R1-VL: Learning to Reason with Multimodal Large Language Models via
  Step-wise Group Relative Policy Optimization
Authors: name: Jingyi Zhang, name: Jiaxing Huang, name: Huanjin Yao, name: Shunyu Liu, name: Xikun Zhang, name: Shijian Lu, name: Dacheng Tao

Recent studies generally enhance MLLMs' reasoning capabilities via supervised
fine-tuning on high-quality chain-of-thought reasoning data, which often leads
models to merely imitate successful reasoning paths without understanding what
the wrong reasoning paths are. In this work, we aim to enhance the MLLMs'
reasoning ability beyond passively imitating positive reasoning paths. To this
end, we design Step-wise Group Relative Policy Optimization (StepGRPO), a new
online reinforcement learning framework that enables MLLMs to self-improve
reasoning ability via simple, effective and dense step-wise rewarding.
Specifically, StepGRPO introduces two novel rule-based reasoning rewards:
Step-wise Reasoning Accuracy Reward (StepRAR) and Step-wise Reasoning Validity
Reward (StepRVR). StepRAR rewards the reasoning paths that contain necessary
intermediate reasoning steps via a soft key-step matching technique, while
StepRAR rewards reasoning paths that follow a well-structured and logically
consistent reasoning process through a reasoning completeness and logic
evaluation strategy. With the proposed StepGRPO, we introduce R1-VL, a series
of MLLMs with outstanding capabilities in step-by-step reasoning. Extensive
experiments over 8 benchmarks demonstrate the superiority of our methods.