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ONNX convert all-MiniLM-L6-v2

Conversion of sentence-transformers/all-MiniLM-L6-v2

This is a sentence-transformers ONNX model: It maps sentences & paragraphs to a 384 dimensional dense vector space and can be used for tasks like clustering or semantic search. This custom model takes last_hidden_state and pooler_output whereas the sentence-transformers exported with default ONNX config only contains last_hidden_state as output.

Usage (HuggingFace Optimum)

Using this model becomes easy when you have optimum installed:

python -m pip install optimum

Then you can use the model like this:

from optimum.onnxruntime.modeling_ort import ORTModelForCustomTasks

model = ORTModelForCustomTasks.from_pretrained("optimum/sbert-all-MiniLM-L6-with-pooler")
tokenizer = AutoTokenizer.from_pretrained("optimum/sbert-all-MiniLM-L6-with-pooler")
inputs = tokenizer("I love burritos!", return_tensors="pt")
pred = model(**inputs)

You will also be able to leverage the pipeline API in transformers:

from transformers import pipeline

onnx_extractor = pipeline("feature-extraction", model=model, tokenizer=tokenizer)
text = "I love burritos!"
pred = onnx_extractor(text)

Evaluation Results

For an automated evaluation of this model, see the Sentence Embeddings Benchmark: https://seb.sbert.net


The project aims to train sentence embedding models on very large sentence level datasets using a self-supervised contrastive learning objective. We used the pretrained nreimers/MiniLM-L6-H384-uncased model and fine-tuned in on a 1B sentence pairs dataset. We use a contrastive learning objective: given a sentence from the pair, the model should predict which out of a set of randomly sampled other sentences, was actually paired with it in our dataset. We developped this model during the Community week using JAX/Flax for NLP & CV, organized by Hugging Face. We developped this model as part of the project: Train the Best Sentence Embedding Model Ever with 1B Training Pairs. We benefited from efficient hardware infrastructure to run the project: 7 TPUs v3-8, as well as intervention from Googles Flax, JAX, and Cloud team member about efficient deep learning frameworks.

Intended uses

Our model is intented to be used as a sentence and short paragraph encoder. Given an input text, it ouptuts a vector which captures the semantic information. The sentence vector may be used for information retrieval, clustering or sentence similarity tasks. By default, input text longer than 256 word pieces is truncated.

Training procedure


We use the pretrained nreimers/MiniLM-L6-H384-uncased model. Please refer to the model card for more detailed information about the pre-training procedure.


We fine-tune the model using a contrastive objective. Formally, we compute the cosine similarity from each possible sentence pairs from the batch. We then apply the cross entropy loss by comparing with true pairs.

Hyper parameters

We trained ou model on a TPU v3-8. We train the model during 100k steps using a batch size of 1024 (128 per TPU core). We use a learning rate warm up of 500. The sequence length was limited to 128 tokens. We used the AdamW optimizer with a 2e-5 learning rate. The full training script is accessible in this current repository: train_script.py.

Training data

We use the concatenation from multiple datasets to fine-tune our model. The total number of sentence pairs is above 1 billion sentences. We sampled each dataset given a weighted probability which configuration is detailed in the data_config.json file.

Dataset Paper Number of training tuples
Reddit comments (2015-2018) paper 726,484,430
S2ORC Citation pairs (Abstracts) paper 116,288,806
WikiAnswers Duplicate question pairs paper 77,427,422
PAQ (Question, Answer) pairs paper 64,371,441
S2ORC Citation pairs (Titles) paper 52,603,982
S2ORC (Title, Abstract) paper 41,769,185
Stack Exchange (Title, Body) pairs - 25,316,456
Stack Exchange (Title+Body, Answer) pairs - 21,396,559
Stack Exchange (Title, Answer) pairs - 21,396,559
MS MARCO triplets paper 9,144,553
GOOAQ: Open Question Answering with Diverse Answer Types paper 3,012,496
Yahoo Answers (Title, Answer) paper 1,198,260
Code Search - 1,151,414
COCO Image captions paper 828,395
SPECTER citation triplets paper 684,100
Yahoo Answers (Question, Answer) paper 681,164
Yahoo Answers (Title, Question) paper 659,896
SearchQA paper 582,261
Eli5 paper 325,475
Flickr 30k paper 317,695
Stack Exchange Duplicate questions (titles) 304,525
AllNLI (SNLI and MultiNLI paper SNLI, paper MultiNLI 277,230
Stack Exchange Duplicate questions (bodies) 250,519
Stack Exchange Duplicate questions (titles+bodies) 250,460
Sentence Compression paper 180,000
Wikihow paper 128,542
Altlex paper 112,696
Quora Question Triplets - 103,663
Simple Wikipedia paper 102,225
Natural Questions (NQ) paper 100,231
SQuAD2.0 paper 87,599
TriviaQA - 73,346
Total 1,170,060,424
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