spot/doc/org/ltldo.org

# -*- coding: utf-8 -*-
#+TITLE: =ltldo=
#+DESCRIPTION: Spot's wrapper for third-party LTL translators
#+INCLUDE: setup.org
#+HTML_LINK_UP: tools.html
#+PROPERTY: header-args:sh :results verbatim :exports both

This tool is a wrapper for tools that read LTL/PSL formulas and
(optionally) output automata.

It reads formulas specified using the [[file:ioltl.org][common options for specifying
input]] and passes each formula to a tool (or a list of tools) specified
using options similar to those of [[file:ltlcross.org][=ltlcross=]].  In case that tool
returns an automaton, the resulting automaton is read back by =ltldo=
and is finally output as specified using the [[file:oaut.org][common options for
outputing automata]].

In effect, =ltldo= wraps the I/O interface of the Spot tools on top of
any other tool.

* Example: computing statistics for =ltl3ba=

As a motivating example, consider a scenario where we want to run
[[https://sourceforge.net/projects/ltl3ba/][=ltl3ba=]] on a set of 10 formulas stored in a file.  For each formula
we would like to compute the number of states and edges in the
Büchi automaton produced by =ltl3ba=.

Here is the input file:

#+BEGIN_SRC sh :results silent
cat >sample.ltl <<EOF
1
1 U a
!(!((a U Gb) U b) U GFa)
(b <-> Xc) xor Fb
FXb R (a R (1 U b))
Ga
G(!(c | (a & (a W Gb))) M Xa)
GF((b R !a) U (Xc M 1))
G(Xb | Gc)
XG!F(a xor Gb)
EOF
#+END_SRC
#+RESULTS:

We will first implement this scenario without =ltldo=.

A first problem that the input is not in the correct syntax: although
=ltl3ba= understands =G= and =F=, it does not support =xor= or =M=,
and requires the Boolean operators =||= and =&&=.  This syntax
issue can be fixed by processing the input with [[file:ltlfilt.org][=ltlfilt -s=]].

A second problem is that =ltl3ba= (at least version 1.1.1) can only
process one formula at a time.  So we'll need to call =ltl3ba= in a
loop.

Finally, one way to compute the size of the resulting Büchi automaton
is to pipe the output of =ltl3ba= through [[file:autfilt.org][=autfilt=]].

Here is how the shell command could look like:

#+BEGIN_SRC sh
ltlfilt -F sample.ltl -s |
while read f; do
  ltl3ba -f "$f" | autfilt --stats="$f,%s,%t"
done
#+END_SRC
#+RESULTS:
#+begin_example
true,1,1
true U a,2,4
!(!((a U []b) U b) U []<>a),2,4
(((!b && !Xc) || (b && Xc)) && !<>b) || (<>b && !((!b && !Xc) || (b && Xc))),7,21
<>Xb V (a V (true U b)),6,28
[]a,1,1
[](Xa U (Xa && !(c || (a && ([]b V (a || []b)))))),1,0
[]<>((b V !a) U (true U Xc)),2,4
[](Xb || []c),3,11
X[]!<>((a && ![]b) || (!a && []b)),4,10
#+end_example


Using =ltldo= the above command can be reduced to this:

#+BEGIN_SRC sh
ltldo 'ltl3ba -f %s>%O' -F sample.ltl --stats='%f,%s,%t'
#+END_SRC
#+RESULTS:
#+begin_example
1,1,1
1 U a,2,4
!(!((a U Gb) U b) U GFa),2,4
(b <-> Xc) xor Fb,7,21
FXb R (a R (1 U b)),6,28
Ga,1,1
G(!(c | (a & (a W Gb))) M Xa),1,0
GF((b R !a) U (Xc M 1)),2,4
G(Xb | Gc),3,11
XG!F(a xor Gb),4,10
#+end_example

Note that the formulas look different in both cases, because in the
=while= loop the formula printed has already been processed with
=ltlfilt=, while =ltldo= emits the input string untouched.

