safra: Edges to accepting SCC are accepting

*  src/twaalgos/safra.cc, src/twaalgos/safra.hh: Implement optimisation.
Update function calls with new API.
* src/tests/safra.cc, src/tests/safra.test: Use new API.

src/tests/safra.cc

@@ -20,14 +20,14 @@
 #include <iostream>
 #include <cstring>
 
+#include "ltlparse/public.hh" // ltl::parse
+#include "parseaut/public.hh"
 #include "twa/twagraph.hh"
+#include "twaalgos/degen.hh"
+#include "twaalgos/dot.hh" // print_dot
+#include "twaalgos/hoa.hh" // print_hoa
 #include "twaalgos/safra.hh"
 #include "twaalgos/translate.hh"
-#include "hoaparse/public.hh"
-#include "ltlparse/public.hh"
-#include "twaalgos/dotty.hh"
-#include "twaalgos/hoa.hh"
-#include "twaalgos/degen.hh"
 
 
 int help()
@@ -37,11 +37,14 @@ int help()
   std::cerr << "\t--hoa file.hoa\tinput file has hoa format\n";
   std::cerr << "\t-p\tpretty print states\n";
   std::cerr << "\t-H\toutput hoa format\n";
+  std::cerr << "\t-b\treduce result using bisimulation\n";
+  std::cerr << "\t--emit_scc\ttransitions to accpting scc are accepting\n";
   return 1;
 }
 
 int main(int argc, char* argv[])
 {
+  bool emit_scc = false;
   bool sim = false;
   bool in_hoa = false;
   bool in_ltl = false;
@@ -77,6 +80,8 @@ int main(int argc, char* argv[])
         pretty_print = true;
       else if (!strncmp(argv[i], "-b", 2))
         sim = true;
+      else if (!strncmp(argv[i], "--emit_scc", 2))
+        emit_scc = true;
     }
 
   if (!input)
@@ -88,33 +93,32 @@ int main(int argc, char* argv[])
     {
       spot::ltl::parse_error_list pel;
       const spot::ltl::formula* f =
-      spot::ltl::parse(input, pel, spot::ltl::default_environment::instance(),
+      spot::ltl::parse_infix_psl(input, pel);
-                       false);
       if (spot::ltl::format_parse_errors(std::cerr, input, pel))
         return 2;
       spot::translator trans(dict);
       trans.set_pref(spot::postprocessor::Deterministic);
       auto tmp = trans.run(f);
-      res = spot::tgba_determinisation(tmp, sim, pretty_print);
+      res = spot::tgba_determinisation(tmp, sim, pretty_print, emit_scc);
       f->destroy();
     }
   else if (in_hoa)
     {
-      spot::hoa_parse_error_list pel;
+      spot::parse_aut_error_list pel;
-      auto aut = spot::hoa_parse(input, pel, dict);
+      auto aut = spot::parse_aut(input, pel, dict);
-      if (spot::format_hoa_parse_errors(std::cerr, input, pel))
+      if (spot::format_parse_aut_errors(std::cerr, input, pel))
         return 2;
-      res = tgba_determinisation(aut->aut, sim, pretty_print);
+      res = tgba_determinisation(aut->aut, sim, pretty_print, emit_scc);
     }
-  res->merge_transitions();
+  res->merge_edges();
 
   if (out_hoa)
     {
-      spot::hoa_reachable(std::cout, res, "t");
+      spot::print_hoa(std::cout, res, "t");
       std::cout << std::endl;
     }
   else if (out_dot)
-    spot::dotty_reachable(std::cout, res);
+    spot::print_dot(std::cout, res);
   else
     assert(false);
 }

src/tests/safra.test

@@ -87,7 +87,7 @@ EOF
 
 cat >out.exp << EOF
 HOA: v1
-States: 6
+States: 5
 Start: 0
 AP: 2 "a" "b"
 acc-name: Buchi
@@ -101,9 +101,9 @@ State: 1
 [0&1] 2
 [!0&1] 3 {0}
 State: 2
+[0&1] 1 {0}
 [!0&1] 3 {0}
 [0&!1] 4
-[0&1] 5
 State: 3
 [0&!1] 0
 [0&1] 2
@@ -111,15 +111,52 @@ State: 3
 State: 4
 [0] 1 {0}
 [!0&1] 3 {0}
-State: 5
-[0] 1 {0}
-[!0&1] 3 {0}
 --END--
 EOF
 
