Deep Learning: Classification Problems

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Questions and Answers

How many gradient updates will the model perform after 5 epochs?

  • 3,135
  • 2,345 (correct)
  • 4,690
  • 1,000

What is the purpose of implementing the example from scratch in TensorFlow?

  • To replace Keras functionality entirely.
  • To reimplement backpropagation fully.
  • To understand basic tensor operations in depth.
  • To demonstrate understanding of deep learning mathematics. (correct)

What does the output of a Dense layer depend on?

  • The value of the activation function only.
  • The number of epochs completed.
  • The weights W and input, plus the bias b. (correct)
  • The network's architecture exclusively.

In the NaiveDense class, which method is responsible for applying the transformation?

<p><strong>call</strong>() (C)</p> Signup and view all the answers

Which activation function is typically used for the last layer in a Dense layer implementation?

<p>softmax (A)</p> Signup and view all the answers

What is the effect of updating the weights in the opposite direction from the gradient?

<p>It will reduce the loss on each iteration. (B)</p> Signup and view all the answers

What does mini-batch stochastic gradient descent utilize?

<p>A random subset of samples for each iteration. (A)</p> Signup and view all the answers

What is a naive solution for adjusting the weight coefficient in a model?

<p>Freeze all weights except the one being considered and test different values. (A)</p> Signup and view all the answers

If changing the weight coefficient from 0.3 to 0.35 increases the loss, what can be inferred?

<p>Increasing the coefficient decreases the model's performance. (D)</p> Signup and view all the answers

Why is it important to select a reasonable value for the learning rate?

<p>It influences the speed of descent on the loss curve. (C)</p> Signup and view all the answers

What is true stochastic gradient descent?

<p>It uses a single sample at each iteration. (A)</p> Signup and view all the answers

Why is adjusting coefficients one at a time in a model not efficient?

<p>Each adjustment requires computing two forward passes. (D)</p> Signup and view all the answers

What is the primary optimization technique used in modern neural networks?

<p>Gradient descent. (A)</p> Signup and view all the answers

What might happen if the learning rate is set too high?

<p>The updates may overshoot and diverge randomly. (D)</p> Signup and view all the answers

What characteristic of functions used in models allows for gradient-based optimization?

<p>They are differentiable and change smoothly. (A)</p> Signup and view all the answers

What does batch gradient descent do differently compared to mini-batch SGD?

<p>It performs updates based on the entire dataset. (B)</p> Signup and view all the answers

What is the role of the gradient in training a neural network?

<p>It shows the direction in which to adjust coefficients to minimize loss. (B)</p> Signup and view all the answers

What primarily differentiates mini-batch SGD from true SGD?

<p>The batch size of samples drawn. (D)</p> Signup and view all the answers

What happens when the weight coefficient is decreased from 0.3 to 0.25?

<p>The loss decreases, suggesting better model performance. (D)</p> Signup and view all the answers

Which is a consequence of having a learning rate that is too small?

<p>The model may get stuck in local minima. (B)</p> Signup and view all the answers

What is one of the disadvantages of relying solely on one-at-a-time coefficient adjustments?

<p>It ignores the interactions between different coefficients. (D)</p> Signup and view all the answers

What will happen if the optimization process using SGD is executed with a small learning rate near a local minimum?

<p>The process could get stuck at the local minimum. (A)</p> Signup and view all the answers

How does momentum help in the context of SGD optimization?

<p>It helps the optimization 'ball' move past local minima towards the global minimum. (A)</p> Signup and view all the answers

In the context of the algorithm presented, which variable represents the current velocity?

<p>velocity (B)</p> Signup and view all the answers

What role does the momentum factor play in the optimization process?

<p>It amplifies the effect of past gradients. (A)</p> Signup and view all the answers

What is a potential issue when calculating gradients for complex expressions in backpropagation?

<p>The gradients might become unstable. (C)</p> Signup and view all the answers

Which statement best describes how to update the parameter 'w' in the provided momentum implementation?