In fact, as we will discuss below, =ltl3ba= is a tool that =ltldo=
already knows about, so there is a shorter way to run the above
command:

#+BEGIN_SRC sh :exports code
ltldo ltl3ba -F sample.ltl --stats='%f,%s,%t'
#+END_SRC
#+RESULTS:
#+begin_example
1,1,1
1 U a,2,4
!(!((a U Gb) U b) U GFa),2,4
(b <-> Xc) xor Fb,7,21
FXb R (a R (1 U b)),6,28
Ga,1,1
G(!(c | (a & (a W Gb))) M Xa),1,0
GF((b R !a) U (Xc M 1)),2,4
G(Xb | Gc),3,11
XG!F(a xor Gb),4,10
#+end_example

* Example: running =spin= and producing HOA

Here is another example, where we use Spin to produce two automata in
the [[http://adl.github.io/hoaf/][HOA format]].  Spin has no support for HOA, but =ltldo= simply
converts the never claim produced by =spin= into this format.

#+BEGIN_SRC sh :wrap SRC hoa
ltldo 'spin -f %s>%O' -f a -f GFa
#+END_SRC

#+RESULTS:
#+BEGIN_SRC hoa
HOA: v1
States: 2
Start: 0
AP: 1 "a"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels state-acc colored
properties: deterministic
--BODY--
State: 0 {0}
[0] 1
State: 1 {0}
[t] 1
--END--
HOA: v1
States: 2
Start: 0
AP: 1 "a"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels state-acc complete
--BODY--
State: 0
[0] 1
[t] 0
State: 1 {0}
[t] 0
--END--
#+END_SRC

Again, using the shorthands defined below, the previous command can be
simplified to just this:

#+BEGIN_EXAMPLE sh
  ltldo spin -f a -f GFa
#+END_EXAMPLE

* Syntax for specifying tools to call

The syntax for specifying how a tool should be called is the same as
in [[file:ltlcross.org][=ltlcross=]].  Namely, the following sequences are available.

#+BEGIN_SRC sh :exports results
ltldo --help | sed -n '/character sequences:/,/^$/p' | sed '1d;$d'
#+END_SRC

#+RESULTS:
:   %%                         a single %
:   %f,%s,%l,%w                the formula as a (quoted) string in Spot, Spin,
:                              LBT, or Wring's syntax
:   %F,%S,%L,%W                the formula as a file in Spot, Spin, LBT, or
:                              Wring's syntax
:   %O                         the automaton output in HOA, never claim, LBTT, or
:                              ltl2dstar's format

Contrarily to =ltlcross=, it this not mandatory to specify an output
filename using one of the sequence for that last line.  For instance,
we could simply run a formula though =echo= to compare different
output syntaxes:

#+BEGIN_SRC sh
ltldo -f 'p0 U p1' -f 'GFp0' 'echo %f, %s, %l, %w'
#+END_SRC
#+RESULTS:
: (p0) U (p1), (p0) U (p1), U p0 p1, (p0=1) U (p1=1)
: (G(F(p0))), ([](<>(p0))), G F p0, (G(F(p0=1)))

In this case (i.e., when the command does not specify any output
filename), =ltldo= will not output anything.


As will =ltlcross=, multiple commands can be given, and they will be
executed on each formula in the same order.

A typical use-case is to compare statistics of different tools:

#+BEGIN_SRC sh
ltldo -F sample.ltl 'spin -f %s>%O' 'ltl3ba -f %s>%O' --stats=%T,%f,%s,%e
#+END_SRC

#+RESULTS:
#+begin_example
spin -f %s>%O,1,2,2
ltl3ba -f %s>%O,1,1,1
spin -f %s>%O,1 U a,2,3
ltl3ba -f %s>%O,1 U a,2,3
spin -f %s>%O,!(!((a U Gb) U b) U GFa),23,86
ltl3ba -f %s>%O,!(!((a U Gb) U b) U GFa),2,3
spin -f %s>%O,(b <-> Xc) xor Fb,12,23
ltl3ba -f %s>%O,(b <-> Xc) xor Fb,7,11
spin -f %s>%O,FXb R (a R (1 U b)),28,176
ltl3ba -f %s>%O,FXb R (a R (1 U b)),6,20
spin -f %s>%O,Ga,1,1
ltl3ba -f %s>%O,Ga,1,1
spin -f %s>%O,G(!(c | (a & (a W Gb))) M Xa),15,51
ltl3ba -f %s>%O,G(!(c | (a & (a W Gb))) M Xa),1,0
spin -f %s>%O,GF((b R !a) U (Xc M 1)),12,60
ltl3ba -f %s>%O,GF((b R !a) U (Xc M 1)),2,4
spin -f %s>%O,G(Xb | Gc),4,8
ltl3ba -f %s>%O,G(Xb | Gc),3,5
spin -f %s>%O,XG!F(a xor Gb),8,21
ltl3ba -f %s>%O,XG!F(a xor Gb),4,7
#+end_example

Here we used =%T= to output the name of the tool used to translate the
formula =%f= as an automaton with =%s= states and =%e= edges.
If you feel that =%T= has too much clutter, you can give each tool
a shorter name by prefixing its command with ={name}=.

