ignore false edges in emptiness checks and scc_info

Based on reports by Florian Renkin and Jens Kreber.

* spot/twaalgos/bfssteps.cc, spot/twaalgos/couvreurnew.cc,
spot/twaalgos/gtec/gtec.cc, spot/twaalgos/gv04.cc,
spot/twaalgos/magic.cc, spot/twaalgos/sccinfo.cc
spot/twaalgos/se05.cc, spot/twaalgos/tau03.cc: Ignore bddfalse edges.
* spot/twaalgos/gtec/gtec.hh: Remove debugging function.
* tests/core/neverclaimread.test: Adjust.
* tests/python/ecfalse.py: New test file.
* tests/Makefile.am: Add it.
* NEWS: Mention the bug.

NEWS

@@ -119,6 +119,9 @@ New in spot 2.8.7.dev (not yet released)
   - Relabeling automata could introduce false edges.  Those are now
     removed.
 
+  - Emptiness checks, and scc_info should now ignore edges labeled
+    with false.
+
 New in spot 2.8.7 (2020-03-13)
 
   Bugs fixed:

spot/twaalgos/bfssteps.cc

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2014, 2015, 2018 Laboratoire de Recherche et
+// Copyright (C) 2014, 2015, 2018, 2020 Laboratoire de Recherche et
 // Développement de l'Epita (LRDE)
 // Copyright (C) 2004  Laboratoire d'Informatique de Paris 6 (LIP6),
 // département Systèmes Répartis Coopératifs (SRC), Université Pierre
@@ -78,6 +78,10 @@ namespace spot
         todo.pop_front();
         for (auto i: a_->succ(src))
           {
+            // skip false transitions
+            if (SPOT_UNLIKELY(i->cond() == bddfalse))
+              continue;
+
             const state* dest = filter(i->dst());
 
             if (!dest)

spot/twaalgos/couvreurnew.cc

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2016-2019 Laboratoire de Recherche et Développement
+// Copyright (C) 2016-2020 Laboratoire de Recherche et Développement
 // de l'Epita (LRDE).
 //
 // This file is part of Spot, a model checking library.
@@ -41,7 +41,8 @@ namespace spot
     public:
       explicitproxy(explicit_iterator it)
         : it_(it)
-      {}
+      {
+      }
 
       const explicitproxy*
       operator->() const
@@ -73,6 +74,12 @@ namespace spot
         return it_->acc;
       }
 
+      bdd
+      cond() const
+      {
+        return it_->cond;
+      }
+
       void
       next()
       {
@@ -704,7 +711,7 @@ namespace spot
               assert(ecs_->root.size() == arc.size());
 
             // We are looking at the next successor in SUCC.
-            auto succ = todo.top().second;
+            auto& succ = todo.top().second;
 
             // If there are no more successors, backtrack.
             if (succ->done())
@@ -744,6 +751,14 @@ namespace spot
 
             // We have a successor to look at.
             inc_transitions();
+
+            // Ignore false edges
+            if (SPOT_UNLIKELY(succ->cond() == bddfalse))
+              {
+                succ->next();
+                continue;
+              }
+
             // Fetch the values we are interested in...
             auto acc = succ->acc();
             if (!need_accepting_run)
@@ -763,7 +778,7 @@ namespace spot
             state_t dest = succ->dst();
             // ... and point the iterator to the next successor, for
             // the next iteration.
-            todo.top().second->next();
+            succ->next();
 
             // We do not need succ from now on.
 

spot/twaalgos/gtec/gtec.cc

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2008, 2011, 2014-2016, 2018-2019 Laboratoire de
+// Copyright (C) 2008, 2011, 2014-2016, 2018-2020 Laboratoire de
 // Recherche et Développement de l'Epita (LRDE).
 // Copyright (C) 2003, 2004, 2005, 2006 Laboratoire d'Informatique de
 // Paris 6 (LIP6), département Systèmes Répartis Coopératifs (SRC),
@@ -109,6 +109,8 @@ namespace spot
           do
             {
               inc_transitions();
+              if (SPOT_UNLIKELY(i->cond() == bddfalse))
+                continue;
 
               const state* s = i->dst();
               auto j = ecs_->h.find(s);
@@ -219,9 +221,15 @@ namespace spot
         // of the arc) we are interested in...
         const state* dest = succ->dst();
         acc_cond::mark_t acc = succ->acc();
+        trace << "-> " << dest << ' ' << acc << ' ' << succ->cond();
         // ... and point the iterator to the next successor, for
         // the next iteration.
-        succ->next();
+        {
+          bdd cond = succ->cond();
+          succ->next();
+          if (SPOT_UNLIKELY(cond == bddfalse))
+            continue;
+        }
         // We do not need SUCC from now on.
 