 run 0 ../safra --hoa double_b.hoa -H > out.hoa
 diff out.hoa out.exp
 
+# Test emit_scc optim
+cat > out.exp << EOF
+HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels trans-acc deterministic
+--BODY--
+State: 0 "{₀0₀}"
+[0] 1 {0}
+State: 1 "{₀0 1₀}"
+[0] 1 {0}
+[!0&1] 2 {0}
+State: 2 "{₀1₀}"
+[1] 2 {0}
+[0&!1] 2
+--END--
+EOF
+
+cat > in.hoa << EOF
+HOA: v1
+States: 2
+Start: 0
+AP: 2 "a" "b"
+Acceptance: 1 Inf(0)
+--BODY--
+State: 0
+[0] 0 {0}
+[0] 1
+State: 1
+[1] 1 {0}
+[0] 1
+--END--
+EOF
+
+run 0 ../safra --hoa in.hoa --emit_scc -p -H > out.hoa
+diff out.hoa out.exp
+
 # Formulas from bench/dtgbasat/formulas
 cat >formulae <<EOF
 X((a M F((!c & !b) | (c & b))) W (G!c U b))

src/twaalgos/safra.cc

@@ -24,6 +24,7 @@
 
 #include "safra.hh"
 #include "twaalgos/degen.hh"
+#include "twaalgos/sccinfo.hh"
 #include "twaalgos/simulation.hh"
 
 namespace spot
@@ -141,7 +142,7 @@ namespace spot
     {
       assert(max_acc < 32);
       unsigned mask = (1 << max_acc) - 1;
-      for (auto& t: aut->transitions())
+      for (auto& t: aut->edges())
         {
           t.acc &= mask;
         }
@@ -166,26 +167,30 @@ namespace spot
     }
 
   }
-  auto
+
+  void
   safra_state::compute_succs(const const_twa_graph_ptr& aut,
                              const std::vector<unsigned>& bddnums,
                              std::unordered_map<bdd,
                                              std::pair<unsigned, unsigned>,
-                                             bdd_hash>& deltas) const -> succs_t
+                                             bdd_hash>& deltas,
+                              succs_t& res) const
   {
-    succs_t res;
     // Given a bdd returns index of associated safra_state in res
     std::map<unsigned, unsigned> bdd2num;
     for (auto& node: nodes_)
       {
         for (auto& t: aut->out(node.first))
           {
+            // deltas precalculate all transitions in edge t
             auto p = deltas[t.cond];
             for (unsigned j = p.first; j < p.second; ++j)
               {
                 auto i = bdd2num.insert(std::make_pair(bddnums[j], res.size()));
                 unsigned idx;
                 if (!i.second)
+                  // No new state added, so get pre-existing state whichi is an
+                  // index in the vector of safra states (res)
                   idx = i.first->second;
                 else
                   {
@@ -203,9 +208,17 @@ namespace spot
     for (auto& s: res)
       {
         safra_state& tmp = s.first;
+        tmp.ungreenify_last_brace();
         s.first.color_ = tmp.finalize_construction();
       }
-    return res;
+  }
+
+  void safra_state::ungreenify_last_brace()
+  {
+    // Step A4: For a brace to emit green it must surround other braces.
+    // Hence, the last brace cannot emit green as it is the most inside brace.
+    for (auto& n: nodes_)
+        is_green_[n.second.back()] = false;
   }
 
   unsigned safra_state::finalize_construction()
@@ -218,7 +231,7 @@ namespace spot
       {
         if (nb_braces_[i] == 0)
           {
-            // It is impossible to emit red == -1 as those transitions would
+            // It is impossible to emit red == -1 as those edges would
             // lead us in a sink states which are not created here.
             assert(i >= 1);
             red = std::min(red, 2 * i - 1);
@@ -301,12 +314,10 @@ namespace spot
                                 unsigned dst, const acc_cond::mark_t acc)
   {
     std::vector<node_helper::brace_t> copy = braces;
-    // TODO handle multiple accepting sets
     if (acc.count())
       {
-        assert(acc.has(0) && acc.count() == 1 &&
+        assert(acc.has(0) && acc.count() == 1 && "Only one TBA are accepted");
-               "Only one TBA are accepted at the moment");
+        // Accepting edge generate new braces: step A1
-        // Accepting transition generate new braces: step A1
         copy.emplace_back(nb_braces_.size());
         // nb_braces_ gets updated later so put 0 for now
         nb_braces_.emplace_back(0);
@@ -333,9 +344,6 @@ namespace spot
     // After inserting new node, update the brace count per node
     for (auto b: i.first->second)
       ++nb_braces_[b];
-    // Step A4: For a brace to emit green it must surround other braces.
-    // Hence, the last brace cannot emit green as it is the most inside brace.
-    is_green_[i.first->second.back()] = false;
   }
 
   // Called only to initialize first state
@@ -367,16 +375,32 @@ namespace spot
     return nodes_ < other.nodes_;
   }
 
