Model reference · open weights

stella_en

stella_en is an open-weight embedding model from NovaSearch, listed in the AxForge catalogue. AxForge can bring it up on EU-owned hardware for you on request — with the licence handled where one is required.

Embeddings NovaSearch 2 variants 77k downloads/mo
Request this model on EU hardware All served models Not on the shared API today — deployed on request.

About

What stella_en is

Updates We released a Jasper and Stella model technology report and code.(2025.1) Report: https://arxiv.org/abs/2412.19048 Codes: https://github.com/NovaSearch-Team/RAG-Retrieval Introduction The models are trained based on Alibaba-NLP/gte-large-en-v1.5 and Alibaba-NLP/gte-Qwen2-1.5B-instruct. Thanks for their contributions! We simplify usage of prompts, providing two prompts for most general tasks, one is for s2p, another one is for s2s. Prompt of s2p task(e.g. retrieve task): Prompt of s2s task(e.g. semantic textual similarity task): The models are finally trained by MRL, so they have multiple dimensions: 512, 768, 1024, 2048, 4096, 6144 and 8192. The higher the dimension, the better the performance. Generally speaking, 1024d is good enough. The MTEB score of 1024d is only 0.001 lower than 8192d. Model directory structure The model directory structure is very simple, it is a standard SentenceTransformer directory with a series of 2Dense{dims} folders, where dims represents the final vector dimension. For example, the 2Dense256 folder stores Linear weights that convert vector dimensions to 256 dimensions. Please refer to the following chapters for specific instructions on how to use them. Usage You can use SentenceTransformers or transformers library to encode text. Sentence Transformers Transformers infinityemb Usage via infinity, MIT Licensed. Citation FAQ Q: The details of training? A: The training method and datasets will be released in the future. (specific time unknown, may be provided in a paper) Q: How to choose a suitable prompt for my own task? A: In most cases, please use the s2p and s2s prompts. These two prompts account for the vast majority of the training data. Q: How to reproduce MTEB results? A: Please use evaluation scripts in Alibaba-NLP/gte-Qwen2-1.5B-instruct or intfloat/e5-mistral-7b-instruct Q: Why each dimension has a linear weight? A: MRL has multiple training methods, we choose this method which has the best performance. Q: What is the sequence length of models? A: 512 is recommended, in our experiments, almost all models perform poorly on specialized long text retrieval datasets. Besides, the model is trained on datasets of 512 length

Summarised from the published model card. Read the full card on the HuggingFace links below.

Specifications

What it is

MakerNovaSearch
TypeEmbedding models
Parameters (lead)435M
Context8k tokens
Variants2
Runs withsentence-transformers
Released2024-07-12
Popularity77k downloads / month
Likes265
LicenceOpen weights

How it works

How embedding models work

Your textsentence / documentEncodermaps meaningVectorlist of numbersAn embedding model turns text into a vector, so similar meanings sit close together — the basis of search and RAG.

Variants

Sizes & precisions

Open weights ship in several sizes and precisions. One page, all the variants — pick the one that fits your GPU. VRAM figures are estimates from model size.

VariantParamsPrecisionVRAMFits 16 GBWeights
stella_en_400M_v5435MBF16~1 GBWeights ↗
stella_en_1.5B_v51.5BBF16~3.5 GBWeights ↗

Benchmarks

Reported results

As published on the model card — the maker's own numbers, not measured by AxForge.

TaskDatasetMetricScore
ClassificationMTEB AmazonCounterfactualClassification (en)accuracy92.358
ClassificationMTEB AmazonCounterfactualClassification (en)ap70.813
ClassificationMTEB AmazonCounterfactualClassification (en)ap_weighted70.813
ClassificationMTEB AmazonCounterfactualClassification (en)f188.951
ClassificationMTEB AmazonCounterfactualClassification (en)f1_weighted92.686
ClassificationMTEB AmazonCounterfactualClassification (en)main_score92.358
ClassificationMTEB AmazonPolarityClassificationaccuracy97.195
ClassificationMTEB AmazonPolarityClassificationap96.082
ClassificationMTEB AmazonPolarityClassificationap_weighted96.082
ClassificationMTEB AmazonPolarityClassificationf197.194
ClassificationMTEB AmazonPolarityClassificationf1_weighted97.194
ClassificationMTEB AmazonPolarityClassificationmain_score97.195
ClassificationMTEB AmazonReviewsClassification (en)accuracy59.528
ClassificationMTEB AmazonReviewsClassification (en)f159.21
ClassificationMTEB AmazonReviewsClassification (en)f1_weighted59.21
ClassificationMTEB AmazonReviewsClassification (en)main_score59.528
RetrievalMTEB ArguAnamain_score64.24
RetrievalMTEB ArguAnamap_at_140.398
RetrievalMTEB ArguAnamap_at_1056.215
RetrievalMTEB ArguAnamap_at_10056.834
RetrievalMTEB ArguAnamap_at_100056.835
RetrievalMTEB ArguAnamap_at_2056.747
RetrievalMTEB ArguAnamap_at_352.181
RetrievalMTEB ArguAnamap_at_554.628

Using it via the API

Call it like any OpenAI endpoint

Once AxForge deploys stella-en for you, it answers on the OpenAI-compatible API — the same base URL and keys as every other model. (stella-en below is illustrative; you get the exact model name on deployment.)

$ curl -sS https://api.axforge.ai/v1/embeddings \
  -H "Authorization: Bearer $AXFORGE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"stella-en","input":"text to embed"}'

Details

Languages, data & research

Tags

sentence-transformers pytorch safetensors new feature-extraction mteb transformers sentence-similarity custom_code model-index text-embeddings-inference endpoints_compatible onnx qwen2

Papers

Licence

Open weights

Open weights under mit — commercial use is permitted. Deploy it on AxForge EU hardware on request. Read the licence ↗

Sources

Weights & code

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