherche et Développement de l'Epita (LRDE).
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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 3 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 this program. If not, see <http://www.gnu.org/licenses/>.
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#pragma once
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#include <spot/twa/twagraph.hh>
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#include <spot/tl/formula.hh>
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namespace spot
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{
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/// \addtogroup twa_reduction
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/// @{
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/// \brief Construct a minimal deterministic monitor.
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///
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/// The automaton will be converted into minimal deterministic
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/// monitor. All useless SCCs should have been previously removed
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/// (using scc_filter() for instance). Then the automaton will be
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/// determinized and minimized using the standard DFA construction
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/// as if all states were accepting states.
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///
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/// For more detail about monitors, see the following paper:
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/** \verbatim
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@InProceedings{ tabakov.10.rv,
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author = {Deian Tabakov and Moshe Y. Vardi},
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title = {Optimized Temporal Monitors for SystemC{$^*$}},
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booktitle = {Proceedings of the 10th International Conferance
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on Runtime Verification},
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pages = {436--451},
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year = 2010,
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volume = {6418},
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series = {Lecture Notes in Computer Science},
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month = nov,
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publisher = {Spring-Verlag}
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}
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\endverbatim */
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/// (Note: although the above paper uses Spot, this function did not
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/// exist in Spot at that time.)
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///
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/// \param a the automaton to convert into a minimal deterministic monitor
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/// \pre Dead SCCs should have been removed from \a a before
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/// calling this function.
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SPOT_API twa_graph_ptr minimize_monitor(const const_twa_graph_ptr& a);
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/// \brief Minimize a Büchi automaton in the WDBA class.
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///
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/// This takes a TGBA whose language is representable by a Weak
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/// Deterministic Büchi Automaton, and construct a minimal WDBA for
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/// this language. This essentially chains three algorithms:
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/// determinization, acceptance adjustment (Löding's coloring
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/// algorithm), and minimization (using a Moore-like approach).
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///
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/// If the input automaton does not represent a WDBA language, the
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/// resulting automaton is still a WDBA, but it will accept a
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/// superset of the original language. Use the
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/// minimize_obligation() function if you are not sure whether it is
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/// safe to call this function.
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///
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/// The construction is inspired by the following paper, however we
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/// guarantee that the output language is a subsets of the original
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/// language while they don't.
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/** \verbatim
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@InProceedings{ dax.07.atva,
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author = {Christian Dax and Jochen Eisinger and Felix Klaedtke},
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title = {Mechanizing the Powerset Construction for Restricted
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Classes of {$\omega$}-Automata},
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year = 2007,
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series = {Lecture Notes in Computer Science},
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publisher = {Springer-Verlag},
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volume = 4762,
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booktitle = {Proceedings of the 5th International Symposium on
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Automated Technology for Verification and Analysis
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(ATVA'07)},
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editor = {Kedar S. Namjoshi and Tomohiro Yoneda and Teruo Higashino
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and Yoshio Okamura},
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month = oct
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}
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\endverbatim */
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SPOT_API twa_graph_ptr minimize_wdba(const const_twa_graph_ptr& a);
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/// \brief Minimize an automaton if it represents an obligation property.
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///
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/// This function attempts to minimize the automaton \a aut_f using the
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/// algorithm implemented in the minimize_wdba() function, and presented
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/// by the following paper:
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///
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/** \verbatim
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@InProceedings{ dax.07.atva,
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author = {Christian Dax and Jochen Eisinger and Felix Klaedtke},
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title = {Mechanizing the Powerset Construction for Restricted
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Classes of {$\omega$}-Automata},
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year = 2007,
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series = {Lecture Notes in Computer Science},
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publisher = {Springer-Verlag},
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volume = 4762,
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booktitle = {Proceedings of the 5th International Symposium on
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Automated Technology for Verification and Analysis
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(ATVA'07)},
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editor = {Kedar S. Namjoshi and Tomohiro Yoneda and Teruo Higashino
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and Yoshio Okamura},
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month = oct
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}
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\endverbatim */
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///
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/// Because it is hard to determine if an automaton corresponds
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/// to an obligation property, you should supply either the formula
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/// \a f expressed by the automaton \a aut_f, or \a aut_neg_f the negation
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/// of the automaton \a aut_neg_f.
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///
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/// \param aut_f the automaton to minimize
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/// \param f the LTL formula represented by the automaton \a aut_f
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/// \param aut_neg_f an automaton representing the negation of \a aut_f
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/// \param reject_bigger Whether the minimal WDBA should be discarded if
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/// it has more states than the input.
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/// \return a new tgba if the automaton could be minimized, \a aut_f if
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/// the automaton cannot be minimized, 0 if we do not know if the
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/// minimization is correct because neither \a f nor \a aut_neg_f
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/// were supplied.
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///
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/// The function proceeds as follows. If the formula \a f or the
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/// automaton \a aut can easily be proved to represent an obligation
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/// formula, then the result of <code>minimize(aut)</code> is
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/// returned. Otherwise, if \a aut_neg_f was not supplied but \a f
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/// was, \a aut_neg_f is built from the negation of \a f. Then we
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/// check that <code>product(aut,!minimize(aut_f))</code> and <code>
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/// product(aut_neg_f,minize(aut))</code> are both empty. If they
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/// are, the the minimization was sound. (See the paper for full
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/// details.)
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///
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/// If \a reject_bigger is set, this function will return the input
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/// automaton \a aut_f when the minimized WDBA has more states than
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/// the input automaton. (More states are possible because of
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/// determinization step during minimize_wdba().) Note that
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/// checking the size of the minimized WDBA occurs before ensuring
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/// that the minimized WDBA is correct.
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SPOT_API twa_graph_ptr
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minimize_obligation(const const_twa_graph_ptr& aut_f,
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formula f = nullptr,
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const_twa_graph_ptr aut_neg_f = nullptr,
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bool reject_bigger = false);
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/// @}
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}
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