CHC-COMP 2023 is the sixth edition of the Competition of Solvers for Constrained Horn Clauses. The competition was run in April 2023 and the results were presented at the 10th Workshop on Horn Clauses for Verification and Synthesis held in Paris, France, on April 23, 2023. This edition featured seven solvers (six competing and one hors concours) and six tracks, each of which dealing with a class of clauses. This report describes the organization of CHC-COMP 2023 and presents its results.
IntroductionConstrained Horn Clauses (CHCs) are a class of first-order logic formulas where the Horn clause format is extended with constraints, that is, formulas of an arbitrary, possibly non-Horn, background theory (such as linear integer arithmetic, arrays, and algebraic data types).CHCs have gained popularity as a formalism well suited for automatic program verification [20,5,9]). Indeed, the last decade has seen impressive progress in the development of solvers for CHCs (CHC solvers), which can now be effectively used as back-end tools for program verification due to their ability to solve satisfiability problems dealing with a variety of background theories. A non-exhaustive list of solvers includes: ADTInd [40], ADTRem [11], Eldarica [25], FreqHorn [16], Golem [7], HSF [20], PCSat [39], RAHFT [27], RInGen [29], SPACER [28], Ultimate TreeAutomizer [13], and VeriMAP [10].CHC-COMP is an annual competition that aims to evaluate state-of-the-art CHC solvers on realistic and publicly available benchmarks; it is open to proposals and contributions from users and developers of CHC solvers, as well as researchers working in the field of CHC solving foundations and its applications.CHC-COMP 2023 1 is the 6th edition of the CHC-COMP, affiliated with the 10th Workshop on Horn Clauses for Verification and Synthesis (HCVS 2023 2 ) held in Paris, France, on April 23, 2023. The deadline for submitting candidate benchmarks was March 24, 2023. The deadlines for submitting tools for the test (optional) and the competition runs were 31 March and 7 April 2023, respectively. The competition was run in the subsequent two weeks, and the results were announced at HCVS 2023. CHC-COMP 2023 featured 7 solvers (6 competing solvers and one hors concours), and 6 tracks, each of which dealing with a class of clauses consisting of linear and nonlinear CHCs with constraints over linear integer arithmetic, arrays, non-recursive/recursive algebraic data types, and a few combinations thereof.This report is structured as follows. Section 2 presents the competition tracks, the technical resources used to run the competition, and the evaluation model adopted to rank the solvers. Section 3 presents the inventory of benchmarks and how the candidate benchmarks have been processed and selected for the competition runs. Sections 4 and 5 present the tools submitted to CHC-COMP 2023 and the results of the competition, respectively. Section 6 presents some closing remarks from the organizers and participants of CHC-COMP 2023. Section 7 collects the tool descriptions con...