Tradeoff: Global vs. Local Robustness?  

Nov 6, 2023

Striking the Balance in AI Training

Several factors contribute to the robustness of AI models during the training phase. These include the quality and diversity of the training data, the choice of architecture and hyperparameters, the regularization techniques used, and the optimization algorithms employed. The careful design of these elements can significantly impact the model’s ability to handle uncertainties and generalizability to new data.  

Global vs. Local Robustness explained 

In the pursuit of robustness, two essential concepts emerge: global robustness and local robustness. Understanding the distinction between these two aspects can help us design AI models that strike the right balance between generalization and adaptability. 

Global Robustness in AI Systems: aiming for Reliability

Global robustness refers to an AI model’s ability to maintain its performance across a broad range of inputs, even when those inputs deviate significantly from the training data. A globally robust model can handle various perturbations and distribution shifts without compromising its reliability. In essence, global robustness focuses on the model’s ability to generalize well to unseen data and diverse conditions. 

Characteristics of globally robust models include: 

Generalization to Unseen Data: Globally robust models demonstrate strong generalization capabilities, making them reliable when exposed to new, previously unseen data. 

Stable Performance: These models exhibit consistent performance under various environmental conditions and input variations, making them more dependable in real-world applications. 

Fewer Adversarial Vulnerabilities: Globally robust models are less susceptible to adversarial attacks, making them more secure against attempts to deceive or manipulate the AI system. 

Global robustness allows AI models to perform well in different environments, making them applicable across diverse use cases. However, pursuing global robustness may lead to a performance trade-off, where the model’s accuracy on specific tasks may not be as high as specialized models. 

Achieving global robustness requires more complex architectures and training procedures, leading to higher computational costs, since all parameters and all their variations need to be taken into account. This in turn means that you need infinite training data to realize global robustness. 

Higher accuracy: Local Robustness in AI Systems 

Local robustness, on the other hand, emphasizes an AI model’s ability to perform well in a specific region of the input space. Instead of focusing on broad generalization, locally robust models are optimized to excel within a limited range of inputs, potentially allowing for higher accuracy on those specific inputs. 

Characteristics of locally robust models include: 

High Performance in Targeted Areas: Locally robust models may outperform globally robust models in specific regions of the input space relevant to the task at hand. 

Potential for Specialization: These models can be fine-tuned to excel in specific niche applications, making them valuable in domain-specific scenarios. 

Local robustness allows for higher accuracy on specific tasks, making them ideal for targeted applications. Focusing on local robustness can result in simpler models and faster training times, since you need fewer samples to train the model at hand.

In the next article, let us examine what this means in practical terms for neural network training and how the two approaches can match. 

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