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arXiv 1606.00511cs.LGcs.DCmath.OC
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深度神经网络的分布式无Hessian优化

Distributed Hessian-Free Optimization for Deep Neural Network

Lehigh University(理海大学);Intel Labs(英特尔实验室)

Xi He, Dheevatsa Mudigere, Mikhail Smelyanskiy, Martin Takáč

摘要:

训练深度神经网络是一个高维、高度非凸的优化问题。随机梯度下降(SGD)算法及其变体是当前最先进的解决方案。然而,由于问题的非凸性性质,观察到SGD在鞍点附近减慢。最近的实证研究表明,通过有效地检测和逃逸鞍点,更有可能提高训练性能。为此,我们重新审视了深度网络的无海森优化方法。我们还开发了它的分布式变体,并展示了SGD的卓越扩展潜力,它允许更有效地利用更大的计算资源,从而实现大型模型和更快的时间来获得所需的解决方案。此外,不同于截断牛顿法(Marten的HF),忽略负曲率信息,通过使用朴素的共轭梯度法和高斯-牛顿海森近似信息-我们提出了一种新的算法来探索负曲率方向,通过稳定的双共轭方法解决的子问题,涉及可能的不确定的随机海森信息。我们表明,这些技术加快了标准MNIST数据集和TIMIT语音识别问题的训练过程,表现出强大的性能,批量大小高达一个数量级。对于一个简单的4层网络,最多可在16个CPU节点上实现接近线性的加速,说明了这种增加的扩展潜力。

英文摘要:

Training deep neural network is a high dimensional and a highly non-convex optimization problem. Stochastic gradient descent (SGD) algorithm and it's variations are the current state-of-the-art solvers for this task. However, due to non-covexity nature of the problem, it was observed that SGD slows down near saddle point. Recent empirical work claim that by detecting and escaping saddle point efficiently, it's more likely to improve training performance. With this objective, we revisit Hessian-free optimization method for deep networks. We also develop its distributed variant and demonstrate superior scaling potential to SGD, which allows more efficiently utilizing larger computing resources thus enabling large models and faster time to obtain desired solution. Furthermore, unlike truncated Newton method (Marten's HF) that ignores negative curvature information by using naïve conjugate gradient method and Gauss-Newton Hessian approximation information - we propose a novel algorithm to explore negative curvature direction by solving the sub-problem with stabilized bi-conjugate method involving possible indefinite stochastic Hessian information. We show that these techniques accelerate the training process for both the standard MNIST dataset and also the TIMIT speech recognition problem, demonstrating robust performance with upto an order of magnitude larger batch sizes. This increased scaling potential is illustrated with near linear speed-up on upto 16 CPU nodes for a simple 4-layer network.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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