Difference between revisions of "Jobs/M2 2015 ADL SAT-based Minimization"

From LRDE

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|Reference id=M2 2015 ADL SAT-based Minimization
 
|Reference id=M2 2015 ADL SAT-based Minimization
 
|Title=Minimization of Büchi automata using SAT-solving
 
|Title=Minimization of Büchi automata using SAT-solving
|Dates=5-6 months in 2015
+
|Dates=5-6 months in 2016
 
|Research field=Automata Theory
 
|Research field=Automata Theory
 
|Related project=Spot
 
|Related project=Spot
 
|Advisor=Alexandre Duret-Lutz
 
|Advisor=Alexandre Duret-Lutz
|General presentation of the field=The Spot library (http://spot.lip6.fr/) contains many algorithms for translating LTL formulas into Büchi automata, and to simplify these formulas and automata. A recently added technique (in Spot version 1.2) allows us to minimize deterministic Büchi automata using a SAT-solver.
+
|General presentation of the field=The Spot library (http://spot.lip6.fr/) contains many algorithms for translating LTL formulas into Büchi automata, and to simplify these formulas and automata. A recently added technique allows us to minimize deterministic Büchi automata using a SAT-solver; the implementation is actually not restricted to Büchi and can work with deterministic omega-automata with any acceptance conditions.
   
To minimize a n-state deterministic Büchi automaton (an NP-complete problem) we encode its equivalence with a (n-1)-state deterministic
+
To minimize a n-state deterministic omega-automaton (an NP-complete problem) we encode its equivalence with a (n-1)-state deterministic
Büchi automaton as a SAT problem, and let a SAT solver do the work of finding a solution. If such a solution is found, we try again, looking for a (n-2) state automaton, etc.
+
omega-automaton as a SAT problem, and let a SAT solver do the work of finding a solution. If such a solution is found, we try again, looking for a (n-2) state automaton, etc.
 
|Prerequisites=This internship targets students who:
 
|Prerequisites=This internship targets students who:
* have some experience in C++ programming and Unix development (experience with git would be a welcome bonus)
+
* have some experience in C++ programming and Unix development (experience with git and emacs would be a welcome bonus)
 
* like to write clean and useful code (Spot is an open-source library used by other projects)
 
* like to write clean and useful code (Spot is an open-source library used by other projects)
 
* like to optimize
 
* like to optimize
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this for each iteration. The goal of this internship is to improve this situation in multiple ways:
 
this for each iteration. The goal of this internship is to improve this situation in multiple ways:
 
* implement purely technical optimizations (like direct communication with the SAT solver, bypassing any temporary files)
 
* implement purely technical optimizations (like direct communication with the SAT solver, bypassing any temporary files)
* take advantage of feature offered by modern SAT solvers (for instance an "incremental SAT-solver" can be given new constraints after it has found a solution, without needing to restart from scratch)
+
* take advantage of features offered by modern SAT solvers (for instance an "incremental SAT-solver" can be given new constraints after it has found a solution, without needing to restart from scratch)
* implement optimization to the encoding of the SAT-problem, based on structural properties of the automaton (we have some ideas)
+
* implement optimizations to the encoding of the SAT-problem, based on structural properties of the automaton (we have some ideas)
   
In a second, step, we would like to generalize the existing technique to non-deterministic automata, or to different
+
In a second step, we would like to generalize the existing technique to non-deterministic automata (first as input, and then as output as well).
  +
|References=* On the usage of a SAT-solver for minimization: https://www.lrde.epita.fr/~adl/dl/adl/baarir.15.lpar.pdf
types of acceptance conditions (i.e., not Büchi).
 
|References=* On the usage of a SAT-solver for minimization: https://www.lrde.epita.fr/~adl/dl/adl/baarir.14.forte.pdf
+
* For the present usage of SAT-based minimization in Spots: https://spot.lrde.epita.fr/satmin.html
* For the present usage of SAT-based minimization in Spot: http://spot.lip6.fr/userdoc/satmin.html
 
 
|Contact=<adl at lrde . epita . fr>
 
|Contact=<adl at lrde . epita . fr>
 
|Compensation=1000 € gross/month
 
|Compensation=1000 € gross/month
|Future work opportunities=If you have performed the internship satisfactorily, we would like it to be followed by a PhD thesis.
+
|Future work opportunities=This internship can easily be prolonged as a PhD thesis.
 
|Type=Master Internship
 
|Type=Master Internship
 
|Language=en
 
|Language=en

Revision as of 18:33, 19 November 2015

Minimization of Büchi automata using SAT-solving
Reference id

M2 2015 ADL SAT-based Minimization

Dates

5-6 months in 2016

Research field

Automata Theory

Related project

Spot

Advisor

Alexandre Duret-Lutz

General presentation of the field

The Spot library (http://spot.lip6.fr/) contains many algorithms for translating LTL formulas into Büchi automata, and to simplify these formulas and automata. A recently added technique allows us to minimize deterministic Büchi automata using a SAT-solver; the implementation is actually not restricted to Büchi and can work with deterministic omega-automata with any acceptance conditions.

To minimize a n-state deterministic omega-automaton (an NP-complete problem) we encode its equivalence with a (n-1)-state deterministic omega-automaton as a SAT problem, and let a SAT solver do the work of finding a solution. If such a solution is found, we try again, looking for a (n-2) state automaton, etc.

Prerequisites

This internship targets students who:

  • have some experience in C++ programming and Unix development (experience with git and emacs would be a welcome bonus)
  • like to write clean and useful code (Spot is an open-source library used by other projects)
  • like to optimize
  • would like do get familiar with the amazing world of SAT-solvers and Büchi automata.
Objectives

Presently, our first implementation saves the SAT problem as a huge file before calling the SAT-solver, and it does this for each iteration. The goal of this internship is to improve this situation in multiple ways:

  • implement purely technical optimizations (like direct communication with the SAT solver, bypassing any temporary files)
  • take advantage of features offered by modern SAT solvers (for instance an "incremental SAT-solver" can be given new constraints after it has found a solution, without needing to restart from scratch)
  • implement optimizations to the encoding of the SAT-problem, based on structural properties of the automaton (we have some ideas)

In a second step, we would like to generalize the existing technique to non-deterministic automata (first as input, and then as output as well).

Benefit for the candidate
References
Place LRDE: How to get to us
Compensation

1000 € gross/month

Future work opportunities

This internship can easily be prolonged as a PhD thesis.

Contact

<adl at lrde . epita . fr> <adl at lrde . epita . fr>