In the following example, we moved the formula used on its own line
using the trick that the command =echo %f= will not be subject to
=--stats= (since it does not declare any output automaton).

#+BEGIN_SRC sh
ltldo -F sample.ltl  --stats=%T,%s,%e \
      'echo "#" %f' '{spin}spin -f %s>%O' '{ltl3ba}ltl3ba -f %s>%O'
#+END_SRC

#+RESULTS:
#+begin_example
# (1)
spin,2,2
ltl3ba,1,1
# (1) U (a)
spin,2,3
ltl3ba,2,3
# (!((!(((a) U (G(b))) U (b))) U (G(F(a)))))
spin,23,86
ltl3ba,2,3
# ((b) <-> (X(c))) xor (F(b))
spin,12,23
ltl3ba,7,11
# (F(X(b))) R ((a) R ((1) U (b)))
spin,28,176
ltl3ba,6,20
# (G(a))
spin,1,1
ltl3ba,1,1
# (G((!((c) | ((a) & ((a) W (G(b)))))) M (X(a))))
spin,15,51
ltl3ba,1,0
# (G(F(((b) R (!(a))) U ((X(c)) M (1)))))
spin,12,60
ltl3ba,2,4
# (G((X(b)) | (G(c))))
spin,4,8
ltl3ba,3,5
# (X(G(!(F((a) xor (G(b)))))))
spin,8,21
ltl3ba,4,7
#+end_example

Much more readable!

#+BEGIN_SRC sh :results silent :exports results
rm -f sample.ltl
#+END_SRC

* Shorthands for existing tools

There is a list of existing tools for which =ltldo= (and =ltlcross=)
have built-in specifications.  This list can be printed using the
=--list-shorthands= option:

#+BEGIN_SRC sh
ltldo --list-shorthands
#+END_SRC
#+RESULTS:
#+begin_example
If a COMMANDFMT does not use any %-sequence, and starts with one of
the following regexes, then the string on the right is appended.

  delag                                    %f>%O
  lbt                                      <%L>%O
  ltl2ba                                   -f %s>%O
  ltl2(da|dgra|dpa|dra|ldba|na|nba|ngba)   %f>%O
  ltl2dstar                                --output-format=hoa %[MW]L %O
  ltl2tgba                                 -H %f>%O
  ltl3(ba|dra|hoa|tela)                    -f %s>%O
  modella                                  %[MWei^]L %O
  spin                                     -f %s>%O
  owl.* ltl2[bdeglnpr]+a\b                 -f %f>%O
  owl.* ltl2delta2\b                       -f %f
  owl.* ltl-utilities\b                    -f %f

Any {name} and directory component is skipped for the purpose of
matching those prefixes.  So for instance
  '{DRA} ~/mytools/ltl2dstar-0.5.2'
will be changed into
  '{DRA} ~/mytools/ltl2dstar-0.5.2 --output-format=hoa %[MW]L %O'
#+end_example

Therefore, you can type the following to obtain a Dot output (as
requested with =-d=) for the neverclaim produced by =ltl2ba -f a=.

#+BEGIN_SRC sh :prologue export SPOT_DOTEXTRA= SPOT_DOTDEFAULT=
ltldo ltl2ba -f a -d
#+END_SRC
#+RESULTS:
#+begin_example
digraph "" {
  rankdir=LR
  label="\n[Büchi]"
  labelloc="t"
  node [shape="circle"]
  I [label="", style=invis, width=0]
  I -> 0
  0 [label="0", peripheries=2]
  0 -> 1 [label="a"]
  1 [label="1", peripheries=2]
  1 -> 1 [label="1"]
}
#+end_example

The =ltl2ba= argument passed to =ltldo= was interpreted as if you had
typed ={ltl2ba}ltl2ba -f %s>%O=.

