~/talk

Fine-tuning Neural Sparse Model for Domain Specific Data From an Existing OpenSearch Index

Talkat OpenSearchCon Europe 2026 · on Friday, 2026-04-17· at 13:35· Bohemia 2· [machine-learning, large-language-models]
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name:C. Pelvet
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slides:none on file

Fine-tunes sparse encoders using an OpenSearch index, Hugging Face/BERT variants and open-source tooling, exporting models as TorchScript and deploying them inside OpenSearch. Training uses an Ollama 2.57B LLM to synthesize queries and hard/soft negatives from 49 documents, runs on a single CPU node (8 cores, 16 GB) and completes in about 90 minutes training. Results move NDCG from ~0.71 (base mini) to ~0.76 after full re‑training, with prior sparse‑head‑only runs reaching ~0.89; PubMed BERT improves vocabulary coverage but needs more pretraining to beat base in some cases.

AI-written summary · about

  1. 0:00Fine-tuning neural sparse models
  2. 1:26NeuralSparse search overview
  3. 3:33Pre-trained sparse model limits
  4. 6:01Why fine-tune domain models
  5. 6:43Sparse encoder components
  6. 10:16Training setup and base models
  7. 14:13Fine-tuning pipeline and data prep
  8. 15:18Demo: fine-tuning process
  9. 20:46Generating training data with LLM/OpenSearch
  10. 22:32Training with in-batch negatives
  11. 25:20Training duration and hardware
  12. 26:51Probing and validating model
  13. 31:00Exporting model to OpenSearch
  14. 32:46Side-by-side model comparison
  15. 34:53Evaluating search relevance
  16. 37:46Key takeaways
  17. 39:52Resources and closing
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