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minimize_wdba: fix handling of input with useless SCCs

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* spot/twaalgos/minimize.cc (minimize_wdba): Diminish the color of
terminal SCCs that are incomplete, as if they had a non-accepting
sink as successor.
* spot/twaalgos/strength.hh, spot/twaalgos/strength.cc
(is_terminal_automaton): Add an option to ignore trivial SCC as we did
before, since it matters for deciding membership to the guarantee
class.
(is_safety_mwdba): Rewrite as ...
(is_safety_automaton): ... generalizating to any acceptance, and
ignoring trivial SCCs.
* bin/ltlfilt.cc, python/ajax/spotcgi.in, spot/tl/hierarchy.cc,
tests/core/ikwiad.cc: Adjust usage of is_terminal_automaton and
is_safety_automaton().
* tests/core/hierarchy.test: Add a problematic formula as test-case.
* NEWS: Mention the bug.
This commit is contained in:
Alexandre Duret-Lutz 2017-01-11 18:06:41 +01:00
parent 7d9ce0d6fc
commit c9918f6407
9 changed files with 94 additions and 50 deletions
Download patch file Download diff file Expand all files Collapse all files

7
spot/tl/hierarchy.cc
View file

@ -66,8 +66,11 @@ namespace spot
auto min = minimize_obligation(aut, f);
if (aut != min) // An obligation.
{
bool g = is_terminal_automaton(min);
bool s = is_safety_mwdba(min);
scc_info si(min);
// The minimba WDBA can have some trivial accepting SCCs
// that we should ignore in is_terminal_automaton().
bool g = is_terminal_automaton(min, &si, true);
bool s = is_safety_automaton(min, &si);
if (g)
return s ? 'B' : 'G';
else

25
spot/twaalgos/minimize.cc
View file

@ -1,5 +1,5 @@
// -*- coding: utf-8 -*-
// Copyright (C) 2010, 2011, 2012, 2013, 2014, 2015, 2016 Laboratoire de
// Copyright (C) 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 Laboratoire de
// Recherche et Développement de l'Epita (LRDE).
//
// This file is part of Spot, a model checking library.
@ -520,7 +520,7 @@ namespace spot
// (i.e., it is not the start of any accepting word).
scc_info sm(det_a);
sm.determine_unknown_acceptance();
unsigned scc_count = sm.scc_count();
// SCC that have been marked as useless.
std::vector<bool> useless(scc_count);
@ -539,18 +539,13 @@ namespace spot
bool transient = sm.is_trivial(m);
auto& succ = sm.succ(m);
if (transient && succ.empty())
{
// A trivial SCC without successor is useless.
useless[m] = true;
d[m] = k - 1;
continue;
}
// Compute the minimum color l of the successors.
// Also SCCs are useless if all their successor are
// useless.
unsigned l = k;
// Compute the minimum color l of the successors. Also SCCs
// are useless if all their successor are useless. Note
// that Löding uses k-1 as level for non-final SCCs without
// successors but that seems bogus: using k+1 will make sure
// that a non-final SCCs without successor (i.e., a useless
// SCC) will be ignored in the computation of the level.
unsigned l = k + 1;
for (unsigned j: succ)
{
is_useless &= useless[j];
@ -575,6 +570,8 @@ namespace spot
}
else
{
if (succ.empty())
is_useless = true;
d[m] = (l - 1) | 1; // largest odd number inferior or equal
}
}