<p>The velocity is first calculated and then added to w using both past and current acceleration/gradient. (C)</p> Signup and view all the answers

What can occur if a small ball simulates the optimization process and lacks sufficient momentum?

<p>It may settle in a local minimum. (C)</p> Signup and view all the answers

Which aspect of the gradient-based optimization is emphasized in the content?

<p>Maintaining convergence stability is crucial in training neural networks. (D)</p> Signup and view all the answers

What is the primary difference between classification and regression in supervised learning?

<p>Classification deals with labeled data of classes, regression deals with continuous scale values. (C)</p> Signup and view all the answers

Which of the following is a method of unsupervised learning?

<p>K-means clustering (C)</p> Signup and view all the answers

Which of the following statements about K-means clustering is true?

<p>K-means clustering uncovers structure in unlabeled data. (D)</p> Signup and view all the answers

What is meant by 'labels on a continuous scale' in regression?

<p>Labels that can take any value within a range. (B)</p> Signup and view all the answers

Which unsupervised learning method focuses on reducing the dimensions of data?

<p>Principal Component Analysis (PCA) (D)</p> Signup and view all the answers

Which statement accurately describes unsupervised learning?

<p>It finds hidden patterns without needing labeled outcomes. (B)</p> Signup and view all the answers

What kind of data is typically used in classification tasks?

<p>Labeled data categorized into classes (D)</p> Signup and view all the answers

Which of the following best describes supervised learning?

<p>Learning that uses input-output pairs with known results. (D)</p> Signup and view all the answers

What does the forward pass in a computation graph entail?

<p>Calculating values from input nodes to loss. (D)</p> Signup and view all the answers

In the backward pass, what is represented by grad(B, A)?

<p>The rate of change of B with respect to A. (B)</p> Signup and view all the answers

If grad(loss_val, x2) = 1, what does this imply about the relationship between loss_val and x2?

<p>A change in x2 results in a proportional change in loss_val. (D)</p> Signup and view all the answers

How does grad(x2, x1) = 1 affect the relationship between x2 and x1?

<p>A change in x1 causes an equivalent change in x2. (C)</p> Signup and view all the answers

What does grad(x1, w) = 2 indicate about x1 when w varies?

<p>x1 doubles for each increment of w. (A)</p> Signup and view all the answers

What role does variable b play in the relationship for grad(x2, b)?

<p>It has a direct proportionality with the change of x2. (D)</p> Signup and view all the answers

What does the concept of reversing the graph during the backward pass help to determine?

<p>It clarifies how inputs affect outputs. (D)</p> Signup and view all the answers

What is the significance of annotating edges with gradient values during the backward pass?

<p>It indicates the relative impact of each variable. (C)</p> Signup and view all the answers

Flashcards

Regression

Supervised learning where the goal is to predict a continuous output value based on labeled data.

Linear Support Vector Regression

A type of supervised learning where the goal is to predict a value on a continuous scale, given labeled data.

RBF Support Vector Regression

A type of supervised learning where the goal is to predict a value on a continuous scale, given labeled data.

Unsupervised Learning

A type of machine learning where the goal is to find patterns and insights from unlabeled data without explicit guidance.

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Clustering

An unsupervised learning technique that groups data points into clusters based on their similarity.

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K-means Clustering

A specific type of clustering algorithm that aims to partition data points into k clusters by minimizing the distance between points within each cluster.

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Cluster Count

The task of identifying the optimal number of clusters to create in a dataset.

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Dimensionality Reduction

An unsupervised learning technique where the goal is to reduce the dimensionality of data while preserving as much information as possible.

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Gradient Descent

A method for training neural networks where the model's parameters are adjusted in the opposite direction of the gradient of the loss function.

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Learning Rate

The amount by which the model parameters are updated in each iteration of gradient descent.

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Mini-Batch Stochastic Gradient Descent (Mini-Batch SGD)

A method of updating the model parameters using the gradient of the loss function computed on a small batch of training data.

