Abstract
The capabilities of large language models (LLMs) and multimodal LLMs (MLLMs) arise from the synergy of the full training pipeline, including data and tokenization, pretraining, and post-training (supervised fine-tuning, preference alignment, reinforcement learning, and continual optimization), rather than any individual stage. Existing surveys mostly adopt a single-stage or single-technique perspective, treating related research as isolated systems without unified stage division or a horizontally comparable basis. This paper proposes a unified stage division and a six-dimensional analytical framework covering data, objective function, optimization strategy, system constraints, evaluation, and risk and governance. We systematically review 395 core references from 2017 to 2026, and present a conceptual map of cross-stage effects: forward constraints of pretraining on post-training, and reverse empowerment of post-training on data and pretraining. We derive three core findings. First, the comparability of scaling laws depends on data quality and mixture, a long-neglected variable. Second, preference alignment methods (RLHF, DPO) and reasoning reinforcement learning with verifiable rewards redefine post-training boundaries, while the Pass@1 versus Pass@K debate remains unresolved. Third, multimodal training poses structural challenges to the pure-text paradigm in tokenizer design, training objectives, and evaluation. The paper provides a cross-stage effects diagram, a method-family map, a practical decision tree, and at least 10 verifiable open problems, with an extensible skeleton for focused sub-surveys per stage. As of the retrieval date, peer-reviewed evidence (A+B) accounts for approximately 79% of the 395 references.
Abstract (translated)
URL
https://arxiv.org/abs/2610.33451
