Office Hours 2: Q&A Session with Zach Mueller

This Q&A session covers various aspects of LLM fine-tuning, including tools, techniques, data sets, and hardware considerations.

This post is part of the following series:

• Mastering LLMs Course Notes: My notes from the course Mastering LLMs: A Conference For Developers & Data Scientists by Hamel Husain and Dan Becker.

Key Takeaways

• Hands-on experience is crucial for learning LLM fine-tuning: Experimenting with code and models is more valuable than solely reading about it.
• Community engagement is essential for feedback and learning: Platforms like Twitter and Discord provide valuable spaces to connect with experts and peers.
• Choosing the right data set is crucial for effective fine-tuning: Synthetic data sets and those that evolve over time offer unique advantages.
• Hardware plays a significant role in LLM training and inference: NVIDIA GPUs remain dominant.
• Model size should be determined by inference constraints and desired quality: Smaller models often provide a good balance between performance and cost.

1. Axolotl vs. HF AutoTrain

• Axolotl and HF AutoTrain address different aspects of LLM training.
• Axolotl focuses on high-level, rapid model training for text-based tasks.
• HF AutoTrain offers a more agnostic approach, allowing for training various models with custom data.
• Key difference: Axolotl prioritizes speed and ease of use, while HF AutoTrain provides greater flexibility.

2. Learning Journey for LLM Engineers

• Practical experience is paramount: Start by experimenting with code and building models.
• Active community engagement is crucial: Seek feedback, ask questions, and share your learnings.
• Focus on practical projects: Choose small, manageable tasks to gain hands-on experience.
• Iterate and learn from mistakes: Analyze results, identify areas for improvement, and continuously refine your approach.

3. Finding Feedback and Community

• Engage with experts on platforms like Twitter and Discord:
• Be proactive and demonstrate effort: Share your work, ask specific questions, and show that you’ve attempted to solve the problem.
• Contribute to the community: Share your learnings, participate in discussions, and help others.

4. Public Data Sets for LLM Fine-Tuning

• Hugging Face Data Sets: Offers a wide variety of data sets suitable for LLM fine-tuning.
• StarCoder 2 Self-Instruct Data Set: Based on code from GitHub, provides benchmarks and a transparent pipeline.
• Instruction Tuning Data Sets: Help understand the principles of fine-tuning and prepare for more complex tasks.
  • Extended Guide: Instruction-tune Llama 2
• Synthetic Data Sets: Offer control over the data generation process and enable testing for overfitting.

5. Accelerate, Torch Compile, and Distributed Training

• FSDP (Fully Sharded Data Parallelism): Essential for training large models by distributing data and model parameters across multiple GPUs.
• DeepSpeed: Offers more configuration options than FSDP, allowing for fine-grained control over offloading and device placement.
• Torch Compile: Primarily an inference-time optimization, but PyTorch aims to integrate it into training workflows.
• Recommendation: Use FSDP for models that fit in memory across all GPUs; consider DeepSpeed for scenarios requiring offloading.

6. Inference Precision and Hardware

• BF16 (BFloat16): Offers a good balance between performance and accuracy for training and inference.
• FP16 (Half Precision): Can be slower than BF16, especially on hardware optimized for BF16.
• Recommendation: Train models in BF16 to ensure compatibility with a wider range of inference hardware.

7. Downsides of FSDP

• All-or-nothing approach: FSDP distributes the entire model across GPUs, which can be limiting if the model doesn’t fit in memory.
• Lack of fine-grained control: Unlike DeepSpeed, FSDP doesn’t allow for selectively offloading specific layers to the CPU.

8. NVLink and GPU Performance

• NVLink: Provides high-bandwidth communication between GPUs, improving performance in multi-GPU setups.
• Impact of NVLink absence: Debated, with some reporting significant performance degradation and others claiming minimal impact.
• Consumer cards and throttling: Consumer-grade GPUs might have driver-level limitations compared to their professional counterparts.
• Recommendation: Consider the RTX A4000 or RTX A4500 over RTX 4090s if budget allows:
  • NVIDIA RTX A4500 (24GB)
    • Product Page
    • Purchase Page
  • NVIDIA RTX A4000 (20GB)
    • Product Page
    • Purchase Page

9. Fine-Tuning vs. Frontier Models

• Fine-tuning can achieve comparable or even surpass the performance of frontier models: Community-driven fine-tuning efforts like Teknium’s models demonstrate this potential.
• Data access remains a challenge: Closed-source models often benefit from significantly larger and proprietary data sets.

