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introduce is_obligation(f)

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This is not optimal yet because it still construct a minimal WDBA
internally, but it's better than the previous way to call
minimize_obligation() since it can avoid constructing the minimized
automaton in a few more cases.

* spot/tl/hierarchy.cc, spot/tl/hierarchy.hh: Introduce
is_obligation().
* bin/ltlfilt.cc: Wire it to --obligation.
* spot/twaalgos/minimize.cc: Implement is_wdba_realizable(),
needed by the above.
* tests/core/obligation.test: Test it.
* bin/man/spot-x.x, NEWS: Document it.
This commit is contained in:
Alexandre Duret-Lutz 2017-11-15 21:51:33 +01:00
parent f7ee9ed18e
commit 50fe34a55a
7 changed files with 214 additions and 29 deletions
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62
spot/twaalgos/minimize.cc
View file

@ -46,6 +46,7 @@
#include <spot/twaalgos/isdet.hh>
#include <spot/twaalgos/dualize.hh>
#include <spot/twaalgos/remfin.hh>
#include <spot/tl/hierarchy.hh>
namespace spot
{
@ -581,6 +582,54 @@ namespace spot
return res;
}
// Declared in tl/hierarchy.cc, but defined here because it relies on
// other internal functions from this file.
SPOT_LOCAL bool is_wdba_realizable(formula f, twa_graph_ptr aut = nullptr);
bool is_wdba_realizable(formula f, twa_graph_ptr aut)
{
if (f.is_syntactic_obligation())
return true;
if (aut == nullptr)
aut = ltl_to_tgba_fm(f, make_bdd_dict(), true);
if (!aut->is_existential())
throw std::runtime_error
("is_wdba_realizable() does not support alternation");
if ((f.is_syntactic_persistence() || aut->prop_weak())
&& (f.is_syntactic_recurrence() || is_deterministic(aut)))
return true;
if (is_terminal_automaton(aut))
return true;
// FIXME: we do not need to minimize the wdba to test realizability.
auto min_aut = minimize_wdba(aut);
if (!is_deterministic(aut)
&& !product(aut, remove_fin(dualize(min_aut)))->is_empty())
return false;
twa_graph_ptr aut_neg;
if (is_deterministic(aut))
{
aut_neg = remove_fin(dualize(aut));
}
else
{
aut_neg = ltl_to_tgba_fm(formula::Not(f), aut->get_dict());
aut_neg = scc_filter(aut_neg, true);
}
if (is_terminal_automaton(aut_neg))
return true;
return product(min_aut, aut_neg)->is_empty();
}
twa_graph_ptr
minimize_obligation(const const_twa_graph_ptr& aut_f,
formula f,
@ -591,6 +640,9 @@ namespace spot
throw std::runtime_error
("minimize_obligation() does not support alternation");
// FIXME: We should build scc_info once, pass it to minimize_wdba
// and reuse it for is_terminal_automaton(), and
// is_weak_automaton().
auto min_aut_f = minimize_wdba(aut_f);
if (reject_bigger)
@ -601,16 +653,16 @@ namespace spot
return std::const_pointer_cast<twa_graph>(aut_f);
}
// If the input automaton was already weak and deterministic, the
// output is necessary correct.
if (aut_f->prop_weak() && is_deterministic(aut_f))
return min_aut_f;
// if f is a syntactic obligation formula, the WDBA minimization
// must be correct.
if (f && f.is_syntactic_obligation())
return min_aut_f;
// If the input automaton was already weak and deterministic, the
// output is necessary correct.
if (aut_f->prop_weak() && is_deterministic(aut_f))
return min_aut_f;
// If aut_f is a guarantee automaton, the WDBA minimization must be
// correct.
if (is_terminal_automaton(aut_f))