spot/doc/org/ltlfilt.org
Alexandre Duret-Lutz bb2c697072 org: add a description for each page
Part of #176.

* doc/org/autfilt.org, doc/org/compile.org, doc/org/concepts.org,
doc/org/csv.org, doc/org/dstar2tgba.org, doc/org/genltl.org,
doc/org/hoa.org, doc/org/install.org, doc/org/ioltl.org,
doc/org/ltl2tgba.org, doc/org/ltl2tgta.org, doc/org/ltlcross.org,
doc/org/ltldo.org, doc/org/ltlfilt.org, doc/org/ltlgrind.org,
doc/org/oaut.org, doc/org/randaut.org, doc/org/randltl.org,
doc/org/satmin.org, doc/org/tools.org, doc/org/tut.org,
doc/org/tut01.org, doc/org/tut02.org, doc/org/tut03.org,
doc/org/tut10.org, doc/org/tut20.org, doc/org/tut21.org,
doc/org/tut22.org, doc/org/tut30.org, doc/org/upgrade2.org: Here.
* doc/org/index.org: Also add keywords in case it is useful, and
use a more descripting title for search engines.
2016-05-10 10:48:33 +02:00

478 lines
18 KiB
Org Mode

# -*- coding: utf-8 -*-
#+TITLE: =ltlfilt=
#+DESCRIPTION: Spot command-line tool for filtering, tranforming, and converting LTL formulas.
#+SETUPFILE: setup.org
#+HTML_LINK_UP: tools.html
This tool is a filter for LTL formulas. (It will also work with PSL
formulas.) It can be used to perform a number of tasks. Essentially:
- converting formulas from one syntax to another,
- transforming formulas,
- selecting formulas matching some criterion.
* Changing syntaxes
Because it read and write formulas, =ltlfilt= accepts
all the [[file:ioltl.org][common input and output options]].
Additionally, if no =-f= or =-F= option is specified, =ltlfilt=
will read formulas from the standard input.
For instance the following will convert two LTL formulas expressed
using infix notation (with different names supported for the same
operators) and convert it into LBT's syntax.
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt -l -f 'p1 U (p2 & GFp3)' -f 'X<>[]p4'
#+END_SRC
#+RESULTS:
: U p1 & p2 G F p3
: X F G p4
Conversely, here is how to rewrite formulas expressed using the
LBT's Polish notation. Let's take the following four formulas
taken from examples distributed with =scheck=:
#+BEGIN_SRC sh :results verbatim :exports both
cat >scheck.ltl<<EOF
! | G p0 & G p1 F p3
| | X p7 F p6 & | | t p3 p7 U | f p3 p3
& U & X p0 X p4 F p1 X X U X F p5 U p0 X X p3
U p0 & | p0 p5 p1
EOF
#+END_SRC
#+RESULTS:
These can be turned into something easier to read (to the human) with:
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt --lbt-input -F scheck.ltl
#+END_SRC
#+RESULTS:
: !(Gp0 | (Gp1 & Fp3))
: Xp7 | Fp6 | p3
: ((Xp0 & Xp4) U Fp1) & XX(XFp5 U (p0 U XXp3))
: p0 U ((p0 | p5) & p1)
* Altering the formula
As with [[file:randltl.org][=randltl=]], the =-r= option can be used to simplify formulas.
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt --lbt-input -F scheck.ltl -r
#+END_SRC
#+RESULTS:
: F!p0 & (F!p1 | G!p3)
: p3 | Xp7 | Fp6
: Fp1 & XX(XFp5 U (p0 U XXp3))
: p0 U (p1 & (p0 | p5))
You may notice that operands of n-ary operators such as =&= or =|= can
be reordered by =ltlfilt= even when the formula is not changed
otherwise. This is because Spot internally order all operands of
commutative and associative operators, and that this order depends on
the order in which the subformulas are first encountered. Adding
transformation options such as =-r= may alter this order. However
this difference is semantically insignificant.
Formulas can be easily negated using the =-n= option, rewritten into
negative normal form using the =--nnf= option, and the =W= and =M=
operators can be rewritten using =U= and =R= using the =--remove-wm=
option (note that this is already done when a formula is output in
Spin's syntax).
Another way to alter formula is to rename the atomic propositions it
uses. The =--relabel=abc= will relabel all atomic propositions using
letters of the alphabet, while =--relabel=pnn= will use =p0=, =p1=,
etc. as in LBT's syntax.
