postprocess: call restrict_dead_end_edges_here()

Related to issue #587.

* spot/twaalgos/postproc.cc, spot/twaalgos/postproc.hh: Add
support for option "rde".
* bin/spot-x.cc, NEWS: Mention it.
* tests/core/deadends.test, tests/core/ltl2tgba2.test,
tests/python/atva16-fig2a.ipynb, tests/python/deadends.py: Adjust test
cases to reflect the improvement.
* tests/core/ltlsynt.test: Also adjust this test case, which is the
only one worsened.  Some extra gates are generated when translating
GFa<->GFb with --algo=ds or --algo=sd.  Issue #588 would be one way to
fix that.

NEWS

@@ -6,7 +6,7 @@ New in spot 2.12.0.dev (not yet released)
     edges leading to dead-ends.  See the description of
     restrict_dead_end_edges_here() below.
 
-   Library:
+  Library:
 
    - restrict_dead_end_edges_here() can reduce non-determinism (but
      not remove it) by restricting the label L of some edge (S)-L->(D)
@@ -14,6 +14,10 @@ New in spot 2.12.0.dev (not yet released)
      itself.  The conditions are detailled in the documentation of
      this function.
 
+   - spot::postprocessor will now call restrict_dead_end_edges_here()
+     in its highest setting.  This can be fine-tuned with the "rde"
+     extra option, see the spot-x (7) man page for detail.
+
 New in spot 2.12  (2024-05-16)
 
   Build:

bin/spot-x.cc

@@ -206,6 +206,12 @@ it can cause the created temporary automata to have incompatible \
 combinations of atomic propositions that will be eventually be removed. \
 This relabeling is attempted after relabel-bool.  By default, N=8.  Setting \
 this value to 0 will disable the rewriting.") },
+    { DOC("rde", "Disable (0), or enable (1) the 'restrict-dead-end-edges' \
+optimization.  A dead-end-edge is one that move to a state that has only \
+itself as successors.  The label of such edges can be simplified in some \
+situtation, reducing non-determinism slightly.  By default (-1), this is \
+enabled only in --high mode, or if both --medium and --deterministic are \
+used.") },
     { DOC("wdba-minimize", "Set to 0 to disable WDBA-minimization, to 1 to \
 always try it, or 2 to attempt it only on syntactic obligations or on automata \
 that are weak and deterministic.  The default is 1 in --high mode, else 2 in \

spot/twaalgos/postproc.cc

@@ -38,6 +38,7 @@
 #include <spot/twaalgos/parity.hh>
 #include <spot/twaalgos/cobuchi.hh>
 #include <spot/twaalgos/cleanacc.hh>
+#include <spot/twaalgos/deadends.hh>
 #include <spot/twaalgos/toparity.hh>
 #include <spot/twaalgos/zlktree.hh>
 
@@ -108,6 +109,7 @@ namespace spot
         wdba_det_max_ = opt->get("wdba-det-max", 4096);
         simul_trans_pruning_ = opt->get("simul-trans-pruning", 512);
         acd_ = opt->get("acd", 1);
+        rde_ = opt->get("rde", -1);
 
         if (sat_acc_ && sat_minimize_ == 0)
           sat_minimize_ = 1;        // Dicho.
@@ -527,6 +529,14 @@ namespace spot
           }
       }
 
+    // Restricting dead-end edges only makes sense on non-deterministic
+    // automata.  rde_ == 0 disable this.  rde_ > 0 enable it.
+    // By default (rde_ < 0), we only enable this on High and Medium+Det.
+    if (!dba && rde_ != 0 && !is_deterministic(sim) &&
+        (rde_ > 0 || (level_ == High ||
+                      (level_ == Medium && PREF_ == Deterministic))))
+      restrict_dead_end_edges_here(sim);
+
     // If WDBA failed, but the simulation returned a deterministic
     // automaton, use it as dba.
     assert(dba || sim);

spot/twaalgos/postproc.hh

@@ -271,6 +271,7 @@ namespace spot
     int wdba_det_max_ = 4096;
     bool acd_ = true;
     bool acd_was_used_;
+    int rde_ = -1;
   };
   /// @}
 }

tests/core/deadends.test

@@ -59,7 +59,8 @@ FG((Gp2 | Xp3) & (F!p2 | X!p3))
 GFp0 & FGp1 & FGp2 & GFp3
 EOF
 