         // Are we going to a new state?
@@ -321,10 +329,12 @@ namespace spot
   {
     for (auto iter: shy->ecs_->aut->succ(s))
       {
+        shy->inc_transitions();
+        if (SPOT_UNLIKELY(iter->cond() == bddfalse))
+          continue;
         q.emplace_back(iter->acc(),
                        iter->dst());
         shy->inc_depth();
-        shy->inc_transitions();
       }
   }
 
@@ -372,24 +382,28 @@ namespace spot
   }
 
 #ifdef TRACE
-  couvreur99_check_shy::dump_queue(std::ostream& os)
+  namespace
   {
-    os << "--- TODO ---\n";
+    template<class T>
-    unsigned lvl = 0;
+    void dump_queue(const T& todo)
-    for (auto& ti: todo)
+    {
-      {
+      trace << "--- TODO ---\n";
-        ++lvl;
+      unsigned lvl = 0;
-        os << '#' << lvl << " s:" << ti.s << " n:" << ti.n
+      for (auto& ti: todo)
-           << " q:{";
+        {
-        for (auto qi = ti.q.begin(); qi != ti.q.end();)
+          ++lvl;
-          {
+          trace << '#' << lvl << " s:" << ti.s << " n:" << ti.n
-            os << qi->s;
+                << " q:{";
-            ++qi;
+          for (auto qi = ti.q.begin(); qi != ti.q.end();)
-            if (qi != ti.q.end())
+            {
-              os << ", ";
+              trace << qi->s;
-          }
+              ++qi;
-        os << "}\n";
+              if (qi != ti.q.end())
-      }
+                trace << ", ";
+            }
+          trace << "}\n";
+        }
+    }
   }
 #endif
 
@@ -410,7 +424,7 @@ namespace spot
     for (;;)
       {
 #ifdef TRACE
-        dump_queue();
+        dump_queue(todo);
 #endif
 
         assert(ecs_->root.size() == 1 + arc.size());

spot/twaalgos/gtec/gtec.hh

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2008, 2013-2016, 2018-2019 Laboratoire de Recherche
+// Copyright (C) 2008, 2013-2016, 2018-2020 Laboratoire de Recherche
 // et Développement de l'Epita (LRDE).
 // Copyright (C) 2003, 2004, 2005, 2006 Laboratoire d'Informatique de
 // Paris 6 (LIP6), département Systèmes Répartis Coopératifs (SRC),
@@ -218,11 +218,6 @@ namespace spot
 
     void clear_todo();
 
-#ifdef SPOT_TRACE
-    /// Dump the queue for debugging.
-    void dump_queue(std::ostream& os = std::cerr);
-#endif
-
     /// Whether successors should be grouped for states in the same SCC.
     bool group_;
     // If the "group2" option is set (it implies "group"), we

spot/twaalgos/gv04.cc

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2008, 2010, 2011, 2013-2019 Laboratoire de
+// Copyright (C) 2008, 2010, 2011, 2013-2020 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
@@ -120,6 +120,10 @@ namespace spot
                 trace << " No more successors" << std::endl;
                 pop();
               }
+            else if (SPOT_UNLIKELY(iter->cond() == bddfalse))
+              {
+                continue;
+              }
             else
               {
                 const state* s_prime = iter->dst();

spot/twaalgos/magic.cc

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2011, 2013-2019  Laboratoire de recherche et
+// Copyright (C) 2011, 2013-2020  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
@@ -199,6 +199,8 @@ namespace spot
                 // Go down the edge (f.s, <label, acc>, s_prime)
                 f.it->next();
                 inc_transitions();
+                if (SPOT_UNLIKELY(label == bddfalse))
+                  continue;
                 typename heap::color_ref c = h.get_color_ref(s_prime);
                 if (c.is_white())
                   {
@@ -286,6 +288,8 @@ namespace spot
                 // Go down the edge (f.s, <label, acc>, s_prime)
                 f.it->next();
                 inc_transitions();
+                if (SPOT_UNLIKELY(label == bddfalse))
+                  continue;
                 typename heap::color_ref c = h.get_color_ref(s_prime);
                 if (c.is_white())
                   {