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt --lbt-input -F scheck.ltl -r --relabel=abc
#+END_SRC
#+RESULTS:
: F!a & (F!b | G!c)
: a | Xb | Fc
: Fa & XX(XFb U (c U XXd))
: a U (b & (a | c))
Note that the relabeling is reset between each formula: =p3= became
=c= in the first formula, but it became =d= in the third.
Another use of relabeling is to get rid of complex atomic propositions
such as the one shown when [[file:ioltl.org][presenting lenient mode]]:
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt --lenient --relabel=pnn -f '(a < b) U (process[2]@ok)'
#+END_SRC
#+RESULTS:
: p0 U p1
Finally, there is a second variant of the relabeling procedure that is
enabled by =--relabel-bool=abc= or =--relabel-book=pnn=. With this
option, Boolean subformulas that do not interfere with other
subformulas will be changed into atomic propositions. For instance:
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt -f '(a & !b) & GF(a & !b) & FG(!c)' --relabel-bool=pnn
ltlfilt -f '(a & !b) & GF(a & !b) & FG(!c & a)' --relabel-bool=pnn
#+END_SRC
#+RESULTS:
: p0 & GFp0 & FGp1
: p0 & p1 & GF(p0 & p1) & FG(p0 & p2)
In the first formula, the independent =a & !b= and =!c= subformulae
were respectively renamed =p0= and =p1=. In the second formula, =a &
!b= and =!c & a= are dependent so they could not be renamed; instead
=a=, =!b= and =c= were renamed as =p0=, =p1= and =p2=.
This option was originally developed to remove superfluous formulas
from benchmarks of LTL translators. For instance the automata
generated for =GF(a|b)= and =GF(p0)= should be structurally
equivalent: replacing =p0= by =a|b= in the second automaton should
turn in into the first automaton, and vice-versa. (However algorithms
dealing with =GF(a|b)= might be slower because they have to deal with
more atomic propositions.) So given a long list of LTL formulas, we
can combine =--relabel-bool= and =-u= to keep only one instance of
formulas that are equivalent after such relabeling. We also suggest
to use =--nnf= so that =!FG(a -> b)= would become =GF(p0)=
as well. For instance here are some LTL formulas extracted from an
[[http://www.fi.muni.cz/~xrehak/publications/verificationresults.ps.gz][industrial project]]:
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt --nnf -u --relabel-bool <<EOF
G (hfe_rdy -> F !hfe_req)
G (lup_sr_valid -> F lup_sr_clean )
G F (hfe_req)
reset && X G (!reset)
G ( (F hfe_clk) && (F ! hfe_clk) )
G ( (F lup_clk) && (F ! lup_clk) )
G F (lup_sr_clean)
G ( ( !(lup_addr_5_ <-> (X lup_addr_5_)) || !(lup_addr_6_ <-> (X lup_addr_6_)) || !(lup_addr_7_ <-> (X lup_addr_7_)) || !(lup_addr_8_ <-> (X lup_addr_8_)) ) -> ( (X !lup_sr_clean) && X ( (!( !(lup_addr_5_ <-> (X lup_addr_5_)) || !(lup_addr_6_ <-> (X lup_addr_6_)) || !(lup_addr_7_ <-> (X lup_addr_7_)) || !(lup_addr_8_ <-> (X lup_addr_8_)) )) U lup_sr_clean ) ) )
G F ( !(lup_addr_5_ <-> (X lup_addr_5_)) || !(lup_addr_6_ <-> (X lup_addr_6_)) || !(lup_addr_7_ <-> (X lup_addr_7_)) || !(lup_addr_8_ <-> (X lup_addr_8_)) )
(lup_addr_8__5__eq_0)
((hfe_block_0__eq_0)&&(hfe_block_1__eq_0)&&(hfe_block_2__eq_0)&&(hfe_block_3__eq_0))
G ((lup_addr_8__5__eq_0) -> X( (lup_addr_8__5__eq_0) || (lup_addr_8__5__eq_1) ) )
G ((lup_addr_8__5__eq_1) -> X( (lup_addr_8__5__eq_1) || (lup_addr_8__5__eq_2) ) )
G ((lup_addr_8__5__eq_2) -> X( (lup_addr_8__5__eq_2) || (lup_addr_8__5__eq_3) ) )
G ((lup_addr_8__5__eq_3) -> X( (lup_addr_8__5__eq_3) || (lup_addr_8__5__eq_4) ) )