Those shorthand patterns are only tested if the command string does
not contain any =%= character.  They should always patch a prefix of
the command, ignoring any leading directory.  This makes it possible
to add options:

#+BEGIN_SRC sh
ltldo ltl3ba 'ltl3ba -H2' -f GFa --stats='%T, %s states, %e edges'
#+END_SRC
#+RESULTS:
: ltl3ba, 2 states, 4 edges
: ltl3ba -H2, 1 states, 2 edges

* Transparent renaming

If you have ever tried to use =spin=, =ltl2ba=, or =ltl3ba=, to translate
a formula such as =[]!Error=, you have noticed that it does not work:

#+BEGIN_SRC sh :prologue "exec 2>&1" :epilogue true
spin -f '[]!Error'
#+END_SRC
#+RESULTS:
: tl_spin: expected predicate, saw 'E'
: tl_spin: []!Error
: -------------^

All these tools are based on the same LTL parser, that allows
only atomic propositions starting with a lowercase letter.

Running the same command through =ltldo= will work:

#+BEGIN_SRC sh
ltldo spin -f '[]!Error' -s
#+END_SRC
#+RESULTS:
: never {
: accept_init:
:   if
:   :: (!(Error)) -> goto accept_init
:   fi;
: }

(We need the =-s= option to obtain a never claim, instead of the
default HOA output.)

What happened is that =ltldo= renamed the atomic propositions in the
formula before calling =spin=.  So =spin= actually received the
formula =[]!p0= and produced a never claim using =p0=.  That never
claim was then relabeled by =ltldo= to use =Error= instead of =p0=.

This renaming occurs any time some command uses =%s= or =%S= and the
formula has atomic propositions incompatible with Spin's conventions;
or when some command uses =%l= or =%L=, and the formula has
atomic propositions incompatible with [[http://www.tcs.hut.fi/Software/maria/tools/lbt/][LBT's conventions]].

For =%f=, =%w=, =%F=, and =%W=, no relabeling is automatically
performed, but you can pass option =--relabel= if you need to force it
for some reason (e.g., if you have a tool that uses almost Spot's
syntax, but cannot cope with double-quoted atomic propositions).

There are some cases where the renaming is not completely transparent.
For instance if a translator tool outputs some HOA file named after
the formula translated, the name will be output unmodified (since this
can be any text string, there is no way for =ltldo= to assume it is
an LTL formula).  In the following example, you can see that the
automaton uses the atomic proposition =Error=, but its name contains a
reference to =p0=.

#+BEGIN_SRC sh :wrap SRC hoa
ltldo 'ltl3ba -H' -f '[]!Error'
#+END_SRC
#+RESULTS:
#+BEGIN_SRC hoa
HOA: v1
name: "BA for [](!(p0))"
States: 1
Start: 0
AP: 1 "Error"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels state-acc colored
properties: deterministic
--BODY--
State: 0 "accept_init" {0}
[!0] 0
--END--
#+END_SRC

If this is a problem, you can always force a new name with the
=--name= option:

#+BEGIN_SRC sh :wrap SRC hoa
ltldo 'ltl3ba -H' -f '[]!Error' --name='BA for %f'
#+END_SRC

#+RESULTS:
#+BEGIN_SRC hoa
HOA: v1
name: "BA for []!Error"
States: 1
Start: 0
AP: 1 "Error"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels state-acc colored
properties: deterministic
--BODY--
State: 0 "accept_init" {0}
[!0] 0
--END--
#+END_SRC

* Acting as a portfolio of translators
   :PROPERTIES:
   :CUSTOM_ID: portfolio
   :END:

Here is a formula on which different translators produce Büchi automata of
different sizes (states and edges):

#+BEGIN_SRC sh
ltldo ltl2ba ltl3ba 'ltl2tgba -s' -f 'F(a & Xa | FGa)' \
      --stats='%T: %s st. (%n non-det.), %e ed.'
#+END_SRC

#+RESULTS:
: ltl2ba: 5 st. (2 non-det.), 9 ed.
: ltl3ba: 3 st. (1 non-det.), 4 ed.
: ltl2tgba -s: 3 st. (0 non-det.), 5 ed.