-ltl2tgba -F input.ltl | tee output.aut |
+# disable rde so we can apply it manually
+ltl2tgba -x rde=0 -F input.ltl | tee output.aut |
   autfilt --restrict-dead --stats="%T %t %M" |
   while read in out f; do
     : $in : $out : "$f"
@@ -68,3 +69,12 @@ ltl2tgba -F input.ltl | tee output.aut |
   done
 
 autcross -F output.aut --language-preserved 'autfilt --restrict-dead'
+
+# by default, the result of ltl2tgba is already restricted
+ltl2tgba -F input.ltl |
+  autfilt --restrict-dead --stats="%T %t %M" |
+  while read in out f; do
+    : $in : $out : "$f"
+    test $in -ne $out && exit 1
+    :
+  done

tests/core/ltl2tgba2.test

@@ -273,7 +273,7 @@ and-fg,32, $fg42, $fg42, $fg42, $fg42, $fg42, $fg42
 !sb-patterns,5, 2,7, 2,7, 2,7, 2,7, 3,12, 3,12
 !sb-patterns,6, 3,11, 4,14, 3,11, 4,14, 3,11, 4,14
 !sb-patterns,7, 4,16, 4,16, 4,16, 4,16, 4,16, 4,16
-!sb-patterns,9, 3,13, 3,13, 4,17, 4,17, 5,21, 5,21
+!sb-patterns,9, 3,12, 3,12, 4,17, 4,17, 5,21, 5,21
 !sb-patterns,10, 2,6, 2,6, 2,6, 2,6, 2,6, 2,6
 !sb-patterns,11, 1,0, 1,0, 1,0, 1,0, 1,0, 1,0
 !sb-patterns,12, 1,0, 1,0, 1,0, 1,0, 1,0, 1,0
@@ -340,7 +340,7 @@ and-fg,32, $fg42, $fg42, $fg42, $fg42, $fg42, $fg42
 !hkrss-patterns,53, 4,32, 4,32, 4,32, 4,32, 4,32, 4,32
 !hkrss-patterns,54, 4,32, 4,32, 4,32, 4,32, 4,32, 4,32
 !hkrss-patterns,55, 5,12, 6,12, 5,12, 6,12, 5,12, 6,12
-!p-patterns,2, 2,15, 2,15, 3,19, 3,19, 4,23, 4,23
+!p-patterns,2, 2,14, 2,14, 3,19, 3,19, 4,23, 4,23
 !p-patterns,3, 3,41, 3,41, 3,41, 3,41, 3,41, 3,41
 !p-patterns,4, 1,1, 1,1, 1,1, 1,1, 1,1, 1,1
 !p-patterns,5, 2,6, 2,6, 2,6, 2,6, 2,6, 2,6
@@ -379,7 +379,7 @@ FG(a | Fb), 3,15, 3,15, 3,15, 3,15, 1,4
 FG(a & Fb), 2,7, 2,7, 3,9, 3,9, 1,4
 GF(a & Gb), 2,7, 2,7, 3,9, 3,9, 1,4
 GF(a | Gb), 2,7, 2,7, 3,12, 3,12, 1,4
-Ge | GF(Ge & X(c & Fd)), 4,31, 4,31, 6,39, 6,39, 2,16
+Ge | GF(Ge & X(c & Fd)), 4,30, 4,30, 6,39, 6,39, 2,16
 F(GF(b & Gc) | Ge), 3,22, 3,22, 4,26, 4,26, 1,8
 EOF
 

tests/core/ltlsynt.test

@@ -22,40 +22,43 @@
 set -e
 
 cat >exp <<EOF
-parity 17;
+parity 18;
-0 1 0 7,8;
+0 2 0 7,8;
-8 1 1 2;
+8 2 1 2;
 2 3 0 11,12;
 12 3 1 2,3;
 3 2 0 13,14;
 14 2 1 2,3;
-13 2 1 1,4;
+13 2 1 4,5;
-4 1 0 8,15;
+5 2 0 8,17;
-15 1 1 5,6;
+17 2 1 5,6;
-6 1 0 8,15;
+6 1 0 10,18;
-5 2 0 16,17;
+18 1 1 5,6;
-17 2 1 2;
+10 1 1 2;
-16 2 1 5,6;
+4 1 0 15,16;
+16 1 1 2,3;
+15 1 1 4,5;
+11 3 1 4,5;
+7 2 1 0,1;
 1 1 0 9,10;
-10 1 1 2,3;
+9 1 1 0,1;
-9 1 1 1,5;
+parity 15;
-11 3 1 1,4;
+0 2 0 1,2;
-7 1 1 1,2;
-parity 13;
-0 1 0 1,2;
 2 1 1 3;
-3 3 0 5,4;
+3 3 0 4,5;
-4 2 1 12,3;
+5 2 1 6,3;
-12 2 0 5,4;
+6 2 0 4,5;
-5 1 1 6,7;
+4 1 1 7,8;
-7 1 0 9,8;
+8 2 0 10,9;
-8 3 1 12,3;
+9 3 1 6,3;
-9 1 1 11,10;
+10 2 1 11,8;
-10 2 0 9,8;
+11 1 0 12,9;
-11 1 0 9,8;
+12 1 1 11,8;
-6 1 0 13,4;
+7 1 0 13,5;
-13 1 1 6,10;
+13 1 1 7,8;
-1 1 1 6,3;
+1 2 1 14,0;
+14 1 0 15,2;
+15 1 1 14,0;
 parity 5;
 0 1 0 2,3;
 3 3 1 1;