G ((lup_addr_8__5__eq_4) -> X( (lup_addr_8__5__eq_4) || (lup_addr_8__5__eq_5) ) )
G ((lup_addr_8__5__eq_5) -> X( (lup_addr_8__5__eq_5) || (lup_addr_8__5__eq_6) ) )
G ((lup_addr_8__5__eq_6) -> X( (lup_addr_8__5__eq_6) || (lup_addr_8__5__eq_7) ) )
G ((lup_addr_8__5__eq_7) -> X( (lup_addr_8__5__eq_7) || (lup_addr_8__5__eq_8) ) )
G ((lup_addr_8__5__eq_8) -> X( (lup_addr_8__5__eq_8) || (lup_addr_8__5__eq_9) ) )
G ((lup_addr_8__5__eq_9) -> X( (lup_addr_8__5__eq_9) || (lup_addr_8__5__eq_10) ) )
G ((lup_addr_8__5__eq_10) -> X( (lup_addr_8__5__eq_10) || (lup_addr_8__5__eq_11) ) )
G ((lup_addr_8__5__eq_11) -> X( (lup_addr_8__5__eq_11) || (lup_addr_8__5__eq_12) ) )
G ((lup_addr_8__5__eq_12) -> X( (lup_addr_8__5__eq_12) || (lup_addr_8__5__eq_13) ) )
G ((lup_addr_8__5__eq_13) -> X( (lup_addr_8__5__eq_13) || (lup_addr_8__5__eq_14) ) )
G ((lup_addr_8__5__eq_14) -> X( (lup_addr_8__5__eq_14) || (lup_addr_8__5__eq_15) ) )
G ((lup_addr_8__5__eq_15) -> X( (lup_addr_8__5__eq_15) || (lup_addr_8__5__eq_0) ) )
G (((X hfe_clk) -> hfe_clk)->((hfe_req->X hfe_req)&&((!hfe_req) -> (X !hfe_req))))
G (((X lup_clk) -> lup_clk)->((lup_sr_clean->X lup_sr_clean)&&((!lup_sr_clean) -> (X !lup_sr_clean))))
EOF
#+END_SRC
#+RESULTS:
: G(a | Fb)
: GFa
: a & XG!a
: G(Fa & F!a)
: G((((!a & X!a) | (a & Xa)) & ((!b & X!b) | (b & Xb)) & ((!c & X!c) | (c & Xc)) & ((!d & X!d) | (d & Xd))) | (X!e & X((((!a & X!a) | (a & Xa)) & ((!b & X!b) | (b & Xb)) & ((!c & X!c) | (c & Xc)) & ((!d & X!d) | (d & Xd))) U e)))
: GF((!a & Xa) | (a & X!a) | (!b & Xb) | (b & X!b) | (!c & Xc) | (c & X!c) | (!d & Xd) | (d & X!d))
: a
: G(!a | X(a | b))
: G((!b & Xb) | ((!a | Xa) & (a | X!a)))
Here 29 formulas were reduced into 9 formulas after relabeling of
Boolean subexpression and removing of duplicate formulas. In other
words the original set of formulas contains 9 different patterns.
An option that can be used in combination with =--relabel= or
=--relabel-bool= is =--define=. This causes the correspondence of old
a new names to be printed as a set of =#define= statements.
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt -f '(a & !b) & GF(a & !b) & FG(!c)' --relabel-bool=pnn --define --spin
#+END_SRC
#+RESULTS:
: #define p0 (a && !b)
: #define p1 (!c)
: p0 && []<>p0 && <>[]p1
This can be used for instance if you want to use some complex atomic
propositions with third-party translators that do not understand them.
For instance the following sequence show how to use =ltl3ba= to create
a neverclaim for an LTL formula containing atomic propositions that
=ltl3ba= cannot parse:
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt -f '"proc@loc1" U "proc@loc2"' --relabel=pnn --define=ltlex.def --spin |
ltl3ba -F - >ltlex.never
cat ltlex.def ltlex.never
#+END_SRC
#+RESULTS:
#+begin_example
#define p0 ((proc@loc1))
#define p1 ((proc@loc2))
never { /* p0 U p1 */
T0_init:
if
:: (!p1 && p0) -> goto T0_init
:: (p1) -> goto accept_all
fi;
accept_all:
skip
}
#+end_example
As a side note, the tool [[file:ltldo.org][=ltldo=]] might be a simpler answer to this syntactic problem:
#+BEGIN_SRC sh :results verbatim :exports both
ltldo ltl3ba -f '"proc@loc1" U "proc@loc2"' --spin
#+END_SRC
#+RESULTS:
: never {
: T0_init:
: if
: :: ((proc@loc1) && (!(proc@loc2))) -> goto T0_init
: :: ((proc@loc2)) -> goto accept_all
: fi;
: accept_all:
: skip
: }
This case also relabels the formula before calling =ltl3ba=, and it
then rename all the atomic propositions in the output.
