DEEPCHECKS GLOSSARY

LLM Fine Tuning

What is LLM Fine-Tuning?

Large language models (LLMs) excel at a broad range of tasks. However, they often struggle when tackling smaller, niche, domain-specific problems. This is where fine-tuning becomes essential. By leveraging pre-trained models to recognize features and patterns of a larger dataset, fine-tuning involves additional training on specialized, domain-specific data.

Developing an LLM from scratch can be expensive, making fine-tuning a cost-effective alternative. It also improves performance in focused areas by leveraging cutting-edge LLMs for specialized problems at lower computational costs.

Why is fine-tuning Necessary?

The decision to fine-tune LLMs often depends on specific domain or task-specific objectives. Let’s look at some of the key reasons to fine-tune an LLM:

Limited data

Companies often struggle to obtain large volumes of labeled data for a specific domain or task, which can be time-consuming and costly. Fine-tuning helps alleviate this problem by allowing companies to adapt pre-trained LLMs to the limited labeled data set available, minimizing cost and maximizing performance and efficiency.

Customization

Each domain has its unique terminologies, linguistic nuances, and contextual patterns. Fine-tuning pre-trained LLMs enables the model to better understand and adapt to these intricacies, producing more relevant and accurate output. This is particularly useful in sentiment analysis and content generation scenarios for specific domains, such as medical reports, legal documents, business analytics, or other proprietary data.

Efficiency

Training LLMs from scratch demands significant computational resources and time. However, fine-tuning a pre-trained model is often more efficient because it bypasses the initial training stages, allowing for quicker convergence to a solution.

Compliance

Strict compliance laws across many businesses limit sensitive data transfer outside designated geographic areas. This is especially prevalent in fields like law, banking, and healthcare, where protecting sensitive information is paramount. By fine-tuning, businesses can ensure regulatory compliance by training LLMs on local, secure infrastructure using proprietary data. Additionally, this method improves security and privacy by removing the possibility of exposing confidential data to outside models.

How does fine-tuning LLMs work?

Fine-tuning is more intricate than it looks on the surface. Typically, it extends beyond minor tweaks to an LLM. It is a critical stage in refining and adapting an LLM’s capabilities to handle domain-specific workloads. The fundamental premise of fine-tuning is based on the broader concept of transfer learning, a popular machine-learning approach in which knowledge learned from one problem is transferred to another. However, fine-tuning requires rigorous processes, careful preparation, and a clear understanding. The procedure can be summarized as follows:

Fine-tuning LLMs work

Step 1: Identify the Task and Gather the Relevant Dataset

Before beginning, the specific task that the LLM will specialize in must be clearly defined. This could range from sentiment analysis and text summarization to generating domain-specific content based on medical or legal documents.

Once the task is finalized, the next step is to gather a relevant dataset for fine-tuning. The dataset should be pertinent to the defined task and contain enough samples to help the LLM learn the intricacies. It is essential to consider the quality and diversity of the data when compiling the dataset.

Step 2: Preprocessing

Before continuing with fine-tuning, the essential preprocessing steps must be completed. Tokenization, separating the dataset into training and testing sets, and encoding or structuring the data to make it more understandable to LLMs are common strategies used for this purpose.

Step 3: Initialize the LLM with Pre-Trained Weights

An appropriate pre-trained LLM can be chosen and initialized with its pre-trained weights. The weights signify the massive amount of knowledge the model gained from its initial training phase, which serves as a good starting point for the fine-tuning process.

Key factors such as performance, training data, and model size need to be considered when choosing a pre-trained model. A model that more closely matches the requirement of the chosen task will increase the effectiveness of the fine-tuning process, making the fine-tuned model more suitable for the intended application.

Step 4: Fine-Tune the LLM

The actual fine-tuning process occurs at this step, where the LLM is trained on the chosen task-specific dataset by adjusting its weights and biases. Configuring the right fine-tuning parameters is crucial for achieving efficient performance. Common parameters that need to be set and tuned include the learning rate, number of training epochs, and batch size. The learning rate is often kept low to prevent the model from deviating too far from its original knowledge. It is common practice to freeze some of the earlier layers in the model to preserve the base knowledge while capturing task-specific knowledge in the final layers. These techniques help maintain a balance between leveraging pre-existing knowledge and adapting to the new task.

Step 5: Evaluate and Iterate

Following the training procedure, the fine-tuned model is validated against a validation dataset. Its overall efficacy and generalization skills are quantitatively assessed using metrics such as accuracy, loss, precision, and recall.

The fine-tuned model can be iteratively trained with modified parameters until the desired performance is achieved. This gradual fine-tuning process is standard practice to ensure the model is well-suited for the specific task.

LLM Fine-Tuning approaches

The standard process for fine-tuning LLMs is well-established and widely practiced. However, specific fine-tuning strategies can vary since new cutting-edge methods are introduced regularly. Below are several state-of-the-art LLM fine-tuning strategies used widely.

  • Low Ranking Adaptation (LoRA): LoRA fine-tunes large language models using a low-rank approximation to reduce computational and financial costs for models like GPT-3.
  • Quantized LoRA (QLoRA): QLoRA uses a 4-bit quantized pre-trained model and backpropagates through low-rank adapters to minimize memory usage during fine-tuning while preserving full 16-bit fine-tuning performance.
  • Parameter-Efficient Fine Tuning (PEFT): PEFT lowers computational and storage costs, avoids catastrophic forgetting, and fine-tunes pre-trained language models by modifying a small set of parameters. It provides excellent results for applications like image classification and stable diffusion dreambooth.
  • DeepSpeed: DeepSpeed is a software library that accelerates training for large language models with memory-efficient distributed training. It optimizes fine-tuning jobs using Hugging Face’s Trainer API and provides scripts for existing fine-tuning processes.

Challenges and limitations of LLM Fine-tuning

Fine-tuning LLMs can sometimes lead to suboptimal results. Special effort needs to be taken to avoid the following pitfalls,

  • Overfitting: If the task-specific dataset is small or unrepresentative, fine-tuning may result in the model becoming unfairly specialized to the training set, which may negatively impact performance on new data.
  • Catastrophic Forgetting: If the model is fine-tuned for particular tasks, its generalizability may diminish, causing it to forget previously learned general knowledge.
  • Bias Amplification: Fine-tuning can amplify pre-trained model biases, posing ethical concerns and resulting in biased predictions.
  • Model Drift: Variations in the environment or data distribution can degrade the performance of a fine-tuned model over time, necessitating continuous monitoring and fine-tuning.
  • Tuning Complexity: Selecting the right hyperparameters for fine-tuning requires careful consideration and takes time. Making the wrong decision can result in overfitting, sluggish convergence, or less-than-ideal performance.