Add an algorithm (from Couvreur) working on BDDs to reduce the

size of TGBAs represented as BDDs by deleting unaccepting SCCs.

* src/eltlparse/eltlparse.yy: Remove a warning.
* src/tgba/tgbabddconcrete.cc, src/tgba/tgbabddconcrete.hh,
src/tgba/tgbabddcoredata.cc, src/tgba/tgbabddcoredata.hh: Add a
new function delete_unaccepting_scc in both classes.
* src/tgbatest/eltl2tgba.cc, src/tgbatest/spotlbtt.test: Use this
new function in LaCIM for ELTL and bench it.
* src/tgbatest/defs.in: Fix it.
* bench/ltl2tgba/algorithms, bench/ltl2tgba/defs.in: Add LaCIM for
ELTL in benchs.

src/tgba/tgbabddconcrete.cc

@@ -164,4 +164,11 @@ namespace spot
     return data_;
   }
 
+  void
+  tgba_bdd_concrete::delete_unaccepting_scc()
+  {
+    data_.delete_unaccepting_scc(init_);
+    set_init_state(init_);
+  }
+
 }

src/tgba/tgbabddconcrete.hh

@@ -79,6 +79,10 @@ namespace spot
     virtual bdd all_acceptance_conditions() const;
     virtual bdd neg_acceptance_conditions() const;
 
+    /// \brief Delete SCCs (Strongly Connected Components) from the
+    /// TGBA which cannot be accepting.
+    void delete_unaccepting_scc();
+
   protected:
     virtual bdd compute_support_conditions(const state* state) const;
     virtual bdd compute_support_variables(const state* state) const;

src/tgba/tgbabddcoredata.cc

@@ -130,4 +130,67 @@ namespace spot
     acc_set &= acc;
     negacc_set &= !acc;
   }
+
+  void
+  tgba_bdd_core_data::delete_unaccepting_scc(bdd init)
+  {
+    bdd er = bdd_exist(relation, var_set); /// existsRelation
+    bdd s0 = bddfalse;
+    bdd s1 = bdd_exist(bdd_exist(init & relation, var_set), now_set);
+    s1 = bdd_replace(s1, dict->next_to_now);
+
+    /// Find all reachable states
+    while (s0 != s1)
+    {
+      s0 = s1;
+      /// Compute s1 = succ(s0) | s
+      s1 = bdd_replace(bdd_exist(s0 & er, now_set), dict->next_to_now) | s0;
+    }
+
+    /// Find states which can be visited infinitely often while seeing
+    /// all acceptance conditions
+    s0 = bddfalse;
+    while (s0 != s1)
+    {
+      s0 = s1;
+      bdd all = all_acceptance_conditions;
+      while (all != bddfalse)
+      {
+	bdd next = bdd_satone(all);
+	all -= next;
+	s1 = infinitely_often(s1, next, er);
+      }
+    }
+
+    relation = s0 & (relation & bdd_replace(s0, dict->now_to_next));
+  }
+
+  bdd
+  tgba_bdd_core_data::infinitely_often(bdd s, bdd acc, bdd er)
+  {
+    bdd ar = acc & (relation & acceptance_conditions); /// accRelation
+    bdd s0 = bddfalse;
+    bdd s1 = s;
+
+    while (s0 != s1)
+    {
+      s0 = s1;
+      bdd as = bdd_replace(s0, dict->now_to_next) & ar;
+      as = bdd_exist(bdd_exist(as, next_set), var_set) & s0;
+
+      /// Do predStar
+      bdd s0_ = bddfalse;
+      bdd s1_ = bdd_exist(as, acc_set);
+      while (s0_ != s1_)
+      {
+	s0_ = s1_;
+	/// Compute s1_ = pred(s0_) | s0_
+	s1_ = bdd_exist(er & bdd_replace(s0_, dict->now_to_next), next_set);
+	s1_ = (s1_ & s0) | s0_;
+      }
+      s1 = s0_;
+    }
+
+    return s0;
+  }
 }

src/tgba/tgbabddcoredata.hh

@@ -142,6 +142,13 @@ namespace spot
     /// \brief Update the variable sets to take a new acceptance condition
     /// into account.
     void declare_acceptance_condition(bdd prom);
+
+    /// \brief Delete SCCs (Strongly Connected Components) from the
+    /// relation which cannot be accepting.
+    void delete_unaccepting_scc(bdd init);
+
+  private:
+    bdd infinitely_often(bdd s, bdd acc, bdd er);
   };
 }