symplify_acceptance: More rules

Fixes #297. Implement the following rules.

Fin(i) & Fin(j) by f if i and j are complementary
Fin(i) & Inf(i) by f
Inf(i) | Inf(j) by t if i and j are complementary
Fin(i) | Inf(i) by t.

* spot/twaalgos/cleanacc.cc, spot/twaalgos/cleanacc.hh: Here.
* tests/python/merge.py: Add more test cases.
* NEWS: Mention the change.

NEWS

@@ -160,6 +160,16 @@ New in spot 2.4.1.dev (not yet released)
     conditions.   The fmt parameter specify the format to use for that
     name (e.g. to the style used in HOA, or that used by print_dot()).
 
+  - spot::simplify_acceptance() was already merging identical acceptance
+    sets, and detecting complementary sets i and j to perform the following
+    simplifications
+      Fin(i) & Inf(j) = Fin(i)
+      Fin(i) | Inf(j) = Inf(i)
+    It now additionally applies the following rules (again assuming i
+    and j are complementary):
+      Fin(i) & Fin(j) = f          Inf(i) | Inf(j) = t
+      Fin(i) & Inf(i) = f          Fin(i) | Inf(i) = t
+
   Deprecation notices:
 
   (These functions still work but compilers emit warnings.)

spot/twaalgos/cleanacc.cc

@@ -174,6 +174,8 @@ namespace spot
                 {
                   auto tmp = remove_compl_rec(pos, complement);
 
+                  if (!tmp.empty())
+                    {
                       if (tmp.back().sub.op == acc_cond::acc_op::Fin
                           && tmp.front().mark.count() == 1)
                         seen_fin |= tmp.front().mark;
@@ -184,14 +186,25 @@ namespace spot
                           pos -= pos->sub.size + 1;
                           continue;
                         }
+                    }
                   tmp &= std::move(res);
                   std::swap(tmp, res);
                   pos -= pos->sub.size + 1;
                 }
               while (pos > start);
 
+              // Fin(i) & Inf(i) = f;
+              if (inf.front().mark & seen_fin)
+                return acc_cond::acc_code::f();
               for (auto m: seen_fin.sets())
+                {
+                  acc_cond::mark_t cm = complement[m];
+                  // Fin(i) & Fin(!i) = f;
+                  if (cm & seen_fin)
+                    return acc_cond::acc_code::f();
+                  // Inf({!i}) & Fin({i}) = Fin({i})
                   inf.front().mark -= complement[m];
+                }
 
               return inf & res;
             }
@@ -205,6 +218,8 @@ namespace spot
                 {
                   auto tmp = remove_compl_rec(pos, complement);
 
+                  if (!tmp.empty())
+                    {
                       if (tmp.back().sub.op == acc_cond::acc_op::Inf
                           && tmp.front().mark.count() == 1)
                         seen_inf |= tmp.front().mark;
@@ -215,15 +230,25 @@ namespace spot
                           pos -= pos->sub.size + 1;
                           continue;
                         }
+                    }
                   tmp |= std::move(res);
                   std::swap(tmp, res);
                   pos -= pos->sub.size + 1;
                 }
               while (pos > start);
 
+              // Fin(i) | Inf(i) = t;
+              if (fin.front().mark & seen_inf)
+                return acc_cond::acc_code::t();
               for (auto m: seen_inf.sets())
+                {
+                  acc_cond::mark_t cm = complement[m];
+                  // Inf({i}) | Inf({!i}) = t;
+                  if (cm & seen_inf)
+                    return acc_cond::acc_code::t();
+                  // Fin({!i}) | Inf({i}) = Inf({i})
                   fin.front().mark -= complement[m];
-
+                }
               return res | fin;
             }
           case acc_cond::acc_op::Fin:

spot/twaalgos/cleanacc.hh

@@ -23,28 +23,48 @@
 
 namespace spot
 {
+  /// \ingroup twa_algorithms
   /// \brief Remove useless acceptance sets
   ///
+  /// This removes from the automaton the acceptance marks that are
+  /// not used in the acceptance condition.  This also removes from
+  /// the acceptance conditions the terms that corresponds to empty
+  /// or full sets.
+  ///
   /// If \a strip is true (the default), the remaining acceptance set
   /// numbers will be shifted down to reduce maximal number of
   /// acceptance sets used.
   SPOT_API twa_graph_ptr
   cleanup_acceptance_here(twa_graph_ptr aut, bool strip = true);
 
+  /// \ingroup twa_algorithms
   /// \brief Remove useless acceptance sets
+  ///
+  /// This removes from the automaton the acceptance marks that are
+  /// not used in the acceptance condition.  This also removes from
+  /// the acceptance conditions the terms that corresponds to empty
+  /// or full sets.
+  ///
   SPOT_API twa_graph_ptr
   cleanup_acceptance(const_twa_graph_ptr aut);
 
