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Bridging the gap between keyword and semantic search with SPLADE (2024)

Bridging the gap between keyword and semantic search with SPLADE (2024)

2 comments

·May 5, 2025
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jbellis

I'm kind of disappointed in this article, Splade is a cool way to improve results of a TF/IDF index with minimally invasive changes and this obscures that more than it clarifies.

> Next, my SPLADE implementation in Elasticsearch is oversimplified. If you scroll back up to get_splade_embedding, we extract non-zero elements from vec_np (the SPLADE tokens) but discard their associated weights. This is a missed opportunity. The SPLADE papers use these weights for scoring matches.

Yes, exactly, that is the whole point of Splade.

Probably easier to demonstrate if you drop down a level to Lucene, I don't think you will be able to do it easily with Elastic.

Tangentially, I haven't looked closely at SPLATE which tries to marry Splade and ColBERT, but it's an interesting idea. https://arxiv.org/html/2404.13950v1

JnBrymn

You're absolutely right. This was a post I tossed together quickly just to see what could be done without thinking too much. In retrospect, I think this would be better implemented using Elasticsearch sparse vector fields which allow you to specify the value of every token. Maybe I'l make an update post to try again.