Key Assumptions in Large Language Model Development

If you’re an AI engineer, understanding how LLMs are trained and aligned is essential for building high-performance, reliable AI systems. Most large language models follow a 3-step training procedure: Step 1: Pretraining → Goal: Learn general-purpose language representations. → Method: Self-supervised learning on massive unlabeled text corpora (e.g., next-token prediction). → Output: A pretrained LLM, rich in linguistic and factual knowledge but not grounded in human preferences. → Cost: Extremely high (billions of tokens, trillions of FLOPs). → Pretraining is still centralized within a few labs due to the scale required (e.g., Meta, Google DeepMind, OpenAI), but open-weight models like LLaMA 4, DeepSeek V3, and Qwen 3 are making this more accessible. Step 2: Finetuning (Two Common Approaches) → 2a: Full-Parameter Finetuning - Updates all weights of the pretrained model. - Requires significant GPU memory and compute. - Best for scenarios where the model needs deep adaptation to a new domain or task. - Used for: Instruction-following, multilingual adaptation, industry-specific models. - Cons: Expensive, storage-heavy. → 2b: Parameter-Efficient Finetuning (PEFT) - Only a small subset of parameters is added and updated (e.g., via LoRA, Adapters, or IA³). - Base model remains frozen. - Much cheaper, ideal for rapid iteration and deployment. - Multi-LoRA architectures (e.g., used in Fireworks AI, Hugging Face PEFT) allow hosting multiple finetuned adapters on the same base model, drastically reducing cost and latency for serving. Step 3: Alignment (Usually via RLHF) Pretrained and task-tuned models can still produce unsafe or incoherent outputs. Alignment ensures they follow human intent. Alignment via RLHF (Reinforcement Learning from Human Feedback) involves: → Step 1: Supervised Fine-Tuning (SFT) - Human labelers craft ideal responses to prompts. - Model is fine-tuned on this dataset to mimic helpful behavior. - Limitation: Costly and not scalable alone. → Step 2: Reward Modeling (RM) - Humans rank multiple model outputs per prompt. - A reward model is trained to predict human preferences. - This provides a scalable, learnable signal of what “good” looks like. → Step 3: Reinforcement Learning (e.g., PPO, DPO) - The LLM is trained using the reward model’s feedback. - Algorithms like Proximal Policy Optimization (PPO) or newer Direct Preference Optimization (DPO) are used to iteratively improve model behavior. - DPO is gaining popularity over PPO for being simpler and more stable without needing sampled trajectories. Key Takeaways: → Pretraining = general knowledge (expensive) → Finetuning = domain or task adaptation (customize cheaply via PEFT) → Alignment = make it safe, helpful, and human-aligned (still labor-intensive but improving) Save the visual reference, and follow me (Aishwarya Srinivasan) for more no-fluff AI insights ❤️ PS: Visual inspiration: Sebastian Raschka, PhD

Training a Large Language Model (LLM) involves more than just scaling up data and compute. It requires a disciplined approach across multiple layers of the ML lifecycle to ensure performance, efficiency, safety, and adaptability. This visual framework outlines eight critical pillars necessary for successful LLM training, each with a defined workflow to guide implementation: 𝟭. 𝗛𝗶𝗴𝗵-𝗤𝘂𝗮𝗹𝗶𝘁𝘆 𝗗𝗮𝘁𝗮 𝗖𝘂𝗿𝗮𝘁𝗶𝗼𝗻: Use diverse, clean, and domain-relevant datasets. Deduplicate, normalize, filter low-quality samples, and tokenize effectively before formatting for training. 𝟮. 𝗦𝗰𝗮𝗹𝗮𝗯𝗹𝗲 𝗗𝗮𝘁𝗮 𝗣𝗿𝗲𝗽𝗿𝗼𝗰𝗲𝘀𝘀𝗶𝗻𝗴: Design efficient preprocessing pipelines—tokenization consistency, padding, caching, and batch streaming to GPU must be optimized for scale. 𝟯. 