improve partial_degeneralize() on several cases

On these 4 cases, added to pdegen.py, and supplied by Florian Renkin,
partial_degeneralize() is now at least as good as degeneralize_tba(),
and sometimes better.  This is achieved as follows: (1) a
propagate_marks procedure is introduced to propagate marks as far as
possible on the automaton (e.g., common outgoing marks can be push
onto the incoming transitions and vice-versa), (2) the
degeneralization order is compute dynamically, and (3) whenever and
fully-accepting transition is taken in the original automaton, the
destination level is chosen to be the highest existing level.

* spot/twaalgos/degen.cc,
spot/twaalgos/degen.hh (propagate_marks_vector, propagate_marks_here):
New functions.
(partial_degeneralize): Improve, as described above.
* tests/python/pdegen.py: Add test cases.

tests/python/pdegen.py

@@ -1,5 +1,5 @@
 # -*- mode: python; coding: utf-8 -*-
-# Copyright (C) 2019 Laboratoire de Recherche et Développement de
+# Copyright (C) 2019, 2020 Laboratoire de Recherche et Développement de
 # l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
@@ -80,10 +80,10 @@ Acceptance: 2 Fin(0) | Inf(1)
 properties: trans-labels explicit-labels state-acc deterministic
 --BODY--
 State: 0 "2#0"
+[0] 1
+State: 1 "0#0" {0 1}
 [0] 2
-State: 1 "1#0"
-[0] 2
-State: 2 "0#1" {0 1}
+State: 2 "1#0" {1}
 [0] 1
 --END--"""
 
@@ -96,3 +96,65 @@ dd = spot.partial_degeneralize(d, [])
 assert dd.equivalent_to(d)
 assert dd.num_states() == 1
 assert str(dd.get_acceptance()) == 'Inf(1) & Fin(0)'
+
+aut5 = spot.automaton(""" HOA: v1 States: 8 Start: 0 AP: 3 "p0" "p1" "p2"
+acc-name: generalized-Buchi 10 Acceptance: 10
+Inf(0)&Inf(1)&Inf(2)&Inf(3)&Inf(4)&Inf(5)&Inf(6)&Inf(7)&Inf(8)&Inf(9)
+properties: trans-labels explicit-labels trans-acc deterministic --BODY--
+State: 0 [0&!1&2] 3 {2 4 9} State: 1 [!0&1&2] 5 {2 6 7 8} [!0&!1&!2] 0 {2}
+State: 2 [0&!1&2] 3 {1 4 9} State: 3 [0&!1&2] 4 {0 1 5 9} State: 4 [!0&!1&2] 1
+{7} [0&!1&2] 6 {1 2} State: 5 [!0&1&2] 7 {3 5} State: 6 [!0&!1&2] 2 {1 3 5}
+State: 7 [0&!1&!2] 0 {4 7} --END--""")
+
+daut5 = spot.degeneralize_tba(aut5)
+assert daut5.equivalent_to(aut5)
+sets = list(range(aut5.num_sets()))
+pdaut5 = spot.partial_degeneralize(aut5, sets)
+assert pdaut5.equivalent_to(aut5)
+assert daut5.num_states() == 10
+assert pdaut5.num_states() == 8
+
+aut6 = spot.automaton("""HOA: v1 States: 6 Start: 0 AP: 3 "p0" "p1" "p2"
+acc-name: generalized-Buchi 3 Acceptance: 3 Inf(0)&Inf(1)&Inf(2) properties:
+trans-labels explicit-labels trans-acc deterministic --BODY-- State: 0
+[0&!1&!2] 4 {1} State: 1 [!0&!1&!2] 2 {0 1} State: 2 [!0&1&2] 0 {1} State: 3
+[0&1&!2] 5 {1} State: 4 [!0&1&!2] 0 {1 2} [0&!1&!2] 3 {0} State: 5 [!0&1&2] 1
+--END-- """)
+daut6 = spot.degeneralize_tba(aut6)
+assert daut6.equivalent_to(aut6)
+sets = list(range(aut6.num_sets()))
+pdaut6 = spot.partial_degeneralize(aut6, sets)
+assert pdaut6.equivalent_to(aut6)
+assert daut6.num_states() == 8
+assert pdaut6.num_states() == 8
+
+
+aut7 = spot.automaton("""HOA: v1 States: 8 Start: 0 AP: 3 "p0" "p1" "p2"
+acc-name: generalized-Buchi 4 Acceptance: 4 Inf(0)&Inf(1)&Inf(2)&Inf(3)
+properties: trans-labels explicit-labels trans-acc deterministic --BODY--
+State: 0 [0&!1&2] 1 {2 3} State: 1 [0&!1&2] 0 {0 2} [0&!1&!2] 6 State: 2
+[0&1&2] 0 [!0&!1&2] 5 [!0&1&!2] 6 {1} State: 3 [0&!1&2] 5 [0&!1&!2] 6 State: 4
+[!0&!1&!2] 3 State: 5 [0&1&!2] 0 [!0&1&2] 7 State: 6 [0&1&2] 2 {1} State: 7
+[!0&!1&2] 0 {0} [!0&1&!2] 4 --END--""")
+daut7 = spot.degeneralize_tba(aut7)
+assert daut7.equivalent_to(aut7)
+sets = list(range(aut7.num_sets()))
+pdaut7 = spot.partial_degeneralize(aut7, sets)
+assert pdaut7.equivalent_to(aut7)
+assert daut7.num_states() == 11
+assert pdaut7.num_states() == 10
+
+aut8 = spot.automaton("""HOA: v1 States: 8 Start: 0 AP: 3 "p0" "p1" "p2"
+acc-name: generalized-Buchi 5 Acceptance: 5 Inf(0)&Inf(1)&Inf(2)&Inf(3)&Inf(4)
+properties: trans-labels explicit-labels trans-acc deterministic --BODY--
+State: 0 [!0&1&!2] 7 {0} State: 1 [!0&1&2] 1 {4} [0&!1&2] 6 {1 2} State: 2
+[!0&!1&2] 3 {1 2} [0&1&2] 5 State: 3 [0&1&2] 2 {2} State: 4 [!0&!1&!2] 3 State:
+5 [!0&1&!2] 0 {1 3} State: 6 [0&1&2] 4 [0&1&!2] 6 State: 7 [!0&!1&!2] 1
+--END--""")
+daut8 = spot.degeneralize_tba(aut8)
+assert daut8.equivalent_to(aut8)
+sets = list(range(aut8.num_sets()))
+pdaut8 = spot.partial_degeneralize(aut8, sets)
+assert pdaut8.equivalent_to(aut8)
+assert daut8.num_states() == 22
+assert pdaut8.num_states() == 9