Instead of outputting the result of the translation of each formula by each
translator, =ltldo= can also be configured to output the smallest
automaton obtained for each formula:

#+BEGIN_SRC sh :wrap SRC hoa
ltldo ltl2ba ltl3ba 'ltl2tgba -s' -f 'F(a & Xa | FGa)' --smallest
#+END_SRC

#+RESULTS:
#+begin_SRC hoa
HOA: v1
States: 3
Start: 0
AP: 1 "a"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels state-acc
--BODY--
State: 0
[t] 0
[0] 1
State: 1
[0] 2
State: 2 {0}
[t] 2
--END--
#+end_SRC

Therefore, in practice, =ltldo --smallest trans1 trans2 trans3...=
acts like a portfolio of translators, always returning the smallest
produced automaton.

The sorting criterion can be specified using =--smallest= or
=--greatest=, optionally followed by a format string with
=%=-sequences.  The default criterion is =%s,%e=, so the number of
states will be compared first, and in case of equality the number of
edges.  If we desire the automaton that has the fewest states (=%s=),
and in case of equality the smallest number of non-deterministic
states (=%n=), we can use the following command instead.

#+BEGIN_SRC sh
ltldo ltl2ba ltl3ba 'ltl2tgba -s' -f 'F(a & Xa | FGa)' --smallest=%s,%n
#+END_SRC

#+RESULTS:
#+begin_example
HOA: v1
name: "F(a & Xa)"
States: 3
Start: 0
AP: 1 "a"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels state-acc complete
properties: deterministic terminal
--BODY--
State: 0
[!0] 0
[0] 1
State: 1
[!0] 0
[0] 2
State: 2 {0}
[t] 2
--END--
#+end_example

We can of course apply this to a stream of formulas.  For instance
here is a more complex pipeline, where we take 11 patterns from [[https://doi.org/10.1145/302405.302672][Dwyer
et al. (FMSP'98)]], and print which translator among =ltl2ba=,
=ltl3ba=, and =ltl2tgba -s= would produce the smallest automaton.

#+BEGIN_SRC sh
  genltl --dac=10..20 --format=%F:%L,%f |
  ltldo -F-/2 ltl2ba ltl3ba 'ltl2tgba -s' --smallest --stats='%<,%T'
#+END_SRC
#+RESULTS:
#+begin_example
dac-patterns:10,ltl2ba
dac-patterns:11,ltl2ba
dac-patterns:12,ltl2tgba -s
dac-patterns:13,ltl2tgba -s
dac-patterns:14,ltl2tgba -s
dac-patterns:15,ltl2tgba -s
dac-patterns:16,ltl2ba
dac-patterns:17,ltl2tgba -s
dac-patterns:18,ltl2ba
dac-patterns:19,ltl3ba
dac-patterns:20,ltl2ba
#+end_example

Note that in case of equality, only the first translator is returned.
So when =ltl2ba= is output above, it could be (and it probably is, see
below) the case that =ltl3ba= or =ltl2tgba -s= are also producing
automata of equal size.

To understand the above pipeline, remove the =ltldo= invocation.  The
[[file:genltl.org][=genltl=]] command outputs this:

#+BEGIN_SRC sh
genltl --dac=10..20 --format=%F:%L,%f
#+END_SRC
#+RESULTS:
#+begin_example
dac-patterns:10,G((p0 & !p1) -> (!p1 U (!p1 & p2)))
dac-patterns:11,!p0 W (p0 W (!p0 W (p0 W G!p0)))
dac-patterns:12,Fp0 -> ((!p0 & !p1) U (p0 | ((!p0 & p1) U (p0 | ((!p0 & !p1) U (p0 | ((!p0 & p1) U (p0 | (!p1 U p0)))))))))
dac-patterns:13,Fp0 -> (!p0 U (p0 & (!p1 W (p1 W (!p1 W (p1 W G!p1))))))
dac-patterns:14,G((p0 & Fp1) -> ((!p1 & !p2) U (p1 | ((!p1 & p2) U (p1 | ((!p1 & !p2) U (p1 | ((!p1 & p2) U (p1 | (!p2 U p1))))))))))
dac-patterns:15,G(p0 -> ((!p1 & !p2) U (p2 | ((p1 & !p2) U (p2 | ((!p1 & !p2) U (p2 | ((p1 & !p2) U (p2 | (!p1 W p2) | Gp1)))))))))
dac-patterns:16,Gp0
dac-patterns:17,Fp0 -> (p1 U p0)
dac-patterns:18,G(p0 -> Gp1)
dac-patterns:19,G((p0 & !p1 & Fp1) -> (p2 U p1))
dac-patterns:20,G((p0 & !p1) -> (p2 W p1))
#+end_example

This is a two-column CSV file where each line is a description of the
origin of the formula (=%F:%L=), followed by the formula itself
(=%f=).  The =ltldo= from the previous pipeline simply takes its input
from the second column of its standard input (=-F-/2=), runs that
formula through the three translators, picks the smallest automaton
(=--smallest=), and for this automaton, it displays the translator that
was used (=%T=) along with the portion of the CSV file that was before
the input column (=%<=).


