scc_info: determine accepting/rejecting-SCCs for any acceptance

* src/twaalgos/sccinfo.cc, src/twaalgos/sccinfo.hh
(determine_unknown_acceptance): New function to call explicitly
in case one want to know whether the accepting/rejecting status
of all SCCs regardless of the acceptance.
* src/twaalgos/dotty.cc src/twaalgos/sccfilter.cc,
src/twaalgos/sccfilter.hh: Use it.
* src/tests/unambig.test, src/tests/sccdot.test: Add more tests.
* doc/org/oaut.org: Adjust doc for --dot=s, orange is not output
anymore.

doc/org/oaut.org

@@ -676,7 +676,6 @@ they visit some the transitions in the set #0 infinitely often.
 The strongly connected components are displayed using the following colors:
 - *green* components contain an accepting cycle
 - *red* components contain no accepting cycle
-- *orange* components may or may not contain an accepting cycle.  Such an indecision occur only when using =Fin= acceptance primitive, deciding that would require a better algorithm than what the output routine is using.
 - *black* components are trivial (i.e., they contain no cycle)
 - *gray* components are useless (i.e., they are non-accepting, and are only followed by non-accepting components)
 
@@ -741,12 +740,12 @@ digraph G {
   6 [label="6"]
   }
   subgraph cluster_1 {
-  color=orange
+  color=grey
   label=""
   0 [label="0"]
   }
   subgraph cluster_2 {
-  color=orange
+  color=green
   label=""
   8 [label="8"]
   9 [label="9"]

src/tests/sccdot.test

@@ -86,12 +86,12 @@ digraph G {
   6 [label="6"]
   }
   subgraph cluster_1 {
-  color=orange
+  color=grey
   label=""
   0 [label="0"]
   }
   subgraph cluster_2 {
-  color=orange
+  color=green
   label=""
   9 [label="9"]
   10 [label="10"]
@@ -148,3 +148,41 @@ digraph G {
 EOF
 
 diff out.dot expected
+
+# While we are here, make sure scc_filter remove those grey SCCs.
+../../bin/autfilt --small -x simul=0 in.hoa -H > out.hoa
+cat >expected.hoa <<EOF
+HOA: v1
+States: 8
+Start: 0
+AP: 2 "a" "b"
+Acceptance: 3 Fin(2) & (Inf(0)&Inf(1))
+properties: trans-labels explicit-labels trans-acc
+--BODY--
+State: 0
+[0&!1] 2
+[1] 3
+State: 1
+[1] 4
+State: 2
+[0&1] 0 {0 1}
+State: 3
+[1] 1
+[!1] 3
+State: 4
+[!0&1] 4 {0 1}
+[0&1] 4 {0 2}
+[t] 5
+State: 5
+[0&1] 5 {0 1}
+[!0&1] 5 {0 2}
+[t] 6
+State: 6
+[!0&1] 6 {0 2}
+[0&1] 7 {0 1}
+State: 7
+[!0&1] 6 {0 1}
+[0&1] 7 {0 2}
+--END--
+EOF
+diff expected.hoa out.hoa