49
spot/twaalgos/strength.cc
View file

@ -1,6 +1,6 @@
// -*- coding: utf-8 -*-
// Copyright (C) 2010, 2011, 2013, 2014, 2015, 2016 Laboratoire de
// Recherche et Développement de l'Epita (LRDE)
// Copyright (C) 2010, 2011, 2013, 2014, 2015, 2016, 2017 Laboratoire
// de Recherche et Développement de l'Epita (LRDE)
//
// This file is part of Spot, a model checking library.
//
@ -28,7 +28,8 @@ namespace spot
namespace
{
template <bool terminal, bool inweak = false, bool set = false>
bool is_type_automaton(const twa_graph_ptr& aut, scc_info* si)
bool is_type_automaton(const twa_graph_ptr& aut, scc_info* si,
bool ignore_trivial_term = false)
{
// Create an scc_info if the user did not give one to us.
bool need_si = !si;
@ -89,7 +90,7 @@ namespace spot
// A terminal automaton should accept any word that as a prefix
// leading to an accepting edge. In other words, we cannot have
// an accepting edge that goes into a rejecting SCC.
if (terminal && is_term)
if (terminal && is_term && !ignore_trivial_term)
for (auto& e: aut->edges())
if (si->is_rejecting_scc(si->scc_of(e.dst))
&& aut->acc().accepting(e.acc))
@ -103,7 +104,12 @@ namespace spot
if (set)
{
if (terminal)
aut->prop_terminal(is_term && is_weak);
{
if (!ignore_trivial_term)
aut->prop_terminal(is_term && is_weak);
else if (is_term && is_weak)
aut->prop_terminal(true);
}
aut->prop_weak(is_weak);
aut->prop_very_weak(is_single_state_scc && is_weak);
if (inweak)
@ -116,13 +122,15 @@ namespace spot
}
bool
is_terminal_automaton(const const_twa_graph_ptr& aut, scc_info* si)
is_terminal_automaton(const const_twa_graph_ptr& aut, scc_info* si,
bool ignore_trivial_term)
{
trival v = aut->prop_terminal();
if (v.is_known())
return v.is_true();
bool res =
is_type_automaton<true>(std::const_pointer_cast<twa_graph>(aut), si);
is_type_automaton<true>(std::const_pointer_cast<twa_graph>(aut), si,
ignore_trivial_term);
std::const_pointer_cast<twa_graph>(aut)->prop_terminal(res);
return res;
}
@ -170,16 +178,27 @@ namespace spot
is_type_automaton<true, true, true>(aut, si);
}
bool is_safety_mwdba(const const_twa_graph_ptr& aut)
bool is_safety_automaton(const const_twa_graph_ptr& aut, scc_info* si)
{
if (!(aut->acc().is_buchi() || aut->acc().is_all()))
throw std::runtime_error
("is_safety_mwdba() should be called on a Buchi automaton");
if (aut->acc().is_t())
return true;
for (auto& t: aut->edges())
if (!aut->acc().accepting(t.acc))
return false;
return true;
bool need_si = !si;
if (need_si)
si = new scc_info(aut);
bool res = true;
unsigned scount = si->scc_count();
for (unsigned scc = 0; scc < scount; ++scc)
if (!si->is_trivial(scc) && si->is_rejecting_scc(scc))
{
res = false;
break;
}
if (need_si)
delete si;
return res;
}

27
spot/twaalgos/strength.hh
View file

@ -1,6 +1,6 @@
// -*- coding: utf-8 -*-
// Copyright (C) 2010, 2011, 2013, 2014, 2015, 2016 Laboratoire de
// Recherche et Développement de l'Epita (LRDE)
// Copyright (C) 2010, 2011, 2013, 2014, 2015, 2016, 2017 Laboratoire
// de Recherche et Développement de l'Epita (LRDE)
//
// This file is part of Spot, a model checking library.
//
@ -29,6 +29,9 @@ namespace spot
/// are complete, and no accepting transitions lead to a
/// non-accepting SCC.
///
/// If ignore_trivial_scc is set, accepting transitions from trivial
/// SCCs are ignored.
///
/// This property guarantees that a word is accepted if it has some
/// prefix that reaches an accepting transition.
///
@ -41,8 +44,8 @@ namespace spot
/// the prop_terminal() property of the automaton as a side-effect,
/// so further calls will return in constant-time.
SPOT_API bool
is_terminal_automaton(const const_twa_graph_ptr& aut, scc_info* sm = nullptr);
is_terminal_automaton(const const_twa_graph_ptr& aut, scc_info* sm = nullptr,
bool ignore_trivial_scc = false);
/// \brief Check whether an automaton is weak.
///
@ -95,16 +98,22 @@ namespace spot
is_inherently_weak_automaton(const const_twa_graph_ptr& aut,
scc_info* sm = nullptr);
/// \brief Check whether a minimized WDBA represents a safety
/// property.
/// \brief Check whether an automaton is a safety automaton.
///
/// A safety automaton has only accepting SCCs (or trivial
/// SCCs).
///
/// A minimized WDBA (as returned by a successful run of
/// minimize_obligation()) represent safety property if it contains
/// only accepting transitions.
/// minimize_obligation()) represent safety property if it is a
/// safety automaton.
///
/// \param aut the automaton to check
///
/// \param sm an scc_info object for the automaton if available (it
/// will be built otherwise).
SPOT_API bool
is_safety_mwdba(const const_twa_graph_ptr& aut);
is_safety_automaton(const const_twa_graph_ptr& aut,
scc_info* sm = nullptr);
/// \brief Check whether an automaton is weak or terminal.
///