spot/twaalgos/sccinfo.cc

@@ -158,24 +158,25 @@ namespace spot
                 // Gather all successor SCCs
                 if (track_succs)
                   for (auto& t: aut->out(*s))
-                    for (unsigned d: aut->univ_dests(t))
+                    if (SPOT_LIKELY(t.cond != bddfalse))
-                      {
+                      for (unsigned d: aut->univ_dests(t))
-                        unsigned n = sccof_[d];
+                        {
-                        if (n == num || n == -1U)
+                          unsigned n = sccof_[d];
-                          continue;
+                          if (n == num || n == -1U)
-                        // If edges are cut, we are not able to
+                            continue;
-                        // maintain proper successor information.
+                          // If edges are cut, we are not able to
-                        if (filter_)
+                          // maintain proper successor information.
-                          switch (filter_(t, d, filter_data_))
+                          if (filter_)
-                            {
+                            switch (filter_(t, d, filter_data_))
-                            case edge_filter_choice::keep:
+                              {
-                              break;
+                              case edge_filter_choice::keep:
-                            case edge_filter_choice::ignore:
+                                break;
-                            case edge_filter_choice::cut:
+                              case edge_filter_choice::ignore:
-                              continue;
+                              case edge_filter_choice::cut:
-                            }
+                                continue;
-                        succ.emplace_back(n);
+                              }
-                      }
+                          succ.emplace_back(n);
+                        }
               }
             while (*s++ != curr);
 
@@ -251,6 +252,13 @@ namespace spot
             // Fetch the values we are interested in...
             auto& e = gr.edge_storage(tr_succ);
 
+            // Skip false edges.
+            if (SPOT_UNLIKELY(e.cond == bddfalse))
+              {
+                todo_.top().out_edge = e.next_succ;
+                continue;
+              }
+
             unsigned dest = e.dst;
             if ((int) dest < 0)
               {
@@ -412,7 +420,7 @@ namespace spot
         auto& s = result[src_scc];
         for (auto& t: aut_->out(src))
           {
-            if (scc_of(t.dst) != src_scc)
+            if (scc_of(t.dst) != src_scc || SPOT_UNLIKELY(t.cond == bddfalse))
               continue;
             s.insert(t.acc);
           }
@@ -502,7 +510,7 @@ namespace spot
         bfs_queue.pop_front();
         for (auto& t: aut->out(src))
           {
-            if (filter(t))
+            if (SPOT_UNLIKELY(t.cond == bddfalse) || filter(t))
               continue;
 
             if (match(t))
@@ -573,7 +581,8 @@ namespace spot
         if (scc_of(s) != scc)
           continue;
         for (auto& e: aut_->out(s))
-          if (e.src == e.dst && !filter(e) && acccond.accepting(e.acc))
+          if (e.src == e.dst && SPOT_LIKELY(e.cond != bddfalse)
+              && !filter(e) && acccond.accepting(e.acc))
             {
               // We have found an accepting self-loop.  That's the cycle
               // part of our accepting run.

spot/twaalgos/se05.cc

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2011, 2013-2019  Laboratoire de Recherche et
+// Copyright (C) 2011, 2013-2020  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
@@ -195,6 +195,8 @@ namespace spot
                 // Go down the edge (f.s, <label, acc>, s_prime)
                 f.it->next();
                 inc_transitions();
+                if (SPOT_UNLIKELY(label == bddfalse))
+                  continue;
                 typename heap::color_ref c = h.get_color_ref(s_prime);
                 if (c.is_white())
                   {
@@ -286,6 +288,8 @@ namespace spot
                 // Go down the edge (f.s, <label, acc>, s_prime)
                 f.it->next();
                 inc_transitions();
+                if (SPOT_UNLIKELY(label == bddfalse))
+                  continue;
                 typename heap::color_ref c = h.get_color_ref(s_prime);
                 if (c.is_white())
                   {

spot/twaalgos/tau03.cc

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2011, 2013-2019  Laboratoire de Recherche et
+// Copyright (C) 2011, 2013-2020  Laboratoire de Recherche et
 // Developpement de l'Epita (LRDE).
 // Copyright (C) 2004, 2005  Laboratoire d'Informatique de Paris 6 (LIP6),
 // département Systèmes Répartis Coopératifs (SRC), Université Pierre
@@ -167,6 +167,8 @@ namespace spot
                 // Go down the edge (f.s, <label, acc>, s_prime)
                 f.it->next();
                 inc_transitions();
+                if (SPOT_UNLIKELY(label == bddfalse))
+                  continue;
                 typename heap::color_ref c_prime = h.get_color_ref(s_prime);
                 if (c_prime.is_white())
                   {
@@ -194,11 +196,13 @@ namespace spot
                   {
                    inc_transitions();
                    const state *s_prime = i->dst();
+                   bdd label = i->cond();
+                   auto acc = i->acc();
+                   if (SPOT_UNLIKELY(label == bddfalse))
+                     continue;
                    trace << "DFS_BLUE rescanning the arc from "
                          << a_->format_state(f.s) << "  to "
                          << a_->format_state(s_prime) << std::endl;
-                    bdd label = i->cond();
-                    auto acc = i->acc();
                     typename heap::color_ref c_prime = h.get_color_ref(s_prime);
                     assert(!c_prime.is_white());
                     auto acu = acc | c.get_acc();
@@ -247,6 +251,8 @@ namespace spot
                 // Go down the edge (f.s, <label, acc>, s_prime)
                 f.it->next();
                 inc_transitions();
+                if (SPOT_UNLIKELY(label == bddfalse))
+                  continue;
                 typename heap::color_ref c_prime = h.get_color_ref(s_prime);
                 if (c_prime.is_white())
                   {

