6 Sep
2017
6 Sep
'17
10:38 a.m.
We are happy to announce the release of Spot 2.4.
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. You can find the new release here:
http://www.lrde.epita.fr/dload/spot/spot-2.4.tar.gz
See https://spot.lrde.epita.fr/ for documentation and installation
instructions.
This release contains code contributed by Clément Gillard, Etienne
Renault, Henrich Lauko, Maximilien Colange, Thomas Medioni and myself.
As always, please direct any feedback to <spot(a)lrde.epita.fr>fr>.
New in spot 2.4 (2017-09-06)
Build:
- Spot is now built in C++14 mode, so you need at least GCC 5 or
clang 3.4. The current version of all major linux distributions
ship with at least GCC 6, which defaults to C++14, so this should
not be a problem. In *this* release of Spot, most of the header
files are still C++11 compatible, so you should be able to include
Spot in a C++11 project in case you do not yet want to upgrade.
There is also an --enable-c++17 option to configure in case you
want to force a build of Spot in C++17 mode.
Tools:
- genaut is a new binary that produces families of automata defined
in the literature (in the same way as we have genltl for LTL
formulas).
- autcross is a new binary that compares the output of tools
transforming automata (in the same way as we have ltlcross for
LTL translators).
- genltl learned two generate two new families of formulas:
--fxg-or=RANGE F(p0 | XG(p1 | XG(p2 | ... XG(pn))))
--gxf-and=RANGE G(p0 & XF(p1 & XF(p2 & ... XF(pn))))
The later is a generalization of --eh-pattern=9, for which a
single state TGBA always exists (but previous version of Spot
would build larger automata).
- autfilt learned to build the union (--sum) or the intersection
(--sum-and) of two languages by putting two automata side-by-side
and fiddling with the initial states. This complements the already
implemented intersection (--product) and union (--product-or),
both based on a product.
- autfilt learned to complement any alternating automaton with
option --dualize. (See spot::dualize() below.)
- autfilt learned --split-edges to convert labels that are Boolean
formulas into labels that are min-terms. (See spot::split_edges()
below.)
- autfilt learned --simplify-acceptance to simplify some acceptance
conditions. (See spot::simplify_acceptance() below.)
- autfilt --decompote-strength has been renamed to --decompose-scc
because it can now extract the subautomaton leading to an SCC
specified by number. (The old name is still kept as an alias.)
- The --stats=%c option of tools producing automata can now be
restricted to count complete SCCs, using %[c]c.
- Tools producing automata have a --stats=... option, and tools
producing formulas have a --format=... option. These two options
work similarly, the use of different names is just historical.
Starting with this release, all tools that recognize one of these
two options also accept the other one as an alias.
Library:
- A new library, libspotgen, gathers all functions used to generate
families of automata or LTL formulas, used by genltl and genaut.
- spot::sum() and spot::sum_and() implements the union and the
intersection of two automata by putting them side-by-side and
using non-deterministim or universal branching on the initial
state.
- twa objects have a new property: prop_complete(). This obviously
acts as a cache for the is_complete() function.
- spot::dualize() complements any alternating automaton. Since
the dual of a deterministic automaton is still deterministic, the
function spot::dtwa_complement() has been deprecated and simply
calls spot::dualize().
- spot::decompose_strength() was extended and renamed to
spot::decompose_scc() as it can now also extract a subautomaton
leading to a particular SCC. A demonstration of this feature via
the Python bindings can be found at
https://spot.lrde.epita.fr/ipynb/decompose.html
- The print_dot() function will now display names for well known
acceptance conditions under the formula when option 'a' is used.
We plan to enable 'a' by default in a future release, so a new
option 'A' has been added to hide the acceptance condition.
