  We present CRUXEval (Code Reasoning, Understanding, and eXecution
Evaluation), a benchmark consisting of 800 Python functions (3-13 lines). Each
function comes with an input-output pair, leading to two natural tasks: input
prediction and output prediction. First, we propose a generic recipe for
generating our execution benchmark which can be used to create future variation
of the benchmark. Second, we evaluate twenty code models on our benchmark and
discover that many recent high-scoring models on HumanEval do not show the same
improvements on our benchmark. Third, we show that simple CoT and fine-tuning
schemes can improve performance on our benchmark but remain far from solving
it. The best setup, GPT-4 with chain of thought (CoT), achieves a pass@1 of 75%
and 81% on input and output prediction, respectively. In contrast, Code Llama
34B achieves a pass@1 of 50% and 46% on input and output prediction,
highlighting the gap between open and closed source models. As no model is
close to acing CRUXEval, we provide examples of consistent GPT-4 failures on
simple programs as a lens into its code reasoning capabilities and areas for
improvement.
