Adding a Dense Layer on top of SentenceTransformer

What will you learn?

In this tutorial, you will learn how to enhance the functionality of the powerful SentenceTransformer library by adding a custom dense layer on top of it. This customization allows for fine-tuning the model for specific tasks or extracting embeddings tailored to your needs in Python.

Introduction to the Problem and Solution

When working with the advanced SentenceTransformer library, there are instances where additional layers, such as a dense layer, need to be added on top of the existing model. By incorporating these additional layers, users can fine-tune the model for specific tasks or extract embeddings that align with their unique requirements. In this guide, we will explore how to seamlessly integrate a dense layer after the SentenceTransformer model.


from sentence_transformers import SentenceTransformer
import torch.nn as nn

# Load pre-trained SentenceTransformer model
model = SentenceTransformer('paraphrase-MiniLM-L6-v2')

# Define our custom dense layer on top of the loaded model 
class CustomSentenceModel(nn.Module):
    def __init__(self):
        super(CustomSentenceModel, self).__init__()
        self.sentence_embedder = model
        self.dense_layer = nn.Linear(in_features=768, out_features=256)

    def forward(self, input_ids):
        embeddings = self.sentence_embedder(input_ids)
        output = self.dense_layer(embeddings)
        return output

# Initialize our custom sentence model
custom_model = CustomSentenceModel()

# Copyright PHD

Note: Ensure you have installed sentence_transformers library using pip install sentence-transformers.


  • Loading Pre-trained Model: We start by loading a pre-trained SentenceTransformer model.
  • Custom Dense Layer Class: We define a custom neural network class that includes both the loaded transformer and an additional dense layer.
  • Forward Method: The forward() method processes inputs through both components sequentially.
  • Initialization: Finally, we instantiate our new custom sentence embedding model.
    1. How can I install the necessary libraries for this task?

      • You can use pip to install required libraries: pip install sentence-transformers.
    2. Can I use different pre-trained models from SentenceTransformers?

      • Yes, you can choose from various pre-trained models provided by SentenceTransformers based on your requirements.
    3. Do I need GPU for this operation?

      • While not mandatory, having access to GPU can significantly speed up training and inference processes in deep learning tasks.
    4. Is it possible to fine-tune this custom architecture further?

      • Absolutely! You can adapt hyperparameters or even train additional layers based on your specific use case.
    5. What if I want to save my custom trained models?

      • You can save PyTorch models using, PATH) for future use or deployment.

By adding a dense layer on top of SentenceTransformers, users can extend its functionality according to their unique requirements. This customization enables fine-tuning for specific tasks and extraction of tailored embeddings in NLP projects using Python. Leveraging these steps and exploring customization options offered by PyTorch empowers users to effectively utilize state-of-the-art transformer capabilities while ensuring scalability and performance optimization.

Leave a Comment