Guide to Fine Tuning LLMs: Methods & Best Practices
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October 24, 2024, 19 min read time

Published by Vedant Sharma in Additional Blogs

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Large language models (LLMs) are powerful tools in natural language processing. They can generate text, translate languages, summarize, and answer questions. However, they aren’t always a perfect fit for specific tasks.

Fine-tuning helps adjust LLMs for particular needs. You can improve how well it performs that task by training a pre-existing LLM with a small, task-specific dataset. For example, Google found that fine-tuning a model for sentiment analysis boosted accuracy by 10%.

This article will explain how fine-tuning LLMs improves accuracy, reduces costs, and improves results for specific tasks.

What is fine-tuning, and why do you need it?

Fine-tuning is tweaking a large language model (LLM) that has already been trained on general language data to improve its performance at specific tasks. While models like GPT know a lot about language, they aren’t experts in certain areas. Fine-tuning helps these models learn from focused data, improving their accuracy for particular jobs or domains.

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Here’s why fine-tuning is useful:

  • Customization

Every field, like law, medicine, or business, has unique language, terms, and patterns. A general model might need to understand those specifics fully. Fine-tuning helps the model learn those unique details. This makes it much better at generating content that fits your exact needs. For example, a model fine-tuned on medical reports will understand medical jargon and produce more relevant, accurate information.

  • Data Compliance

Handling sensitive information is very important in healthcare, finance, or law industries. There are strict rules about how to manage and use data. Fine-tuning allows you to train the model on your private or regulated data, ensuring it follows all the rules while keeping your information safe. This way, you don’t risk exposing sensitive data to outside models.

  • Limited labeled data

Sometimes, gathering a lot of labeled data for a specific task takes time and effort. Fine-tuning is helpful here because it lets you train a model with less labeled data and still get good results. Even if your dataset is small, the model can learn from it and improve its performance for your specific needs.

In short, fine-tuning helps turn a general language model into a specialized one that can more accurately handle your unique tasks, keep your data safe, and work well even with smaller datasets.

When to Fine-Tune Models

Fine-tuning is a smart way to make large language models (LLMs) work better for specific tasks or situations. Instead of training a whole model from scratch, which can be time-consuming and resource-intensive, you can adjust an existing model to meet your needs. Here’s when fine-tuning is especially useful:

  • Improve performance for specific tasks: If you need the model to do something very specific, fine-tuning helps. For example, you can use the model to write poems in a certain style, translate languages more accurately, or summarize legal documents. The model gets better at handling the task by fine-tuning it with examples of this kind of work. The model might be too broad without fine-tuning and give less precise results.

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  • Adapt to new data: Data changes over time. Think of how language evolves or how companies update their products and services. If your model relies on old data, it might not give the best results. Fine-tuning allows the model to learn from new data and stay updated. For instance, if you run a news site, you can fine-tune the model regularly so it keeps up with the latest information and trends.
  • Perform better in specific domains: Fine-tuning makes a huge difference if you need the model to work well in a specific area like healthcare, law, or customer support. A general language model might need to help understand technical jargon or industry-specific terms. By fine-tuning it with domain-specific data, you train the model to understand better and generate content related to that field. For example, a fine-tuned model for customer support can respond more accurately and in a way that feels more personalized to your customer's issues.
  • Cater to a specific audience: Sometimes, you need the model to speak to a particular audience or mirror a specific style or tone. Fine-tuning can help here, too. For instance, the model should use more casual and fun language if your audience is teens. On the other hand, if it’s a business audience, you’ll want it to be more formal and professional. Fine-tuning helps shape the model’s responses to fit the audience you have in mind.
  • Gain new skills for a new task: Sometimes, you need the model to do something entirely new, like answer questions on a new topic or help with a different kind of task that it wasn’t originally trained for. Fine-tuning lets you build these new skills into the model. For example, a general model might know how to answer basic questions, but with fine-tuning, you could teach it to answer more complex, domain-specific questions like those in medical diagnostics or financial analysis.
  • Reduce costs and improve efficiency: Large models can be expensive to run and slow to produce results. Fine-tuning can help you take the strengths of a big model and distill them into a smaller, more efficient version that still gets the job done. This saves costs in terms of computing power and makes the model faster, reducing latency. You’re cutting down the model’s size while keeping its brainpower, which can be crucial for applications where speed and cost matter.
  • Work with limited data: Sometimes, you need more labeled data to train a model from scratch. Collecting and labeling massive datasets can be expensive and time-consuming. Fine-tuning is helpful here because it allows you to refine an already-trained model using a small, specialized dataset. Even with limited data, you can improve the model's performance significantly, making it more accurate and relevant for your specific task or domain.