* Filtering
=ltlfilt= supports many ways to filter formulas:
#+BEGIN_SRC sh :results verbatim :exports results
ltlfilt --help | sed -n '/Filtering options.*:/,/^$/p' | sed '1d;$d'
#+END_SRC
#+RESULTS:
#+begin_example
--ap=N match formulas which use exactly N atomic
propositions
--boolean match Boolean formulas
--bsize=RANGE match formulas with Boolean size in RANGE
--equivalent-to=FORMULA match formulas equivalent to FORMULA
--eventual match pure eventualities
--guarantee match guarantee formulas (even pathological)
--implied-by=FORMULA match formulas implied by FORMULA
--imply=FORMULA match formulas implying FORMULA
--ltl match only LTL formulas (no PSL operator)
--obligation match obligation formulas (even pathological)
--safety match safety formulas (even pathological)
--size=RANGE match formulas with size in RANGE
--stutter-insensitive, --stutter-invariant
match stutter-insensitive LTL formulas
--syntactic-guarantee match syntactic-guarantee formulas
--syntactic-obligation match syntactic-obligation formulas
--syntactic-persistence match syntactic-persistence formulas
--syntactic-recurrence match syntactic-recurrence formulas
--syntactic-safety match syntactic-safety formulas
--syntactic-stutter-invariant, --nox
match stutter-invariant formulas syntactically
(LTL-X or siPSL)
--universal match purely universal formulas
-u, --unique drop formulas that have already been output (not
affected by -v)
-v, --invert-match select non-matching formulas
#+end_example
Most of the above options should be self-explanatory. For instance
the following command will extract all formulas from =scheck.ltl=
which do not represent guarantee properties.
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt --lbt-input -F scheck.ltl -v --guarantee
#+END_SRC
#+RESULTS:
: !(Gp0 | (Gp1 & Fp3))
Combining =ltlfilt= with [[file:randltl.org][=randltl=]] makes it easier to generate random
formulas that respect certain constraints. For instance let us
generate 10 formulas that are equivalent to =a U b=:
#+BEGIN_SRC sh :results verbatim :exports both
randltl -n -1 a b | ltlfilt --equivalent-to 'a U b' -n 10
#+END_SRC
#+RESULTS:
#+begin_example
a U b
(b W Fb) & ((Fb xor (a W b)) -> (a U b))
(b U (a W b)) U b
!(!b W (!a & !b))
(a M (a <-> (a xor !a))) U b
(a U b) | ((a & Xa) M Gb)
(a | b) U b
(b xor !b) -> ((b W a) U b)
(!a -> ((a W b) W (a & b))) U b
(a U b) | (Ga U b)
#+end_example
The =-n -1= option to =randltl= will cause it to output an infinite
stream of random formulas. =ltlfilt=, which reads its standard input
by default, will select only those equivalent to =a U b=. The output
of =ltlfilt= is limited to 10 formulas using =-n 10=. (As would using
=| head -n 10=.) Less trivial formulas could be obtained by adding
the =-r= option to =randltl= (or equivalently adding the =-r= and =-u=
option to =ltlfilt=).
Another similar example, that requires two calls to =ltlfilt=, is the
generation of random pathological safety formulas. Pathological
safety formulas are safety formulas that do not /look/ so
syntactically. We can generate some starting again with =randltl=,
then ignoring all syntactic safety formulas, and keeping only the
safety formulas in the remaining list.
#+BEGIN_SRC sh :results verbatim :exports both
randltl -r -n -1 a b | ltlfilt -v --syntactic-safety | ltlfilt --safety -n 10
#+END_SRC
#+RESULTS:
#+begin_example
G(!b | Gb | X(b & Fa))
((!a | X(!a R (!b U !a))) & X((!a & !b) | (a & b))) | (a & X(((!a & b) | (a & !b)) & (b R a)))
(F!a & (a | G!a)) R Xa
(b M XGb) W XXa
G(Xa & (!a U G!b))
(a & F!a) R X(a | b)
!a | (a & (a M !b))
b U XGb
(!a | (a R (!a | Xa))) M X!a
Ga | (!b U !a)
#+end_example
=ltlfilt='s filtering ability can also be used to answer questions
about a single formula. For instance is =a U (b U a)= equivalent to
=b U a=?
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt -f 'a U (b U a)' --equivalent-to 'b U a'
#+END_SRC
#+RESULTS:
: a U (b U a)
The command prints the formula and returns an exit status of 0 if the
two formulas are equivalent. It would print nothing and set the exit
status to 1, were the two formulas not equivalent.