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Stochastic Gradient Descent (SGD)

A method of updating the model parameters using the gradient of the loss function computed on a single training sample.

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Batch Gradient Descent

A method of updating the model parameters using the gradient of the loss function computed on the entire training dataset.

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Local Minimum

A local minimum in the loss function is a point where the loss is lower than any nearby point, but not necessarily the lowest point overall.

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Forward Pass

The forward pass involves running the model on input data to obtain predictions.

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Backward Pass

The backward pass involves calculating the gradient of the loss function with respect to the model's parameters.

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Loss Function

A measure of how well a model is performing on a given dataset. It quantifies the difference between the model's predictions and the actual values.

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Differentiable

The ability of a function to have its output smoothly change based on small changes in its input. This allows us to calculate the gradient of the function.

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Gradient

This mathematical tool describes the rate of change of a function at a specific point. In machine learning, it tells us how much the loss function changes with respect to each weight in the model.

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Weight

A scalar coefficient used in a neural network model to adjust the contribution of different input features. These coefficients are typically represented by 'w' in mathematical notation.

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Weight Update

The process of iteratively updating the weights in a neural network based on the calculated gradients. This aims to minimize the loss function and improve the model's accuracy.

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Evaluation

The process of evaluating a model's performance on a separate dataset that was not used during training. This helps to assess the model's ability to generalize to unseen data.

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Momentum in Optimization

A technique used in optimization to help the model escape local minima by incorporating the 'momentum' of past parameter updates. It considers not only the current gradient but also the direction of past movements.

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Gradient Calculation

The process of calculating the gradient of a function with respect to its parameters. It's essential for optimization algorithms that use gradients to find the best parameter values.

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Backpropagation Algorithm

A method for efficiently calculating the gradients of a neural network's loss function with respect to its weights and biases. It uses the chain rule of calculus to compute gradients from the output back to the input.

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Model Optimization

The process of changing the parameters of a model to minimize the loss function. It typically involves using gradient-based optimization algorithms, like gradient descent.

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Model Evaluation

The process of evaluating the model's performance on a separate dataset (not used for training). Used to assess the model's generalization ability.

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Gradient (grad)

The amount by which a value changes as another value changes. It measures the sensitivity of one value to the change in another value.

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Computation Graph

A representation of a computation, where nodes represent values and edges represent operations that connect those values.

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y_true (Input)

The value that the model tries to predict based on the input data.

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loss_val (Output)

The value that the model predicts after processing the input data.

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Gradient-based Optimization

The process of updating the model's parameters to minimize the difference between the model's predictions and the true values.

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Parameters (w, b)

The values that the model learns from the data to make predictions. They control how the model processes information.

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Dense Layer

A type of neural network layer that performs a linear transformation on its input, followed by an activation function. It implements the formula: output = activation(dot(W, input) + b), where W and b are the model parameters and activation is an element-wise function.

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Activation Function

A function that is applied element-wise to the output of a dense layer, introducing non-linearity and allowing the network to learn more complex patterns. Examples include ReLU, sigmoid, and softmax.

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Epoch

The process of training a model on a dataset multiple times, where each pass through the entire dataset is considered an epoch. This helps in finding better model parameters.

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Weighted sum of inputs

The weighted sum of inputs to a neuron, which determines the neuron's activation value. It represents the linear contribution of each input.

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Study Notes

Deep Learning: Classification

  • Classification problems involve predicting the category or class of an input.
  • Examples include spam detection (is an email spam or not?), image recognition (is this a picture of a cat, dog, or bird?), and sentiment analysis (is this review positive or negative?).
  • Data for classification problems includes both input features and corresponding labels.
  • Binary classification means dividing items into two categories (spam/not spam).
  • Multi-class classification involves more than two categories (e.g., classifying images of different fruits).
  • Multilabel classification allows for multiple labels assigned to a single input (e.g., tagging an article with multiple topics).

