Transfer Learning in Deep Learning: A comprehensive Guide

January 8, 2024 by
Transfer Learning in Deep Learning: A comprehensive Guide
DxTalks, Ibrahim Kazeem

Transfer learning is a powerful technique in deep learning where a model trained on one task is reused as the starting point for a model on a second task. This technique allows us to take advantage of knowledge already learned instead of training a model from scratch.

In this blog post, we will provide a beginner-friendly explanation of transfer learning in deep learning.

  •  What makes transfer learning so useful?
  •   How do we actually implement it?

We will cover the intuition behind it, walk through concrete examples, and explain the practical steps to apply transfer learning to your own deep learning projects.

By the end, you will understand this essential technique to make your models more accurate and your training more efficient.

What is Transfer Learning in Deep learning?

Transfer learning is a way to take a deep learning model that has already been trained on a large dataset and reuse parts of it for another related task. For example, you might have a model trained to recognize animals like cats and dogs.

Instead of starting from scratch to create a new model to recognize other animals like horses and cows, you could start with the animal recognition model and retrain just the parts you need to recognize the new animals.

This works because deep learning models learn hierarchies of patterns and features. The early layers learn very general patterns like edges and textures. The later layers learn more specialized, high-level patterns related to the specifics of the original training data.

By reusing the early and middle layers that contain more general features, we can dramatically speed up training for similar tasks. Fine-tuning the later layers with new data helps the model adapt to recognize new types of objects without forgetting everything it previously learned.

Transfer learning enables deep learning with much less data than training new models from scratch.

Importance of Transfer Learning in Deep Learning

Transfer learning provides three main benefits that make deep learning more practical:

1.              Saves data requirements

Deep learning models have millions or billions of parameters that must be tuned based on large datasets. Transfer learning allows you to reuse parts of a model already tuned on big data rather than tuning a whole new model from scratch. For example, by reusing a model tuned on ImageNet's millions of images, you may only need thousands of images to fine-tune it for a new task instead of millions. This enables deep learning with less data.

2.            Saves compute resources

Training deep learning models is very computationally intensive, often requiring specialized GPUs. You can save significant computing resources by freezing the initial layers of a pre-trained model and only retraining the later layers. Rather than weeks of expensive model training, fine-tuning a pre-trained model may only take hours or days. This makes deep learning more accessible.

3.            Enables real-world applications

Deep learning breakthroughs often come from models trained on massive academic datasets like ImageNet or BERT. Transfer learning allows practitioners to adapt these advanced models to detect specific objects/patterns critical for real applications versus just general interest categories. For instance, reef scientists can take a model trained on 1000 everyday object categories and adapt it to identify 25 specific coral species on a local reef. This practical tuning is only possible thanks to transfer learning.

4.           Domain Adaptation:

In scenarios where the source and target domains differ slightly, transfer learning helps in adapting the model to the target domain. For instance, a model trained on one type of image dataset can be fine-tuned to perform well on a similar but distinct image dataset, mitigating the challenges posed by domain shifts.

5.            Resource Efficiency:

Training deep neural networks demands significant computational resources. Transfer learning reduces the computational burden by reusing pre-trained models, making it more feasible for researchers and developers with limited resources to experiment and innovate.

6. Improved Generalization:

By leveraging knowledge from diverse tasks, transfer learning enhances the model's ability to generalize to new, unseen data. This generalization is crucial for real-world applications where the model needs to perform well on various inputs.

7. Task-Specific Customization:

Transfer learning enables model customization for specific tasks. The pre-trained model provides a foundation, and the subsequent training on task-specific data tailors the model to the nuances of the particular problem at hand.

Step-by-step Process of Transferring Deep Learning

Transfer learning is a powerful technique in deep learning that allows a pre-trained model to be adapted for a new task, saving time and resources. Here's a step-by-step breakdown of the process in simple terms:

1. Choose a Pre-trained Model:

In deep learning, selecting a pre-trained model is akin to picking a knowledgeable guide for your journey. Models like VGG16, ResNet, or Inception are akin to seasoned explorers, having traversed vast datasets to grasp intricate details. These models serve as a foundation, possessing a wealth of insights beneficial for various tasks.

2. Understanding Layers:

Within a neural network's architecture lie layers, each akin to a skilled artisan extracting unique features from the data canvas. Transfer learning involves preserving the early layers' wisdom, focusing on general features like edges and textures. Meanwhile, the later layers, responsible for more specialized features, are adjusted or replaced to suit the nuances of your new task.

