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Improving Machine Classification with Contextual Information

A new method enhances image classification accuracy by focusing on context.

― 5 min read


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Table of Contents

In this article, we discuss a novel approach to improve how machines classify information, particularly images. Traditional systems often struggle when faced with new or altered data, leading to errors. Our method focuses on using Context to enhance accuracy and reliability in Classifications.

Background

Image classification involves teaching machines to recognize and label images based on their content. Commonly used methods have made significant strides, outperforming humans in some cases. However, these systems typically rely on fixed assumptions about the data, which can lead to failures when the data changes or is distorted.

The Problem with Traditional Classification

Most conventional classification systems predict a single outcome for each input. This means they look at each image in isolation without considering the surrounding information or context. This approach can work well in stable conditions but fails when data becomes corrupted or distorted. Studies have shown that systems using standard Activation Functions, like ReLU, perform poorly under stress, leading to what is known as "feature collapse.” This collapse inhibits the system's reliability.

Context and Classification

Drawing parallels from the field of Natural Language Processing (NLP), where the meaning of words changes based on context, we argue that classification systems should also consider the broader context around each sample. For instance, classifying an image of a dog should not only rely on the dog’s features but also on the environment or other surrounding details.

Introducing Quantile Activation

To address the limitations of existing methods, we propose a new activation function called Quantile Activation. Instead of outputting standard values, this method provides the relative position or quantile of a sample within its context. By doing this, each neuron in the system can adapt its output to better reflect the sample's contextual information. This shift allows for a more nuanced approach to classification.

Experimentation and Results

Our research involved extensive experimentation using various datasets known for their robustness against distortions. We utilized datasets like CIFAR10C and MNISTC to test our method. The results indicate that systems employing Quantile Activation outperform traditional classifiers across different architectures. Even when faced with severe distortions, our approach shows improved accuracy and consistency in predictions.

How Quantile Activation Works

Quantile Activation works by adjusting the outputs of each neuron based on the distribution of values observed in its context. This adaptation helps maintain the class structure within the data even when distortions occur. Essentially, if a neuron notices that the input distribution changes, it recalibrates its function to ensure that outputs remain reliable.

Comparison with Standard Methods

In tests, we compared our method against commonly used activation functions like ReLU and pReLU. We found that while traditional methods experience a drop in performance under distorted conditions, our approach maintains stability and accuracy.

Challenges and Solutions

A major challenge with incorporating context into classification is the computational expense. Traditional methods often require evaluating many samples to classify a single image, which can be slow and resource-intensive. We tackled this by focusing on the context of individual neurons, allowing for efficient processing without compromising accuracy.

Training and Inference

The process of training our system involves adjusting the weights of each neuron based on the context distribution. During inference, we have two approaches to consider: either tracking quantiles for single sample evaluation or ensuring that multiple samples from the same context are processed together. Our current practice favors the latter, as it provides improved classification based on surrounding context.

Calibration and Robustness

One of the highlights of our approach is its ability to maintain calibration across various scenarios. Calibration refers to how well the predicted probabilities match the actual outcomes. Greater calibration means that if a model predicts a class with 70% certainty, it should ideally be correct about 70% of the time. Our method shows promise in achieving consistent calibration even when data undergoes different levels of distortion.

Future Directions

While our findings support the effectiveness of Quantile Activation, there remains room for improvement. Future research could explore better ways to synchronize context distributions across multiple systems, especially as we move to train on larger datasets. Additionally, further investigations could reveal deeper connections between our approach and biological neuron behavior, potentially leading to more robust systems.

Broad Implications

The potential impact of our work extends beyond mere accuracy in classifications. By shifting the focus to context, we can better handle biases in datasets and allow for a more equitable representation of different classes. More reliable classification systems can enhance various applications, from self-driving cars to medical diagnostics.

Conclusion

In summary, our research provides a framework for improving classification systems by considering context and adapting neuron outputs accordingly. This method shows significant promise in increasing robustness and reliability in the face of distortions. As technology evolves, our approach could lead to more effective applications across many fields, paving the way for better, more intelligent systems that learn from their environment.

Original Source

Title: Quantile Activation: Correcting a Failure Mode of ML Models

Abstract: An established failure mode for machine learning models occurs when the same features are equally likely to belong to class 0 and class 1. In such cases, existing ML models cannot correctly classify the sample. However, a solvable case emerges when the probabilities of class 0 and 1 vary with the context distribution. To the best of our knowledge, standard neural network architectures like MLPs or CNNs are not equipped to handle this. In this article, we propose a simple activation function, quantile activation (QACT), that addresses this problem without significantly increasing computational costs. The core idea is to adapt the outputs of each neuron to its context distribution. The proposed quantile activation, QACT, produces the relative quantile of the sample in its context distribution, rather than the actual values, as in traditional networks. A practical example where the same sample can have different labels arises in cases of inherent distribution shift. We validate the proposed activation function under such shifts, using datasets designed to test robustness against distortions : CIFAR10C, CIFAR100C, MNISTC, TinyImagenetC. Our results demonstrate significantly better generalization across distortions compared to conventional classifiers, across various architectures. Although this paper presents a proof of concept, we find that this approach unexpectedly outperforms DINOv2 (small) under large distortions, despite DINOv2 being trained with a much larger network and dataset.

Authors: Aditya Challa, Sravan Danda, Laurent Najman, Snehanshu Saha

Last Update: 2024-12-24 00:00:00

Language: English

Source URL: https://arxiv.org/abs/2405.11573

Source PDF: https://arxiv.org/pdf/2405.11573

Licence: https://creativecommons.org/licenses/by-nc-sa/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to arxiv for use of its open access interoperability.

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