So, it needs to press the left and right buttons correctly to find the lowest spot In our case, the ball is optimizing it's position (from left to right) to find the lowest point in the bucket. Imagine further that the red ball is trying to find the bottom of the bucket. Imagine that you had a red ball inside of a rounded bucket like in the picture below. By learning about Gradient Descent, we will then be able to improve our toy neural network through parameterization and tuning, and ultimately make it a lot more powerful. In this tutorial, we will walk through Gradient Descent, which is arguably the simplest and most widely used neural network optimization algorithm. Many of these optimizations are good for different purposes, and in some cases several can be used together. We actually have a plethora of different nonlinear optimization methods that we could use with backpropagation: The takeaway here is that backpropagation doesn't optimize! It moves the error information from the end of the network to all the weights inside the network so that a different algorithm can optimize those weights to fit our data. This ultimately allowed us to change these weights using a different algorithm, Gradient Descent. Backpropagation allowed us to measure how each weight in the network contributed to the overall error. In Part 1, I laid out the basis for backpropagation in a simple neural network. Synapse_0 -= (alpha * X.T.dot(layer_1_delta)) Synapse_1 -= (alpha * layer_1.T.dot(layer_2_delta)) Synapse_1 = 2*np.random.random((hidden_dim,1)) - 1 Synapse_0 = 2*np.random.random((3,hidden_dim)) - 1 I'll tweet it out when it's complete Feel free to follow if you'd be interested in reading more and thanks for all the feedback! This tutorial teaches gradient descent via a very simple toy example, a short python implementation.įollowup Post: I intend to write a followup post to this one adding popular features leveraged by state-of-the-art approaches (likely Dropout, DropConnect, and Momentum). Summary: I learn best with toy code that I can play with.
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