Is the formula =F(a & X(!a & Gb))= stutter-invariant?
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt -f 'F(a & X(!a & Gb))' --stutter-invariant
#+END_SRC
#+RESULTS:
: F(a & X(!a & Gb))
Yes it is. And since it is stutter-invariant, there exist some
equivalent formulas that do not use =X= operator. The =--remove-x=
option gives one:
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt -f 'F(a & X(!a & Gb))' --remove-x
#+END_SRC
#+RESULTS:
: F(a & ((a & (a U (!a & Gb)) & ((!b U !a) | (b U !a))) | (!a & (!a U (a & !a & Gb)) & ((!b U a) | (b U a))) | (b & (b U (!a & Gb & !b)) & ((!a U !b) | (a U !b))) | (!b & (!b U (!a & b & Gb)) & ((!a U b) | (a U b))) | (!a & Gb & (G!a | Ga) & (Gb | G!b))))
We could even verify that the resulting horrible formula is equivalent
to the original one:
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt -f 'F(a & X(!a & Gb))' --remove-x | ltlfilt --equivalent-to 'F(a & X(!a & Gb))'
#+END_SRC
#+RESULTS:
: F(a & ((a & (a U (!a & Gb)) & ((!b U !a) | (b U !a))) | (!a & (!a U (a & !a & Gb)) & ((!b U a) | (b U a))) | (b & (b U (!a & Gb & !b)) & ((!a U !b) | (a U !b))) | (!b & (!b U (!a & b & Gb)) & ((!a U b) | (a U b))) | (!a & Gb & (G!a | Ga) & (Gb | G!b))))
It is therefore equivalent (otherwise the output would have been empty).
The difference between =--size= and =--bsize= lies in the way Boolean
subformula are counted. With =--size= the size of the formula is
exactly the number of atomic propositions and operators used. For
instance the following command generates 10 random formulas with size
5 (the reason [[file:randltl.org][=randltl=]] uses =--tree-size=8= is because the "tree" of
the formula generated randomly can be reduced by trivial
simplifications such as =!!f= being rewritten to =f=, yielding
formulas of smaller sizes).
#+BEGIN_SRC sh :results verbatim :exports both
randltl -n -1 --tree-size=8 a b | ltlfilt --size=5 -n 10
#+END_SRC
#+RESULTS:
#+begin_example
!F!Ga
X!(a U b)
!G(a & b)
(b W a) W 0
b R X!b
GF!Xa
Xb & Ga
a xor !Fb
a xor FXb
!(0 R Fb)
#+end_example
With =--bsize=, any Boolean subformula is counted as "1" in the total
size. So =F(a & b & c)= would have Boolean-size 2. This type of size
is probably a better way to classify formulas that are going to be
translated as automata, since transitions are labeled by Boolean
formulas: the complexity of the Boolean subformulas has little
influence on the overall translation. Here are 10 random formula with
Boolean-size 5:
#+BEGIN_SRC sh :results verbatim :exports both
randltl -n -1 --tree-size=12 a b | ltlfilt --bsize=5 -n 10
#+END_SRC
#+RESULTS:
#+begin_example
Gb xor Fa
FX!Fa
!(Fb U b)
(a -> !b) & XFb
X(b & Xb)
0 R (a U !b)
XXa R !b
(!a & !(!a xor b)) xor (0 R b)
GF(1 U b)
(a U b) R b
#+end_example
* Using =--format=
The =--format= option can be used the alter the way formulas are output (for instance use
#+HTML: <code>--latex --format='$%f$'</code>
to enclose formula in LaTeX format with =$...$=). You may also find
=--format= useful in more complex scenarios. For instance you could
print only the line numbers containing formulas matching some
criterion. In the following, we print only the numbers of the lines
of =scheck.ltl= that contain guarantee formulas:
#+BEGIN_SRC sh :results verbatim :exports both
ltlfilt --lbt-input -F scheck.ltl --guarantee --format=%L
#+END_SRC
#+RESULTS:
: 2
: 3
: 4
[[file:csv.org][More examples of how to use =--format= to create CSV files are on a
separate page]]
#+BEGIN_SRC sh :results verbatim :exports both
rm -f ltlex.def ltlex.never
#+END_SRC
# LocalWords: ltlfilt num toc LTL PSL syntaxes LBT's SRC GFp scheck
# LocalWords: ltl EOF lbt Gp Fp Xp XFp XXp randltl ary nnf wm abc
# LocalWords: pnn Xb Fc XFb XXd sed boolean bsize nox Gb Fb Xa XGb
# LocalWords: XF XXa