improve acceptance simplifications using useless colors

This fixes issue #418.

* spot/twa/acc.cc,
spot/twa/acc.hh (acc_cond::acc_code::useless_colors_patterns): New
method to detect patterns of colors allowing other colors to be added
or removed at will.
* spot/twaalgos/cleanacc.cc (simplify_acceptance_here): Use the above
patterns to remove some useless colors from transitions and hope that
this can help simplify the acceptance condition.
* spot/twaalgos/degen.cc (propagate_marks_vector): Use the pattern to
add more colors.
* tests/core/ltl2tgba2.test: Add the test case from issue #418.
* tests/core/ltl2dstar4.test, tests/core/satmin3.test,
tests/core/sccdot.test, tests/core/sim3.test,
tests/python/automata.ipynb, tests/python/decompose.ipynb,
tests/python/merge.py, tests/python/pdegen.py, tests/python/remfin.py,
tests/python/toparity.py, tests/python/tra2tba.py: Adjust all test
cases.
* NEWS: Mention this new feature.

tests/core/ltl2dstar4.test

@@ -34,7 +34,7 @@ ltlfilt -f '(GFa -> GFb) & (GFc -> GFd)' -l |
 ltl2dstar --ltl2nba=spin:ltl2tgba@-s $STR - - |
 autfilt --tgba --stats '%S %E %A %s %e %t %a %d' |
 tee out
-test "`cat out`" = '9 144 4 18 98 202 2 0'
+test "`cat out`" = '9 144 4 16 92 186 2 0'
 
 ltlfilt -f '(GFa -> GFb) & (GFc -> GFd)' -l |
 ltl2dstar --ltl2nba=spin:ltl2tgba@-s $STR - - |

tests/core/ltl2tgba2.test

@@ -471,4 +471,6 @@ test "4,1" = `ltl2tgba -D -x wdba-minimize=2 "$f" --stats=%s,%d`
 test "4,0" = `ltl2tgba -D -x wdba-minimize=0 "$f" --stats=%s,%d`
 test "4,1" = `ltl2tgba -D --med "$f" --stats=%s,%d`
 
-:
+# Issue #418.
+f='(G!a | G!b | G!c) & (FG!a2 | GFb2 | GFc2) & (GFc2 | FG!b2 | GFa2)'
+test 28 = `ltl2tgba -D -G -S --stats=%s "$f"`

tests/core/satmin3.test

@@ -1,6 +1,6 @@
 #!/bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2017, 2019 Laboratoire de Recherche et Développement
+# Copyright (C) 2017, 2019, 2020 Laboratoire de Recherche et Développement
 # de l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
@@ -24,37 +24,36 @@ set -e
 
 # Make sure the SPOT_SATSOLVER envar works.
 
-# DRA produced by ltl2dstar for GFp0 -> GFp1, but manually modified
-# so that simulation-based reduction do not reduce it to 1 state right away.
+# DRA for GFp0 -> GFp1 produced using the SAT-based synthesis (i.e.,
+# "minimization with fixed number of states").  We used to take the
+# output of ltl2dstar, unfortunately our preprocessing reduced that to
+# one state right away, even after some manual touches.
+
 cat >test.hoa <<EOF
 HOA: v1
 States: 4
-properties: implicit-labels trans-labels no-univ-branch deterministic complete
-acc-name: Rabin 2
-Acceptance: 4 (Fin(0)&Inf(1))|(Fin(2)&Inf(3))
 Start: 0
 AP: 2 "p0" "p1"
+acc-name: Rabin 2
+Acceptance: 4 (Fin(0) & Inf(1)) | (Fin(2) & Inf(3))
+properties: trans-labels explicit-labels state-acc complete
+properties: deterministic
 --BODY--
-State: 0 {0}
-1  {1}  /* manual addition */
-0
-3
-2
-State: 1 {1}
-1
-0
-3
-2
-State: 2 {0 3}
-1
-0
-3
-2
-State: 3 {1 3}
-1
-0
-3
-2
+State: 0 {1 2}
+[!0&!1] 1
+[!0&1] 2
+[0] 3
+State: 1 {0}
+[0&!1] 1
+[!0&!1] 2
+[1] 3
+State: 2 {1}
+[0&!1] 1
+[!0&!1] 2
+[1] 3
+State: 3 {0 3}
+[0 | 1] 2
+[!0&!1] 3
 --END--
 EOF
 
@@ -69,7 +68,7 @@ grep 'autfilt: SPOT_SATSOLVER should use %O' err
 
 SPOT_SATSOLVER='false %I %O' \
   autfilt --sat-minimize test.hoa --stats=%s >output
-test `cat output` = 4
+test `cat output` = 3
 
 SPOT_SATSOLVER='this-does-not-exist %I %O' \
               autfilt --sat-minimize test.hoa --stats=%s 2>err && exit

tests/core/sccdot.test

@@ -156,7 +156,7 @@ HOA: v1
 States: 8
 Start: 0
 AP: 2 "a" "b"
-Acceptance: 3 (Inf(0)&Inf(1)) & Fin(2)
+Acceptance: 2 Inf(0) & Fin(1)
 properties: trans-labels explicit-labels trans-acc
 --BODY--
 State: 0
@@ -165,24 +165,24 @@ State: 0
 State: 1
 [1] 4
 State: 2
-[0&1] 0 {0 1}
+[0&1] 0 {0}
 State: 3
 [1] 1
-[!1] 3 {2}
+[!1] 3 {1}
 State: 4
-[!0&1] 4 {0 1}
-[0&1] 4 {0 2}
+[!0&1] 4 {0}
+[0&1] 4 {1}
 [t] 5
 State: 5
-[0&1] 5 {0 1}
-[!0&1] 5 {0 2}
+[0&1] 5 {0}
+[!0&1] 5 {1}
 [t] 6
 State: 6
-[!0&1] 6 {0 2}
-[0&1] 7 {0 1}
+[!0&1] 6 {1}
+[0&1] 7 {0}
 State: 7
-[!0&1] 6 {0 1}
-[0&1] 7 {0 2}
+[!0&1] 6 {0}
+[0&1] 7 {1}
 --END--
 EOF
 diff expected.hoa out.hoa

tests/core/sim3.test

@@ -1,6 +1,6 @@
 #! /bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2015, 2018, 2019 Laboratoire de Recherche et Développement
+# Copyright (C) 2015, 2018, 2019, 2020 Laboratoire de Recherche et Développement
 # de l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
@@ -52,7 +52,7 @@ test "`autfilt --small input --stats=%S,%s`" = 7,1
 autfilt -S --high --small input -H > out
 cat >expected <<EOF
 HOA: v1
-States: 5
+States: 4
 Start: 0
 AP: 2 "b" "a"
 acc-name: Streett 1
@@ -61,28 +61,19 @@ properties: trans-labels explicit-labels state-acc complete
 properties: deterministic
 --BODY--
 State: 0
-[!1] 1
-[1] 3
+[t] 1
 State: 1 {1}
-[0&!1] 1
+[0] 1
 [!0&!1] 2
-[0&1] 3
-[!0&1] 4
+[!0&1] 3
 State: 2
-[0&!1] 1
+[0] 1
 [!0&!1] 2
-[0&1] 3
-[!0&1] 4
-State: 3 {0 1}
-[0&!1] 1
+[!0&1] 3
+State: 3 {0}
+[0] 1
 [!0&!1] 2
-[0&1] 3
-[!0&1] 4
-State: 4 {0}
-[0&!1] 1
-[!0&!1] 2
-[0&1] 3
-[!0&1] 4
+[!0&1] 3
 --END--
 EOF
 diff out expected