Remove do_simplify opt from split_2step

Removing this option to guarante that all arenas
are alternating

* spot/twaalgos/synthesis.hh: Here
* spot/twaalgos/synthesis.cc: Here
* spot/twaalgos/mealy_machine.cc: API change
* tests/python/aiger.py: API change
* tests/python/mealy.py: API change
* tests/python/split.py: API change

spot/twaalgos/mealy_machine.cc

@@ -507,7 +507,7 @@ namespace spot
     // Split if the initial aut was split
     if (orig_is_split)
       {
-        mmc = split_2step(mmc, outs, false, false);
+        mmc = split_2step(mmc, outs, false);
         bool orig_init_player =
             mm->get_named_prop<std::vector<bool>>("state-player")
                 ->at(mm->get_init_state_number());
@@ -582,7 +582,7 @@ namespace spot
     mm->purge_unreachable_states();
     if (orig_is_split)
       {
-        mm = split_2step(mm, outs, false, false);
+        mm = split_2step(mm, outs, false);
         alternate_players(mm, init_player, false);
         mm->set_named_prop("synthesis-outputs", new bdd(outs));
       }

spot/twaalgos/synthesis.cc

@@ -135,8 +135,7 @@ namespace spot
 {
   twa_graph_ptr
   split_2step(const const_twa_graph_ptr& aut,
-              const bdd& output_bdd, bool complete_env,
+              const bdd& output_bdd, bool complete_env)
-              bool do_simplify)
   {
     auto split = make_twa_graph(aut->get_dict());
     split->copy_ap_of(aut);
@@ -216,25 +215,6 @@ namespace spot
         e_cache.clear();
 
         auto out_cont = aut->out(src);
-        // Short-cut if we do not want to
-        // split the edges of nodes that have
-        // a single outgoing edge
-        if (do_simplify
-            && (++out_cont.begin()) == out_cont.end())
-          {
-            // "copy" the edge
-            const auto& e = *out_cont.begin();
-            split->new_edge(src, e.dst, e.cond, e.acc);
-            // Check if it needs to be completed
-            if (complete_env)
-              {
-                bdd missing = bddtrue - bdd_exist(e.cond, output_bdd);
-                if (missing != bddfalse)
-                  split->new_edge(src, get_sink_con_state(), missing);
-              }
-            // We are done for this state
-            continue;
-          }
 
         // Avoid looping over all minterms
         // we only loop over the minterms that actually exist
@@ -433,9 +413,11 @@ namespace spot
     out->copy_acceptance_of(aut);
     out->copy_ap_of(aut);
 
-    // split_2step is not guaranteed to produce
+    // split_2step is guaranteed to produce an alternating arena
-    // states that alternate between env and player do to do_simplify
     auto owner = get_state_players(aut);
+#ifndef NDEGUB
+    (void) owner;
+#endif
 
     std::vector<unsigned> state_map(aut->num_states(), unseen_mark);
     auto seen = [&](unsigned s){return state_map[s] != unseen_mark; };
@@ -456,31 +438,17 @@ namespace spot
         todo.pop_front();
 