- The print_dot() function has a new experimental option 'x' to
output labels are LaTeX formulas. This is meant to be used in
conjunction with the dot2tex tool. See
https://spot.lrde.epita.fr/oaut.html#dot2tex
- A new named property for automata called "original-states" can be
used to record the origin of a state before transformation. It is
currently defined by the degeneralization algorithms, and by
transform_accessible() and algorithms based on it (like
remove_ap::strip(), decompose_scc()). This is realy meant as an
aid for writing algorithms that need this mapping, but it can also
be used to debug these algorithms: the "original-states"
information is displayed by the dot printer when the 'd' option is
passed. For instance in
% ltl2tgba 'GF(a <-> Fb)' --dot=s
% ltl2tgba 'GF(a <-> Fb)' | autfilt -B --dot=ds
the second command outputs an automaton with states that show
references to the first one.
- A new named property for automata called "degen-levels" keeps track
of the level of a state in a degeneralization. This information
complements the one carried in "original-states".
- A new named property for automata called "simulated-states" can be
used to record the origin of a state through simulation. The
behavior is similar to "original-states" above. Determinization
takes advantage of this in its pretty print.
- The new function spot::acc_cond::is_streett_like() checks whether
an acceptance condition is conjunction of disjunctive clauses
containing at most one Inf and at most one Fin. It builds a
vector of pairs to use if we want to assume the automaton has
Streett acceptance. The dual function is
spot::acc_cond::is_rabin_like() works similarly.
- The degeneralize() function has learned to consider acceptance
marks common to all edges comming to a state to select its initial
level. A similar trick was already used in sbacc(), and saves a
few states in some cases.
- There is a new spot::split_edges() function that transforms edges
(labeled by Boolean formulas over atomic propositions) into
transitions (labeled by conjunctions where each atomic proposition
appear either positive or negative). This can be used to
preprocess automata before feeding them to algorithms or tools
that expect transitions labeled by letters.
- spot::scc_info has two new methods to easily iterate over the
edges of an SCC: edges_of() and inner_edges_of().
- spot::scc_info can now be passed a filter function to ignore
or cut some edges.
- spot::scc_info now keeps track of acceptance sets that are common
to all edges in an SCC. These can be retrieved using
scc_info::common_sets_of(scc), and they are used by scc_info to
classify some SCCs as rejecting more easily.
- The new function acc_code::remove() removes all the given
acceptance sets from the acceptance condition.
- It is now possible to change an automaton acceptance condition
directly by calling twa::set_acceptance().
- spot::cleanup_acceptance_here now takes an additional boolean
parameter specifying whether to strip useless marks from the
automaton. This parameter is defaulted to true, in order to
keep this modification backward-compatible.
- The new function spot::simplify_acceptance() is able to perform
some simplifications on an acceptance condition, and might lead
to the removal of some acceptance sets.
- The function spot::streett_to_generalized_buchi() is now able to
work on automata with Streett-like acceptance.
- The function for converting deterministic Rabin automata to
deterministic Büchi automata (when possible), internal to the
remove_fin() procedure, has been updated to work with
transition-based acceptance and with Rabin-like acceptance.
- spot::relabel_here() was used on automata to rename atomic
propositions, it can now replace atomic propositions by Boolean
subformula. This makes it possible to use relabeling maps
produced by relabel_bse() on formulas.
- twa_graph::copy_state_names_from() can be used to copy the state
names from another automaton, honoring "original-states" if
present.
- Building automata for LTL formula with a large number N of atomic
propositions can be costly, because several loops and
data-structures are exponential in N. However a formula like
((a & b & c) | (d & e & f)) U ((d & e & f) | (g & h
& i))
can be translated more efficiently by first building an automaton
for (p0 | p1) U (p1 | p2), and then substituting p0, p1, p2 by the
appropriate Boolean formula. Such a trick is now attempted
for translation of formulas with 4 atomic propositions or
more (this threshold can be changed, see -x relabel-bool=N in
the spot-x(7) man page).
