# HNSW

A dead-simple pure Elixir Hierarchical Navigable Small World (HNSW) module.

[You can read a deep dive explanation of HNSW here](https://www.pinecone.io/learn/series/faiss/hnsw/).

## Why?

The Elixir NX project has a project called [hnswlib](https://github.com/elixir-nx/hnswlib), which is a NIF wrapper around [the C++ hnswlib library](https://github.com/nmslib/hnswlib). While I love the fact that you can write NIFs in order to drop down to higher performing languages, and to bind to libraries that exist in these languages, I always tend to find myself having issues with NIFs. Sometimes it's because memory usage may not be properly reflected by the BEAM (since a NIF may not control the memory allocated by the library), sometimes the interface works in a non-intuitive way because the original library isn't necessarily compatible, tracing and the like is usually more problematic, and on top of all of that, there's a pretty big cognitive overhead to NIFs - you need to know the other language, and the other language is either C, C++, or Rust, all three of which are notoriously complex.

So, whenever I find myself seeing things that are only NIFs, I tend to want to find a pure Elixir version of the same thing. Sure, the performance might not be 100% on par (although you can get pretty much on par, see Jason versus jiffy for example), but at least the cognitive overhead is lower, the function can be traced with the BEAM, and other developers don't need to learn a brand new language just to use it.

## Installation

If [available in Hex](https://hex.pm/docs/publish), the package can be installed
by adding `hnsw` to your list of dependencies in `mix.exs`:

```elixir
def deps do
  [
    {:hnsw, "~> 0.1.0"}
  ]
end
```

Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
be found at <https://hexdocs.pm/hnsw>.