EvoPart: An Open, Lightweight, and Strong Hypergraph Partitioner Evolved with LLM Coder

Hypergraph partitioning is a fundamental NP-hard problem in VLSI physical design, scientific computing and, increasingly, LLM infrastructure. Yet the field lacks an open partitioner that is at once lightweight, strong and fast: the most influential tool, hMETIS, is closed-source, and the leading open framework, KaHyPar, spans some 27,000 lines of C++, so recent work typically wraps hMETIS as a black box or replaces a single sub-step of KaHyPar. Coding agents such as AlphaEvolve and its open-source counterpart OpenEvolve offer a way forward, having already found better programs for problems including matrix multiplication. Building on OpenEvolve, we design a harness for evolving a whole solver rather than a single heuristic: it places programs in the MAP-Elites grid by behavior (running time and relative strength across k) rather than text, deduplicates programs by partition fingerprinting, and feeds the measured per-instance cut and wall time back into the prompt. Starting from a round-robin initial program whose cut is 97× KaHyPar's, a single 200-iteration run yields EvoPart: a lightweight and strong partitioner of 1,186 lines of single-threaded C++ in one file, 22.5× less code than KaHyPar. On the full ISPD98 and Titan23 benchmarks, its cut is 5.5% lower than KaHyPar's in 70% of KaHyPar's wall time and 5.1% lower than hMETIS's at equal wall time, with 30 of the 40 instances unseen during evolution. Two of its components are, to our knowledge, absent from existing partitioners: racing two coarsenings with opposite net-size priorities inside the restarts, and re-partitioning the final blocks pair by pair. We release the partitioner and the harness at https://anonymous.4open.science/r/EvoPart-4F6C.