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AISB opportunities Bulletin Item

Several PhD positions in Theoretical Computer Science, Bordeaux & Cachan, FRANCE

The ANR project REACHARD proposes several PhD positions on reachability problems for counter 
systems, including vector addition systems and related models.  The PhD position will take place 
either at LaBRI ( or at LSV (, France. 
The duration is 3 years, with an annual salary of 21,000 euros after tax + benefits (e.g. social 

See also


Candidates should hold a Master degree in Computer Science (ideally with courses in formal 
verification, theoretical computer science and mathematical structures for CS) or equivalently 
is graduated from a Computer Science Engineering School with a strong background in theoretical 
computer science.

Applications should be sent to
Required documents are:
- a detailed curriculum vitae
- a copy of the master
- a reference letter by their master supervisor.


Many standard verification problems can be rephrased as reachability problems, and there exist 
powerful methods for infinite-state systems; see e.g. the theory of well-structured transition 
systems.  However, obtaining decision procedures is not the ultimate goal, which we rather see 
in crafting provably optimal algorithms---required for practical use.  In the ANR project REACHARD,
we focus on algorithmic issues for the verification of counter systems, more specifically to 
reachability problems for vector addition systems with states (VASS) and related models.

More specifically, the main objective of the ANR project REACHARD is to propose a satisfactory 
solution to the reachability problem for vector addition systems, that will provide significant 
improvements both conceptually and computationally.  Recent breakthroughs on the problem and on 
related problems for variant models should also allow us to propose solutions for several 
extensions, including for instance VASS with one zero-test or branching VASS.  Furthermore, the 
goal is to take advantage of the new proof techniques involving semilinear separators designed 
by J. Leroux in order to design algorithms that are amenable for implementation.  We propose to 
develop original techniques in order to solve the following difficult issues:

- to understand the mathematical structure of reachability sets and relations in vector addition 

- to develop new techniques for the computational analysis of reachability problems that are 
verification problems connected in some way to the reachability problem for VASS or their extensions,

- to design algorithms, most probably on the lines of Karp & Miller algorithms, plus relating 
flattening methods and semilinearity,

- to widen the scope of our analysis to models richer than VASS, including models with restricted 
zero-tests or with branching computations.


Mathematical Structures for Reachability Sets and Relations

Semilinearity of Vector Addition Systems with States

Computational Analysis for Reachability Problems

Counter machine reachability sets computation


Any further inquiry should be sent to