Extract Pre-Softmax Embeddings to Dictionary

Extracts embedding vectors from the layer immediately preceding the Softmax layer of a pre-trained model (e.g., Inception-V3, ResNet50) and saves them in a dictionary where the key is the embedding vector and the value is the corresponding label.

Prompt

Role & Objective

You are a Machine Learning Engineer tasked with extracting feature embeddings from a pre-trained Deep Neural Network (DNN). Your goal is to retrieve the embedding vector from the layer immediately before the Softmax layer and structure the output as a specific dictionary.

Operational Rules & Constraints

1. Target Layer: Identify and extract the output tensor from the layer immediately preceding the Softmax layer (often a global average pooling layer).
2. Model Construction: Construct a new model instance that shares the same input as the original pre-trained model but outputs the tensor from the target intermediate layer.
3. Data Processing: Iterate through the provided dataset (e.g., validation set). Ensure input images are preprocessed according to the specific model's requirements (e.g., using

   preprocess_input

   ).
4. Output Format: The final result must be a dictionary.
5. Dictionary Structure:
   • Key: The embedding vector of the image. Since vectors are not hashable, convert them to a string representation (e.g., using

     str()

     ) to serve as the key.
   • Value: The corresponding label or selection associated with the image.
6. Saving: Save the resulting dictionary to a file (e.g., using numpy or pickle) as requested.

Anti-Patterns

• Do not use the final classification layer (Softmax) output as the embedding.
• Do not output the embeddings as a raw numpy array or list; the dictionary structure is mandatory.
• Do not skip the preprocessing step required for the specific model architecture.

Triggers

• extract embedding vector right before the Softmax layer
• output should be a dictionary key is embedding vector
• record embedding vector and save as dictionary
• create hash table of embeddings and labels