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Exploring the Connectivity and Geometry of Neural Network Landscapes: Star-Shaped Paths and Geodesic Distances


Konsep Inti
Neural network landscapes exhibit surprising connectivity and geometric properties, including star-shaped connectivity between global minima and near-convex geodesic distances, even for highly non-convex models.
Abstrak

The paper conducts a fine-grained analysis of the mode connectivity phenomenon in neural network landscapes. The key findings are:

  1. Overparameterized neural networks, including two-layer ReLU networks and linear networks, exhibit a strong form of connectivity called "star-shaped connectivity". This means there exists a "center" minimum that is linearly connected to a finite set of typical global minima.

  2. The geodesic distance between global minima, normalized by their Euclidean distance, monotonically decreases towards 1 as the network width increases. This suggests the landscape becomes increasingly convex-like as the network becomes more overparameterized.

  3. These theoretical results are supported by extensive experiments on MNIST and CIFAR-10 datasets, validating the star-shaped connectivity and near-convex geodesic distances for practical neural network models.

The findings provide new insights into the underlying geometry and topology of neural network loss landscapes, which have important implications for understanding optimization and generalization in deep learning.

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by Zhanran Lin,... pada arxiv.org 04-10-2024

https://arxiv.org/pdf/2404.06391.pdf
Exploring Neural Network Landscapes

Pertanyaan yang Lebih Dalam

What are the potential implications of the star-shaped connectivity and near-convex geodesic distances for the optimization and generalization of neural networks

The star-shaped connectivity and near-convex geodesic distances in neural network landscapes have significant implications for optimization and generalization. Optimization: The star-shaped connectivity suggests that there exist paths connecting multiple minima simultaneously, potentially aiding optimization algorithms in navigating the landscape efficiently. This connectivity can help algorithms escape poor local minima and converge to better solutions. Near-convex geodesic distances imply that the landscape is not highly non-convex, making optimization easier. Algorithms like stochastic gradient descent (SGD) may find smoother paths to global minima, leading to faster convergence and better optimization performance. Generalization: The presence of star-shaped connectivity can contribute to better generalization by ensuring that different minima are connected, allowing the model to explore a wider range of solutions during training. Near-convex geodesic distances suggest that the landscape is structured in a way that promotes better generalization. Models trained on such landscapes may exhibit improved performance on unseen data due to the smoother and more connected nature of the optimization paths.

How do these landscape properties relate to the inductive biases and learning dynamics of different neural network architectures and training algorithms

The landscape properties of star-shaped connectivity and near-convex geodesic distances are closely related to the inductive biases and learning dynamics of neural network architectures and training algorithms. Inductive Biases: The star-shaped connectivity may reflect the inductive bias of neural networks to prefer solutions that are connected in the parameter space. This bias can influence the types of solutions the network learns and how it generalizes to unseen data. Near-convex geodesic distances can shape the learning dynamics by providing smoother paths for optimization algorithms. This can affect how quickly the model converges and the quality of the solutions it reaches. Learning Dynamics: Different neural network architectures may exhibit varying degrees of star-shaped connectivity and near-convex geodesic distances, impacting how they learn and generalize. Training algorithms like SGD may benefit from these landscape properties by efficiently exploring the parameter space and finding better solutions.

Are there other non-local geometric structures in neural network landscapes that could be uncovered through similar fine-grained analyses

While star-shaped connectivity and near-convex geodesic distances are important non-local geometric structures in neural network landscapes, there may be other properties that could be uncovered through similar fine-grained analyses. Some potential areas for exploration include: Curvature Analysis: Investigating the curvature of the landscape at different points, such as minima, saddle points, and plateaus, to understand how it influences optimization and generalization. Symmetry and Invariance: Exploring how symmetries and invariances in the data and model architecture manifest in the landscape geometry, affecting the connectivity of solutions. High-Dimensional Structures: Studying the high-dimensional structures of the landscape, such as the presence of valleys, ridges, and basins, to uncover how they impact optimization dynamics. By conducting detailed analyses of these and other geometric properties, researchers can gain deeper insights into the behavior of neural networks during training and inference.
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