Adding sat-based minimization for mealy machines

* spot/twaalgos/mealy_machine.hh,
spot/twaalgos/mealy_machine.cc: Here
* spot/twaalgos/Makefile.am: Here
* tests/python/mealy.py: Added tests
* tests/Makefile.am: Adding mealy.py
* python/spot/impl.i: Here

spot/twaalgos/Makefile.am

@@ -1,5 +1,5 @@
 ## -*- coding: utf-8 -*-
-## Copyright (C) 2008-2018, 2020 Laboratoire de Recherche et
+## Copyright (C) 2008-2018, 2020-2021 Laboratoire de Recherche et
 ## Développement de l'Epita (LRDE).
 ## Copyright (C) 2003-2005 Laboratoire d'Informatique de Paris 6
 ## (LIP6), département Systèmes Répartis Coopératifs (SRC), Université
@@ -66,6 +66,7 @@ twaalgos_HEADERS = \
   magic.hh \
   mask.hh \
   minimize.hh \
+  mealy_machine.hh \
   couvreurnew.hh \
   neverclaim.hh \
   parity.hh \
@@ -136,6 +137,7 @@ libtwaalgos_la_SOURCES = \
   magic.cc \
   mask.cc \
   minimize.cc \
+  mealy_machine.cc \
   couvreurnew.cc \
   ndfs_result.hxx \
   neverclaim.cc \

spot/twaalgos/mealy_machine.hh

@@ -0,0 +1,70 @@
+// -*- coding: utf-8 -*-
+// Copyright (C) 2021 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/>.
+
+#pragma once
+
+#include <spot/twa/twagraph.hh>
+
+namespace spot
+{
+  /// \brief Minimizes an (in)completely specified mealy machine
+  ///        Based on signature inclusion or equality. This is not guaranteed
+  ///        to find the minimal number of states but is usually faster.
+  ///        This also comes at another drawback:
+  ///        All applicable sequences have to be infinite. Finite
+  ///        traces are disregarded
+  /// \Note The graph does not have to be split into env and player
+  ///        states as for minimize_mealy
+  SPOT_API
+  void minimize_mealy_fast_here(twa_graph_ptr& mm,
+                              bool use_inclusion = false);
+
+  /// \brief Like minimize_mealy_fast_here
+  SPOT_API
+  twa_graph_ptr minimize_mealy_fast(const const_twa_graph_ptr& mm,
+                                    bool use_inclusion = false);
+
+  /// \brief Minimizes an (in)completely specified mealy machine
+  ///        The approach is basically described in \cite abel2015memin
+  /// \param premin Use minimize_mealy_fast before applying the
+  ///               main algorithm if demanded AND
+  ///               the original machine has no finite trace.
+  ///               -1 : Do not use;
+  ///                0 : Use without inclusion;
+  ///                1 : Use with inclusion
+  /// \param keep_split Whether or not to keep the automaton states
+  ///                   partitioned into player and env states
+  /// \pre Graph must be split into env states and player states,
+  ///      such that they alternate. Edges leaving env states must be labeled
+  ///      with input proposition and edges leaving player states must be
+  ///      labeled with output propositions.
+  SPOT_API
+  twa_graph_ptr minimize_mealy(const const_twa_graph_ptr& mm,
+                               int premin = -1,
+                               bool keep_split = true);
+
+
+  /// \brief Test if the mealy machine \a right is a specialization of
+  /// the mealy machine \a left. That is all input sequences valid for left
+  /// must be applicable for right and the induced sequence of output signals
+  /// of right must imply the ones of left
+  SPOT_API bool is_mealy_specialization(const_twa_graph_ptr left,
+                                        const_twa_graph_ptr right,
+                                        bool verbose = false);
+}