What are the key differences between retrieval-based APIs like Assistant_API and fine-tuned GPT models?

Below is an explanation outlining the main differences:

Retrieval-Based API (e.g., Assistant_API)

• Mechanism:
  This type of API retrieves relevant parts of your documents by comparing the query against a pre-computed vector representation—for example, using cosine similarity. Essentially, it selects context from your provided documents that are closely related to the query.

• Usage:
  It's commonly used in retrieval-augmented generation (RAG) setups where the retrieved context is fed into a generative model so that responses reference or are grounded in your specific documents.

GPT Models

• Mechanism:
  GPTs are large language models that have been pre-trained on broad datasets. They learn a vast amount of language patterns and general knowledge during training. They are not "retrieving" from any external documents unless explicitly set up to do so as part of an augmented system.

• Customization:
  When you fine-tune a GPT model on your specific documents, it essentially adjusts its parameters based on that data. In this case, the model "learns" from the data rather than performing a runtime similarity search. However, it still relies on the patterns learned during its large-scale pre-training.

Summary

• The Assistant_API approach relies on a similarity search (like cosine similarity) to dynamically pull in the most relevant portions of your documents when responding to a query.
• GPT models are not inherently retrieval-based; they generate responses based on their learned representations. They can be fine-tuned on your data, but this means the knowledge is integrated into the model weights rather than being dynamically looked up.

In essence, your understanding is partially correct: retrieval-based APIs match query vectors against stored document vectors (using methods like cosine similarity), while GPTs generate text based on learned knowledge, unless they are augmented with an external retrieval mechanism.