Commit 61bf5daa authored by Alexandre Duret-Lutz's avatar Alexandre Duret-Lutz
Browse files

Add code example using the postprocessor.

* doc/org/tut30.org: New file.
* doc/Makefile.am, doc/org/tut.org: Add it.
parent 87cb58d0
......@@ -91,6 +91,7 @@ ORG_FILES = \
org/tut20.org \
org/tut21.org \
org/tut22.org \
org/tut30.org \
org/satmin.org \
org/satmin.tex \
org/setup.org \
......
......@@ -17,6 +17,7 @@ three interfaces supported by Spot: shell commands, Python, or C++.
- [[file:tut02.org][Relabeling Formulas]]
- [[file:tut10.org][Translating an LTL formula into a never claim]]
- [[file:tut20.org][Converting a never claim into HOA]]
- [[file:tut30.org][Converting Rabin (or Other) to Büchi, and simplifying it]]
* Examples in Python and C++
......
# -*- coding: utf-8 -*-
#+TITLE: Converting Rabin (or Other) to Büchi, and simplifying it
#+SETUPFILE: setup.org
#+HTML_LINK_UP: tut.html
Consider the following Rabin automaton, generated by =ltl2dstar=:
#+BEGIN_SRC sh :results verbatim :exports code
ltldo ltl2dstar -f 'F(Xp1 xor XXp1)' -H > tut30.hoa
#+END_SRC
#+RESULTS:
#+NAME: tut30in
#+BEGIN_SRC sh :results verbatim :exports none
autfilt tut30.hoa --dot=.a
#+END_SRC
#+RESULTS: tut30in
#+begin_example
digraph G {
rankdir=LR
label=<(Fin(<font color="#5DA5DA">⓿</font>) &amp; Inf(<font color="#F17CB0">❶</font>)) | (Fin(<font color="#FAA43A">❷</font>) &amp; Inf(<font color="#B276B2">❸</font>)) | (Fin(<font color="#60BD68">❹</font>) &amp; Inf(<font color="#F15854">❺</font>))>
labelloc="t"
node [shape="circle"]
fontname="Lato"
node [fontname="Lato"]
edge [fontname="Lato"]
node[style=filled, fillcolor="#ffffa0"] edge[arrowhead=vee, arrowsize=.7]
I [label="", style=invis, width=0]
I -> 6
0 [label=<0<br/><font color="#FAA43A">❷</font><font color="#F15854">❺</font>>]
0 -> 2 [label=<!p1>]
0 -> 4 [label=<p1>]
1 [label=<1<br/><font color="#FAA43A">❷</font><font color="#F15854">❺</font>>]
1 -> 4 [label=<!p1>]
1 -> 3 [label=<p1>]
2 [label=<2<br/><font color="#B276B2">❸</font><font color="#60BD68">❹</font>>]
2 -> 0 [label=<!p1>]
2 -> 4 [label=<p1>]
3 [label=<3<br/><font color="#B276B2">❸</font><font color="#60BD68">❹</font>>]
3 -> 4 [label=<!p1>]
3 -> 1 [label=<p1>]
4 [label=<4<br/><font color="#F17CB0">❶</font><font color="#FAA43A">❷</font><font color="#60BD68">❹</font>>]
4 -> 4 [label=<!p1>]
4 -> 4 [label=<p1>]
5 [label=<5<br/><font color="#FAA43A">❷</font><font color="#60BD68">❹</font>>]
5 -> 2 [label=<!p1>]
5 -> 3 [label=<p1>]
6 [label=<6<br/><font color="#FAA43A">❷</font><font color="#60BD68">❹</font>>]
6 -> 5 [label=<!p1>]
6 -> 5 [label=<p1>]
}
#+end_example
#+BEGIN_SRC dot :file tut30in.png :cmdline -Tpng :var txt=tut30in :exports results
$txt
#+END_SRC
#+RESULTS:
[[file:tut30in.png]]
Our goal is to generate an equivalent Büchi automaton, preserving
determinism if possible. However nothing of what we will write is
specific to Rabin acceptance: the same code will convert automata with
any acceptance to Büchi acceptance.
* Shell
We use =autfilt= with option =-B= to request Büchi acceptance and
state-based output, =-D= to express a preference for deterministic
output, and =-H= for output in the HOA format. Using option
=-D/--deterministic= (or =--small=) actually activates the
"postprocessing" routines of Spot: the acceptance will not only be
changed to Büchi, but simplification routines (useless SCCs removal,
simulation-based reductions, acceptance sets simplifications,
WDBA-minimization, ...) will also be applied.