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Why Fine-Tuning is Better Than Starting from Scratch

Training a model from scratch requires tons of data, time, and computing power. In contrast, fine-tuning is quicker and more efficient because it builds on the existing knowledge in a pre-trained model. Adjusting this knowledge with task-specific data requires less training time or data. This makes fine-tuning a practical choice, especially if you work on a smaller project or have limited resources.

However, there are some risks. One common issue with fine-tuning is "catastrophic forgetting." This means that during the fine-tuning process, the model might lose some of the general knowledge it gained in the original training. In other words, while it improves at the task you fine-tuned, it might worsen at others. To avoid this, you must carefully balance fine-tuning so the model doesn’t lose its broader language understanding.

Fine-tuning helps you make large language models more effective for specialized tasks. Whether you want to improve performance, adapt to new data, cater to specific audiences, or reduce costs, fine-tuning allows you to customize the model to fit your needs without starting from scratch. Just be mindful of balancing the fine-tuning process to avoid losing the model's general language abilities.

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Methods for Fine-Tuning LLMs

Here are some ways to fine-tune large language models:

  1. Instruction Fine-Tuning: Instruction fine-tuning trains the model to follow specific commands using examples. For instance, if you want the model to improve summarization, you provide it with instructions like "summarize this text" and examples to learn from. This method teaches the model how to respond to clear prompts, making it better at handling targeted tasks.
  2. Parameter-Efficient Fine-Tuning (PEFT): PEFT focuses on updating only a small portion of the model’s parameters, saving memory and computational resources. Techniques like LoRA (Low-Rank Adaptation) help significantly reduce the number of trainable parameters. This approach prevents the model from forgetting its original knowledge while fine-tuning, making it more efficient and cost-effective, especially for larger models.
  3. Task-Specific Fine-Tuning: This method adapts the model to perform a specific task or work within a particular domain, like translating text or analyzing sentiment. It requires more data and training time but ensures the model excels. While it can sometimes lead to the model forgetting other tasks, task-specific fine-tuning delivers high accuracy for specialized applications.
  4. Transfer Learning: Transfer learning uses a pre-trained model and fine-tunes it for a particular task with limited data. It builds on the model's knowledge, making it faster and more accurate than training a model from scratch. This is useful when data or resources are scarce.
  5. Multi-Task Learning: Multi-task learning involves simultaneously training a model on various tasks, like summarizing, translating, and identifying entities. This method improves the model’s ability to handle multiple tasks without forgetting how to perform others. However, it requires a large, diverse dataset, which can be hard to gather. It’s best when the model needs to handle many different tasks well.
  6. Sequential Fine-Tuning: In sequential fine-tuning, you fine-tune the model in steps for related tasks. For example, you might first adapt the model to medical language and then focus on pediatric cardiology. This method helps the model improve at increasingly specialized tasks while keeping its overall knowledge intact, making it highly effective in niche areas.

Each of these fine-tuning methods offers unique advantages based on your specific goals and constraints, whether saving resources, targeting a specific task, or handling multiple tasks simultaneously.

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Best Practices for Fine-Tuning LLMs

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Fine-tuning a pre-trained model for your needs involves a structured approach to achieve the best results. Here are some key practices to follow for successful fine-tuning:

  • Data Preparation
    Start by preparing your data carefully. This means cleaning the dataset, fixing missing values, and formatting it to match the model’s input requirements. The quality of your data plays a big role in how well the model will perform. You can also use data augmentation techniques to expand your dataset, such as adding variations of the existing data. This helps the model become more flexible and improves its ability to handle different scenarios.

    Proper data preparation ensures that the model learns effectively from your information and can deliver more accurate and relevant outputs. Think of it like prepping ingredients before cooking—good prep leads to a better final dish!
  • Choose the Right Pre-Trained Model
    Selecting the best pre-trained model is key. You want to pick a model that fits your task as closely as possible. Consider factors like the model's architecture, how it handles input and output, and how large or complex it is. Also, check how well it performs on tasks similar to yours.
  • Set the Right Fine-Tuning Parameters
    Fine-tuning requires tweaking certain parameters to get the best performance. These include the learning rate (how fast the model learns), the number of training epochs (how many times the model sees the data), and batch size (how many examples the model processes at once).

