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Keep acceptance conditions on transitions going to accepting SCCs

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by default in scc_filter().

Doing so helps the degeneralization algorithm, because it will
have more opportunity to be in an accepting level when it reaches
the accepting SCCs.

* src/tgbaalgos/sccfilter.cc (filter_iter::filter_iter): Take a
remove_all_useless argument.
(filter_iter::process_link): Use the flag to decide whether to
filter acceptance conditions going to accepting SCCs.
(scc_filter): Take a remove_all_useless argument and pass it to
filter_iter.
* src/tgbaalgos/sccfilter.hh (filter_iter): Add the new argument
and document the function.
* src/tgbatest/tgbatests/ltl2tgba.cc (main): Add option use -R3
for remove_all_useless=false and add -R3f for
remove_all_useless=true.
* src/tgbatest/ltl2tgba.test: Show one case where -R3f makes
the degeneralization worse than -R3.
This commit is contained in:
Alexandre Duret-Lutz 2010-03-06 00:18:33 +01:00
parent 2140256004
commit 27b419ce17
5 changed files with 93 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

23
ChangeLog
View file

@ -1,3 +1,26 @@
2010-03-06 Alexandre Duret-Lutz <adl@lrde.epita.fr>
Keep acceptance conditions on transitions going to accepting SCCs
by default in scc_filter().
Doing so helps the degeneralization algorithm, because it will
have more opportunity to be in an accepting level when it reaches
the accepting SCCs.
* src/tgbaalgos/sccfilter.cc (filter_iter::filter_iter): Take a
remove_all_useless argument.
(filter_iter::process_link): Use the flag to decide whether to
filter acceptance conditions going to accepting SCCs.
(scc_filter): Take a remove_all_useless argument and pass it to
filter_iter.
* src/tgbaalgos/sccfilter.hh (filter_iter): Add the new argument
and document the function.
* src/tgbatest/tgbatests/ltl2tgba.cc (main): Add option use -R3
for remove_all_useless=false and add -R3f for
remove_all_useless=true.
* src/tgbatest/ltl2tgba.test: Show one case where -R3f makes
the degeneralization worse than -R3.
2010-03-05 Alexandre Duret-Lutz <adl@lrde.epita.fr>
Simplify F(a)|F(b) as F(a|b). Add similar rule for G(a)&G(b).

34
src/tgbaalgos/sccfilter.cc
View file

@ -1,5 +1,5 @@
// Copyright (C) 2009 Laboratoire de Recherche et Developpement de
// l'Epita (LRDE).
// Copyright (C) 2009, 2010 Laboratoire de Recherche et Developpement
// de l'Epita (LRDE).
//
// This file is part of Spot, a model checking library.
//
@ -64,13 +64,14 @@ namespace spot
filter_iter(const tgba* a,
const scc_map& sm,
const std::vector<bool>& useless,
bdd useful, bdd strip)
bdd useful, bdd strip, bool remove_all_useless)
: tgba_reachable_iterator_depth_first(a),
out_(new T(a->get_dict())),
sm_(sm),
useless_(useless),
useful_(useful),
strip_(strip)
strip_(strip),
all_(remove_all_useless)
{
out_->set_acceptance_conditions(useful);
}
@ -96,10 +97,16 @@ namespace spot
create_transition(this->automata_, out_, in_s, in, out_s, out);
out_->add_conditions(t, si->current_condition());
// Do not output any acceptance condition if either the source or
// the destination state do not belong to an accepting state.
if (sm_.accepting(sm_.scc_of_state(in_s))
&& sm_.accepting(sm_.scc_of_state(out_s)))
// Regardless of all_, do not output any acceptance condition
// if the destination is not in an accepting SCC.
//
// If all_ is set, do not output any acceptance condition if the
// source is not in the same SCC as dest.
//
// (See the documentation of scc_filter() for a rational.)
unsigned u = sm_.scc_of_state(out_s);
if (sm_.accepting(u)
&& (!all_ || u == sm_.scc_of_state(in_s)))
out_->add_acceptance_conditions
(t, (bdd_exist(si->current_acceptance_conditions(), strip_)
& useful_));
@ -111,12 +118,13 @@ namespace spot
const std::vector<bool>& useless_;
bdd useful_;
bdd strip_;
bool all_;
};
} // anonymous
tgba* scc_filter(const tgba* aut)
tgba* scc_filter(const tgba* aut, bool remove_all_useless)
{
scc_map sm(aut);
sm.build_map();
@ -160,7 +168,8 @@ namespace spot
if (af)
{
filter_iter<tgba_explicit_formula> fi(af, sm, ss.useless_scc_map,
useful, strip);
useful, strip,
remove_all_useless);
fi.run();
tgba_explicit_formula* res = fi.result();
res->merge_transitions();
@ -169,7 +178,8 @@ namespace spot
else
{
filter_iter<tgba_explicit_string> fi(aut, sm, ss.useless_scc_map,
useful, strip);
useful, strip,
remove_all_useless);
fi.run();
tgba_explicit_string* res = fi.result();
res->merge_transitions();
@ -177,6 +187,4 @@ namespace spot
}
}
}

