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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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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
///