We are happy to announce the release of Spot 2.5.
Spot is a library of algorithms for manipulating LTL formulas and
omega-automata (objects as commonly used in model checking).
A detailed list of new features in this new release is given at the end
of this email. The main features of this release are algorithms for
working with parity acceptance, new functions to convert to co-Büchi
when possible, a new tool for LTL synthesis, and some speedup
of our determinization algorithm.
You can find the new release here:
http://www.lrde.epita.fr/dload/spot/spot-2.5.tar.gz
See https://spot.lrde.epita.fr/ for documentation and installation
instructions.
(Note that due to some technical issues on our side, it might
be a few days before the packages for Debian *unstable*
are updated.)
This release contains code contributed by Alexandre Gbaguidi Aïsse,
Thibaud Michaud, Laurent Xu, Maximilien Colange, Etienne Renault,
and myself.
As always, please direct any feedback to <spot(a)lrde.epita.fr>.
New in spot 2.5 (2018-01-20)
Build:
- We no longer distribute the doxygen-generated documentation in
the tarball of Spot to save space. This documentation is still
available online at https://spot.lrde.epita.fr/doxygen/. If you
want to build a local copy you can configure Spot with
--enable-doxygen, or simply run "cd doc && make doc".
- All the images that illustrate the documentation have been
converted to SVG, to save space and improve quality.
Tools:
- ltlsynt is a new tool for synthesizing a controller from LTL/PSL
specifications.
- ltlcross learned --reference=COMMANDFMT to specify a translator
that should be trusted. Doing so makes it possible to reduce the
number of tests to be performed, as all other translators will be
compared to the reference's output when available. Multiple
reference can be given; in that case other tools are compared
against the smallest reference automaton.
- autcross, ltlcross, and ltldo learned --fail-on-timeout.
- ltl2tgba, autfilt, and dstar2tgba have some new '--parity' and
'--colored-parity' options to force parity acceptance on the
output. Different styles can be requested using for instance
--parity='min odd' or --parity='max even'.
- ltl2tgba, autfilt, and dstar2tgba have some new '--cobuchi' option
to force co-Büchi acceptance on the output. Beware: if the input
language is not co-Büchi realizable the output automaton will
recognize a superset of the input. Currently, the output is
always state-based.
- genltl learned to generate six new families of formulas, taken from
the SYNTCOMP competition on reactive synthesis, and from from
Müller & Sickert's GandALF'17 paper:
--gf-equiv=RANGE (GFa1 & GFa2 & ... & GFan) <-> GFz
--gf-implies=RANGE (GFa1 & GFa2 & ... & GFan) -> GFz
--ms-example=RANGE GF(a1&X(a2&X(a3&...)))&F(b1&F(b2&F(b3&...)))
--ms-phi-h=RANGE FG(a|b)|FG(!a|Xb)|FG(a|XXb)|FG(!a|XXXb)|...
--ms-phi-r=RANGE (FGa{n}&GFb{n})|((FGa{n-1}|GFb{n-1})&(...))
--ms-phi-s=RANGE (FGa{n}|GFb{n})&((FGa{n-1}&GFb{n-1})|(...))
- autfilt learned --streett-like to convert automata with DNF
acceptance into automata with Streett-like acceptance.
- autfilt learned --acceptance-is=ACC to filter automata by
acceptance condition. ACC can be the name of some acceptance
class (e.g. Büchi, Fin-less, Streett-like) or a precise acceptance
formula in the HOA syntax.
- ltldo learned to limit the number of automata it outputs using -n.
- ltlfilt learned to measure wall-time using --format=%r, and
cpu-time with --format=%R.
- The --format=%g option of tools that output automata used to
print the acceptance condition as a *formula* in the HOA format.
This %g may now take optional arguments to print the acceptance
*name* in different formats. For instance
... | autfilt -o '%[s]g.hoa'
will separate a stream of automata into different files named
by their acceptance name (Buchi, co-Buchi, Streett, etc.) or
"other" if no name is known for the acceptance condition.
