SMT solvers are essential for applications in artificial intelligence, software verification, and optimisation. However, no single solver excels across all formula types, and different applications may require the use of different solvers. While the SMT-LIB language enables multi-solver support, it also incurs heavy I/O overhead. To address this, we introduce Smt.ml , an SMT-solver frontend for OCaml that simplifies integration with various solvers through a consistent interface. Its parametric encoding facilitates the easy addition of new solver backends, while optimisations like formula simplification, result caching, and detailed error feedback enhance performance and usability. Furthermore, Smt.ml is the only SMT frontend that includes a simplification-management engine for streamlining the integration of new formula simplifications and the verification of their correctness. Our evaluation demonstrates that Smt.ml ’s results are consistent with those of its backend solvers and that its optimisations are highly effective on formulas generated from the symbolic execution of an extensive program-analysis benchmark.

Abstract Tools that manipulate OCaml code can sometimes fail even on correct programs. Identifying and understanding the cause of the error usually involves manually reducing the size of the program, so as to obtain a shorter program causing the same error—a long, sometimes complex and rarely interesting task. Our work consists in automating this task using a minimiser, or delta-debugger. To do so, we propose a list of unitary heuristics, i.e. small-scale reductions, applied through a dichotomy-based state-of-the-art algorithm. These proposals are implemented in the free Chamelon tool. Although designed to assist the development of an OCaml compiler, Chamelon can be adapted to all kinds of projects that manipulate OCaml code. It can analyse multifile projects and efficiently minimise real-world programs, reducing their size by one to several orders of magnitude. It is currently used to assist the industrial development of the flambda2 optimising compiler.

We show that reachability and termination for lossy channel systems is exactly at level Fomegaomega in the fast-growing hierarchy of recursive functions, the first level that dominates all multiply-recursive functions.