postproc: integrate tgba_determinize()

* spot/twa/acc.hh: Add a smaller version of is_parity().
* spot/twaalgos/postproc.cc: Call tgba_determinize() if asked for
Generic acceptance and Deterministic output.
* bin/common_post.cc: Add 'G' as a shorthand for --generic.
* doc/org/ltl2tgba.org: Illustrate =ltl2tgba -G -D=.

bin/common_post.cc

@@ -1,6 +1,6 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2012, 2013, 2014, 2015 Laboratoire de Recherche et
-// Développement de l'Epita (LRDE).
+// 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.
 //
@@ -32,8 +32,7 @@ bool level_set = false;
 bool pref_set = false;
 
 enum {
-  OPT_GENERIC = 1,
-  OPT_HIGH,
+  OPT_HIGH = 1,
   OPT_LOW,
   OPT_MEDIUM,
   OPT_SMALL,
@@ -44,6 +43,8 @@ static const argp_option options[] =
   {
     /**************************************************/
     { nullptr, 0, nullptr, 0, "Output automaton type:", 2 },
+    { "generic", 'G', nullptr, 0,
+      "any acceptance condition is allowed", 0 },
     { "tgba", OPT_TGBA, nullptr, 0,
       "Transition-based Generalized Büchi Automaton (default)", 0 },
     { "ba", 'B', nullptr, 0,
@@ -57,7 +58,9 @@ static const argp_option options[] =
     /**************************************************/
     { nullptr, 0, nullptr, 0, "Simplification goal:", 20 },
     { "small", OPT_SMALL, nullptr, 0, "prefer small automata (default)", 0 },
-    { "deterministic", 'D', nullptr, 0, "prefer deterministic automata", 0 },
+    { "deterministic", 'D', nullptr, 0, "prefer deterministic automata "
+      "(combine with --generic to be sure to obtain a deterministic "
+      "automaton)", 0 },
     { "any", 'a', nullptr, 0, "no preference, do not bother making it small "
       "or deterministic", 0 },
     /**************************************************/
@@ -73,7 +76,7 @@ static const argp_option options_disabled[] =
   {
     /**************************************************/
     { nullptr, 0, nullptr, 0, "Output automaton type:", 2 },
-    { "generic", OPT_GENERIC, nullptr, 0,
+    { "generic", 'G', nullptr, 0,
       "any acceptance is allowed (default)", 0 },
     { "tgba", OPT_TGBA, nullptr, 0,
       "Transition-based Generalized Büchi Automaton", 0 },
@@ -88,7 +91,9 @@ static const argp_option options_disabled[] =
     /**************************************************/
     { nullptr, 0, nullptr, 0, "Simplification goal:", 20 },
     { "small", OPT_SMALL, nullptr, 0, "prefer small automata", 0 },
-    { "deterministic", 'D', nullptr, 0, "prefer deterministic automata", 0 },
+    { "deterministic", 'D', nullptr, 0, "prefer deterministic automata "
+      "(combine with --generic to be sure to obtain a deterministic "
+      "automaton)", 0 },
     { "any", 'a', nullptr, 0, "no preference, do not bother making it small "
       "or deterministic", 0 },
     /**************************************************/
@@ -120,15 +125,15 @@ parse_opt_post(int key, char*, struct argp_state*)
       pref = spot::postprocessor::Deterministic;
       pref_set = true;
       break;
+    case 'G':
+      type = spot::postprocessor::Generic;
+      break;
     case 'M':
       type = spot::postprocessor::Monitor;
       break;
     case 'S':
       sbacc = spot::postprocessor::SBAcc;
       break;
-    case OPT_GENERIC:
-      type = spot::postprocessor::Generic;
-      break;
     case OPT_HIGH:
       level = spot::postprocessor::High;
       simplification_level = 3;

doc/org/ltl2tgba.org

@@ -3,11 +3,22 @@
 #+SETUPFILE: setup.org
 #+HTML_LINK_UP: tools.html
 
-This tool translates LTL or PSL formulas into two kinds of Büchi
-automata, or to monitors.  The default is to output Transition-based
-Generalized Büchi Automata (hereinafter abbreviated TGBA), but more
-traditional Büchi automata (BA) may be requested using the =-B=
-option.
+This tool translates LTL or PSL formulas into different types of
+automata.
+
+The inner algorithm produces Transition-based Generalized Büchi
+Automata, hence the name of the tools, but =ltl2tgba= has grown and
+now offers several options to adjust the type of automaton output.
+Those options will be covered in more detail below, but here is
+a quick summary:
+
+- =--tgba= (the default) outputs Transition-based Generalized
+Büchi Automata
+- =--ba= (or =-B=) outputs state-based Büchi automata
+- =--monitor= (or =-M=) outputs Monitors
+- =--generic --deterministic= (or =-GD=) will do whatever it takes to
+  produce a deterministic automaton, and may output generalized Büchi,
+  or parity acceptance.
 