- Tools that produce formulas now support --format=%[OP]n to
display the nesting depth of operator OP.
- The new -x tls-impl=N option allows to fine-tune the
implication-based simplification rules of ltl2tgba. See the
spot-x(7) man page for details.
- All tools learned to check the SPOT_OOM_ABORT environment
variable. This is only useful for debuging out-of-memory
conditions. See the spot-x(7) man page for details.
New functions in the library:
- spot::iar() and spot::iar_maybe() use index appearance records (IAR)
to translate Rabin-like automata into equivalent parity automaton.
This translation preserves determinism and is especially useful when
the input automaton is deterministic.
- spot::print_aiger() encodes an automaton as an AIGER circuit, as
required by the SYNTCOMP competition. It relies on a new named
property "synthesis outputs" that describes which atomic
propositions are to be encoded as outputs of the circuits.
- spot::dnf_to_streett() converts any automaton with a DNF
acceptance condition into a Streett-like automaton.
- spot::nsa_to_nca(), spot::dfn_to_nca(), spot::dfn_to_dca(), and
spot::nsa_to_dca(), convert automata with DNF or Streett-like
acceptance into deterministic or non-deterministic co-Büchi
automata. spot::to_dca() and spot::to_nca() dispatch between
these four functions. The language of produced automaton includes
the original language, but may be larger if the original automaton
is not co-Büchi realizable. Based on Boker & Kupferman FOSSACS'11
paper. Currently only supports state-based output.
- spot::scc_info::states_on_acc_cycle_of() returns all states
visited by any accepting cycle of the specified SCC. It only
works on automata with Streett-like acceptance.
- spot::is_recurrence(), spot::is_persistence(), and
spot::is_obligation() test if a formula is a recurrence,
persistance or obligation. The SPOT_PR_CHECK and SPOT_O_CHECK
environment variables can be used to select between multiple
implementations of these functions (see the spot-x(7) man page).
- spot::is_colored() checks if an automaton is colored
(i.e., every transition belongs to exactly one acceptance set).
- spot::change_parity() converts between different parity acceptance
conditions.
- spot::colorize_parity() transforms an automaton with parity
acceptance into a colored automaton (which is often what people
working with parity automata expect).
- spot::cleanup_parity_acceptance() simplifies a parity acceptance
condition.
- spot::parity_product() and spot::parity_product_or() are
specialized (but expensive) products that preserve parity
acceptance.
- spot::remove_univ_otf() removes universal transitions on the fly
from an alternating Büchi automaton using Miyano and Hayashi's
breakpoint algorithm.
- spot::stutter_invariant_states(),
spot::stutter_invariant_letters(),
spot::highlight_stutter_invariant_states(), ... These functions
help study a stutter-sensitive automaton and detect the subset of
states that are stutter-invariant. See
https://spot.lrde.epita.fr/ipynb/stutter-inv.html for examples.
- spot::acc_cond::name(fmt) is a new method that names well-known
acceptance conditions. The fmt parameter specifies the format to
use for that name (e.g. to the style used in HOA, or that used by
print_dot()).
- spot::formula::is_leaf() method can be used to detect formulas
without children (atomic propositions, or constants).
- spot::nesting_depth() computes the nesting depth of any LTL
operator.
- spot::check_determinism() sets both prop_semi_deterministic()
and prop_universal() appropriately.
Improvements to existing functions in the library:
- spot::tgba_determinize() has been heavily rewritten and
optimized. The algorithm has (almost) not changed, but it is
much faster now. It also features an optimization for
stutter-invariant automata that may produce slightly smaller
automata.
- spot::scc_info now takes an optional argument to disable some
features that are expensive and not always necessary. By
default scc_info tracks the list of all states that belong to an
SCC (you may now ask it not to), tracks the successor SCCs of
each SCC (that can but turned off), and explores all SCCs of the
automaton (you may request to stop on the first SCC that is
found accepting).
