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<a class="navbar-brand" href="week40-bs.html">Week 40: Gradient descent methods (continued) and start Neural networks</a>
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<!-- navigation toc: --> <li><a href="._week40-bs001.html#plans-for-week-40" style="font-size: 80%;"><b>Plans for week 40</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs002.html#summary-from-last-week-using-gradient-descent-methods-limitations" style="font-size: 80%;"><b>Summary from last week, using gradient descent methods, limitations</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs003.html#overview-video-on-stochastic-gradient-descent" style="font-size: 80%;"><b>Overview video on Stochastic Gradient Descent</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs004.html#batches-and-mini-batches" style="font-size: 80%;"><b>Batches and mini-batches</b></a></li>
<!-- navigation toc: --> <li><a href="#stochastic-gradient-descent-sgd" style="font-size: 80%;"><b>Stochastic Gradient Descent (SGD)</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs006.html#stochastic-gradient-descent" style="font-size: 80%;"><b>Stochastic Gradient Descent</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs007.html#computation-of-gradients" style="font-size: 80%;"><b>Computation of gradients</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs008.html#sgd-example" style="font-size: 80%;"><b>SGD example</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs009.html#the-gradient-step" style="font-size: 80%;"><b>The gradient step</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs010.html#simple-example-code" style="font-size: 80%;"><b>Simple example code</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs011.html#when-do-we-stop" style="font-size: 80%;"><b>When do we stop?</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs012.html#slightly-different-approach" style="font-size: 80%;"><b>Slightly different approach</b></a></li>
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<!-- navigation toc: --> <li><a href="._week40-bs014.html#code-with-a-number-of-minibatches-which-varies" style="font-size: 80%;"><b>Code with a Number of Minibatches which varies</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs015.html#replace-or-not" style="font-size: 80%;"><b>Replace or not</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs016.html#momentum-based-gd" style="font-size: 80%;"><b>Momentum based GD</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs017.html#more-on-momentum-based-approaches" style="font-size: 80%;"><b>More on momentum based approaches</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs018.html#momentum-parameter" style="font-size: 80%;"><b>Momentum parameter</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs019.html#second-moment-of-the-gradient" style="font-size: 80%;"><b>Second moment of the gradient</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs020.html#rms-prop" style="font-size: 80%;"><b>RMS prop</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs021.html#adam-optimizer-https-arxiv-org-abs-1412-6980" style="font-size: 80%;"><b>"ADAM optimizer":"https://arxiv.org/abs/1412.6980"</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs022.html#algorithms-and-codes-for-adagrad-rmsprop-and-adam" style="font-size: 80%;"><b>Algorithms and codes for Adagrad, RMSprop and Adam</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs023.html#practical-tips" style="font-size: 80%;"><b>Practical tips</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs024.html#automatic-differentiation" style="font-size: 80%;"><b>Automatic differentiation</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs025.html#using-autograd" style="font-size: 80%;"><b>Using autograd</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs026.html#autograd-with-more-complicated-functions" style="font-size: 80%;"><b>Autograd with more complicated functions</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs027.html#more-complicated-functions-using-the-elements-of-their-arguments-directly" style="font-size: 80%;"><b>More complicated functions using the elements of their arguments directly</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs028.html#functions-using-mathematical-functions-from-numpy" style="font-size: 80%;"><b>Functions using mathematical functions from Numpy</b></a></li>
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<!-- navigation toc: --> <li><a href="._week40-bs034.html#recommended-to-avoid" style="font-size: 80%;"><b>Recommended to avoid</b></a></li>
