126 research outputs found
A Metric Encoding for Bounded Model Checking (extended version)
In Bounded Model Checking both the system model and the checked property are
translated into a Boolean formula to be analyzed by a SAT-solver. We introduce
a new encoding technique which is particularly optimized for managing
quantitative future and past metric temporal operators, typically found in
properties of hard real time systems. The encoding is simple and intuitive in
principle, but it is made more complex by the presence, typical of the Bounded
Model Checking technique, of backward and forward loops used to represent an
ultimately periodic infinite domain by a finite structure. We report and
comment on the new encoding technique and on an extensive set of experiments
carried out to assess its feasibility and effectiveness
Extended ASP tableaux and rule redundancy in normal logic programs
We introduce an extended tableau calculus for answer set programming (ASP).
The proof system is based on the ASP tableaux defined in [Gebser&Schaub, ICLP
2006], with an added extension rule. We investigate the power of Extended ASP
Tableaux both theoretically and empirically. We study the relationship of
Extended ASP Tableaux with the Extended Resolution proof system defined by
Tseitin for sets of clauses, and separate Extended ASP Tableaux from ASP
Tableaux by giving a polynomial-length proof for a family of normal logic
programs P_n for which ASP Tableaux has exponential-length minimal proofs with
respect to n. Additionally, Extended ASP Tableaux imply interesting insight
into the effect of program simplification on the lengths of proofs in ASP.
Closely related to Extended ASP Tableaux, we empirically investigate the effect
of redundant rules on the efficiency of ASP solving.
To appear in Theory and Practice of Logic Programming (TPLP).Comment: 27 pages, 5 figures, 1 tabl
A pearl on SAT solving in Prolog
A succinct SAT solver is presented that exploits the control provided by delay declarations to implement watched literals and unit propagation. Despite its brevity the solver is surprisingly powerful and its elegant use of Prolog constructs is presented as a programming pearl
Tarmo: A Framework for Parallelized Bounded Model Checking
This paper investigates approaches to parallelizing Bounded Model Checking
(BMC) for shared memory environments as well as for clusters of workstations.
We present a generic framework for parallelized BMC named Tarmo. Our framework
can be used with any incremental SAT encoding for BMC but for the results in
this paper we use only the current state-of-the-art encoding for full PLTL.
Using this encoding allows us to check both safety and liveness properties,
contrary to an earlier work on distributing BMC that is limited to safety
properties only.
Despite our focus on BMC after it has been translated to SAT, existing
distributed SAT solvers are not well suited for our application. This is
because solving a BMC problem is not solving a set of independent SAT instances
but rather involves solving multiple related SAT instances, encoded
incrementally, where the satisfiability of each instance corresponds to the
existence of a counterexample of a specific length. Our framework includes a
generic architecture for a shared clause database that allows easy clause
sharing between SAT solver threads solving various such instances.
We present extensive experimental results obtained with multiple variants of
our Tarmo implementation. Our shared memory variants have a significantly
better performance than conventional single threaded approaches, which is a
result that many users can benefit from as multi-core and multi-processor
technology is widely available. Furthermore we demonstrate that our framework
can be deployed in a typical cluster of workstations, where several multi-core
machines are connected by a network
- …