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toparity: revert symmetry-based optimization of LAR

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Fixes #390.

* spot/twaalgos/toparity.cc: Revert the relevant part of 516e9536.
* tests/python/toparity.py: Add test case.
* NEWS: Mention the issue.
This commit is contained in:
Alexandre Duret-Lutz 2019-06-18 17:35:57 +02:00
parent ed52f3c48c
commit c66b3d88d0
3 changed files with 32 additions and 99 deletions
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5
NEWS
View file

@ -138,6 +138,11 @@ New in spot 2.7.5.dev (not yet released)
could produce a different number of edges for the same input in
two different transition order.
- A symmetry-based optimization of the LAR algorithm performed in
spot::to_parity() turned out to be incorrect. The optimization
has been removed. "ltlsynt --algo=lar" is the only code using
this function currently.
New in spot 2.7.5 (2019-06-05)
Build:

116
spot/twaalgos/toparity.cc
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@ -34,19 +34,10 @@ namespace spot
{
unsigned state;
std::vector<unsigned> perm;
std::vector<unsigned> count;
bool operator<(const lar_state& s) const
{
if (state == s.state)
{
if (perm == s.perm)
return count < s.count;
else
return perm < s.perm;
}
else
return state < s.state;
return state == s.state ? perm < s.perm : state < s.state;
}
std::string to_string() const
@ -54,15 +45,13 @@ namespace spot
std::stringstream s;
s << state << " [";
unsigned ps = perm.size();
for (unsigned i = 0; i < ps; ++i)
for (unsigned i = 0; i != ps; ++i)
{
if (i > 0)
s << ", ";
unsigned p = perm[i];
s << p << '@' << count[p];
s << ',';
s << perm[i];
}
s << ']';
return s.str();
}
};
@ -83,42 +72,10 @@ namespace spot
twa_graph_ptr run()
{
auto symm = aut_->acc().get_acceptance().symmetries();
// we need to know for each symmetry class:
// - its id
// - its elements in order (any arbitrary order will do)
// - its size
std::vector<acc_cond::mark_t> classes;
std::vector<unsigned> acc2class(aut_->num_sets(), -1U);
std::vector<unsigned> accpos(aut_->num_sets(), -1U);
for (unsigned k : aut_->acc().all_sets().sets())
{
unsigned r = symm[k];
if (k == r) // new class
{
acc2class[k] = classes.size();
accpos[k] = 0;
classes.push_back({k});
}
else
{
unsigned c = acc2class[r];
acc2class[k] = c;
accpos[k] = classes[c].count();
classes[c].set(k);
}
}
// create resulting automaton
res_ = make_twa_graph(aut_->get_dict());
res_->copy_ap_of(aut_);
struct stack_elem
{
unsigned num;
lar_state s;
};
std::deque<stack_elem> todo;
std::deque<lar_state> todo;
auto get_state = [this, &todo](const lar_state& s)
{
auto it = lar2num.emplace(s, -1U);
@ -126,21 +83,16 @@ namespace spot
{
unsigned nb = res_->new_state();
it.first->second = nb;
todo.push_back({nb, s});
todo.push_back(s);
}
return it.first->second;
};
// initial state
{
std::vector<unsigned> p0;
std::vector<unsigned> c0;
for (unsigned i = 0; i < classes.size(); ++i)
{
p0.push_back(i);
c0.push_back(0);
}
lar_state s0{aut_->get_init_state_number(), p0, c0};
for (unsigned k : aut_->acc().all_sets().sets())
p0.push_back(k);
lar_state s0{aut_->get_init_state_number(), p0};
unsigned init = get_state(s0); // put s0 in todo
res_->set_init_state(init);
}
@ -148,67 +100,39 @@ namespace spot
// main loop
while (!todo.empty())
{
lar_state current = std::move(todo.front().s);
unsigned src_num = todo.front().num;
lar_state current = todo.front();
todo.pop_front();
// TODO todo could store this number to avoid one lookup
unsigned src_num = get_state(current);
for (const auto& e : aut_->out(current.state))
{
// find the new permutation
std::vector<unsigned> new_perm = current.perm;
std::vector<unsigned> new_count = current.count;
std::vector<unsigned> hits(new_count.size(), 0);
unsigned h = 0;
for (unsigned k : e.acc.sets())
{
unsigned c = acc2class[k];
if (accpos[k] == new_count[c])
new_count[c] += 1;
else
++hits[c];
if (new_count[c] == classes[c].count())
{
new_count[c] = 0;
auto it =
std::find(new_perm.begin(), new_perm.end(), c);
assert(it != new_perm.end());
auto it = std::find(new_perm.begin(), new_perm.end(), k);
h = std::max(h, unsigned(new_perm.end() - it));
std::rotate(it, it+1, new_perm.end());
}
}
lar_state dst{e.dst, new_perm, new_count};
lar_state dst{e.dst, new_perm};
unsigned dst_num = get_state(dst);
// do the h last elements satisfy the acceptance condition?
acc_cond::mark_t m({});
for (auto c = new_perm.end() - h; c != new_perm.end(); ++c)
m |= classes[*c];
for (auto c = new_perm.begin(); c != new_perm.end() - h; ++c)
{
for (unsigned k : classes[*c].sets())
{
if (hits[*c] == 0)
break;
m.set(k);
--hits[*c];
}
}
acc_cond::mark_t m(new_perm.end() - h, new_perm.end());
if (aut_->acc().accepting(m))
res_->new_edge(src_num, dst_num, e.cond, {2*m.count()});
res_->new_edge(src_num, dst_num, e.cond, {2*h});
else
res_->new_edge(src_num, dst_num, e.cond, {2*m.count()+1});
res_->new_edge(src_num, dst_num, e.cond, {2*h+1});
}
}
// parity max even
unsigned nb_colors = 2*aut_->num_sets() + 2;
res_->set_acceptance(nb_colors,
acc_cond::acc_code::parity(true, false, nb_colors));
// inherit properties of the input automaton
res_->prop_copy(aut_, { false, false, true, false, true, true });
res_->set_acceptance(2*aut_->num_sets() + 2,
acc_cond::acc_code::parity(true, false, 2*aut_->num_sets() + 2));
if (pretty_print)
{

6
tests/python/toparity.py
View file

@ -1,6 +1,6 @@
#!/usr/bin/python3
# -*- mode: python; coding: utf-8 -*-
# Copyright (C) 2018 Laboratoire de Recherche et Développement de
# Copyright (C) 2018, 2019 Laboratoire de Recherche et Développement de
# l'EPITA.
#
# This file is part of Spot, a model checking library.
@ -45,3 +45,7 @@ for f in spot.randltl(5, 2000):
p = spot.to_parity(n)
assert spot.are_equivalent(n, p)
# Issue #390.
a = spot.translate('!(GFa -> (GFb & GF(!b & !Xb)))', 'gen', 'det');
b = spot.to_parity(a);
assert a.equivalent_to(b)