Exploring Nearest Neighbor Algorithms with FAISS, ScaNN, and DiskANN -AI Simplified Series

Tamilselvan Subramanian
3 min readFeb 13, 2024

Imagine you’re at a giant library with millions of books. You stumble upon an amazing story and want to find similar ones to dive into next. Checking each book one by one would take forever! Enter the world of nearest neighbor algorithms, your super-fast librarians who help you find similar books quickly and efficiently. This article explores three popular algorithms: FAISS, ScaNN, and DiskANN, all working towards the same goal — finding the closest matches in a vast sea of data.

Finding Your Literary Soulmates with FAISS: (Facebook AI Similarity Search)

Think of FAISS as a librarian who remembers the first few pages of many books. When you ask for similar stories, FAISS quickly scans those beginnings to find a few that match yours like summarizing the plots. Then, it takes a closer look at these promising candidates, like reading deeper chapters, to identify the best recommendations. This approach balances speed and accuracy, making FAISS suitable for moderate-sized collections (millions of books)

Scaling Up the Search with ScaNN:

Now imagine a library with billions of books! ScaNN becomes your librarian here. Instead of remembering individual pages, ScaNN groups books by themes and styles. So, when you ask for similar stories, ScaNN quickly narrows down the search to the relevant section (e.g., fantasy, mystery) and then finds the best match within that group. This makes ScaNN super fast for handling huge datasets, but it might miss some hidden gems outside the initial category selection.

Conquering the Infinite Library with DiskANN:

What if the library contains hundreds of billions of books? That’s where DiskANN steps in. Think of it as a librarian with two resources: a small bookshelf holding frequently borrowed books and a giant digital index for the rest. When you ask for similar stories, DiskANN first checks the bookshelf for quick matches. If not found, it consults the digital index, bringing the relevant book to the shelf for closer inspection. This efficient combination makes DiskANN perfect for massive datasets, sacrificing some speed for handling immense quantities of data.

Choosing Your Super Librarian:

Each algorithm has its strengths and weaknesses. While FAISS is great for smaller libraries, ScaNN excels in speed for massive collections, and DiskANN tackles truly astronomical datasets. Consider your data size, desired speed, and accuracy requirements to pick your perfect literary guide. Remember, the quest for similar stories is just one example! These algorithms are used in various fields, from image search to fraud detection, helping us navigate the vast data landscapes of our digital world.

This simplified explanation aims to spark your curiosity about nearest neighbor algorithms. As you delve deeper, remember, the world of data exploration is an exciting adventure waiting to be unraveled!

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