28
src/tgbaalgos/sccfilter.hh
View file

@ -1,5 +1,5 @@
// Copyright (C) 2009 Laboratoire de Recherche et Developpement de
// l'Epita (LRDE).
// Copyright (C) 2009, 2010 Laboratoire de Recherche et Developpement
// de l'Epita (LRDE).
//
// This file is part of Spot, a model checking library.
//
@ -26,8 +26,28 @@
namespace spot
{
// Prune unaccepting SCCs and remove superfluous acceptance conditions.
tgba* scc_filter(const tgba* aut);
/// \brief Prune unaccepting SCCs and remove superfluous acceptance
/// conditions.
///
/// This functions will explore the SCCs of the automaton and remove
/// dead SCCs (unaccepting, and with no exit path leading to an
/// accepting SCC).
///
/// Additionally, this will try to remove useless acceptance
/// conditions. This operation may diminish the number of
/// acceptance condition of the automaton, for instance when two
/// acceptance conditions are always used together we only keep one
/// (but it will never remove all acceptance conditions, even if it
/// would be OK to have zero).
///
/// Acceptance conditions on transitions going to non-accepting SCC
/// are all removed. Acceptance conditions going to an accepting
/// SCC and coming from another SCC are only removed if \a
/// remove_all_useless is set. The default value of \a
/// remove_all_useless is \c false because some algorithms (like the
/// degeneralization) will work better if transition going to an
/// accepting SCC are accepting.
tgba* scc_filter(const tgba* aut, bool remove_all_useless = false);
}

12
src/tgbatest/ltl2tgba.cc
View file

@ -195,6 +195,10 @@ syntax(char* prog)
<< " -R2t remove transitions using delayed simulation"
<< std::endl
<< " -R3 use SCC to reduce the automata" << std::endl
<< " -R3f clean more acceptance conditions that -R3" << std::endl
<< " "
<< "(prefer -R3 over -R3f if you degeneralize with -D, -DS, or -N)"
<< std::endl
<< " -Rd display the simulation relation" << std::endl
<< " -RD display the parity game (dot format)" << std::endl
<< std::endl
@ -280,6 +284,7 @@ main(int argc, char** argv)
bool from_file = false;
int reduc_aut = spot::Reduce_None;
int redopt = spot::ltl::Reduce_None;
bool scc_filter_all = false;
bool symbolic_scc_pruning = false;
bool display_reduce_form = false;
bool display_rel_sim = false;
@ -560,6 +565,11 @@ main(int argc, char** argv)
{
reduc_aut |= spot::Reduce_Scc;
}
else if (!strcmp(argv[formula_index], "-R3f"))
{
reduc_aut |= spot::Reduce_Scc;
scc_filter_all = true;
}
else if (!strcmp(argv[formula_index], "-R3b"))
{
symbolic_scc_pruning = true;
@ -806,7 +816,7 @@ main(int argc, char** argv)
if (reduc_aut & spot::Reduce_Scc)
{
tm.start("reducing A_f w/ SCC");
a = aut_scc = spot::scc_filter(a);
a = aut_scc = spot::scc_filter(a, scc_filter_all);
tm.stop("reducing A_f w/ SCC");
}

14
src/tgbatest/ltl2tgba.test
View file

@ -75,3 +75,17 @@ for opt in '' -D -DS; do
grep 'transitions: 6$' stdout
grep 'states: 4$' stdout
done
# Make sure '(G (p -> F q)) && ((X (p) U q) || ! X (p U (p && q)))'
# has 6 states and 15 transitions, before and after degeneralization.
f='(G (p -> F q)) && ((X (p) U q) || ! X (p U (p && q)))'
for opt in '' -D -DS; do
../ltl2tgba -k -f -R3 $opt "$f" > stdout
grep 'transitions: 15$' stdout
grep 'states: 6$' stdout
done
# Note: this is worse with -R3f.
../ltl2tgba -k -f -R3f -DS "$f" > stdout
grep 'transitions: 17$' stdout
grep 'states: 7$' stdout