We present a new general-purpose synthesis technique for generating programs from input-output examples. Our method, called metric program synthesis, relaxes the observational equivalence idea (used widely in bottom-up enumerative synthesis) into a weaker notion of observational similarity, with the goal of reducing the search space that the synthesizer needs to explore. Our method clusters programs into equivalence classes based on an expert-provided distance metric and constructs a version space that compactly represents “approximately correct” programs. Then, given a “close enough” program sampled from this version space, our approach uses a distance-guided repair algorithm to find a program that exactly matches the given input-output examples. We have implemented our proposed metric program synthesis technique in a tool called SyMetric and evaluate it in three different domains considered in prior work. Our evaluation shows that SyMetric outperforms other domain-agnostic synthesizers that use observational equivalence and that it achieves results competitive with domain-specific synthesizers that are either designed for or trained on those domains.

@article{paperbot1899,
  title = {Inductive Program Synthesis Guided by Observational Program Similarity},
  author = {Jack Feser and Işıl Dillig and Armando Solar-Lezama},
  journal = {Proceedings of the ACM on Programming Languages},
  volume = {7},
  number = {OOPSLA2},
  year = {2023},
  doi = {10.1145/3622830}
}