tests/Makefile.am

@@ -377,6 +377,7 @@ TESTS_python = \
   python/declenv.py \
   python/decompose_scc.py \
   python/dualize.py \
+  python/ecfalse.py \
   python/except.py \
   python/gen.py \
   python/genem.py \

tests/core/neverclaimread.test

@@ -1,6 +1,6 @@
 #!/bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2010-2015, 2017-2018 Laboratoire
+# Copyright (C) 2010-2015, 2017-2018, 2020 Laboratoire
 # de Recherche et Développement de l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
@@ -340,7 +340,7 @@ digraph "-" {
   1 [label="1", peripheries=2]
   }
   subgraph cluster_1 {
-  color=red
+  color=black
   label=""
   0 [label="0"]
   }

tests/python/ecfalse.py

@@ -0,0 +1,86 @@
+# -*- mode: python; coding: utf-8 -*-
+# Copyright (C) 2020 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/>.
+
+import spot
+from buddy import bddfalse, bddtrue
+
+a = spot.automaton("""
+HOA: v1
+States: 2
+Start: 1
+AP: 2 "p0" "p1"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+--BODY--
+State: 0
+[!0 | 1] 0 {0}
+[0&!1] 1
+State: 1
+/* we want this edge to be false, but the parser
+   would ignore it if we wrote it here */
+[0] 0 {0}
+[!1] 1
+--END--
+""")
+# Make the false edge.
+for e in a.out(1):
+    if e.dst == 0:
+        e.cond = bddfalse
+
+assert a.accepting_run() is None
+assert a.is_empty()
+
+for name in ['SE05', 'CVWY90', 'GV04', 'Cou99(shy)', 'Cou99', 'Tau03']:
+    print(name)
+    ec = spot.make_emptiness_check_instantiator(name)[0].instantiate(a)
+    res = ec.check()
+    if res is not None:
+        print(res.accepting_run())
+    assert res is None
+
+si = spot.scc_info(a)
+assert si.scc_count() == 1 # only one accessible SCC
+a.set_init_state(0)
+si = spot.scc_info(a)
+assert si.scc_count() == 2
+
+a = spot.automaton("""HOA: v1 States: 11 Start: 0 AP: 2 "a" "b" Acceptance: 8
+(Fin(0) | Inf(1)) & (Fin(2) | Inf(3)) & ((Fin(4) & Inf(5)) | (Fin(6) & Inf(7)))
+properties: trans-labels explicit-labels trans-acc --BODY-- State: 0 [!0&!1] 1
+{0 4 6 7} [!0&!1] 2 {0 5 6} [!0&!1] 3 {3 4 6 7} [!0&!1] 4 {3 5 6} State: 1
+[0&1] 5 {2 5 7} [0&1] 6 {2 7} [0&1] 7 {2 3 5 7} [0&1] 8 {2 3 7} [0&1] 0 {2 5 7}
+[0&1] 9 {2 7} State: 2 [0&1] 1 {2} [0&1] 3 {2 3} [0&1] 10 {2} State: 3 [0&1] 0
+{3 5 7} [0&1] 9 {3 7} State: 4 [!0&!1] 5 {4 6} [!0&!1] 6 {7} [0&1] 10 {3}
+State: 5 State: 6 State: 7 [!0&!1] 1 {4 6 7} [!0&!1] 2 {5 6} State: 8 [!0&!1] 2
+{4} State: 9 [!0&!1] 2 {0 4} [!0&!1] 4 {3 4} State: 10 --END-- """)
+
+r = a.accepting_run()
+assert r is not None
+assert r.replay(spot.get_cout())
+for e in a.out(7):
+    if e.dst == 2:
+        e.cond = bddfalse
+s = a.accepting_run()
+assert s is not None
+assert s.replay(spot.get_cout())
+for e in a.out(2):
+    if e.dst == 1:
+        e.cond = bddfalse
+s = a.accepting_run()
+assert s is None