13,616 research outputs found
Non-Termination Inference of Logic Programs
We present a static analysis technique for non-termination inference of logic
programs. Our framework relies on an extension of the subsumption test, where
some specific argument positions can be instantiated while others are
generalized. We give syntactic criteria to statically identify such argument
positions from the text of a program. Atomic left looping queries are generated
bottom-up from selected subsets of the binary unfoldings of the program of
interest. We propose a set of correct algorithms for automating the approach.
Then, non-termination inference is tailored to attempt proofs of optimality of
left termination conditions computed by a termination inference tool. An
experimental evaluation is reported. When termination and non-termination
analysis produce complementary results for a logic procedure, then with respect
to the leftmost selection rule and the language used to describe sets of atomic
queries, each analysis is optimal and together, they induce a characterization
of the operational behavior of the logic procedure.Comment: Long version (algorithms and proofs included) of a paper submitted to
TOPLA
Inference of termination conditions for numerical loops in Prolog
We present a new approach to termination analysis of numerical computations
in logic programs. Traditional approaches fail to analyse them due to non
well-foundedness of the integers. We present a technique that allows overcoming
these difficulties. Our approach is based on transforming a program in a way
that allows integrating and extending techniques originally developed for
analysis of numerical computations in the framework of query-mapping pairs with
the well-known framework of acceptability. Such an integration not only
contributes to the understanding of termination behaviour of numerical
computations, but also allows us to perform a correct analysis of such
computations automatically, by extending previous work on a constraint-based
approach to termination. Finally, we discuss possible extensions of the
technique, including incorporating general term orderings.Comment: To appear in Theory and Practice of Logic Programming. To appear in
Theory and Practice of Logic Programmin
Experiments with a Convex Polyhedral Analysis Tool for Logic Programs
Convex polyhedral abstractions of logic programs have been found very useful
in deriving numeric relationships between program arguments in order to prove
program properties and in other areas such as termination and complexity
analysis. We present a tool for constructing polyhedral analyses of
(constraint) logic programs. The aim of the tool is to make available, with a
convenient interface, state-of-the-art techniques for polyhedral analysis such
as delayed widening, narrowing, "widening up-to", and enhanced automatic
selection of widening points. The tool is accessible on the web, permits user
programs to be uploaded and analysed, and is integrated with related program
transformations such as size abstractions and query-answer transformation. We
then report some experiments using the tool, showing how it can be conveniently
used to analyse transition systems arising from models of embedded systems, and
an emulator for a PIC microcontroller which is used for example in wearable
computing systems. We discuss issues including scalability, tradeoffs of
precision and computation time, and other program transformations that can
enhance the results of analysis.Comment: Paper presented at the 17th Workshop on Logic-based Methods in
Programming Environments (WLPE2007
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