+  /// @{
+  /// \ingroup twa_algorithms
   /// \brief Simplify an acceptance condition
   ///
-  /// Remove useless acceptance sets.
+  /// Does evereything cleanup_acceptance() does, but additionally:
-  /// Merge identical sets.
+  /// merge identical sets, detect whether to sets i and j are
-  /// If some sets are complement to each other, might result in the
+  /// complementary to apply the following reductions:
-  /// simplification of some clause in the acceptance condition.
+  ///   - `Fin(i) & Inf(j) = Fin(i)`
+  ///   - `Fin(i) & Fin(j) = f`
+  ///   - `Fin(i) & Inf(i) = f`
+  ///   - `Fin(i) | Inf(j) = Inf(j)`
+  ///   - `Inf(i) | Inf(j) = t`
+  ///   - `Fin(i) | Inf(i) = t`
   SPOT_API twa_graph_ptr
   simplify_acceptance_here(twa_graph_ptr aut);
 
-  /// \brief Simplify an acceptance condition
   SPOT_API twa_graph_ptr
   simplify_acceptance(const_twa_graph_ptr aut);
+  /// @}
 }

tests/python/merge.py

@@ -113,16 +113,88 @@ assert hoa == """HOA: v1
 States: 3
 Start: 0
 AP: 2 "a" "b"
-Acceptance: 2 (Fin(0) & Inf(0)) | (Fin(1) & Inf(1))
+acc-name: none
+Acceptance: 0 f
+properties: trans-labels explicit-labels state-acc
+--BODY--
+State: 0
+[0] 1
+State: 1
+[0] 1
+[1] 2
+State: 2
+[1] 0
+--END--"""
+
+aut = spot.automaton("""
+HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+Acceptance: 4 (Inf(0) | Fin(1)) & (Inf(2) | Fin(3))
 properties: trans-labels explicit-labels trans-acc
 --BODY--
 State: 0
-[0] 1 {0}
+[0] 1 {0 1}
 State: 1
-[0] 1 {1}
+[0] 1 {2 3}
-[1] 2 {0 1}
+[1] 2 {0 1 3}
 State: 2
-[1] 0 {1}
+[1] 0 {2 3}
+--END--""")
+spot.simplify_acceptance_here(aut)
+hoa = aut.to_str('hoa')
+
+assert hoa == """HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+Acceptance: 2 Fin(1) | Inf(0)
+properties: trans-labels explicit-labels trans-acc
+--BODY--
+State: 0
+[0] 1
+State: 1
+[0] 1 {0 1}
+[1] 2 {1}
+State: 2
+[1] 0 {0 1}
+--END--"""
+
+aut = spot.automaton("""
+HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+Acceptance: 4 (Inf(0) | Fin(1)) & (Inf(2) | Fin(3))
+properties: trans-labels explicit-labels trans-acc
+--BODY--
+State: 0
+[0] 1 {0 1}
+State: 1
+[0] 1 {2 3}
+[1] 2 {0 1 2 3}
+State: 2
+[1] 0 {2 3}
+--END--""")
+spot.simplify_acceptance_here(aut)
+hoa = aut.to_str('hoa')
+
+assert hoa == """HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+acc-name: all
+Acceptance: 0 t
+properties: trans-labels explicit-labels state-acc
+--BODY--
+State: 0
+[0] 1
+State: 1
+[0] 1
+[1] 2
+State: 2
+[1] 0
 --END--"""
 
 aut = spot.automaton("""HOA: v1
@@ -645,3 +717,69 @@ State: 1
 [0] 1
 [!0] 0
 --END--"""
+
+aut = spot.automaton("""HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+Acceptance: 4 Fin(0) & Fin(1) & Inf(2)
+--BODY--
+State: 0
+[0] 1 {0}
+State: 1
+[0] 1 {1 2}
+[1] 2 {0 2}
+State: 2
+[1] 0 {1}
+--END--""")
+spot.simplify_acceptance_here(aut)
+hoa = aut.to_str('hoa')
+assert hoa == """HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+acc-name: none
+Acceptance: 0 f
+properties: trans-labels explicit-labels state-acc
+--BODY--
+State: 0
+[0] 1
+State: 1
+[0] 1
+[1] 2
+State: 2
+[1] 0
+--END--"""
+
+aut = spot.automaton("""HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+Acceptance: 4 Inf(0) | Inf(1) | Inf(2)
+--BODY--
+State: 0
+[0] 1 {0}
+State: 1
+[0] 1 {1 2}
+[1] 2 {0 2}
+State: 2
+[1] 0 {1}
+--END--""")
+spot.simplify_acceptance_here(aut)
+hoa = aut.to_str('hoa')
+assert hoa == """HOA: v1
+States: 3
+Start: 0
+AP: 2 "a" "b"
+acc-name: all
+Acceptance: 0 t
+properties: trans-labels explicit-labels state-acc
+--BODY--
+State: 0
+[0] 1
+State: 1
+[0] 1
+[1] 2
+State: 2
+[1] 0
+--END--"""