Reward Models Enable Scalable Code Verification by Trading Accuracy for
  Throughput
Authors: name: Gabriel Orlanski; name: Nicholas Roberts; name: Aws Albarghouthi; name: Frederic Sala
Published: 2025-06-11 17:58:21

Abstract: The standard paradigm for solving coding tasks via large language models
(LLMs) is to generate-then-rank programs, where the latter step uses a verifier
in the ranking process. The growing consensus is that a comprehensive verifier
(e.g., a full test suite) should be prioritized over an outcome reward model
(ORM) whenever possible, with little consideration given to the trade-offs
involved. We aim to challenge this assumption by systematically exploring the
tradeoff between speed and accuracy. We find that ORMs play a crucial role in
scaling verification through trading accuracy for speed, even when a
comprehensive verifier is available. Their value becomes especially apparent
when used in a generate-prune-then-rank approach, where a faster but less
accurate verifier removes incorrect solutions prior to ranking -- leading to a
system that is 11.65x faster while only being 8.33% less accurate than the full
test suite. We analyze the generate-prune-then-rank approach and show that it
works by filtering out incorrect but highly ranked solutions. These findings
enable the design of scalable and accurate program ranking systems.