32k context length text embedding models | Hacker News Reader

32k context length text embedding models

blog.voyageai.com

101 pointsfzliu32 comments

Related question:

One year ago simonw said this in a post about embeddings:

[https://news.ycombinator.com/item?id=37985489]

> Lots of startups are launching new “vector databases”—which are effectively databases that are custom built to answer nearest-neighbour queries against vectors as quickly as possible.

> I’m not convinced you need an entirely new database for this: I’m more excited about adding custom indexes to existing databases. For example, SQLite has sqlite-vss and PostgreSQL has pgvector.

Do we still feel specialized vector databases are an overkill?

We have AWS promoting amazon OpenSearch as the default vector database for a RAG knowledge base and that service is not cheap.

Also I would like to understand a bit more about how to pre-process and chunk the data properly in a way that optimizes the vector embeddings, storage and retrieval ... any good guides on the same i cna refer to? Thanks!

Will try to respond in order:

1. It depends on how much embeddings we are talking about. Few millions, probably yes, 100s millions/Billions range? You likely need something custom.

2. Vectors are only one way to search for things. If your corpus contains stuff that don't carry semantic weight (think about part numbers) and you want to find the chunk that contains that information you'll likely need something that uses tf-idf.

3. Regarding chunk size, it really depends on your data and the queries your users will do. The denser the content the smaller the chunk size.

4. Preprocessing - again, it depends. If it's PDFs with just texts, try to remove footers / headers from the extracted text. Of it contains tables, look at something like table former to extract a good html representation. Clean up other artifacts from the text (like dashes for like breaking, square brackets with reference numbers for scientific papers, ... ).

I had the same idea, but now I a Postgres database that has very high latency for simple queries because the CPU is busy building large HNSW indexes.

My impression is that it might be best to do vector index construction separately from the rest of the data, for performance reasons. It seems vector indexes are several orders of magnitude more compute intensive than most other database operations.

Personally I feel they are overkill.

For example I’m using duckDB as a vector store for similarity search and RAG. It works really well.

https://github.com/patricktrainer/duckdb-embedding-search

Using a built-in vector extension is convenient if you want to integrate vector similarity (“semantic search”) with faceted search. Some vector stores (e.g., qdrant) support vector attributes that can be matched against, though.

As mentioned by another comment, an advantage of using a separate vector store (on different hardware) is that (re-)building vector indices can cause high CPU load and therefore latency for regular queries to go up.

I work in image diffusion rather than “LLMs.”

RAGs are the ControlNet of image diffusion. They exist for many reasons, some of those are that context windows are small, instruct-style frontier models haven’t been adequately trained on search tasks, and reason #1: people say they need RAGs so an industry sprouts up to give it to them.

Do we need RAGs? I guess for now yes, but in the near future no: 2/3 reasons will be solved by improvements to frontier models that are eminently doable and probably underway already. So let’s answer the question for controlnets instead to illuminate why just because someone asks for something, doesn’t mean it makes any sense.

If you’re Marc Andreesen and you call Mike Ovitz, your conversation about AI art generation is going to go like this: “Hollywood people tell me that they don’t want the AI to make creative decisions, they want AI for VFX or to make short TikTok videos or” something something, “the most important people say they want tools that do not obsolete them.” This trickles down to the lowly art director, who may have an art illustration background but who is already sending stuff overseas to be done in something that resembles functionally a dehumanized art generator. Everybody up and down this value chain has no math or English Lit background so to them, the simplest, most visual UX that doesn’t threaten their livelihood is what they want: Sketch To Image.

Does Sketch to image make sense? No. I mean it makes sense for people who cannot be fucked to do the absolutely minimal amount of lift to write prompts, which is many art professionals who, for the worse, have adopted “I don’t write” as an identity, not merely some technical skill specialization. But once you overcome this incredibly small obstacle of writing 25 words to Ideogram instead of 3 words to Stable Diffusion, it’s obvious: nobody needs to draw something and then have a computer finish it. Of course it’s technologically and scientifically tractable to have all the benefits of controlnets like, well control and consistency, but with ordinary text. But people who buy software want something that is finished, they are not waiting around for R&D projects. They want some other penniless creative to make a viral video using Ideogram or they want their investor’s daughter’s heir boyfriend who is their boss to shove it down their throats.

This is all meant to illustrate that you should not be asking people who don’t know anything what technology they want. They absolutely positively will say “faster horses.” RAGs are faster horses!

I’m baffled by your remarks about sketch-to-image. Maybe I’m missing something in what you mean, but sketch-to-image, to various degrees of completion (that is, it’s more than just sketch-to-image), lets you guide things in a way that prompts simply don’t. It’s rather useful if you’re trying to compose something specific, and plenty useful in other scenarios too.

Does sketch-to-image make sense? Um… yes? Absolutely? I genuinely don’t understand how you could even deny it, let alone act as though that’s the obvious answer?

Am I misunderstanding something of your meaning?

What’s the benefit of generating embeddings for such large chunks? Do people use these large contexts to include lots of document specific headers/footers or are they actually generating embeddings of single large documents?

I don’t understand how the math works out on those vectors

> What’s the benefit of generating embeddings for such large chunks?

Not an expert, but I believe now that we can fit more tokens into an LLM's context window, we can avoid a number of problems by providing additional context around any chunk of text that might be useful to the LLM. Solves the problem of misinterpretation of the important bit by the LLM.