src/tests/unambig.test

@@ -95,6 +95,54 @@ State: 1
 [0] 1 {0}
 [!0] 1
 --END--
+HOA: v1
+States: 3
+Start: 0
+AP: 2 "b" "a"
+Acceptance: 4 (Fin(1) & Inf(2)) | (Fin(0) & Inf(3))
+properties: trans-labels explicit-labels trans-acc complete
+--BODY--
+State: 0
+[!0&!1] 1 {1}
+[0&!1] 0 {1 3}
+[!0&1] 1 {2}
+[0&1] 0 {2 3}
+State: 1
+[!0&!1] 2 {1}
+[0&!1] 2 {1 3}
+[!0&1] 1 {2}
+[0&1] 1 {2 3}
+State: 2
+[!0&!1] 2 {1}
+[0&!1] 2 {1 3}
+[!0&1] 2 {1}
+[0&1] 2 {1 3}
+[!0] 0  /* extra transition */
+--END--
+HOA: v1
+States: 3
+Start: 0
+Start: 2 /* extra initial state */
+AP: 2 "b" "a"
+Acceptance: 4 (Fin(1) & Inf(2)) | (Fin(0) & Inf(3))
+properties: trans-labels explicit-labels trans-acc complete
+--BODY--
+State: 0
+[!0&!1] 1 {1}
+[0&!1] 0 {1 3}
+[!0&1] 1 {2}
+[0&1] 0 {2 3}
+State: 1
+[!0&!1] 2 {1}
+[0&!1] 2 {1 3}
+[!0&1] 1 {2}
+[0&1] 1 {2 3}
+State: 2
+[!0&!1] 2 {1}
+[0&!1] 2 {1 3}
+[!0&1] 2 {1}
+[0&1] 2 {1 3}
+--END--
 EOF
 
 run 1 $autfilt -q --is-unambiguous input

src/twaalgos/dotty.cc

@@ -478,6 +478,8 @@ namespace spot
 	start();
 	if (si)
 	  {
+	    si->determine_unknown_acceptance();
+
 	    unsigned sccs = si->scc_count();
 	    for (unsigned i = 0; i < sccs; ++i)
 	      {
@@ -493,6 +495,8 @@ namespace spot
 		else if (si->is_rejecting_scc(i))
 		  os_ << "  color=red\n";
 		else
+		  // May only occur if the call to
+		  // determine_unknown_acceptance() above is removed.
 		  os_ << "  color=orange\n";
 
 		if (name_ || opt_show_acc_)

src/twaalgos/sccfilter.cc

@@ -264,6 +264,7 @@ namespace spot
       scc_info* si = given_si;
       if (!si)
 	si = new scc_info(aut);
+      si->determine_unknown_acceptance();
 
       F filter(si, std::forward<Args>(args)...);
 

src/twaalgos/sccfilter.hh

@@ -1,6 +1,6 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2009, 2010, 2012, 2013, 2014 Laboratoire de Recherche et
+// Copyright (C) 2009, 2010, 2012, 2013, 2014, 2015 Laboratoire de
-// Developpement de l'Epita (LRDE).
+// Recherche et Developpement de l'Epita (LRDE).
 //
 // This file is part of Spot, a model checking library.
 //
@@ -35,16 +35,16 @@ namespace spot
   /// dead SCCs (i.e. SCC that are not accepting, and those with no
   /// exit path leading to an accepting SCC).
   ///
-  /// Additionally, this will try to remove useless acceptance
+  /// Additionally, for Generalized Büchi acceptance, this will try to
-  /// conditions.  This operation may diminish the number of
+  /// remove useless acceptance conditions.  This operation may
-  /// acceptance condition of the automaton (for instance when two
+  /// diminish the number of acceptance condition of the automaton
-  /// acceptance conditions are always used together we only keep one)
+  /// (for instance when two acceptance conditions are always used
-  /// but it will never remove all acceptance conditions, even if it
+  /// together we only keep one) but it will never remove all
-  /// would be OK to have zero.
+  /// acceptance conditions, even if it would be OK to have zero.
   ///
-  /// Acceptance conditions on transitions going to non-accepting SCC
+  /// Acceptance conditions on transitions going to rejecting SCCs are
-  /// are all removed.  Acceptance conditions going to an accepting
+  /// all removed.  Acceptance conditions going to an accepting SCC
-  /// SCC and coming from another SCC are only removed if \a
+  /// and coming from another SCC are only removed if \a
   /// remove_all_useless is set.  The default value of \a
   /// remove_all_useless is \c false because some algorithms (like the
   /// degeneralization) will work better if transitions going to an
@@ -53,7 +53,7 @@ namespace spot
   /// If \a given_sm is supplied, the function will use its result
   /// without computing a map of its own.
   ///
-  /// \warning Calling scc_filter on a TGBA that has the SBA property
+  /// \warning Calling scc_filter on a TωA that has the SBA property
   /// (i.e., transitions leaving accepting states are all marked as
   /// accepting) may destroy this property.  Use scc_filter_states()
   /// instead.
@@ -63,10 +63,10 @@ namespace spot
 
