Proving Non-Termination and Lower Runtime Bounds with LoAT (System Description)

Abstract

We present the new version of the Loop Acceleration Tool (LoAT), a powerful tool for proving non-termination and worst-case lower bounds for programs operating on integers. It is based on the novel calculus from [18,19] for loop acceleration, i.e., transforming loops into nondeterministic straight-line code, and for finding non-terminating configurations. To implement it efficiently, LoAT uses a new approach based on SMT solving and unsat cores. An extensive evaluation shows that LoAT is highly competitive with other state-of-the-art tools for proving non-termination. While no other tool is able to deduce worst-case lower bounds for full integer programs, we also demonstrate that LoAT significantly outperforms its predecessors from [16,17].