- The LTL simplification routines learned that an LTL formula like
G(a & XF(b & XFc & Fd) can be simplified to G(a & Fb & Fc &
Fd),
and dually F(a | XG(b | XGc | Gd)) = F(a | Gb | Gc | Gd).
When working with SERE, the simplification of "expr[*0..1]" was
improved. E.g. {{a[*]|b}[*0..1]} becomes {a[*]|b} instead of
{{a[+]|b}[*0..1]}.
- The new function spot::to_weak_alternating() is able to take an
input automaton with generalized Büchi/co-Büchi acceptance and
convert it to a weak alternating automaton.
- spot::sbacc() is can now also convert alternating automata
to state-based acceptance.
- spot::sbacc() and spot::degeneralize() learned to merge
accepting sinks.
- If the SPOT_BDD_TRACE environment variable is set, statistics
about BDD garbage collection and table resizing are shown.
- The & and | operators for acceptannce conditions have been changed
slightly to be more symmetrical. In older versions, operator &
would move Fin() terms to the front, but that is not the case
anymore. Also operator & was already grouping all Inf() terms
(for efficiency reasons), in this version operator | is
symmetrically grouping all Fin() terms.
- The automaton parser is now reentrant, making it possible to
process automata from different streams at the same time (i.e.,
using multiple spot::automaton_stream_parser instances at once).
- The print_hoa() and parse_automaton() functions have been updated
to recognize the "exist-branch" property of the non-released HOA
v1.1, as well as the new meaning of property "deterministic". (In
HOA v1 "properties: deterministic" means that the automaton has no
existential branching; in HOA v1.1 it disallows universal
branching as well.) The meaning of "deterministic" in Spot has
been adjusted to these new semantics, see "Backward-incompatible
changes" below.
- The parser for HOA now recognizes and verifies correct use of the
"univ-branch" property. This is known to be a problem with option
-H1 of ltl3ba 1.1.2 and ltl3dra 0.2.4, so the environment variable
SPOT_HOA_TOLERANT can be set to disable the diagnostic.
Python:
- The 'spot.gen' package exports the functions from libspotgen.
See https://spot.lrde.epita.fr/ipynb/gen.html for examples.
Bugs fixed:
- When the remove_fin() function was called on some automaton with
Inf-less acceptance involving at least one disjunction (e.g.,
generalized co-Büchi), it would sometimes output an automaton with
transition-based acceptance but marked as state-based.
- The complete() function could complete an empty co-Büchi automaton
into an automaton accepting everything.
Backward-incompatible changes:
- spot::acc_cond::mark_t::operator bool() has been marked as
explicit. The implicit converion to bool (and, via bool, to int)
was a source of bugs.
- spot::twa_graph::set_init_state(const state*) has been removed.
It was never used. You always want to use
spot::twa_graph::set_init_state(unsigned) in practice.
- The previous implementation of spot::is_deterministic() has been
renamed to spot::is_universal(). The new version of
spot::is_deterministic() requires the automaton to be both
universal and existential. This should not make any difference in
existing code unless you work with the recently added support for
alternating automata.
- spot::acc_cond::mark_t::sets() now returns an internal iterable
object instead of an std::vector<unsigned>.
- The color palette optionally used by print_dot() has been extended
from 9 to 16 colors. While the first 8 colors are similar, they
are a bit more saturated now.
Deprecation notices:
(These functions still work but compilers emit warnings.)
- spot::decompose_strength() is deprecated, it has been renamed
to spot::decompose_scc().
- spot::dtwa_complement() is deprecated. Prefer the more generic
spot::dualize() instead.
- The spot::twa::prop_deterministic() methods have been renamed to
spot::twa::prop_universal() for consistency with the change to
is_deterministic() listed above. We have kept
spot::twa::prop_deterministic() as a deprecated synonym for
spot::twa::prop_universal() to help backward compatibility.
- The spot::copy() function is deprecated. Use
spot::make_twa_graph() instead.
--
Alexandre Duret-Lutz