𝗠𝗼𝗱𝗲𝗹 𝗔𝗿𝗰𝗵𝗶𝘁𝗲𝗰𝘁𝘂𝗿𝗲 𝗗𝗲𝘀𝗶𝗴𝗻: Select architectures based on task requirements. Configure embeddings, attention heads, and regularization, and then conduct mock tests to validate the architectural choices. 𝟰. 𝗧𝗿𝗮𝗶𝗻𝗶𝗻𝗴 𝗦𝘁𝗮𝗯𝗶𝗹𝗶𝘁𝘆 and 𝗢𝗽𝘁𝗶𝗺𝗶𝘇𝗮𝘁𝗶𝗼𝗻: Ensure convergence using techniques such as FP16 precision, gradient clipping, batch size tuning, and adaptive learning rate scheduling. Loss monitoring and checkpointing are crucial for long-running processes. 𝟱. 𝗖𝗼𝗺𝗽𝘂𝘁𝗲 & 𝗠𝗲𝗺𝗼𝗿𝘆 𝗢𝗽𝘁𝗶𝗺𝗶𝘇𝗮𝘁𝗶𝗼𝗻: Leverage distributed training, efficient attention mechanisms, and pipeline parallelism. Profile usage, compress checkpoints, and enable auto-resume for robustness. 𝟲. 𝗘𝘃𝗮𝗹𝘂𝗮𝘁𝗶𝗼𝗻 & 𝗩𝗮𝗹𝗶𝗱𝗮𝘁𝗶𝗼𝗻: Regularly evaluate using defined metrics and baseline comparisons. Test with few-shot prompts, review model outputs, and track performance metrics to prevent drift and overfitting. 𝟳. 𝗘𝘁𝗵𝗶𝗰𝗮𝗹 𝗮𝗻𝗱 𝗦𝗮𝗳𝗲𝘁𝘆 𝗖𝗵𝗲𝗰𝗸𝘀: Mitigate model risks by applying adversarial testing, output filtering, decoding constraints, and incorporating user feedback. Audit results to ensure responsible outputs. 🔸 𝟴. 𝗙𝗶𝗻𝗲-𝗧𝘂𝗻𝗶𝗻𝗴 & 𝗗𝗼𝗺𝗮𝗶𝗻 𝗔𝗱𝗮𝗽𝘁𝗮𝘁𝗶𝗼𝗻: Adapt models for specific domains using techniques like LoRA/PEFT and controlled learning rates. Monitor overfitting, evaluate continuously, and deploy with confidence. These principles form a unified blueprint for building robust, efficient, and production-ready LLMs—whether training from scratch or adapting pre-trained models.

Most large language models are trained to predict the next token in a left-to-right (L2R) manner. However, Apple researchers discovered that right-to-left (R2L) models can significantly outperform L2R models on specific multiple-choice question (MCQ) tasks! I just read this new paper "Reversal Blessing: Thinking Backward May Outpace Thinking Forward in Multi-choice Questions" that challenges our assumptions about how language models process information. This "reverse thinking" approach uses Bayesian inference to evaluate answer choices based on their likelihood of generating the question, rather than the traditional approach of evaluating questions to predict answers. Surprising Results: The researchers trained both L2R and R2L models with identical data and computational resources across different model sizes (2B-8B parameters). - R2L models consistently outperformed L2R on logical reasoning tasks (LogiQA) - R2L excelled at commonsense understanding tasks (OpenbookQA, CommonsenseQA) - R2L showed dramatic improvement on truthfulness assessment (TruthfulQA - 51% better!) What's fascinating is that these improvements held across different model sizes, datasets, and random seeds, suggesting this isn't just statistical noise. Why Does This Work? The researchers explored three hypotheses for why R2L performs better on certain tasks: 1. Calibration - R2L naturally "auto-normalizes" different answer choices, avoiding the "surface competition" issue where semantically similar answers (like "dog" and "puppy") split probability mass 2. Computability - Different directional factorizations have varying computational complexity 3. Conditional Entropy - The optimal reasoning direction corresponds to lower conditional entropy Through controlled simulation studies with arithmetic tasks, they found strong evidence supporting the conditional entropy hypothesis - the direction with lower conditional entropy tends to perform better. Implications This research suggests exciting possibilities for future language model development: - We might benefit from models that can reason in multiple directions - Alternative factorizations beyond L2R and R2L could further enhance LLM capabilities - Task-specific reasoning directions could boost performance on targeted applications The study suggests that our default assumptions about "forward thinking" might not always be optimal.

