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merge_states: don't call defrag_states if unnecessary

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* spot/twa/twagraph.cc (merge_states): Return the number
of removed states, and use that to decide if defrag_states
is needed.
* spot/twa/twagraph.hh, NEWS: Document that.
* tests/core/tgbagraph.test, tests/core/twagraph.cc: Adjust test case.
This commit is contained in:
Alexandre Duret-Lutz 2021-07-13 10:20:14 +02:00
parent d019ea61fe
commit 4570c735f3
5 changed files with 40 additions and 12 deletions
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2
NEWS
View file

@ -228,6 +228,8 @@ New in spot 2.9.7.dev (not yet released)
before attempting to detect mergeable states. When merging states
with identical outgoing transitions, it will now also consider
self-looping transitions has having identical destinations.
Additionally, this function now returns the number of states that
have been merged (and therefore removed from the automaton).
Python:

7
spot/twa/twagraph.cc
View file

@ -289,7 +289,7 @@ namespace spot
g_.chain_edges_();
}
void twa_graph::merge_states()
unsigned twa_graph::merge_states()
{
if (!is_existential())
throw std::runtime_error(
@ -379,7 +379,10 @@ namespace spot
else
s = -1U;
defrag_states(remap, st);
unsigned merged = num_states() - st;
if (merged)
defrag_states(remap, st);
return merged;
}
void twa_graph::purge_unreachable_states(shift_action* f, void* action_data)

15
spot/twa/twagraph.hh
View file

@ -579,8 +579,19 @@ namespace spot
///
/// The implementation will sort the edges of the automaton to
/// ease the comparison between two states. This may miss some
/// self-loop based in non-deterministic automata.
void merge_states();
/// self-loop equivalences in non-deterministic automata.
///
/// States whose input have been redirected as a consequence of a
/// merge are removed from the automaton. This procedure
/// therefore renumber states.
///
/// Merging states might create duplicate transitions in the
/// automaton. For instance (1)-a->(2) and (1)-a->(3) will become
/// (1)-a->(1) and (1)-a->(1) if (1), (2) and (3) are merged into
/// (1).
///
/// \return the number of states that have been merged and removed.
unsigned merge_states();
/// \brief Remove all dead states
///

12
tests/core/tgbagraph.test
View file

@ -1,6 +1,6 @@
#!/bin/sh
# -*- coding: utf-8 -*-
# Copyright (C) 2014-2018, 2020 Laboratoire de Recherche et
# Copyright (C) 2014-2018, 2020, 2021 Laboratoire de Recherche et
# Développement de l'Epita (LRDE).
#
# This file is part of Spot, a model checking library.
@ -291,16 +291,20 @@ State: 2
[t] 0&1
--END--
HOA: v1
States: 1
Start: 0
States: 2
Start: 1
AP: 0
acc-name: all
Acceptance: 0 t
properties: trans-labels explicit-labels state-acc complete
properties: deterministic
--BODY--
State: 0
[t] 0
State: 1
[t] 0
[t] 0
[t] 0
[t] 0
--END--
EOF

16
tests/core/twagraph.cc
View file

@ -1,5 +1,5 @@
// -*- coding: utf-8 -*-
// Copyright (C) 2014-2018 Laboratoire de Recherche et Développement
// Copyright (C) 2014-2019, 2021 Laboratoire de Recherche et Développement
// de l'Epita (LRDE).
//
// This file is part of Spot, a model checking library.
@ -167,14 +167,22 @@ static void f5()
auto s1 = tg->new_state();
auto s2 = tg->new_state();
auto s3 = tg->new_state();
auto s4 = tg->new_state();
auto s5 = tg->new_state();
tg->set_init_state(s3);
tg->set_init_state(s5);
tg->new_edge(s1, s2, bddtrue);
tg->new_edge(s2, s2, bddtrue);
tg->new_edge(s3, s2, bddtrue);
tg->new_edge(s4, s4, bddtrue);
tg->new_edge(s5, s1, bddtrue);
tg->new_edge(s5, s2, bddtrue);
tg->new_edge(s5, s3, bddtrue);
tg->new_edge(s5, s4, bddtrue);
tg->merge_states();
unsigned out = tg->merge_states();
std::cerr << out << '\n';
assert(out == 3);
spot::print_hoa(std::cout, tg) << '\n';
}