CrossGemma Cross-Encoder: Semantic Similarity (STS)

Cross encoders are high performing encoder models that compare two texts and output a 0-1 score. I've found the cross-encoders/roberta-large-stsb model to be very useful in creating evaluators for LLM outputs. They're simple to use, fast and very accurate.

I trained this one using google's gemma encoder model google/embeddinggemma-300m.

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Features

• High performing: Achieves Pearson: 0.9175 and Spearman: 0.9135 on the STS-Benchmark test set.
• Efficient architecture: Based on the Gemma-encoder design (300M parameters), offering very fast inference speeds.
• Extended context length: Processes sequences up to 2048 tokens, good for LLM output evals.
• Diversified training: Pretrained on dleemiller/wiki-sim and fine-tuned on sentence-transformers/stsb.

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Performance

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Usage

To use EttinX for semantic similarity tasks, you can load the model with the Hugging Face sentence-transformers library:

from sentence_transformers import CrossEncoder

# Load CrossEncoder model
model = CrossEncoder("dleemiller/CrossGemma-sts-300m")

# Predict similarity scores for sentence pairs
sentence_pairs = [
    ("It's a wonderful day outside.", "It's so sunny today!"),
    ("It's a wonderful day outside.", "He drove to work earlier."),
]
scores = model.predict(sentence_pairs)

print(scores)  # Outputs: array([0.9184, 0.0123], dtype=float32)

Output

The model returns similarity scores in the range [0, 1], where higher scores indicate stronger semantic similarity.

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Training Details

Pretraining

The model was pretrained on the pair-score-sampled subset of the dleemiller/wiki-sim dataset. This dataset provides diverse sentence pairs with semantic similarity scores, helping the model build a robust understanding of relationships between sentences.

• Classifier Dropout: a somewhat large classifier dropout of 0.3, to reduce overreliance on teacher scores.
• Objective: STS-B scores from dleemiller/ModernCE-large-sts.

Fine-Tuning

Fine-tuning was performed on the sentence-transformers/stsb dataset.

Validation Results

The model achieved the following test set performance after fine-tuning:

• Pearson Correlation: 0.9175
• Spearman Correlation: 0.9135

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Model Card

• Architecture: embeddinggemma-300m
• Tokenizer: Custom tokenizer trained with modern techniques for long-context handling.
• Pretraining Data: dleemiller/wiki-sim (pair-score-sampled)
• Fine-Tuning Data: sentence-transformers/stsb

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Thank You

Thanks to the Google Deep Mind team for providing the encodergemma model, and the Sentence Transformers team for their leadership in transformer encoder models.

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License

This model is licensed under the Apache 2.0.