EffiReasonTrans: RL-Optimized Reasoning for Code Translation

Code translation is a crucial task in software development and maintenance.
While recent advancements in large language models (LLMs) have improved
automated code translation accuracy, these gains often come at the cost of
increased inference latency, hindering real-world development workflows that
involve human-in-the-loop inspection. To address this trade-off, we propose
EffiReasonTrans, a training framework designed to improve translation accuracy
while balancing inference latency. We first construct a high-quality
reasoning-augmented dataset by prompting a stronger language model,
DeepSeek-R1, to generate intermediate reasoning and target translations. Each
(source code, reasoning, target code) triplet undergoes automated syntax and
functionality checks to ensure reliability. Based on this dataset, we employ a
two-stage training strategy: supervised fine-tuning on reasoning-augmented
samples, followed by reinforcement learning to further enhance accuracy and
balance inference latency. We evaluate EffiReasonTrans on six translation
pairs. Experimental results show that it consistently improves translation
accuracy (up to +49.2% CA and +27.8% CodeBLEU compared to the base model) while
reducing the number of generated tokens (up to -19.3%) and lowering inference
latency in most cases (up to -29.0%). Ablation studies further confirm the
complementary benefits of the two-stage training framework. Additionally,
EffiReasonTrans demonstrates improved translation accuracy when integrated into
agent-based frameworks. Our code and data are available at
https://github.com/DeepSoftwareAnalytics/EffiReasonTrans.