 * TGBA and BA
 
@@ -448,6 +459,13 @@ Note that options =--deterministic= and =--small= express
 /preferences/.  They certainly do /not/ guarantee that the output will
 be deterministic, or will be the smallest automaton possible.
 
+In particular, for properties more complex than obligations, it is
+possible that no deterministic TGBA exist, and even if it exists,
+=ltl2tgba= might not find it: so a non-deterministic automaton can be
+returned in this case.  If you absolutely want a deterministic
+automaton, [[#generic][read on about the =--generic= option below]].
+
+
 An example formula where the difference between =-D= and =--small= is
 flagrant is =Ga|Gb|Gc=:
 
@@ -697,6 +715,49 @@ to experiment with the different settings on a small version of the
 pattern, and select the lowest setting that satisfies your
 expectations.
 
+* Deterministic automata with =--generic=
+   :PROPERTIES:
+   :CUSTOM_ID: generic
+   :END:
+
+   The =--generic= (or =-G=) option allows =ltl2tgba= to use more
+   complex acceptance.  Combined with =--deterministic= (or =-D=) this
+   allows the use of a determinization algorithm that produce automata
+   with parity acceptance.
+
+   For instance =FGa= is the typical formula for which not
+   deterministic TGBA exists.
+
+#+NAME: ltl2tgba-fga
+#+BEGIN_SRC sh :results verbatim :exports none
+ltl2tgba "FGa" -D -d.a
+#+END_SRC
+
+#+BEGIN_SRC dot :file ltl2tgba-fga.png :cmdline -Tpng :var txt=ltl2tgba-fga :exports results
+  $txt
+#+END_SRC
+
+#+RESULTS:
+[[file:ltl2tgba-fga.png]]
+
+   But with =--generic=, =ltl2tgba= will output the following Rabin automaton:
+
+#+NAME: ltl2tgba-fga-D
+#+BEGIN_SRC sh :results verbatim :exports none
+ltl2tgba "FGa" -G -D -d.a
+#+END_SRC
+
+#+BEGIN_SRC dot :file ltl2tgba-fga-D.png :cmdline -Tpng :var txt=ltl2tgba-fga-D :exports results
+  $txt
+#+END_SRC
+
+#+RESULTS:
+[[file:ltl2tgba-fga-D.png]]
+
+Note that determinization algorithm implemented actually outputs
+parity acceptance, but =Fin(0)&Inf(1)= can be interpreted either as
+=Rabin 1= or =parity min odd 2=.
+
 * Translating multiple formulas for statistics
 
 If multiple formulas are given to =ltl2tgba=, the corresponding

spot/twa/acc.hh

@@ -1,6 +1,6 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2014, 2015 Laboratoire de Recherche et Développement de
-// l'Epita.
+// Copyright (C) 2014, 2015, 2016 Laboratoire de Recherche et
+// Développement de l'Epita.
 //
 // This file is part of Spot, a model checking library.
 //
@@ -1040,6 +1040,12 @@ namespace spot
     // check whether the condition is logically equivalent to some
     // parity acceptance condition.
     bool is_parity(bool& max, bool& odd, bool equiv = false) const;
+    bool is_parity() const
+    {
+      bool max;
+      bool min;
+      return is_parity(max, min);
+    }
 
     // Return (true, m) if there exist some acceptance mark m that
     // does not satisfy the acceptance condition.  Return (false, 0U)

spot/twaalgos/postproc.cc

@@ -33,6 +33,7 @@
 #include <spot/twaalgos/totgba.hh>
 #include <spot/twaalgos/sbacc.hh>
 #include <spot/twaalgos/sepsets.hh>
+#include <spot/twaalgos/determinize.hh>
 
 namespace spot
 {
@@ -175,21 +176,19 @@ namespace spot
     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)
+	  a = do_scc_filter(a, true);
       }
 
-    if (PREF_ == Any && level_ == Low)
-      if (type_ == Generic
+    if (PREF_ == Any && level_ == Low
+	&& (type_ == Generic
 	    || type_ == TGBA
 	    || (type_ == BA && a->is_sba())
-	  || (type_ == Monitor && a->num_sets() == 0))
+	    || (type_ == Monitor && a->num_sets() == 0)))
       {
-	  if (tgb_used)
-	    a = do_scc_filter(a, true);
 	if (COMP_)
 	  a = complete(a);
 	if (SBACC_)
@@ -365,14 +364,26 @@ namespace spot
 	  }
       }
 
+    if (PREF_ == Deterministic && type_ == Generic && !dba)
+      {
+	dba = tgba_determinize(to_generalized_buchi(sim));
+	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).  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.
+    // 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() no yet updated to mix sat-minimize and Generic");
 	unsigned target_acc;
 	if (type_ == BA)
 	  target_acc = 1;
@@ -393,10 +404,8 @@ namespace spot
 	    // 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;
+	      in = degeneralize_tba(dba);
 	  }
 	else
 	  {