Transcription of !Neural!Networks!for!Machine!Learning! !Lecture!6a ...
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Neural Networks for Machine Learning Lecture 6a Overview of mini- batch gradient descent Geoffrey Hinton with Ni@sh Srivastava Kevin Swersky Reminder: The error surface for a linear neuron The error surface lies in a space with a horizontal axis for each weight and one ver@cal axis for the error. For a linear neuron with a squared error, it is a quadra@c bowl. Ver@cal cross- sec@ons are parabolas. Horizontal cross- sec@ons are ellipses. For mul@- layer, non- linear nets the error surface is much more complicated. But locally, a piece of a quadra@c bowl is usually a very good E w1 w2 Convergence speed of full batch learning when the error surface is a quadra@c bowl Going downhill reduces the error, but the direc@on of steepest descent does not point at the minimum unless the ellipse is a c
Stochas@c!gradientdescent • If!the!datasetis!highly!redundant,!the! gradienton!the!firsthalf!is!almost iden@cal!to!the!gradienton!the! second!half.!!
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