   /// \brief Prune unaccepting SCCs.
   ///
-  /// This is an abridged version of scc_filter(), that only remove
+  /// This is an abridged version of scc_filter(), that only removes
   /// useless states, without touching at the acceptance conditions.
   ///
-  /// Especially, if the input TGBA has the SBA property, (i.e.,
+  /// Especially, if the input TωA has the SBA property, (i.e.,
   /// transitions leaving accepting states are all marked as
   /// accepting), then the output TGBA will also have that property.
   SPOT_API twa_graph_ptr

src/twaalgos/sccinfo.cc

@@ -22,6 +22,7 @@
 #include <algorithm>
 #include <queue>
 #include "twa/bddprint.hh"
+#include "twaalgos/mask.hh"
 #include "misc/escape.hh"
 
 namespace spot
@@ -225,16 +226,23 @@ namespace spot
 	root_.front().node.trivial_ = false;
       }
 
+    determine_usefulness();
+  }
+
+  void scc_info::determine_usefulness()
+  {
     // An SCC is useful if it is not rejecting or it has a successor
     // SCC that is useful.
     unsigned scccount = scc_count();
     for (unsigned i = 0; i < scccount; ++i)
       {
+
 	if (!node_[i].is_rejecting())
 	  {
 	    node_[i].useful_ = true;
 	    continue;
 	  }
+	node_[i].useful_ = false;
 	for (auto j: node_[i].succ())
 	  if (node_[j.dst].is_useful())
 	    {
@@ -295,6 +303,29 @@ namespace spot
     return support;
   }
 
+  void scc_info::determine_unknown_acceptance()
+  {
+    std::vector<bool> k;
+    unsigned n = scc_count();
+    bool changed = false;
+    for (unsigned s = 0; s < n; ++s)
+      if (!is_rejecting_scc(s) && !is_accepting_scc(s))
+	{
+	  auto& node = node_[s];
+	  if (k.empty())
+	    k.resize(aut_->num_states());
+	  for (auto i: node.states_)
+	    k[i] = true;
+	  if (mask_keep_states(aut_, k, node.states_.front())->is_empty())
+	    node.rejecting_ = true;
+	  else
+	    node.accepting_ = true;
+	  changed = true;
+	}
+    if (changed)
+      determine_usefulness();
+  }
+
   std::ostream&
   dump_scc_info_dot(std::ostream& out,
 		    const_twa_graph_ptr aut, scc_info* sccinfo)

src/twaalgos/sccinfo.hh

@@ -58,7 +58,8 @@ namespace spot
       }
 
       scc_node(acc_cond::mark_t acc, bool trivial):
-	acc_(acc), trivial_(trivial), accepting_(false), useful_(false)
+	acc_(acc), trivial_(trivial), accepting_(false),
+	rejecting_(false), useful_(false)
       {
       }
 
@@ -112,6 +113,8 @@ namespace spot
     std::vector<scc_node> node_;
     const_twa_graph_ptr aut_;
 
+    // Update the useful_ bits.  Called automatically.
+    void determine_usefulness();
 
     const scc_node& node(unsigned scc) const
     {
@@ -198,6 +201,10 @@ namespace spot
       return node(scc).is_rejecting();
     }
 
+    // Study the SCC that are currently reported neither as accepting
+    // nor rejecting because of the presence of Fin sets
+    void determine_unknown_acceptance();
+
     bool is_useful_scc(unsigned scc) const
     {
       return node(scc).is_useful();