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<!-- navigation toc: --> <li><a href="._week40-bs039.html#same-code-but-now-with-momentum-gradient-descent" style="font-size: 80%;"><b>Same code but now with momentum gradient descent</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs037.html#but-noen-of-these-can-compete-with-newton-s-method" style="font-size: 80%;"><b>But noen of these can compete with Newton's method</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs038.html#including-stochastic-gradient-descent-with-autograd" style="font-size: 80%;"><b>Including Stochastic Gradient Descent with Autograd</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs039.html#same-code-but-now-with-momentum-gradient-descent" style="font-size: 80%;"><b>Same code but now with momentum gradient descent</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs040.html#similar-second-order-function-now-problem-but-now-with-adagrad" style="font-size: 80%;"><b>Similar (second order function now) problem but now with AdaGrad</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs041.html#rmsprop-for-adaptive-learning-rate-with-stochastic-gradient-descent" style="font-size: 80%;"><b>RMSprop for adaptive learning rate with Stochastic Gradient Descent</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs042.html#and-finally-adam-https-arxiv-org-pdf-1412-6980-pdf" style="font-size: 80%;"><b>And finally "ADAM":"https://arxiv.org/pdf/1412.6980.pdf"</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs043.html#and-logistic-regression" style="font-size: 80%;"><b>And Logistic Regression</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs044.html#introducing-jax-https-jax-readthedocs-io-en-latest" style="font-size: 80%;"><b>Introducing "JAX":"https://jax.readthedocs.io/en/latest/"</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs045.html#introduction-to-neural-networks" style="font-size: 80%;"><b>Introduction to Neural networks</b></a></li>
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<!-- navigation toc: --> <li><a href="._week40-bs047.html#neural-network-types" style="font-size: 80%;"><b>Neural network types</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs048.html#feed-forward-neural-networks" style="font-size: 80%;"><b>Feed-forward neural networks</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs049.html#convolutional-neural-network" style="font-size: 80%;"><b>Convolutional Neural Network</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs050.html#recurrent-neural-networks" style="font-size: 80%;"><b>Recurrent neural networks</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs051.html#other-types-of-networks" style="font-size: 80%;"><b>Other types of networks</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs052.html#multilayer-perceptrons" style="font-size: 80%;"><b>Multilayer perceptrons</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs053.html#why-multilayer-perceptrons" style="font-size: 80%;"><b>Why multilayer perceptrons?</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs054.html#illustration-of-a-single-perceptron-model-and-a-multi-perceptron-model" style="font-size: 80%;"><b>Illustration of a single perceptron model and a multi-perceptron model</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs055.html#examples-of-xor-or-and-and-gates" style="font-size: 80%;"><b>Examples of XOR, OR and AND gates</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs056.html#does-logistic-regression-do-a-better-job" style="font-size: 80%;"><b>Does Logistic Regression do a better Job?</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs057.html#adding-neural-networks" style="font-size: 80%;"><b>Adding Neural Networks</b></a></li>
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<!-- navigation toc: --> <li><a href="._week40-bs062.html#mathematical-model" style="font-size: 80%;"><b>Mathematical model</b></a></li>
<!-- navigation toc: --> <li><a href="._week40-bs063.html#matrix-vector-notation" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Matrix-vector notation</a></li>
<!-- navigation toc: --> <li><a href="._week40-bs064.html#matrix-vector-notation-and-activation" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Matrix-vector notation and activation</a></li>
<!-- navigation toc: --> <li><a href="._week40-bs065.html#activation-functions" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Activation functions</a></li>
<!-- navigation toc: --> <li><a href="._week40-bs066.html#activation-functions-logistic-and-hyperbolic-ones" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Activation functions, Logistic and Hyperbolic ones</a></li>
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<a name="part0005"></a>
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<h2 id="stochastic-gradient-descent-sgd" class="anchor">Stochastic Gradient Descent (SGD) </h2>
<p>In stochastic gradient descent, the extreme case is the case where we
have only one batch, that is we include the whole data set.
</p>
<p>This process is called Stochastic Gradient
Descent (SGD) (or also sometimes on-line gradient descent). This is
relatively less common to see because in practice due to vectorized
code optimizations it can be computationally much more efficient to
evaluate the gradient for 100 examples, than the gradient for one
example 100 times. Even though SGD technically refers to using a
single example at a time to evaluate the gradient, you will hear
people use the term SGD even when referring to mini-batch gradient
descent (i.e. mentions of MGD for &#8220;Minibatch Gradient Descent&#8221;, or BGD
for &#8220;Batch gradient descent&#8221; are rare to see), where it is usually
assumed that mini-batches are used. The size of the mini-batch is a
hyperparameter but it is not very common to cross-validate or bootstrap it. It is
usually based on memory constraints (if any), or set to some value,
e.g. 32, 64 or 128. We use powers of 2 in practice because many
vectorized operation implementations work faster when their inputs are
sized in powers of 2.
</p>
<p>In our notes with SGD we mean stochastic gradient descent with mini-batches.</p>
<p>
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