We are happy to announce the release of Spot 2.6.
Spot is a library of algorithms for manipulating LTL formulas and
omega-automata (objects as commonly used in model checking).
This release contains code contributed by Maximilien Colange, Antoine
Martin, and myself. 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-2.6.tar.gz
See https://spot.lrde.epita.fr/ for documentation and installation
instructions. Note that the unstable Debian packages and
stable RPM packages should be available within 24h.
As always, please direct any feedback to <spot(a)lrde.epita.fr>.
New in spot 2.6 (2018-07-04)
Command-line tools:
- autfilt learned --is-colored to filter automata that use
exactly one acceptance set per mark or transition.
- autfilt learned --has-univ-branching and --has-exist-branching
to keep automata that have universal branching, or that make
non-deterministic choices.
- autcross' tool specifications now have %M replaced by the name of
the input automaton.
- autcross now aborts if there is any parser diagnostic for the
input automata (previous versions would use the input automaton
whenever the parser would manage to read something).
- ltlcross, ltldo, and autcross learned shorthands to call
delag, ltl2dra, ltl2dgra, and nba2dpa.
- When autfilt is asked to build a Büchi automaton from
of a chain of many products, as in
"autfilt -B --product 1.hoa ... --product n.hoa in.hoa"
then it will automatically degeneralize the intermediate
products to avoid exceeding the number of supported
acceptance sets.
- genltl learned to generate six new families of LTL formulas:
--gf-equiv-xn=RANGE GF(a <-> X^n(a))
--gf-implies-xn=RANGE GF(a -> X^n(a))
--sejk-f=RANGE[,RANGE] f(0,j)=(GFa0 U X^j(b)), f(i,j)=(GFai U
G(f(i-1,j)))
--sejk-j=RANGE (GFa1&...&GFan) -> (GFb1&...&GFbn)
--sejk-k=RANGE (GFa1|FGb1)&...&(GFan|FGbn)
--sejk-patterns[=RANGE] φ₁,φ₂,φ₃ from Sikert et al's [CAV'16]
paper (range should be included in 1..3)
- genltl --ms-example can now take a two-range argument,
(as --sejk-f above).
Build:
- ./configure --enable-max-accsets=N let you specify a maximum
number of acceptance sets that Spot should support. The default
is still 32, but this limit is no longer hardcoded. Larger values
will cost additional memory and time.
- We know distribute RPM packages for Fedora 28. See
file:///home/adl/git/spot/doc/userdoc/install.html#Fedora
Library:
- The PSL/LTL simplification routine learned the following:
q R Xf = X(q R f) if q is suspendable
q U Xf = X(q U f) if q is suspendable
{SERE;1} = {1} if {SERE} accepts [*0]
{SERE;1} = {SERE} if {SERE} does not accept [*0]
- gf_guarantee_to_ba() is a specialized construction for translating
formulas of the form GF(guarantee) to BA or DBA, and
fg_safety_to_dca() is a specialized construction for translating
formulas of the form FG(safety) to DCA. These are generalizations
of some constructions proposed by J. Esparza, J. Křentínský, and
S. Sickert (LICS'18).
These are now used by the main translation routine, and can be
disabled by passing -x '!gf-guarantee' to ltl2tgba. For example,
here are the size of deterministic transition-based generalized
Büchi automata constructed from four GF(guarantee) formulas with
two versions of Spot, and converted to other types of
deterministic automata by other tools distributed with Owl 18.06.
"x(y)" means x states and y acceptance sets.
ltl2tgba -D delag ltl2dra
2.5 2.6 18.06 18.06
------------------------- ----------- -------------
GF(a <-> XXa) 9(1) 4(1) 4(2) 9(4)
GF(a <-> XXXa) 27(1) 8(1) 8(2) 25(4)
GF(((a & Xb) | XXc) & Xd) 6(1) 4(1) 16(1) 5(2)
GF((b | Fa) & (b R Xb)) 6(2) 2(1) 3(4) 3(4)
Note that in the above the automata produced by 'ltl2tgba -D' in
version 2.5 were not deterministic (because -D is only a
preference). They are deterministic in 2.6 and other tools.
- spot::product() and spot::product_or() learned to produce an
automaton with a simpler acceptance condition if one of the
argument is a weak automaton. In this case the resulting
acceptance condition is (usually) that of the other argument.
- spot::product_susp() and spot::product_or_susp() are new
functions for building products between an automaton A and
a "suspendable" automaton B. They are also optimized for
the case that A is weak.