10. Ensuring Prompting and Tokenization Consistency

• Hugging Face Pipelines: Provide a reliable way to load and use fine-tuned models for inference.
• Chat Templating: Hugging Face’s chat templates offer a standardized approach to prompting, but they might not be directly compatible with all tools.
• Thorough Testing: Always test inference with the same tokenization and prompting procedures used during training.

11. Running Inference on an 8 Billion Parameter Model with a 24GB GPU

• Quantization: Techniques like AWQ (AutoAWQ) can reduce model size and memory footprint, enabling inference on less powerful hardware.
• Offloading: Offloading parts of the model to the CPU can enable inference on limited VRAM, but it comes with a performance trade-off.

12. Training Models in 8-Bit Precision

• Instability: Training in 8-bit precision (INT8 or FP8) can lead to instability and convergence issues.
• Experimental Support: While frameworks like PyTorch are adding support for 8-bit training, it remains experimental.
• BF16 with FP8: Some hardware platforms utilize a combination of BF16 and FP8 for training, potentially offering a middle ground.

13. Limitations of Accelerate

• Accelerate as a wrapper: Accelerate primarily acts as a wrapper around existing distributed training frameworks, so its failures often stem from underlying issues.
• Timeout issues: Occasional timeout problems have been observed, but the root cause remains unclear.

14. Relevance of Chinchilla Scaling Laws

• Still relevant for optimal resource allocation: Chinchilla scaling laws provide guidance on balancing parameters and data size for a given compute budget.
• Don’t guarantee the best model: Continuously training a model until convergence often yields the best results, regardless of scaling laws.
• Under-trained models and fine-tuning: Models trained with fewer steps than suggested by scaling laws might be more amenable to fine-tuning.

15. Relevance of TensorFlow for LLM Fine-Tuning

• PyTorch dominance: PyTorch has become the dominant framework for LLM research and development.
• TensorFlow’s role: TensorFlow, particularly Keras, still serves as a backend in some LLM frameworks, but its popularity has diminished.

16. Training on Apple Silicon

• Inference: Apple Silicon performs well for LLM inference tasks.
• Training: Training support is improving but remains behind NVIDIA GPUs in terms of maturity and performance.
• Hardware limitations: Apple’s system-on-a-chip architecture and lack of dedicated server-grade GPUs pose challenges for large-scale training.

17. Serving Multiple LoRAs with Accelerate Inference

• VLLM: Supports loading and switching between multiple LoRAs during inference.
• Hot-swapping: VLLM allows for selecting different LoRAs on a per-request basis, enabling dynamic model customization.

18. Mixture of LoRAs

• Concept: Training multiple LoRAs specializing in different tasks and using a router to dynamically select the most appropriate LoRA for a given input.
• Kraken Model: An example of a model that utilizes dynamic model routing with multiple expert models.
  • VAGOsolutions/Kraken-LoRA

19. Choosing a Fine-Tuning Project

• Personal interest and relevance: Select projects that align with your interests and current work.
• Replicating existing work: Recreating existing projects is a valuable learning experience.
• Data availability: Choose projects with readily available or easily obtainable data sets.
• Document your process: Keep track of your experiments, results, and lessons learned.

20. Constraints and Sweet Spots in Fine-Tuning

• Budget and hardware: Determine the available compute resources and select a model size accordingly.
• Inference time and cost: Prioritize inference efficiency, as it significantly impacts real-world deployment costs.
• Iteration speed: Smaller models allow for faster experimentation and iteration cycles.
• Quality requirements: Balance model size with the desired performance level for the specific task.
  • 7 to 8 billion parameter models are often the sweet spot in real-world projects.

21. Fine-Tuning on Phi-3

• Limited real-world performance: Despite its size, Phi-3 has not demonstrated competitive performance in practical applications.
• Data and training methodology: Potential issues with the training data or methodology might contribute to its shortcomings.

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About Me:

I’m Christian Mills, a deep learning consultant specializing in practical AI implementations. I help clients leverage cutting-edge AI technologies to solve real-world problems.

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