Abstract. We show how the problem of nontermination proving can be reduced to a question of underapproximation search guided by a safety prover. This reduction leads to new nontermination proving implementation strategies based on existing tools for safety proving. Our preliminary implementation beats existing tools. Furthermore, our approach leads to easy support for programs with unbounded nondeterminism.
Abstract. We show how Max-SMT-based invariant generation can be exploited for proving non-termination of programs. The construction of the proof of nontermination is guided by the generation of quasi-invariants -properties such that if they hold at a location during execution once, then they will continue to hold at that location from then onwards. The check that quasi-invariants can indeed be reached is then performed separately. Our technique considers strongly connected subgraphs of a program's control flow graph for analysis and thus produces more generic witnesses of non-termination than existing methods. Moreover, it can handle programs with unbounded non-determinism and is more likely to converge than previous approaches.
Abstract-When disproving termination using known techniques (e.g. recurrence sets), abstractions that overapproximate the program's transition relation are unsound. In this paper we introduce live abstractions, a natural class of abstractions that can be combined with the recent concept of closed recurrence sets to soundly disprove termination. To demonstrate the practical usefulness of this new approach we show how programs with nonlinear, nondeterministic, and heap-based commands can be shown nonterminating using linear overapproximations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.