         for (const auto& i : aut->out(cur))
-          {
-            // if the dst is also owned env
-            if (!owner[i.dst])
-              {
-                // This can only happen if there is only
-                // one outgoing edges for cur
-                assert(([&aut, cur]()->bool
-                          {
-                            auto out_cont = aut->out(cur);
-                            return (++(out_cont.begin()) == out_cont.end());
-                          })());
-                if (!seen(i.dst))
-                  todo.push_back(i.dst);
-                out->new_edge(cur_m, map_s(i.dst), i.cond, i.acc);
-                continue; // Done with cur
-              }
           for (const auto& o : aut->out(i.dst))
             {
+              assert((owner.at(cur) != owner.at(o.src))
+                     && (owner.at(cur) == owner.at(o.dst)
+                     && "Arena is not alternating!"));
               if (!seen(o.dst))
                 todo.push_back(o.dst);
               out->new_edge(cur_m, map_s(o.dst),
                             i.cond & o.cond, i.acc | o.acc);
             }
       }
-      }
     out->set_init_state(map_s(aut->get_init_state_number()));
     // Try to set outputs
     if (bdd* outptr = aut->get_named_prop<bdd>("synthesis-outputs"))
@@ -952,7 +920,7 @@ namespace spot
               << bv->paritize_time << " seconds\n";
         if (bv)
           sw.start();
-        dpa = split_2step(tmp, outs, true, false);
+        dpa = split_2step(tmp, outs, true);
         colorize_parity_here(dpa, true);
         if (bv)
           bv->split_time += sw.stop();
@@ -975,7 +943,7 @@ namespace spot
               << " states\n";
         if (bv)
           sw.start();
-        dpa = split_2step(aut, outs, true, false);
+        dpa = split_2step(aut, outs, true);
         colorize_parity_here(dpa, true);
         if (bv)
           bv->split_time += sw.stop();
@@ -988,8 +956,7 @@ namespace spot
       case solver::SPLIT_DET:
       {
         sw.start();
-        auto split = split_2step(aut, outs,
+        auto split = split_2step(aut, outs, true);
-                                true, false);
         if (bv)
           bv->split_time += sw.stop();
         if (vs)
@@ -1045,7 +1012,7 @@ namespace spot
 
         if (bv)
           sw.start();
-        dpa = split_2step(dpa, outs, true, false);
+        dpa = split_2step(dpa, outs, true);
         colorize_parity_here(dpa, true);
         if (bv)
           bv->split_time += sw.stop();

spot/twaalgos/synthesis.hh

@@ -25,8 +25,8 @@
 
 namespace spot
 {
-  /// \brief make each transition (conditionally, see do_simplify)
+  /// \brief make each transition a 2-step transition, transforming
-  ///        a 2-step transition
+  ///        the graph into an alternating arena
   ///
   /// Given a set of atomic propositions I, split each transition
   ///     p -- cond --> q                cond in 2^2^AP
@@ -45,16 +45,13 @@ namespace spot
   ///                     are treated as inputs
   /// \param complete_env Whether the automaton should be complete for the
   ///                     environment, i.e. the player of I
-  /// \param do_simplify  If a state has a single outgoing transition
-  ///                     we do not necessarily have to split it
-  ///                     to solve the game
   /// \note: This function also computes the state players
   /// \note: If the automaton is to be completed for both env and player
   ///        then egdes between the sinks will be added
   /// (assuming that the environnement/player of I) plays first
   SPOT_API twa_graph_ptr
   split_2step(const const_twa_graph_ptr& aut,
-              const bdd& output_bdd, bool complete_env, bool do_simplify);
+              const bdd& output_bdd, bool complete_env);
 
 
   /// \brief make each transition a 2-step transition.

tests/python/aiger.py

@@ -3333,7 +3333,7 @@ for strat_string, (ins_str, outs_str) in strats:
         outs &= buddy.bdd_ithvar(strat.register_ap(aout))
 
     spot.set_synthesis_outputs(strat, outs)
-    strat_s = spot.split_2step(strat, outs, False, False)
+    strat_s = spot.split_2step(strat, outs, False)
 
     for m in ["isop", "ite", "both"]:
         for ss in [""] + [f"+sub{ii}" for ii in range(3)]:

tests/python/mealy.py

@@ -378,7 +378,7 @@ for (mealy_str, nenv_min) in test_auts:
             ins = ins & buddy.bdd_ithvar(mealy.register_ap(aap.ap_name()))
         else:
             assert("""Aps must start with either "i" or "o".""")
-    mealy_min_us_s = spot.split_2step(mealy_min_us, outs, False, False)
+    mealy_min_us_s = spot.split_2step(mealy_min_us, outs, False)
     assert(spot.is_mealy_specialization(mealy, mealy_min_us_s, True))
 
 

tests/python/split.py

@@ -46,7 +46,7 @@ def do_split(f, out_list):
     outputs = spot.buddy.bddtrue
     for a in out_list:
         outputs &= spot.buddy.bdd_ithvar(aut.get_dict().varnum(spot.formula(a)))
-    s = spot.split_2step(aut, outputs, False, False)
+    s = spot.split_2step(aut, outputs, False)
     return aut, s
 
 aut, s = do_split('(FG !a) <-> (GF b)', ['b'])