If you are curious about the actual size of the automata produced by
=ltl2ba=, =ltl3ba=, and =ltl2tgba -s= in the above example, you can
quickly build a CSV file using the following pipeline where each
command appends a new column.  We wrap =ltl2ba= and =ltl3ba= with
=ltldo= so that they can process one column of the CSV that is input,
and output statistics in CSV as output.  =ltl2tgba= does not need
that, as it already supports those features. In the resulting CSV
file, displayed as a table below, entries like =2s 4e 0d= represent an
automaton with 2 states, 4 edges, and that is not deterministic.
(We have a [[file:csv.org][separate page]] with more examples of reading and writing CSV
files.)

#+NAME: small-bench
#+BEGIN_SRC sh :exports code
echo input,ltl2ba,ltl3ba,ltl2tgba -s
genltl --dac=10..20 --format=%F:%L,%f |
  ltldo -F-/2 ltl2ba --stats '%<,%f,%ss %ee %dd' |
  ltldo -F-/2 ltl3ba --stats '%<,%f,%>,%ss %ee %dd' |
  ltl2tgba -s -F-/2 --stats '%<,%>,%ss %ee %dd'
#+END_SRC

#+BEGIN_SRC sh :results output raw :exports results :noweb yes
sed '
$d
s/|/\\vert{}/g
s/--/@@html:--@@/g
s/^/| /
s/$/ |/
s/,/|/g
s/"//g
1a\
|-|\
|<c>|<r>|<r>|<r>|
' <<EOF
<<small-bench()>>
EOF
#+END_SRC

#+ATTR_HTML: :class table-pre
#+RESULTS:
|      input      |     ltl2ba |     ltl3ba | ltl2tgba -s |
|-----------------+------------+------------+-------------|
|       <c>       |        <r> |        <r> |         <r> |
| dac-patterns:10 |   2s 4e 0d |   2s 4e 1d |    2s 4e 1d |
| dac-patterns:11 |   5s 9e 1d |   5s 9e 1d |    5s 9e 1d |
| dac-patterns:12 |  8s 29e 0d |  8s 20e 0d |   7s 17e 1d |
| dac-patterns:13 |  8s 17e 0d |  8s 17e 0d |   6s 12e 1d |
| dac-patterns:14 | 16s 62e 0d | 11s 33e 0d |   7s 19e 1d |
| dac-patterns:15 | 10s 47e 0d | 10s 41e 0d |   6s 17e 1d |
| dac-patterns:16 |   1s 1e 1d |   1s 1e 1d |    1s 1e 1d |
| dac-patterns:17 |   4s 7e 0d |   4s 7e 0d |    3s 5e 1d |
| dac-patterns:18 |   2s 3e 0d |   2s 3e 1d |    2s 3e 1d |
| dac-patterns:19 |   4s 8e 0d |   3s 6e 0d |    3s 7e 1d |
| dac-patterns:20 |   2s 4e 0d |   2s 4e 1d |    2s 4e 1d |

#+ATTR_HTML: :class table-pre
#+RESULTS:

* Controlling and measuring time

The run time of each command can be restricted with the =-T NUM=
option.  The argument is the maximum number of seconds that each
command is allowed to run.

When a timeout occurs a warning is printed on stderr, and no automaton
(or statistic) is output by =ltdo= for this specific pair of
command/formula.  The processing then continue with other formulas and
tools.  Timeouts are not considered as errors, so they have no effect
on the exit status of =ltldo=.  This behavior can be changed with
option =--fail-on-timeout=, in which case timeouts are considered as
errors.

For each command (that does not terminate with a timeout) the runtime
can be printed using the =%r= escape sequence.  This makes =ltldo= an
alternative to [[file:ltlcross.org][=ltlcross=]] for running benchmarks without any
verification.