CodeI/O: Condensing Reasoning Patterns via Code Input-Output Prediction
Authors: name: Junlong Li, name: Daya Guo, name: Dejian Yang, name: Runxin Xu, name: Yu Wu, name: Junxian He

Reasoning is a fundamental capability of Large Language Models. While prior
research predominantly focuses on enhancing narrow skills like math or code
generation, improving performance on many other reasoning tasks remains
challenging due to sparse and fragmented training data. To address this issue,
we propose CodeI/O, a novel approach that systematically condenses diverse
reasoning patterns inherently embedded in contextually-grounded codes, through
transforming the original code into a code input-output prediction format. By
training models to predict inputs/outputs given code and test cases entirely in
natural language as Chain-of-Thought (CoT) rationales, we expose them to
universal reasoning primitives -- like logic flow planning, state-space
searching, decision tree traversal, and modular decomposition -- while
decoupling structured reasoning from code-specific syntax and preserving
procedural rigor. Experimental results demonstrate CodeI/O leads to consistent
improvements across symbolic, scientific, logic, math & numerical, and
commonsense reasoning tasks. By matching the existing ground-truth outputs or
re-executing the code with predicted inputs, we can verify each prediction and
further enhance the CoTs through multi-turn revision, resulting in CodeI/O++
and achieving higher performance. Our data and models are available at
https://github.com/hkust-nlp/CodeIO.