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stutter: fix sl, sl2 to never accept on added self-loop

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Fixes #401, reported by Victor Khomenko.

* spot/twaalgos/stutter.cc (sl, sl2): If {} is accepting, upgrade the
acceptance condition.
* tests/core/stutter-tgba.test, tests/python/stutter.py: Add test cases.
This commit is contained in:
Alexandre Duret-Lutz 2020-03-12 21:54:13 +01:00
parent 150f815c87
commit b5d688dc97
3 changed files with 72 additions and 8 deletions
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55
spot/twaalgos/stutter.cc
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@ -1,5 +1,5 @@
// -*- coding: utf-8 -*-
// Copyright (C) 2014-2019 Laboratoire de Recherche et Développement de
// Copyright (C) 2014-2020 Laboratoire de Recherche et Développement de
// l'Epita (LRDE).
//
// This file is part of Spot, a model checking library.
@ -277,6 +277,19 @@ namespace spot
// We use the same BDD variables as the input.
res->copy_ap_of(a);
res->copy_acceptance_of(a);
// We are going to create self-loop labeled by {},
// and those should not be accepting. If they are,
// we need to upgrade the acceptance condition.
acc_cond::mark_t toadd = {};
if (res->acc().accepting({}))
{
unsigned ns = res->num_sets();
auto na = res->get_acceptance() & acc_cond::acc_code::inf({ns});
res->set_acceptance(ns + 1, na);
toadd = {ns};
}
// These maps make it possible to convert stutter_state to number
// and vice-versa.
ss2num_map ss2num;
@ -319,7 +332,7 @@ namespace spot
}
// Create the edge.
res->new_edge(src, dest, one, t.acc);
res->new_edge(src, dest, one, t.acc | toadd);
if (src == dest)
self_loop_needed = false;
@ -336,6 +349,36 @@ namespace spot
twa_graph_ptr
sl2_inplace(twa_graph_ptr a)
{
// We are going to create self-loop labeled by {},
// and those should not be accepting. If they are,
// we need to upgrade the acceptance condition.
if (a->acc().accepting({}))
{
unsigned ns = a->num_sets();
auto na = a->get_acceptance() & acc_cond::acc_code::inf({ns});
a->set_acceptance(ns + 1, na);
acc_cond::mark_t toadd = {ns};
for (auto& e: a->edges())
e.acc |= toadd;
}
// The self-loops we add should not be accepting, so try to find
// an unsat mark, and upgrade the acceptance condition if
// necessary.
//
// UM is a pair (bool, mark). If the Boolean is false, the
// acceptance is always satisfiable. Otherwise, MARK is an
// example of unsatisfiable mark.
auto um = a->acc().unsat_mark();
if (!um.first)
{
auto m = a->set_buchi();
for (auto& e: a->edges())
e.acc = m;
um.second = {};
}
acc_cond::mark_t unsat = um.second;
bdd atomic_propositions = a->ap_vars();
unsigned num_states = a->num_states();
unsigned num_edges = a->num_edges();
@ -379,10 +422,10 @@ namespace spot
unsigned tmp = p.first->second; // intermediate state
unsigned i = a->new_edge(src, tmp, one, acc);
assert(i > num_edges);
i = a->new_edge(tmp, tmp, one, {});
i = a->new_edge(tmp, tmp, one, unsat);
assert(i > num_edges);
// No acceptance here to preserve the state-based property.
i = a->new_edge(tmp, dst, one, {});
// unsat acceptance here to preserve the state-based property.
i = a->new_edge(tmp, dst, one, unsat);
assert(i > num_edges);
(void)i;
}
@ -704,7 +747,7 @@ namespace spot
else
{
rword = aword;
aword = sl2(aaut)->intersecting_word(neg);
aword = sl2(aaut)->intersecting_word(aut);
aword->simplify();
}
std::ostringstream os;