Example Classification Problems

  • Examples of binary classification problems include spam detection and image recognition (cat vs. dog).
  • Multi-class classification examples include image recognition with multiple classes (e.g. classifying images of different types of fruits).
  • Multi-label classification examples include articles that can be tagged with multiple topics.

Binary vs. Multi-Class Classification

  • Binary classification deals with two classes.
  • Multi-class classification deals with more than two classes.

What We're Going To Cover

  • Neural network architecture for classification.
  • Input and output shapes of a classification model.
  • Creating custom data for classification tasks.
  • Model building steps, including loss functions, optimizers, training, and evaluation.
  • Model saving and loading.
  • Harnessing non-linearity in models.
  • Different classification evaluation methods.

Classification Inputs and Outputs

  • Input data often consists of normalized pixel values.
  • Output is a probability distribution over the possible categories.

Input and Output Shapes

  • Input data structure for image classification often involves batch size, color channels, width, and height dimensions.
  • Output structure often includes the predicted category and its probabilities.

Architecture of a Classification Model

  • Models usually consist of multiple layers: input, hidden layers, and output.
  • These layers use parameters like input layer shape, hidden layers (neurons per layer), output layer shape, and activation functions.
  • Loss functions are used to quantify the difference between predicted and true output.
  • Optimizers (e.g., SGD, Adam) adjust model parameters to improve accuracy.

Improving A Model

  • Adding layers or increasing the number of hidden units can improve model complexity.
  • Changing activation functions (like ReLU and sigmoid) can alter how the model processes information.
  • Choosing a different optimization function (e.g., Adam, instead of SGD) can influence how the model learns.
  • Adjusting the learning rate can affect the speed and stability of training.
  • Increasing training time (epochs) can improve a model in many cases but results in overfitting sometimes.

The Missing Piece: Non-linearity

  • Linear models can't capture complex relationships in data.
  • Adding non-linear activation functions (e.g., sigmoid, ReLU) allows models to learn complex patterns.
  • These functions introduce non-linearity into the model and allow for a flexible representation of complex data.

The Machine Learning Explorer's Motto

  • Visualize, visualize, visualize (data, model, training, predictions)

The Machine Learning Practitioner's Motto

  • Experiment, experiment, experiment.

Steps in Modelling With PyTorch

  • Construct a model.
  • Prepare the loss function, optimizer, and training loop.
  • Train the model(fit the model) on training data.
  • Evaluate the model on test data(how reliable the model's predictions are).

Classification Evaluation Methods

  • Accuracy measures correct predictions overall.
  • Precision measures the proportion of true positive predictions out of all positive predictions.
  • Recall measures the proportion of true positive predictions out of all actual positive values.
  • F1-score combines precision and recall.
  • Confusion matrices show the counts of different types of predictions.

Anatomy of a Confusion Matrix

  • True positive (TP): model predicts 1 when truth is 1.
  • True negative (TN): model predicts 0 when truth is 0.
  • False positive (FP): model predicts 1 when truth is 0.
  • False negative (FN): model predicts 0 when truth is 1.

Three Datasets (Training, Validation, and Test)

  • Training set: used by the model to learn patterns.
  • Validation set: used to tune model parameters.
  • Test set: used to evaluate the model.

Neural Network Learning Steps

  • Initialize weights and biases with random values.
  • Input data is encoded numerically.
  • Show data to the neural network, get outputs using the forward pass.
  • Update weights based on the difference between predicted vs. actual outputs using back propagation

Learning Strategies

  • Supervised learning (discrete and continuous) involves labeled data.
  • Unsupervised learning (e.g., clustering, dimensionality reduction) uses unlabeled data.

Unsupervised Learning Methods

  • Hierarchical clustering.
  • K-means clustering.
  • Principal Component Analysis (PCA).
  • Singular Value Decomposition.
  • Independent Component Analysis.

Conclusion (Supervised Learning)

  • Labeled data (inputs paired with labels) is essential.
  • Classification labels are categorical, and regression labels are continuous.

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