    Often, engineers freeze some of the model's layers, especially the earlier ones, so they stay the same during training. This helps retain the general knowledge the model learned before fine-tuning. The final layers are then fine-tuned to specialize in your task. This approach balances the model's broad knowledge and the new task-specific features.
  • Validate the Model
    After fine-tuning, it's important to validate the model’s performance. Use a validation set separate from your training data to check how well the model performs. Key metrics like accuracy, precision, recall, and loss will give you insights into how effectively the model handles the task.

    This step helps you see if the model generalizes well to new data or needs further adjustments. Think of it as taking a car for a test drive—you want to ensure it runs smoothly before hitting the road.
  • Iterate and Improve
    Fine-tuning is often an iterative process. After testing the model, you might find areas to improve it. This could mean tweaking parameters like the learning rate or adjusting how many layers are frozen. You could explore other techniques, such as regularization, to avoid overfitting.
  • Deploy the Model
    Once you’re happy with the fine-tuned model, it’s time to deploy it. This means integrating it into your existing systems or applications for use in real-world situations. During deployment, ensure the model runs efficiently on your hardware and software. Also, factors like scalability, speed, and security should be considered to ensure the model performs well under different conditions.

By following best practices—choosing the right model, setting proper parameters, validating, iterating, and deploying—you can transform a general model into a powerful tool for your specific task.

Also read Understanding Agentic LLM: From Concepts to Application Development.

Challenges in Fine-Tuning LLMs

Fine-tuning large language models (LLMs) offers many benefits but comes with challenges. Let's break down some of the key issues:

  • Overfitting
    Overfitting happens when a model gets too focused on the specific details of the dataset it’s trained on, making it great at handling that data but bad at generalizing to new data. This is a common problem in fine-tuning because the datasets are often smaller and more specialized than those used in the model's original training.

    For example, if a fine-tuning dataset contains rare or very specific examples, the model might "learn" these details too well, thinking they are common features. This makes the model less flexible when faced with different data. Overfitting limits the model’s ability to handle real-world tasks, where the input might vary from what it was trained on.
  • Catastrophic Forgetting
    Catastrophic forgetting occurs when a model forgets the general knowledge it learned during its initial training after being fine-tuned with new, specific data. In the case of LLMs, trained on a wide range of topics, fine-tuning for a specific task can cause the model to lose some of its earlier versatility.

    For instance, a model originally trained to understand various subjects may lose its grasp of general concepts if it’s heavily fine-tuned for a niche area like legal documents or medical reports. This is a big challenge because you want the model to specialize in new tasks without losing its broader, more general skills.
  • Bias Amplification
    Bias amplification is when a model not only reflects the biases in the data it was trained on but also intensifies them during fine-tuning. If the fine-tuning dataset contains biased examples, the model can amplify these biases, leading to harmful or unfair outcomes.

    For example, suppose a dataset for fine-tuning includes biased hiring decisions based on gender or ethnicity. In that case, the model might reinforce and worsen these biases, leading to unfair treatment in automated hiring processes. This highlights the importance of carefully selecting diverse and unbiased data for fine-tuning to avoid discriminatory behavior in the model’s output.
  • Complexity of Hyperparameter Tuning
    Hyperparameters like learning rate, batch size, and the number of training epochs are crucial for fine-tuning success. However, finding the right combination of these settings can take time and effort. If the learning rate is too high, the model may learn too quickly and miss important details; if it's too low, the model might need to learn more. Similarly, choosing the wrong batch size or training epochs can result in poor performance or overfitting.

    Finding the best hyperparameters often involves trial and error, which is time-consuming and requires significant computing resources. Running multiple training cycles to fine-tune these parameters can be expensive, especially for large models. Fortunately, new tools and frameworks are being developed to make this process easier, though it remains a significant challenge.

Fine-tuning LLMs can be powerful, but it comes with obstacles like overfitting, catastrophic forgetting, bias amplification, and the complexity of hyperparameter tuning. Awareness of these challenges helps you take the necessary steps, such as carefully selecting datasets and adjusting hyperparameters for the best results.

Conclusion

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