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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
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28
src/tgbaalgos/sccfilter.hh
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@ -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);
}