#+BEGIN_SRC sh :results verbatim :exports both
autfilt -B -D -H tut30.hoa
#+END_SRC
#+RESULTS:
#+begin_example
HOA: v1
States: 5
Start: 1
AP: 1 "p1"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels state-acc complete
properties: deterministic inherently-weak
--BODY--
State: 0 {0}
[t] 0
State: 1
[t] 2
State: 2
[!0] 3
[0] 4
State: 3
[0] 0
[!0] 3
State: 4
[!0] 0
[0] 4
--END--
#+end_example
#+NAME: tut30out
#+BEGIN_SRC sh :results verbatim :exports none
autfilt -B -D tut30.hoa
#+END_SRC
#+RESULTS: tut30out
#+begin_example
digraph G {
rankdir=LR
node [shape="circle"]
fontname="Lato"
node [fontname="Lato"]
edge [fontname="Lato"]
node[style=filled, fillcolor="#ffffa0"] edge[arrowhead=vee, arrowsize=.7]
I [label="", style=invis, width=0]
I -> 1
0 [label="0", peripheries=2]
0 -> 0 [label=<1>]
1 [label="1"]
1 -> 2 [label=<1>]
2 [label="2"]
2 -> 3 [label=<!p1>]
2 -> 4 [label=<p1>]
3 [label="3"]
3 -> 0 [label=<p1>]
3 -> 3 [label=<!p1>]
4 [label="4"]
4 -> 0 [label=<!p1>]
4 -> 4 [label=<p1>]
}
#+end_example
#+BEGIN_SRC dot :file tut30out.png :cmdline -Tpng :var txt=tut30out :exports results
$txt
#+END_SRC
#+RESULTS:
[[file:tut30out.png]]
In the general case transforming an automaton with a complex
acceptance condition into a Büchi automaton can make the output
bigger. However the postprocessing routines may manage to simplify
the result further.
* Python
The Python version uses the =postprocess()= routine:
#+BEGIN_SRC python :results output :exports both
import spot
aut = spot.automaton('tut30.hoa').postprocess('BA', 'deterministic')
print(aut.to_str('hoa'))
#+END_SRC
#+RESULTS:
#+begin_example
HOA: v1
States: 5
Start: 1
AP: 1 "p1"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels state-acc complete
properties: deterministic inherently-weak
--BODY--
State: 0 {0}
[t] 0
State: 1
[t] 2
State: 2
[!0] 3
[0] 4
State: 3
[0] 0
[!0] 3
State: 4
[!0] 0
[0] 4
--END--
#+end_example
The =postprocess()= function has an interface similar to
[[file:tut10.org][the =translate()= function discussed previously]]:
#+BEGIN_SRC python :results output :exports both
import spot
help(spot.postprocess)
#+END_SRC
#+RESULTS:
#+begin_example
Help on function postprocess in module spot:
postprocess(automaton, *args)
Post process an automaton.
This applies a number of simlification algorithms, depending on
the options supplied. Keep in mind that 'Deterministic' expresses
just a preference that may not be satisfied if the input is
not already 'Deterministic'.
The optional arguments should be strings among the following:
- at most one in 'Generic', 'TGBA', 'BA', or 'Monitor'
(type of automaton to build)
- at most one in 'Small', 'Deterministic', 'Any'
(preferred characteristics of the produced automaton)
- at most one in 'Low', 'Medium', 'High'
(optimization level)
- any combination of 'Complete' and 'StateBasedAcceptance'
(or 'SBAcc' for short)
The default corresponds to 'generic', 'small' and 'high'.
#+end_example
* C++
The C++ version of this code is a bit more verbose, because the
=postprocess()= function does not exist. You have to instantiate a
=postprocessor= object, configure it, and then call it for each
automaton to process.
#+BEGIN_SRC C++ :results verbatim :exports both
#include <iostream>
#include "parseaut/public.hh"
#include "twaalgos/postproc.hh"
#include "twaalgos/hoa.hh"
int main()
{
std::string input = "tut30.hoa";
spot::parse_aut_error_list pel;
spot::bdd_dict_ptr dict = spot::make_bdd_dict();
spot::parsed_aut_ptr pa = parse_aut(input, pel, dict);
if (spot::format_parse_aut_errors(std::cerr, input, pel))
return 1;
if (pa->aborted)
{
std::cerr << "--ABORT-- read\n";
return 1;
}
spot::postprocessor post;
post.set_type(spot::postprocessor::BA);
post.set_pref(spot::postprocessor::Deterministic);
post.set_level(spot::postprocessor::High);
auto aut = post.run(pa->aut);
spot::print_hoa(std::cout, aut) << '\n';
return 0;
}
#+END_SRC
#+RESULTS:
#+begin_example
HOA: v1
States: 5
Start: 1
AP: 1 "p1"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels state-acc complete
properties: deterministic inherently-weak
--BODY--
State: 0 {0}
[t] 0
State: 1
[t] 2
State: 2
[!0] 3
[0] 4
State: 3
[0] 0
[!0] 3
State: 4
[!0] 0
[0] 4
--END--
#+end_example
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