3. Freeze Pre-trained Layers:

Imagine freezing a snapshot of the pre-trained model's early layers, preserving their acquired knowledge. By doing so, these layers remain steadfast during the upcoming training on a new dataset, ensuring their wisdom is not altered. This strategic move maintains the integrity of the foundational features.

4. Customize Upper Layers:

The customization phase is akin to tailoring a suit – specific modifications for a perfect fit. Introduce new layers or tweak existing ones atop the frozen layers to align the model with your task. These upper layers are the apprentices, learning from the frozen layers while adapting to the intricacies of your specific objective.

5. Data Preparation:

Before the model begins its training, ensure your new dataset is akin to a well-organized library. Labels, akin to well-defined sections, aid the model in comprehending the diverse contents. Split the dataset into training and validation sets, providing the model with a well-rounded curriculum to learn from.

6. Training the Model:

The training phase unfolds like an educational journey, with the model fine-tuning its understanding of the new dataset. While the early layers stand as pillars of knowledge, the upper layers, like eager students, absorb the nuances specific to your task. This harmonious collaboration refines the model's capabilities for the challenges ahead.

7. Optimizing Hyperparameters:

Think of hyperparameters as the conductors orchestrating the model's learning symphony. Experiment with different settings – adjusting learning rates, batch sizes, and epochs – to fine-tune the model's performance. This meticulous tuning ensures the model's responsiveness to the unique patterns within your dataset.

8. Evaluate and Validate:

With training complete, it's time to evaluate the model's capabilities on the validation set – a litmus test for its adaptability. This step mirrors a performance review, gauging how effectively the model applies its acquired knowledge to new, unseen scenarios. Iterations may be necessary to refine its aptitude further.

9. Inference on New Data:

As the model graduates from its training, it stands ready to embark on the task it was honed for. Deploy the model for making predictions on fresh, uncharted data. This deployment is akin to unleashing a well-prepared expert to tackle the challenges specific to your designated domain.

10. Monitor and Update:

The journey doesn't conclude with deployment; it evolves into a continuous expedition. Monitor the model's performance over time, like a seasoned captain navigating changing tides. Adapt the model as needed, incorporating new insights or tweaking its understanding to ensure it remains effective in an ever-shifting landscape.

Challenges of Transfer learning in deep learning

Transfer learning in deep learning faces the challenge of striking the right balance between old and new knowledge. Imagine teaching a robot to cook based on its past experience with fixing cars.

While it brings some valuable skills, adapting them to the kitchen requires thoughtful adjustments. Similarly, pre-trained models come with knowledge from one task, but seamlessly applying it to a different job demands careful tuning.

The risk lies in either clinging too much to old habits, hindering adaptability, or deviating too much, losing the essence of learned expertise. It's like teaching a dog new tricks without erasing its prior training – finding the sweet spot to efficiently transfer past wisdom while tailoring it to the specific demands of a fresh challenge.

Conclusion – Transfer learning in Deep Learning

Transfer learning in deep learning is akin to empowering a learner with wisdom from a seasoned mentor. It's a potent strategy where pre-trained models, akin to experienced guides, share their insights to expedite learning for new tasks.

By retaining foundational knowledge in frozen layers and customizing upper layers for specific challenges, transfer learning streamlines the model's adaptation. This approach saves time and enhances the model's proficiency in diverse tasks.

Like a skilled apprentice building upon a master's teachings, the model evolves to tackle new challenges effectively. Transfer learning is a transformative tool, enabling efficient knowledge transfer and empowering models to navigate the dynamic landscapes of various tasks with agility and expertise. 

FAQs on Transfer learning in Deep learning

1.              What is Transfer learning in deep learning?

Transfer learning is a technique where a pre-trained model's knowledge on one task is applied to a different but related task. It expedites model training for new tasks by leveraging learned features, saving time and resources.

2.            How does transfer learning work?

In transfer learning, early layers of a pre-trained model capture general features, while later layers are adjusted for specific tasks. The frozen layers retain knowledge, and the upper layers adapt to the nuances of the new task during fine-tuning.

3.            Why is transfer learning important?

Transfer learning is crucial as it allows models to benefit from previously acquired knowledge. Reusing pre-trained models accelerates the learning process for new tasks, especially when limited data is available, making it a powerful tool in deep learning applications.

4.           What are the benefits of transfer learning?

Transfer learning offers time efficiency, resource savings, and improved model performance. It excels in scenarios with limited labeled data, enabling models to generalize better to new tasks. This approach has widespread applications, making it a go-to strategy in the dynamic field of deep learning.