𝗗𝗲𝗲𝗽 𝗗𝗶𝘃𝗲 𝗶𝗻𝘁𝗼 𝗥𝗲𝗮𝘀𝗼𝗻𝗶𝗻𝗴 𝗟𝗮𝗿𝗴𝗲 𝗟𝗮𝗻𝗴𝘂𝗮𝗴𝗲 𝗠𝗼𝗱𝗲𝗹𝘀 Very enlightening paper authored by a team of researchers specializing in computer vision and NLP, this survey underscores that pretraining—while fundamental—only sets the stage for LLM capabilities. The paper then highlights 𝗽𝗼𝘀𝘁-𝘁𝗿𝗮𝗶𝗻𝗶𝗻𝗴 𝗺𝗲𝗰𝗵𝗮𝗻𝗶𝘀𝗺𝘀 (𝗳𝗶𝗻𝗲-𝘁𝘂𝗻𝗶𝗻𝗴, 𝗿𝗲𝗶𝗻𝗳𝗼𝗿𝗰𝗲𝗺𝗲𝗻𝘁 𝗹𝗲𝗮𝗿𝗻𝗶𝗻𝗴, 𝗮𝗻𝗱 𝘁𝗲𝘀𝘁-𝘁𝗶𝗺𝗲 𝘀𝗰𝗮𝗹𝗶𝗻𝗴) as the real game-changer for aligning LLMs with complex real-world needs. It offers: ◼️ A structured taxonomy of post-training techniques ◼️ Guidance on challenges such as hallucinations, catastrophic forgetting, reward hacking, and ethics ◼️ Future directions in model alignment and scalable adaptation In essence, it’s a playbook for making LLMs truly robust and user-centric. 𝗞𝗲𝘆 𝗧𝗮𝗸𝗲𝗮𝘄𝗮𝘆𝘀 𝗙𝗶𝗻𝗲-𝗧𝘂𝗻𝗶𝗻𝗴 𝗕𝗲𝘆𝗼𝗻𝗱 𝗩𝗮𝗻𝗶𝗹𝗹𝗮 𝗠𝗼𝗱𝗲𝗹𝘀 While raw pretrained LLMs capture broad linguistic patterns, they may lack domain expertise or the ability to follow instructions precisely. Targeted fine-tuning methods—like Instruction Tuning and Chain-of-Thought Tuning—unlock more specialized, high-accuracy performance for tasks ranging from creative writing to medical diagnostics. 𝗥𝗲𝗶𝗻𝗳𝗼𝗿𝗰𝗲𝗺𝗲𝗻𝘁 𝗟𝗲𝗮𝗿𝗻𝗶𝗻𝗴 𝗳𝗼𝗿 𝗔𝗹𝗶𝗴𝗻𝗺𝗲𝗻𝘁 The authors show how RL-based methods (e.g., RLHF, DPO, GRPO) turn human or AI feedback into structured reward signals, nudging LLMs toward higher-quality, less toxic, or more logically sound outputs. This structured approach helps mitigate “hallucinations” and ensures models better reflect human values or domain-specific best practices. ⭐ 𝗜𝗻𝘁𝗲𝗿𝗲𝘀𝘁𝗶𝗻𝗴 𝗜𝗻𝘀𝗶𝗴𝗵𝘁𝘀 ◾ 𝗥𝗲𝘄𝗮𝗿𝗱 𝗠𝗼𝗱𝗲𝗹𝗶𝗻𝗴 𝗜𝘀 𝗞𝗲𝘆: Rather than using absolute numerical scores, ranking-based feedback (e.g., pairwise preferences or partial ordering of responses) often gives LLMs a crisper, more nuanced way to learn from human annotations. Process vs. Outcome Rewards: It’s not just about the final answer; rewarding each step in a chain-of-thought fosters transparency and better “explainability.” ◾ 𝗠𝘂𝗹𝘁𝗶-𝗦𝘁𝗮𝗴𝗲 𝗧𝗿𝗮𝗶𝗻𝗶𝗻𝗴: The paper discusses iterative techniques that combine RL, supervised fine-tuning, and model distillation. This multi-stage approach lets a single strong “teacher” model pass on its refined skills to smaller, more efficient architectures—democratizing advanced capabilities without requiring massive compute. ◾ 𝗣𝘂𝗯𝗹𝗶𝗰 𝗥𝗲𝗽𝗼𝘀𝗶𝘁𝗼𝗿𝘆: The authors maintain a GitHub repo tracking the rapid developments in LLM post-training—great for staying up-to-date on the latest papers and benchmarks. Source : https://lnkd.in/gTKW4Jdh ☃ To continue getting such interesting Generative AI content/updates : https://lnkd.in/gXHP-9cW #GenAI #LLM #AI RealAIzation