- When 'generic' acceptance is enabled, the translation routine will
split the input formula on Boolean operators into components that
are syntactically 'obligation', 'suspendable', or 'something
else'. Those will be translated separately and combined with
product()/product_susp(). This is inspired by the ways things are
done in ltl2dstar or delag, and can be disabled by passing option
-xltl-split=0, as in ltl2tgba -G -D -xltl-split=0. Here are the
sizes of deterministic automata (except for ltl3tela which produces
non-deterministic automata) produced with generic acceptance
using two versions of ltl2tgba and other tools for reference.
ltl2tgba -DG delag ltl3tela
2.5 2.6 18.06 1.1.2
------------ ------- --------
FGa0&GFb0 2(2) 1(2) 1(2) 1(2)
(FGa1&GFb1)|FGa0|GFb0 16(6) 1(4) 1(4) 1(9)
(FGa2&GFb2)|((FGa1|GFb1)&FGa0&GFb0) 29(8) 1(6) 1(6) 3(11)
FGa0|GFb0 5(4) 1(2) 1(2) 1(5)
(FGa1|GFb1)&FGa0&GFb0 8(4) 1(4) 1(4) 1(7)
(FGa2|GFb2)&((FGa1&GFb1)|FGa0|GFb0) 497(14) 1(6) 1(6) 1(14)
GFa1 <-> GFz 4(6) 1(3) 1(4) 1(7)
(GFa1 & GFa2) <-> GFz 8(4) 1(3) 1(6) 3(10)
(GFa1 & GFa2 & GFa3) <-> GFz 21(4) 1(4) 1(8) 3(13)
GFa1 -> GFz 5(4) 1(2) 1(2) 1(5)
(GFa1 & GFa2) -> GFz 12(4) 1(3) 1(3) 1(6)
(GFa1 & GFa2 & GFa3) -> GFz 41(4) 1(4) 1(4) 1(7)
FG(a|b)|FG(!a|Xb) 4(2) 2(2) 2(2) 2(3)
FG(a|b)|FG(!a|Xb)|FG(a|XXb) 21(2) 4(3) 4(3) 4(4)
FG(a|b)|FG(!a|Xb)|FG(a|XXb)|FG(!a|XXXb) 170(2) 8(4) 8(4) 8(5)
- For 'parity' output, the 'ltl-split' optimization just separates
obligation subformulas from the rest, where a determinization is
still performed.
ltl2tgba -DP ltl3dra ltl2dpa
2.5 2.6 0.2.3 18.06
-------------- ------- -------
FGp0 & (Gp1 | XFp2) 6(2) 4(1) 4(1) 4(2)
G!p0 | F(p0 & (!p1 W p2)) 5(2) 4(2) n/a 5(2)
(p0 W XXGp0) & GFp1 & FGp2 6(2) 5(2) n/a 6(3)
(The above just show a few cases that were improved. There are
many cases where ltl2dpa still produces smaller automata.)
- The automaton postprocessor will now simplify acceptance
conditions more aggressively, calling spot::simplify_acceptance()
or spot::cleanup_acceptance() depending on the optimization level.
- print_dot(), used to print automata in GraphViz's format,
underwent several changes:
* option "a", for printing the acceptance condition, is now
enabled by default. Option "A", introduced in Spot 2.4, can be
used to hide the acceptance condition in case you do not want
it. This change of course affects the --dot option of all the
command-line tools, as well as the various way to display
automata using the Python bindings.
* when option "1" is used to hide state names and force the
display of state numbers, the actual state names is now moved to
the "tooltip" field of the state. The SVG files produced by
"dot -Tsvg" will show those as popups. This is also done for
state labels of Kripke structures.
* the output digraph is now named using the name of the automaton
if available, or the empty string otherwise. (Previous versions
used to call all digraphs "G".) This name appears as a tooltip
in SVG figures when the mouse is over the acceptance condition.
* a new option "u" hides "true states" behind "exiting
transitions". This can be used to display alternating automata
in a way many people expect.
* a new option "K" cancels the effect of "k" (which uses state
labels whenever possible). This is most useful when one want to
force transition-labeling of a Kripke structure, where "k" is
usually the default.
- spot::twa_graph::merge_states() is a new method that merges states
with the exact same outgoing edges. As it performs no reordering
of the edges, it is better to call it when you know that the edges
in the twa_graph are sorted (e.g. after a call to merge_edges()).
- spot::twa_graph::purge_unreachable_states() now takes a function
which is called with the new numbering of states. This is useful
to update an external structure that references states of the twa
that we want to purge.
