improve gf_guarantee_to_ba

* spot/twaalgos/gfguarantee.cc: Combine the last letter read
with the first one of the next pass when doing transition-based
acceptance.  Also move the initial states to the source of any
accepting transition if the input is deterministic.
* tests/core/ltl2tgba2.test, tests/core/satmin.test,
tests/python/stutter-inv.ipynb: Reduce expected sizes of a few
automata.

spot/twaalgos/gfguarantee.cc

@@ -26,6 +26,7 @@
 #include <spot/twaalgos/ltl2tgba_fm.hh>
 #include <spot/twaalgos/minimize.hh>
 #include <spot/twaalgos/dualize.hh>
+#include <spot/twaalgos/isdet.hh>
 
 namespace spot
 {
@@ -73,16 +74,75 @@ namespace spot
 
       if (!state_based)
         {
+          bool is_det = is_deterministic(aut);
+          bool initial_state_reachable = false;
           for (auto& e: aut->edges())
-            if (term[si.scc_of(e.dst)])
+            if (e.dst == init)
               {
-                e.dst = init;
+                initial_state_reachable = true;
-                e.acc = {0};
+                break;
-              }
-            else
-              {
-                e.acc = {};
               }
+          unsigned nedges = aut->num_edges();
+          unsigned new_init = -1U;
+          // The loop might add new edges, but we just want to iterate
+          // on the initial ones.
+          for (unsigned edge = 1; edge <= nedges; ++edge)
+            {
+              auto& e = aut->edge_storage(edge);
+              if (term[si.scc_of(e.dst)])
+                {
+                  if (initial_state_reachable
+                      // If the source state is the initial state, we
+                      // should not try to combine it with itself...
+                      || e.src == init)
+                    {
+                      e.dst = init;
+                      e.acc = {0};
+                      new_init = init;
+                      continue;
+                    }
+                  // If initial state cannot be reached from another
+                  // state of the automaton, we can get rid of it by
+                  // combining the edge reaching the terminal state
+                  // with the edges leaving the initial state.
+                  bdd econd = e.cond;
+                  bool first = true;
+                  // Combine this edge with any compatible edge from
+                  // the initial state.
+                  for (auto& ei: aut->out(init))
+                    {
+                      bdd cond = ei.cond & econd;
+                      if (cond != bddfalse)
+                        {
+                          if (first)
+                            {
+                              e.dst = ei.dst;
+                              e.acc = {0};
+                              e.cond = cond;
+                              first = false;
+                              if (new_init == -1U)
+                                new_init = e.src;
+                            }
+                          else
+                            {
+                              aut->new_edge(e.src, ei.dst, cond, {0});
+                            }
+
+                        }
+                    }
+                }
+              else
+                {
+                  e.acc = {};
+                }
+            }
+          // In a deterministic and suspendable automaton, all states
+          // recognize the same language, so we can freely move the
+          // initial state.  We decide to use the source of any
+          // accepting transition, in the hope that it will make the
+          // original initial state unreachable.
+          if (is_det && new_init != -1U)
+            aut->set_init_state(new_init);
         }
       else
         {

tests/core/ltl2tgba2.test

@@ -132,8 +132,8 @@ sb-patterns,26, 1,1, 1,1, 1,1, 1,1
 sb-patterns,27, 2,7, 2,7, 2,7, 2,7
 hkrss-patterns,1, 1,2, 1,2, 3,6, 3,6
 hkrss-patterns,2, 1,2, 1,2, 3,6, 3,6
-hkrss-patterns,3, 5,20, 5,20, 5,20, 5,20
+hkrss-patterns,3, 4,16, 4,16, 5,20, 5,20
-hkrss-patterns,4, 9,400, 17,272, 9,400, 17,272
+hkrss-patterns,4, 9,400, 16,256, 9,400, 17,272
 hkrss-patterns,6, 1,2, 1,2, 3,6, 3,6
 hkrss-patterns,7, 2,8, 2,8, 2,8, 2,8
 hkrss-patterns,8, 1,1, 1,1, 1,1, 1,1

tests/core/satmin.test

@@ -660,8 +660,8 @@ cat >expected <<'EOF'
 "!(G((p0) -> ((p1) U (p2))))","15",3
 "!(G((p0) -> ((p1) U (p2))))","16",3
 "!(G((p0) -> ((p1) U (p2))))","17",3
-"G(F((p0) <-> (X(X(p1)))))","1",7
+"G(F((p0) <-> (X(X(p1)))))","1",6
-"G(F((p0) <-> (X(X(p1)))))","2",7
+"G(F((p0) <-> (X(X(p1)))))","2",6
 "G(F((p0) <-> (X(X(p1)))))","3",4
 "G(F((p0) <-> (X(X(p1)))))","4",4
 "G(F((p0) <-> (X(X(p1)))))","6",4

tests/python/stutter-inv.ipynb

@@ -302,7 +302,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7ff49441fc30> >"
+       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f6b5c32c720> >"
       ]
      },
      "metadata": {},
@@ -595,7 +595,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7ff4943ae090> >"
+       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f6b5c358f90> >"
       ]
      },
      "metadata": {},
@@ -804,7 +804,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7ff4943ae090> >"
+       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f6b5c358f90> >"
       ]
      },
      "metadata": {},
@@ -963,7 +963,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7ff49441f810> >"
+       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f6b5c358ea0> >"
       ]
      },
      "metadata": {},
@@ -1062,7 +1062,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7ff4943bf6c0> >"
+       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f6b5c32c750> >"
       ]
      },
      "metadata": {},
@@ -1279,7 +1279,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7ff4943bf690> >"
+       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f6b5c2cb360> >"
       ]
      },
      "metadata": {},
@@ -1446,7 +1446,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7ff494457060> >"
+       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f6b5c2cb480> >"
       ]
      },
      "metadata": {},
@@ -1577,7 +1577,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7ff4943bfea0> >"
+       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f6b5c2cbd50> >"
       ]
      },
      "metadata": {},
@@ -1837,7 +1837,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7ff4943d02d0> >"
+       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f6b5c2dd570> >"
       ]
      },
      "metadata": {},
@@ -2151,7 +2151,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7ff4943d02d0> >"
+       "<spot.impl.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f6b5c2dd570> >"
       ]
      },
      "metadata": {},
@@ -2258,7 +2258,7 @@
       "F(p0 & X(p1 & XFp2))                          4        2          1\n",
       "F(p0 & X(p1 U p2))                            3        1          1\n",
       "G(p0 & Fp1 & Fp2 & Fp3)                       1        1          1\n",
-      "GF((!p0 & Xp0) | (p0 & X!p0) | (!p1 & Xp      5        5          1\n",
+      "GF((!p0 & Xp0) | (p0 & X!p0) | (!p1 & Xp      4        4          1\n",
       "GF((!p0 & Xp0) | (p0 & X!p0) | (!p1 & Xp      9        9          1\n",
       "G(!p0 | !p1 | p2 | X(!p2 | p3 | X(!p1 |       3        0          1\n",
       "G(!p0 | !p1 | p2 | X(!p2 | (p2 U (!p2 U       5        5          1\n",
@@ -2362,7 +2362,7 @@
     {
      "data": {
       "text/plain": [
-       "55.90277777777778"
+       "55.749128919860624"
       ]
      },
      "execution_count": 31,
@@ -2373,13 +2373,6 @@
    "source": [
     "100*sum(sistates_size)/sum(aut_size)"
    ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": []
   }
  ],
  "metadata": {