The Hexlite Solver - Lightweight and Efficient Evaluation of HEX Programs.

HEXLITE is a lightweight solver for the HEX formalism which integrates Answer Set Programming (ASP) with external computations. The main goal of HEXLITE is efficiency and simplicity, both in implementation as well as in installation of the system. We define the Pragmatic HEX Fragment which permits to partition external computations into two kinds: those that can be evaluated during the program instantiation phase, and those that need to be evaluated during the answer set search phase. HEXLITE is written in PYTHON and suitable for evaluating this fragment with external computations that are realized in PYTHON. Most performance-critical tasks are delegated to the PYTHON module of CLINGO. We demonstrate that the Pragmatic HEX Fragment is sufficient for many use cases and that it permits HEXLITE to have superior performance compared to the DLVHEX system in relevant application scenarios.