Dark Side of the Moon researcher Flood Sung recently published a lengthy article, revealing for the first time the development ideas behind the k1.5 model and deeply reflecting on the technological insights brought by the OpenAI o1 model. According to Flood Sung, the importance of Long-CoT (Long Chain of Thought) was actually validated over a year ago by Tim Zhou Xinyu, co-founder of the Dark Side of the Moon. By training small models for multi-digit calculations and transforming the fine-grained calculation processes into Long Chain of Thought data for SFT (Supervised Fine-Tuning).