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Main Authors: Wang, Daniel, Markou, Evan, Campbell, Dylan
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2511.03110
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author Wang, Daniel
Markou, Evan
Campbell, Dylan
author_facet Wang, Daniel
Markou, Evan
Campbell, Dylan
contents While backpropagation--reverse-mode automatic differentiation--has been extraordinarily successful in deep learning, it requires two passes (forward and backward) through the neural network and the storage of intermediate activations. Existing gradient estimation methods that instead use forward-mode automatic differentiation struggle to scale beyond small networks due to the high variance of the estimates. Efforts to mitigate this have so far introduced significant bias to the estimates, reducing their utility. We introduce a gradient estimation approach that reduces both bias and variance by manipulating upstream Jacobian matrices when computing guess directions. It shows promising results and has the potential to scale to larger networks, indeed performing better as the network width is increased. Our understanding of this method is facilitated by analyses of bias and variance, and their connection to the low-dimensional structure of neural network gradients.
format Preprint
id arxiv_https___arxiv_org_abs_2511_03110
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Towards Scalable Backpropagation-Free Gradient Estimation
Wang, Daniel
Markou, Evan
Campbell, Dylan
Machine Learning
While backpropagation--reverse-mode automatic differentiation--has been extraordinarily successful in deep learning, it requires two passes (forward and backward) through the neural network and the storage of intermediate activations. Existing gradient estimation methods that instead use forward-mode automatic differentiation struggle to scale beyond small networks due to the high variance of the estimates. Efforts to mitigate this have so far introduced significant bias to the estimates, reducing their utility. We introduce a gradient estimation approach that reduces both bias and variance by manipulating upstream Jacobian matrices when computing guess directions. It shows promising results and has the potential to scale to larger networks, indeed performing better as the network width is increased. Our understanding of this method is facilitated by analyses of bias and variance, and their connection to the low-dimensional structure of neural network gradients.
title Towards Scalable Backpropagation-Free Gradient Estimation
topic Machine Learning
url https://arxiv.org/abs/2511.03110