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FractalNet: Ultra-Deep Neural Networks Without Residuals (arxiv.org)
2 points by gwern on Jul 5, 2016 | hide | past | pdf | discuss on HN

In plain words: Repeating an expansion rule builds a network with a fractal layout of paths of different lengths, where every signal is filtered, never passed through unchanged. It matched shortcut-based networks on image classification, showing shortcuts aren't essential, and can give quick rough or slower accurate answers.

Abstract · FractalNet: Ultra-Deep Neural Networks without Residuals

We introduce a design strategy for neural network macro-architecture based on self-similarity. Repeated application of a simple expansion rule generates deep networks whose structural layouts are precisely truncated fractals. These networks contain interacting subpaths of different lengths, but do not include any pass-through or residual connections; every internal signal is transformed by a filter and nonlinearity before being seen by subsequent layers. In experiments, fractal networks match the excellent performance of standard residual networks on both CIFAR and ImageNet classification tasks, thereby demonstrating that residual representations may not be fundamental to the success of extremely deep convolutional neural networks. Rather, the key may be the ability to transition, during training, from effectively shallow to deep. We note similarities with student-teacher behavior and develop drop-path, a natural extension of dropout, to regularize co-adaptation of subpaths in fractal architectures. Such regularization allows extraction of high-performance fixed-depth subnetworks. Additionally, fractal networks exhibit an anytime property: shallow subnetworks provide a quick answer, while deeper subnetworks, with higher latency, provide a more accurate answer.

Gustav Larsson, Michael Maire, Gregory Shakhnarovich
arXiv:1605.07648 · cs.CV · submitted May 24, 2016 · updated May 26, 2017
abstract · pdf · html · updated with ImageNet results; published as a conference paper at ICLR 2017; project page at http://people.cs.uchicago.edu/~larsson/fractalnet/

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