You don’t have to reduce a long context to a single embedding vector. Instead, you can compute the token embeddings of a long context and then pool those into say sentence embeddings.

The benefit is that each sentence’s embedding is informed by all of the other sentences in the context. So when a sentence refers to “The company” for example, the sentence embedding will have captured which company that is based on the other sentences in the context.

This technique is called ‘late chunking’ [1], and is based on another technique called ‘late interaction’ [2].

And you can combine late chunking (to pool token embeddings) with semantic chunking (to partition the document) for even better retrieval results. For an example implementation that applies both techniques, check out RAGLite [3].

[1] https://weaviate.io/blog/late-chunking

[2] https://jina.ai/news/what-is-colbert-and-late-interaction-an...

[3] https://github.com/superlinear-ai/raglite

You can achieve the same effect by using LLM to do question answering prior to embedding, it's much more flexible but slower, you can use CoT, or even graph rag. Late chunking is a faster implicit alternative.

I read both those articles, but I still don't get how to do it. It seems the idea is that more of the embedding is informed by context, but do I _do_ late chunking?

My best guess so far is that somehow I embed a long text and then I break up the returned embedding into multiple parts and search each separately? But that doesn't sound right.

You’d need to go a level below the API that most embedding services expose.

A transformer-based embedding model doesn’t just give you a vector for the entire input string, it gives you vectors for each token. These are then “pooled” together (eg averaged, or max-pooled, or other strategies) to reduce these many vectors down into a single vector.

Late chunking means changing this reduction to yield many vectors instead of just one.

The name ‘late chunking’ is indeed somewhat of a misnomer in the sense that the technique does not partition documents into document chunks. What it actually does is to pool token embeddings (of a large context) into say sentence embeddings. The result is that your document is now represented as a sequence of sentence embeddings, each of which is informed by the other sentences in the document.

Then, you want to parition the document into chunks. Late chunking pairs really well with semantic chunking because it can use late chunking's improved sentence embeddings to find semantically more cohesive chunks. In fact, you can cast this as a binary integer programming problem and find the ‘best’ chunks this way. See RAGLite [1] for an implementation of both techniques including the formulation of semantic chunking as an optimization problem.

Finally, you have a sequence of document chunks, each represented as a multi-vector sequence of sentence embeddings. You could choose to pool these sentence embeddings into a single embedding vector per chunk. Or, you could leave the multi-vector chunk embeddings as-is and apply a more advanced querying technique like ColBERT's MaxSim [2].

[1] https://github.com/superlinear-ai/raglite

[2] https://huggingface.co/blog/fsommers/document-similarity-col...

What does it mean to "pool" embeddings? The first article seems to assume the reader is familiar

“Pooling” is just aggregation methods. It could mean taking max or average values, or more exotic methods like attention pooling. It’s meant to reduce the one-per-token dimensionality to one per passage or document.

I thought embedding large chunks would "dilute" the ideas, since large chunks tend to have multiple disparate ideas?

Does it somehow capture _all_ of the ideas, and querying for a single one would somehow match?

Isn't that the point of breaking down into sentences?

Someone mentioned adding context -- but doesn't it calculate embedding on the whole thing? The API Docs list `input` but no separate `context`. https://docs.voyageai.com/reference/embeddings-api

I've found good results from summarizing my documents using a large context model then embedding those summaries using a standard embedding model (e.g. e5)

This way I can tune what aspects of the doc I want to focus retrieval on, it's easier to determine when there are any data quality issues that need to be fixed, and the summaries have turned out to be useful for other use cases in the company.

Agreed. Esp if you gonna call an API, you can call something cheaper than this embeddings model, like 4o-mini, summarize, then use a small embeddings model fine-tuned for your needs locally.

I was critical about these guys before (not about their quality of work but rather about building a business around embeddings). This work though seems interesting and I might even give it a try, esp if they provide a fine-tuning API (is that on the roadmap?)

Not related, but why they don’t have a pricing page? Last time I checked voyageai I had to google their pricing to find the page as it’s not in the nav menu.

What on earth is "OpenAI V3"? Just to be sure I wasn't being obtuse, I Googled it, only to get a bunch of articles pointing back at this post.

It is OpenAI's vector embedding model

https://openai.com/index/new-embedding-models-and-api-update...

API constant is text-embedding-3

You missed the “large” which adds context: “OpenAI V3 large” which is their sota large embedding model.

I wonder if random projections or other similar dimensionality reduction techniques work equally well then using a model specialized in smaller embeddings capturing the same amount of semantical information. This way we could use larger embeddings of open models working very well and yet enjoy faster node to node similarity during searches.

https://hn.algolia.com/?q=https%3A%2F%2Fblog.voyageai.com%2F...

very interesting observation

so the same link has been posted ~10 times in the last one month?

and this is the first time the post got any attention

mixed feelings there

I would like to see an independent benchmark.

This looks quite serious (which would be unsurprising given that Fei-Fei Li and Christopher Ré are involved).

I'm also quite interested in the nuts and bolts: does anyone know what the current accepted leaderboard on this is? I was screwing around with GritLM [1] a few months back and I seem to remember the MTEB [2] was kind of the headline thing at that time, but I might be out of date.

[1] https://arxiv.org/pdf/2402.09906 [2] https://huggingface.co/blog/mteb

I build a RAG system with voyage and it crushed openai embeddings, the difference in retrieval quality was noticeable

What evaluation metrics did you use?

None, I just tested it over and over, with 100 users.

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