tests/python/atva16-fig2a.ipynb

@@ -51,7 +51,7 @@
        "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n",
        "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\"\n",
        " \"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n",
-       "<!-- Generated by graphviz version 2.43.0 (0)\n",
+       "<!-- Generated by graphviz version 2.42.4 (0)\n",
        " -->\n",
        "<!-- Pages: 1 -->\n",
        "<svg width=\"196pt\" height=\"355pt\"\n",
@@ -95,7 +95,7 @@
        "<title>0&#45;&gt;1</title>\n",
        "<path fill=\"none\" stroke=\"black\" d=\"M72.76,-75.16C91.63,-83.74 123.36,-98.16 144.72,-107.87\"/>\n",
        "<polygon fill=\"black\" stroke=\"black\" points=\"151.27,-110.85 143.59,-110.82 148.08,-109.4 144.9,-107.95 144.9,-107.95 144.9,-107.95 148.08,-109.4 146.2,-105.09 151.27,-110.85 151.27,-110.85\"/>\n",
-       "<text text-anchor=\"start\" x=\"99\" y=\"-104.8\" font-family=\"Lato\" font-size=\"14.00\">a | b</text>\n",
+       "<text text-anchor=\"start\" x=\"108.5\" y=\"-104.8\" font-family=\"Lato\" font-size=\"14.00\">a</text>\n",
        "</g>\n",
        "<!-- 2 -->\n",
        "<g id=\"node4\" class=\"node\">\n",
@@ -158,7 +158,7 @@
        "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n",
        "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\"\n",
        " \"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n",
-       "<!-- Generated by graphviz version 2.43.0 (0)\n",
+       "<!-- Generated by graphviz version 2.42.4 (0)\n",
        " -->\n",
        "<!-- Pages: 1 -->\n",
        "<svg width=\"196pt\" height=\"355pt\"\n",
@@ -202,7 +202,7 @@
        "<title>0&#45;&gt;1</title>\n",
        "<path fill=\"none\" stroke=\"black\" d=\"M72.76,-75.16C91.63,-83.74 123.36,-98.16 144.72,-107.87\"/>\n",
        "<polygon fill=\"black\" stroke=\"black\" points=\"151.27,-110.85 143.59,-110.82 148.08,-109.4 144.9,-107.95 144.9,-107.95 144.9,-107.95 148.08,-109.4 146.2,-105.09 151.27,-110.85 151.27,-110.85\"/>\n",
-       "<text text-anchor=\"start\" x=\"99\" y=\"-104.8\" font-family=\"Lato\" font-size=\"14.00\">a | b</text>\n",
+       "<text text-anchor=\"start\" x=\"108.5\" y=\"-104.8\" font-family=\"Lato\" font-size=\"14.00\">a</text>\n",
        "</g>\n",
        "<!-- 2 -->\n",
        "<g id=\"node4\" class=\"node\">\n",
@@ -262,7 +262,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<spot.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7fdd801ca760> >"
+       "<spot.twa_graph; proxy of <Swig Object of type 'std::shared_ptr< spot::twa_graph > *' at 0x7f30b04c1d40> >"
       ]
      },
      "execution_count": 3,
@@ -345,9 +345,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.7"
+   "version": "3.12.4"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 2
+ "nbformat_minor": 4
 }

tests/python/deadends.py

@@ -111,7 +111,7 @@ State: 1
 [0&1&2] 1 {0 1}
 --END--""")
 
-a = spot.translate('GFa & (FGb | FGc) & GFc')
+a = spot.translate('GFa & (FGb | FGc) & GFc', xargs='rde=0')
 s = a.to_str()
 spot.restrict_dead_end_edges_here(a)
 s += a.to_str()