- In some cases, spot::degeneralize() would output Büchi automata
with more SCCs than its input. This was hard to notice, because
very often simulation-based simplifications remove those extra
SCCs. This situation is now detected by spot::degeneralized()
and fixed before returning the automaton. A new optional
argument can be passed to disable this behavior (or use -x
degen-remscc=0 from the command-line).
- The functions for detecting stutter-invariant formulas or
automata have been overhauled. Their interface changed
slightly. They are now fully documented.
- spot::postprocessor::set_type() can now request different forms
of parity acceptance as output. However currently the
conversions are not very smart: if the input does not already
have parity acceptance, it will simply be degeneralized or
determinized.
- spot::postprocessor::set_type() can now request co-Büchi
acceptance as output. This calls the aforementioned to_nca() or
to_dca() functions.
- spot::remove_fin() will now call simplify_acceptance(),
introduced in 2.4, before attempting its different Fin-removal
strategies.
- spot::simplify_acceptance() was already merging identical
acceptance sets, and detecting complementary sets i and j to
perform the following simplifications
Fin(i) & Inf(j) = Fin(i)
Fin(i) | Inf(j) = Inf(i)
It now additionally applies the following rules (again assuming i
and j are complementary):
Fin(i) & Fin(j) = f Inf(i) | Inf(j) = t
Fin(i) & Inf(i) = f Fin(i) | Inf(i) = t
- spot::formula::map(fun) and spot::formula::traverse(fun) will
accept additionnal arguments and pass them to fun(). See
https://spot.lrde.epita.fr/tut03.html for some examples.
Python-specific changes:
- The "product-states" property of automata is now accessible via
spot.twa.get_product_states() and spot.twa.set_product_states().
- twa_word instances can be displayed as SVG pictures, with one
signal per atomic proposition. For some examples, see the use of
the show() method in https://spot.lrde.epita.fr/ipynb/word.html
- The test suite is now using v4 of the Jupyter Notebook format.
- The function rabin_is_buchi_realizable() as its name suggests checks
if a rabin aut. is Büchi realizable. It is heavily based on
tra_to_tba() algorithm.
Deprecation notices:
(These functions still work but compilers emit warnings.)
- spot::scc_info::used_acc(), spot::scc_info::used_acc_of() and
spot::scc_info::acc() are deprecated. They have been renamed
spot::scc_info::marks(), spot::scc_info::marks_of() and
spot::scc_info::acc_sets_of() respectively for clarity.
Backward incompatible changes:
- The spot::closure(), spot::sl2(), spot::is_stutter_invariant()
functions no longer take && arguments. The former two have
spot::closure_inplace() and spot::sl2_inplace() variants. These
functions also do not take a list of atomic propositions as an
argument anymore.
- The spot::bmrand() and spot::prand() functions have been removed.
They were not used at all in Spot, and it is not Spot's objective
to provide such random functions.
- The spot::bdd_dict::register_all_propositions_of() function has
been removed. This low-level function was not used anywhere in
Spot anymore, since it's better to use spot::twa::copy_ap_of().
Bugs fixed:
- spot::simplify_acceptance() could produce incorrect output if the
first edge of the automaton was the only one with no acceptance
set. In spot 2.4.x this function was only used by autfilt
--simplify-acceptance; in 2.5 it is now used in remove_fin().
- spot::streett_to_generalized_buchi() could generate incorrect
automata with empty language if some Fin set did not intersect all
accepting SCCs (in other words, the fix from 2.4.1 was incorrect).
- ltlcross could crash when calling remove_fin() on an automaton
with 32 acceptance sets that would need an additional set.
- the down_cast() helper function used in severaly headers of Spot
was not in the spot namespace, and caused issues with some
configurations of GCC.
--
Alexandre Duret-Lutz
