safra: Add stutter-invarience optimisation

* spot/twaalgos/safra.cc, spot/twaalgos/safra.hh: Here.
* tests/core/safra.cc: Add option.

spot/twaalgos/safra.cc

@@ -240,15 +240,44 @@ safra_state::compute_succs(const const_twa_graph_ptr& aut,
                            std::unordered_map<bdd, unsigned, bdd_hash>& bdd2num,
                            std::vector<bdd>& all_bdds,
                            bool scc_opt,
-                           bool use_bisimulation) const
+                           bool use_bisimulation,
+                           bool use_stutter) const
 {
   for (auto& ap: all_bdds)
     {
-      safra_state ss = compute_succ(aut, ap, scc, implications, is_connected,
-                                    scc_opt, use_bisimulation);
+      safra_state ss = *this;
+
+      if (use_stutter && aut->prop_stutter_invariant())
+        {
+          std::vector<color_t> colors;
+          unsigned int counter = 0;
+          std::map<safra_state, unsigned int> safra2id;
+          bool stop = false;
+          while (!stop)
+            {
+              auto pair = safra2id.insert({ss, counter++});
+              // insert should never fail
+              assert(pair.second);
+              ss = ss.compute_succ(aut, ap, scc, implications, is_connected,
+                                   scc_opt, use_bisimulation);
+              colors.push_back(ss.color_);
+              stop = safra2id.find(ss) != safra2id.end();
+            }
+          // Add color of final transition that loops back
+          colors.push_back(ss.color_);
+          unsigned int loop_start = safra2id[ss];
+          for (auto& min: safra2id)
+            {
+              if (min.second >= loop_start && ss < min.first)
+                ss = min.first;
+            }
+          ss.color_ = *std::min_element(colors.begin(), colors.end());
+        }
+      else
+        ss = compute_succ(aut, ap, scc, implications, is_connected,
+                          scc_opt, use_bisimulation);
       unsigned bdd_idx = bdd2num[ap];
       res.emplace_back(ss, bdd_idx);
-
     }
 }
 
@@ -455,6 +484,18 @@ safra_state::compute_succs(const const_twa_graph_ptr& aut,
   bool
   safra_state::operator<(const safra_state& other) const
   {
+    if (nodes_ == other.nodes_)
+      {
+        for (auto& n: nodes_)
+          {
+            auto it = other.nodes_.find(n.first);
+            assert(it != other.nodes_.end());
+            if (nesting_cmp(n.second, it->second))
+              return true;
+          }
+        return false;
+      }
+
     return nodes_ < other.nodes_;
   }
 
@@ -487,7 +528,7 @@ safra_state::compute_succs(const const_twa_graph_ptr& aut,
   twa_graph_ptr
   tgba_determinisation(const const_twa_graph_ptr& a, bool bisimulation,
                        bool pretty_print, bool scc_opt, bool use_bisimulation,
-                       bool complete)
+                       bool complete, bool use_stutter)
   {
     // Degeneralize
     twa_graph_ptr aut = spot::degeneralize_tba(a);
@@ -569,11 +610,12 @@ safra_state::compute_succs(const const_twa_graph_ptr& aut,
         unsigned src_num = seen.find(curr)->second;
         todo.pop_front();
         curr.compute_succs(aut, succs, scc, implications, is_connected,
-                           bdd2num, num2bdd, scc_opt, use_bisimulation);
+                           bdd2num, num2bdd, scc_opt, use_bisimulation,
+                           use_stutter);
         for (auto s: succs)
           {
             // Don't construct sink state as complete does a better job at this
-            if (s.first.nodes_.size() == 0)
+            if (s.first.nodes_.empty())
               continue;
             auto i = seen.find(s.first);
 	    unsigned dst_num;

spot/twaalgos/safra.hh

@@ -63,7 +63,8 @@ namespace spot
                   std::unordered_map<bdd, unsigned, bdd_hash>& bdd2num,
                   std::vector<bdd>& all_bdds,
                   bool scc_opt,
-                  bool use_bisimulation) const;
+                  bool use_bisimulation,
+                  bool use_stutter) const;
     // Compute successor for transition ap
     safra_state
     compute_succ(const const_twa_graph_ptr& aut,
@@ -107,5 +108,6 @@ namespace spot
                        bool pretty_print = false,
                        bool scc_opt = false,
                        bool use_bisimulation = false,
-                       bool complete = false);
+                       bool complete = false,
+                       bool use_stutter = false);
 }

tests/core/safra.cc

@@ -41,6 +41,9 @@ int help()
   std::cerr << "\t-H\toutput hoa format\n";
   std::cerr << "\t-b\treduce result using bisimulation\n";
   std::cerr << "\t--scc_opt\tUse an SCC-based Safra\n";
+  std::cerr << "\t--bisim_opt\tUse Simulation info to reduce macro-states "
+               "size\n";
+  std::cerr << "\t--stutter\tStutter-invarience optimisation\n";
   return 1;
 }
 
@@ -55,6 +58,7 @@ int main(int argc, char* argv[])
   bool out_hoa = false;
   bool pretty_print = false;
   bool complete = false;
+  bool use_stutter = false;
 
   char* input = nullptr;
   if (argc <= 2)
@@ -90,6 +94,8 @@ int main(int argc, char* argv[])
         scc_opt = true;
       else if (!strncmp(argv[i], "--bisim_opt", 10))
         use_bisim = true;
+      else if (!strncmp(argv[i], "--stutter", 9))
+        use_stutter = true;
       else
         {
           std::cerr << "Warning: " << argv[i] << " not used\n";
@@ -112,7 +118,7 @@ int main(int argc, char* argv[])
       trans.set_pref(spot::postprocessor::Deterministic);
       auto tmp = trans.run(f);
       res = spot::tgba_determinisation(tmp, sim, pretty_print, scc_opt,
-                                       use_bisim, complete);
+                                       use_bisim, complete, use_stutter);
     }
   else if (in_hoa)
     {
@@ -120,7 +126,7 @@ int main(int argc, char* argv[])
       if (aut->format_errors(std::cerr))
         return 2;
       res = tgba_determinisation(aut->aut, sim, pretty_print, scc_opt,
-                                 use_bisim, complete);
+                                 use_bisim, complete, use_stutter);
     }
   res->merge_edges();