+  // All edge going into an accepting SCC are marked as accepting
+  // This helps safra make fewer trees as we immediately see the accepting
+  // edge and don't create useless states
+  void
+  emit_accepting_scc(twa_graph_ptr& aut, scc_info& scc)
+  {
+    for (auto& e: aut->edges())
+      {
+        unsigned src_scc = scc.scc_of(e.src);
+        unsigned dst_scc = scc.scc_of(e.dst);
+        if (src_scc == dst_scc)
+          continue;
+        if (scc.is_accepting_scc(dst_scc))
+          e.acc |= 1;
+      }
+  }
+
   twa_graph_ptr
   tgba_determinisation(const const_twa_graph_ptr& a, bool bisimulation,
-                       bool pretty_print)
+                       bool pretty_print, bool emit_scc)
   {
     // Degeneralize
-    const_twa_graph_ptr aut;
+    twa_graph_ptr aut = spot::degeneralize_tba(a);
-    if (a->acc().is_generalized_buchi())
+    scc_info scc = scc_info(aut);
-      aut = spot::degeneralize_tba(a);
+    if (emit_scc)
-    else
+      emit_accepting_scc(aut, scc);
-      aut = a;
 
 
     bdd allap = bddtrue;
@@ -384,7 +408,7 @@ namespace spot
       typedef std::set<bdd, bdd_less_than> sup_map;
       sup_map sup;
       // Record occurrences of all guards
-      for (auto& t: aut->transitions())
+      for (auto& t: aut->edges())
         sup.emplace(t.cond);
       for (auto& i: sup)
         allap &= bdd_support(i);
@@ -398,7 +422,7 @@ namespace spot
     // Used to convert large bdd to indexes
     std::unordered_map<bdd, std::pair<unsigned, unsigned>, bdd_hash> deltas;
     std::vector<unsigned> bddnums;
-    for (auto& t: aut->transitions())
+    for (auto& t: aut->edges())
       {
         auto it = deltas.find(t.cond);
         if (it == deltas.end())
@@ -428,7 +452,7 @@ namespace spot
                    });
 
     // Given a safra_state get its associated state in output automata.
-    // Required to create new transitions from 2 safra-state
+    // Required to create new edges from 2 safra-state
     power_set seen;
     safra_state init(aut->get_init_state_number(), true);
     unsigned num = res->new_state();
@@ -437,13 +461,14 @@ namespace spot
     std::deque<safra_state> todo;
     todo.push_back(init);
     unsigned sets = 0;
+    using succs_t = safra_state::succs_t;
+    succs_t succs;
     while (!todo.empty())
       {
-        using succs_t = safra_state::succs_t;
         safra_state curr = todo.front();
         unsigned src_num = seen.find(curr)->second;
         todo.pop_front();
-        succs_t succs = curr.compute_succs(aut, bddnums, deltas);
+        curr.compute_succs(aut, bddnums, deltas, succs);
         for (auto s: succs)
           {
             auto i = seen.find(s.first);
@@ -461,15 +486,16 @@ namespace spot
               }
             if (s.first.color_ != -1U)
               {
-                res->new_transition(src_num, dst_num, num2bdd[s.second],
+                res->new_edge(src_num, dst_num, num2bdd[s.second],
                                     {s.first.color_});
                 // We only care about green acc
                 if (s.first.color_ % 2 == 0)
                   sets = std::max(s.first.color_ + 1, sets);
               }
             else
-              res->new_transition(src_num, dst_num, num2bdd[s.second]);
+              res->new_edge(src_num, dst_num, num2bdd[s.second]);
           }
+        succs.clear();
       }
     remove_dead_acc(res, sets);
     res->set_acceptance(sets, acc_cond::acc_code::parity(false, false, sets));

src/twaalgos/safra.hh

@@ -47,11 +47,14 @@ namespace spot
     safra_state(unsigned state_number, bool init_state = false);
     // Given a certain transition_label, compute all the successors of that
     // label, and return that new node.
-    succs_t compute_succs(const const_twa_graph_ptr& aut,
+    void compute_succs(const const_twa_graph_ptr& aut,
                           const std::vector<unsigned>& bddnums,
                           std::unordered_map<bdd,
                                              std::pair<unsigned, unsigned>,
-                                             bdd_hash>& deltas) const;
+                                             bdd_hash>& deltas,
+                           succs_t& res) const;
+    // The outermost brace of each node cannot be green
+    void ungreenify_last_brace();
     // Used when creating the list of successors
     // A new intermediate node is created with  src's braces and with dst as id
     // A merge is done if dst already existed in *this
@@ -74,5 +77,6 @@ namespace spot
   SPOT_API twa_graph_ptr
   tgba_determinisation(const const_twa_graph_ptr& aut,
                        bool bisimulation = false,
-                       bool pretty_print = false);
+                       bool pretty_print = false,
+                       bool emit_scc = false);
 }