Commit f2403c91 authored by Alexandre Duret-Lutz's avatar Alexandre Duret-Lutz
Browse files

run: fix reduce on automata with Fin

Reported by Florian Renkin.

* spot/twaalgos/emptiness.cc (reduce): If the automaton uses Fin
acceptance, check the reduced cycle and revert to the original cycle
if necessary.
* tests/python/intrun.py: New file.
* tests/Makefile.am: Add it.
* spot/twaalgos/emptiness.hh: Improve documentation.
parent 9caba8bf
Pipeline #20394 passed with stage
in 99 minutes and 1 second
......@@ -61,6 +61,11 @@ New in spot 2.9.0.dev (not yet released)
- Improve ltldo diagnostics to fix spurious test-suite failure on
systems with antique GNU libc.
- twa_run::reduce() could reduce accepting runs incorrectly on
automata using Fin in their acceptance condition. This caused
issues in intersecting_run(), exclusive_run(),
intersecting_word(), exclusive_word(), which all call reduce().
New in spot 2.9 (2020-04-30)
Command-line tools:
......
......@@ -304,11 +304,7 @@ namespace spot
{
state_set::const_iterator i = seen.begin();
while (i != seen.end())
{
const state* ptr = *i;
++i;
ptr->destroy();
}
(*i++)->destroy();
}
void
......@@ -353,17 +349,19 @@ namespace spot
{
ensure_non_empty_cycle("twa_run::reduce()");
auto& a = aut;
auto& acc = a->acc();
auto res = std::make_shared<twa_run>(a);
state_set ss;
shortest_path shpath(a);
shpath.set_target(&ss);
// We want to find a short segment of the original cycle that
// contains all acceptance conditions.
// satisfies the acceptance condition.
const state* segment_start; // The initial state of the segment.
const state* segment_next; // The state immediately after the segment.
// Start from the end of the original cycle, and rewind until all
// acceptance sets have been seen.
acc_cond::mark_t seen_acc = {};
......@@ -374,7 +372,7 @@ namespace spot
--seg;
seen_acc |= seg->acc;
}
while (!a->acc().accepting(seen_acc));
while (!acc.accepting(seen_acc));
segment_start = seg->s;
// Now go forward and ends the segment as soon as we have seen all
......@@ -390,7 +388,7 @@ namespace spot
++seg;
}
while (!a->acc().accepting(seen_acc));
while (!acc.accepting(seen_acc));
segment_next = seg == cycle.end() ? cycle.front().s : seg->s;
// Close this cycle if needed, that is, compute a cycle going
......@@ -402,6 +400,29 @@ namespace spot
ss.clear();
assert(s->compare(segment_start) == 0);
(void)s;
// If the acceptance condition uses Fin, it's possible (and
// even quite likely) that the cycle we have constructed this
// way is now rejecting, because the closing steps might add
// unwanted colors. If that is the case, throw the reduced
// cycle away and simply preserve the original one verbatim.
if (acc.uses_fin_acceptance())
{
acc_cond::mark_t seen = {};
for (auto& st: res->cycle)
seen |= st.acc;
if (!acc.accepting(seen))
{
for (auto& st: res->cycle)
st.s->destroy();
res->cycle.clear();
for (auto& st: cycle)
{
twa_run::step st2 = { st.s->clone(), st.label, st.acc };
res->cycle.emplace_back(st2);
}
}
}
}
// Compute the prefix: it's the shortest path from the initial
......
// -*- coding: utf-8 -*-
// Copyright (C) 2011, 2013, 2014, 2015, 2016, 2017, 2018 Laboratoire de
// Copyright (C) 2011, 2013-2018, 2020 Laboratoire de
// Recherche et Developpement de l'Epita (LRDE).
// Copyright (C) 2004, 2005 Laboratoire d'Informatique de Paris 6 (LIP6),
// département Systèmes Répartis Coopératifs (SRC), Université Pierre
......@@ -413,6 +413,12 @@ namespace spot
///
/// Return a run which is still accepting for <code>aut</code>,
/// but is no longer than this one.
///
/// This is done by trying to find a fragment of the accepting
/// single that is accepting, and trying to close a cycle around
/// this fragment with fewer edges than in the original cycle.
/// (This step works best in Fin-less automata.) And then trying
/// to find a shorter prefix leading to any state of the cycle.
twa_run_ptr reduce() const;
/// \brief Project an accepting run
......
......@@ -383,6 +383,7 @@ TESTS_python = \
python/genem.py \
python/implies.py \
python/interdep.py \
python/intrun.py \
python/kripke.py \
python/ltl2tgba.test \
python/ltlf.py \
......
# -*- mode: python; coding: utf-8 -*-
# Copyright (C) 2020 Laboratoire de Recherche et Développement de l'Epita
# (LRDE).
#
# This file is part of Spot, a model checking library.
#
# Spot is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# Spot is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
# License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import spot
# This issue was reported by Florian Renkin. The reduce() call used in
# intersecting_run() was bogus, and could incorrectly reduce a word
# intersecting the product into a word not intersecting the product if the
# acceptance condition uses some Fin.
a, b = spot.automata("""HOA: v1 States: 5 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 trans-acc complete properties: deterministic
--BODY-- State: 0 [t] 3 State: 1 [t] 4 {1} State: 2 [0] 2 {1} [!0] 1 {0} State:
3 [t] 1 {1} State: 4 [!0&1] 4 {3} [!0&!1] 3 [0] 2 {0} --END-- HOA: v1 States: 5
Start: 0 AP: 2 "p0" "p1" Acceptance: 3 Inf(2) | (Fin(0) & Inf(1)) properties:
trans-labels explicit-labels trans-acc complete properties: deterministic
--BODY-- State: 0 [t] 3 State: 1 [t] 4 {1 2} State: 2 [0] 2 {1 2} [!0] 1 {0 2}
State: 3 [t] 1 {1 2} State: 4 [!0&1] 4 {2} [!0&!1] 3 {2} [0] 2 {0 2} --END--""")
r = b.intersecting_run(spot.complement(a));
c = spot.twa_word(r).as_automaton()
assert c.intersects(b)
assert not c.intersects(a)
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