- spot::scc_filter() now automatically turns automata marked as
inherently-weak into weak automata with state-based acceptance.
The acceptance condition is set to Büchi unless the input had
co-Büchi or t acceptance. spot::scc_filter_states() will pass
inherently-weak automata to spot::scc_filter().
- spot::cleanup_parity() and spot::cleanup_parity_here() are smarter
and now remove from the acceptance condition the parity colors
that are not used in the automaton.
- spot::contains() and spot::are_equivalent() can be used to
check language containement between two automata or formulas.
They are most welcome in Python, since we used to redefine
them every now and them. Some examples are shown in
https://spot.lrde.epita.fr/ipynb/contains.html
- aut1->exclusive_word(aut2) is a new method that returns a word
accepted by aut1 or aut2 but not both. The exclusive_run()
variant will return. This is useful when comparing automata and
looking for differences. See also
https://spot.lrde.epita.fr/ipynb/contains.html
- spot::complement_semidet(aut) is a new function that returns the
complement of aut, where aut is a semideterministic automaton. The
function uses the NCSB complementation algorithm proposed by
F. Blahoudek, M. Heizmann, S. Schewe, J. Strejček, and MH. Tsai
(TACAS'16).
- spot::remove_alternation() was slightly improved on very-weak
alternating automata: the labeling of the outgoing transitions in
the resulting TGBA makes it more likely that simulation-based
reductions will reduce it.
- When applied to automata that are not WDBA-realizable,
spot::minimize_wdba() was changed to produce an automaton
recognizing a language that includes the original one. As a
consequence spot::minimize_obligation() and
spot::is_wdba_realizable() now only need one containement check
instead of two.
- Slightly improved log output for the SAT-based minimization
functions. The CSV log files now include an additional column
with the size of the reference automaton, and they now have a
header line. These log files give more details and are more
accurate in the case of incremental SAT-solving.
Python:
- New spot.jupyter package. This currently contains a function for
displaying several arguments side by side in a Jupyter notebook.
See https://spot.lrde.epita.fr/ipynb/alternation.html for some
examples.
- Strings are now implicitely converted into formulas when passed
as arguments to functions that expect formulas. Previously this
was done only for a few functions.
- The Python bindings for sat_minimize() now have display_log and
return_log options; these are demonstrated on the new
https://spot.lrde.epita.fr/ipynb/satmin.html page.
Bugs fixed:
- Python *.py and *.so files are now always installed into the same
directory. This was an issue on systems like Fedora that separate
plateform-specific packages from non-plateform-specific ones.
- print_dot() will correctly escape strings containing \n in HTML
mode.
- The HOA parser will now accept Alias: declarations that occur
before AP:.
- The option --allow-dups of randltl now works properly.
- Converting generalized-co-Büchi to Streett using dnf_to_nca()
could produce bogus automata if the input had rejecting SCCs.
Deprecation notices:
- The type spot::acc_cond::mark_t has been overhauled and uses
a custom bit-vector to represent acceptance sets instead of
storing everything in a "unsigned int". This change is
to accomodate configure's --enable-max-accsets=N option and
has several effect:
* The following shortcuts are deprecated:
acc_cond::mark_t m1 = 0U;
acc_cond::mark_t m2 = -1U;
instead, use:
acc_cond::mark_t m1 = {};
acc_cond::mark_t m2 = acc_cond::mark_t::all();
* acc_cond::mark_t::value_t is deprecated. It is now only
defined when --enable-max-accsets=32 (the default) and
equal to "unsigned" for backward compatibility reasons.
Backward incompatibilities:
- Functions spot::parity_product() and spot::parity_product_or()
were removed. The code was unused, hard to maintain, and bogus.
- The output of print_dot() now include the acceptance condition.
Add option "A" (supported since version 2.4) to cancel that.
- Because genltl now supports LTL pattern with two argumens, using
--format=%L may output two comma-separated integer. This is an
issue if you used to produce CSV files using for instance:
genltl --format='%F,%L,%f' ...
Make sure to quote %L to protect the potential commas:
genltl --format='%F,"%L",%f' ...
- In Spot 2.5 and prior running "ltl2tgba --generic --det" on some
formula would attempt to translate it as deterministic TGBA or
determinize it into an automaton with parity acceptance. Version
2.5 introduced --parity to force parity acceptance on the output.
This version finally gives --generic some more natural semantics:
any acceptance condition can be used.
--
Alexandre Duret-Lutz
