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Prompt Engineering vs Fine-Tuning: Understanding the Pros and Cons

Written by Iris Zarecki | October 29, 2024

Prompt engineering is a process that improves LLM responses by well crafted inputs. Fine-tuning trains a model on domain-specific data. Which to use when?  

Prompt engineering defined 

AI prompt engineering is the process of crafting highly specific instructions to guide a Large Language Model (LLM) to generate a more accurate and relevant response to user queries. It's often employed by LLM agents in generative AI frameworks like Retrieval-Augmented Generation (RAG).

Prompt engineering is essentially asking a question in a way that ensures your enterprise LLM understands exactly what you're looking for. The goal of prompt engineering is to structure prompts – questions, commands, scenarios, and more – in such a way that the model elicits the most useful answer to a particular question.

A well-engineered prompt includes clear context, specific requirements, or sample formats – all of which contributes to LLM grounding. For instance, instead of asking “What is a tree?”, you might prompt the LLM to “Describe the structure and function of a tree and give examples of different types of trees?”. This extra detail narrows down the possible responses and ensures the model’s output is more relevant.

The strength of prompt engineering lies in its simplicity, in the sense that you don’t need to retrain or alter the LLM itself. This makes prompt engineering a cost-effective way to improve results. However, the method does require experimentation to find the optimal wording or structure.

Prompt engineering techniques, such as chain-of-thought prompting, are an integral part of all active retrieval-augmented generation solutions. 

Fine-tuning defined 

Fine-tuning is the process of taking an already trained AI model and adapting it to perform specific tasks or respond in a more focused way.  

An LLM is like an all-purpose tool, capable of doing many things. Fine-tuning adjusts it to become an expert in a specialized area. How does this work? The LLM, which has been trained on a broad range of publicly available information, is given new, domain-specific data related to the task you’d like it to excel at. This new data could be financial or medical records, customer service transcripts, or anything else relevant to your goals. The model then learns from this focused dataset, refining its ability to perform the job at hand.

For example, if you wanted your LLM to excel at legal matters, you’d fine-tune the model by providing it with legal texts, cases, and documents. Fine-tuning helps the model become more accurate and knowledgeable in that area without starting from scratch, saving time and resources. 

Prompt engineering vs fine tuning features 

Prompt engineering and fine-tuning are both techniques that optimize the performance of LLMs and reduce AI hallucinations, but they operate in different ways.  

RAG prompt engineering involves crafting well-structured inputs that guide the LLM to respond more accurately and contextually. Fine-tuning modifies the model itself by training it on specialized data that improves its performance in specific areas.  

So, while prompt engineering shapes how you interact with the LLM, fine-tuning directly enhances the model's knowledge and abilities. Understanding these differences is key to knowing when to use each approach. Here’s a quick guide: 

Feature  Prompt Engineering  Fine-Tuning 
Definition  Crafts effective prompts to guide your LLMs to produce better outputs.  Trains your LLM on a specific dataset to improve its performance on specific tasks. 
Goal  Maximizes the quality of your LLM’s outputs without changing its underlying architecture.  Adapts your LLM to a specific domain or task. 
Method  Generates well-structured, informative, and contextual prompts.  Feeds your LLM with a large dataset of relevant examples and adjusts its internal parameters. 
Resources  Requires human expertise in Natural Language Processing (NLP) and LLM functionality.  Needs a large dataset of relevant examples and resources for training. 
Deployment  Deploys faster, with fewer resources, than fine-tuning.  Tends to be time-consuming and expensive, especially for larger models and datasets. 
Flexibility  Increases flexibility via experimentation and adaptation to different tasks.  Reduces flexibility since the model becomes specialized to a specific domain or task. 
Use cases  Is suitable for a wide range of tasks, including content generation, question answering, and summarization.  Is effective when your LLM's general knowledge is insufficient or when high accuracy is required. 

Pros and cons of prompt engineering vs fine-tuning 

Prompt engineering and fine-tuning are both useful strategies for improving AI performance, each with their own unique advantages and limitations. 

Technique

Pros  Cons 

Prompt engineering 

  • Training-free 
    You can instantly improve results by adjusting how you ask questions, without altering the model. 
  • Cost-effective 
    You invest less time and resources because you’re not retraining the model. 
  • Flexible 
    Applies to a wide range of use cases, since you're using your LLM as is, with tailored prompts for specific needs. 
  • Less control 
    Your LLM’s built-in capabilities may not be well suited to niche tasks. 
  • Unpredictable 
    Multiple (trial and error) attempts may be required to zero in on the best prompts, requiring patience and testing. 

Fine-tuning 

  • Highly customizable 
    Specializes your LLM for certain tasks, leading to more precise and accurate results. 
  • Results-oriented  
    Following fine-tuning, the model becomes more adept at specific areas and operates more efficiently. 
  • Resource-intensive 
    Additional data, computing power, and training time may be required. 
  • Inflexible 
    Once fine-tuned, the model may perform less effectively on tasks outside its specialized domain. 

In short, while prompt engineering offers a quicker, cost-effective solution, fine-tuning provides deeper customization at the expense of resources and flexibility. 

Prompt engineering vs fine tuning with GenAI Data Fusion  

GenAI Data Fusion, the K2View suite of RAG tools, integrates prompt engineering as opposed to fine-tuning processes. Ideal for generative AI use cases that require accurate, contextual, and personalized interactions, GenAI Data Fusion leverages chain-of-thought reasoning to produce more precise, meaningful, and relevant outputs. It features: 

  1. Real-time data access, by dynamically retrieving customer data to craft better prompts leading to better responses. 

  2. Data security, by automatically discovering masking sensitive information and PII (Personally Identifiable Information) during processing. 

  3. Inflight recommendations, by dealing with data service access requests and providing more informed insights in real-time. 

  4. Multi-source data retrieval, by accessing enterprise systems via API, CDC, messaging, or streaming. 

GenAI Data Fusion embeds prompt engineering to enable the most cost-effective, fast-track AI personalization available anywhere. For more comprehensive insights on this subject, our article on RAG vs fine-tuning vs prompt engineering makes for good reading. 

Discover K2View AI Data Fusion, the RAG 
tools with prompt engineering built in.