Advance Machine Learning | 2. Optimization Methods by Abraham | Learn Smarter
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2. Optimization Methods

Optimization methods are fundamental in machine learning, involving algorithms that minimize or maximize objective functions, crucial for the performance of predictive models. This chapter outlines various optimization techniques, including gradient descent, advanced optimizers like Adam, and concepts of convexity, regularization, and hyperparameter tuning. Mastering these techniques is essential to build effective and scalable machine learning models.

Sections

  • 2

    Optimization Methods

    This section covers key concepts and methodologies for optimizing machine learning models, emphasizing various objective functions and optimization techniques.

  • 2.1

    Objective Functions In Machine Learning

    This section discusses the essential role of objective functions in machine learning and the different types utilized.

  • 2.1.1

    Loss Function (Supervised Learning)

    Loss functions are essential to supervised learning, serving as objective functions that the algorithm seeks to minimize to improve model predictions.

  • 2.1.1.1

    Mse (Mean Squared Error)

    Mean Squared Error (MSE) is a common regression loss function that measures the average squared difference between predicted and actual values.

  • 2.1.1.2

    Cross-Entropy Loss

    Cross-entropy loss measures the performance of a classification model whose output is a probability value between 0 and 1.

  • 2.1.2

    Likelihood Function (Probabilistic Models)

    The likelihood function plays a pivotal role in probabilistic models, focusing on maximizing log-likelihood to improve model accuracy.

  • 2.1.2.1

    Maximizing Log-Likelihood

    Maximizing log-likelihood is crucial for probabilistic models, where the aim is to enhance the fit of the model to observed data.

  • 2.1.3

    Regularized Objective Functions

    Regularized objective functions include additional penalty terms to avoid overfitting during optimization.

  • 2.1.3.1

    L1 Or L2 Penalties

    L1 and L2 penalties are techniques used in optimization that add regularization terms to objective functions to prevent overfitting in machine learning models.

  • 2.2

    Convex And Non-Convex Optimization

    This section discusses the distinction between convex and non-convex optimization functions in machine learning, highlighting their importance in ensuring model performance.

  • 2.2.1

    Convex Optimization

    Convex optimization ensures that a function has a global minimum, making it crucial for various learning algorithms.

  • 2.2.2

    Non-Convex Optimization

    Non-convex optimization involves functions that can have multiple local minima and saddle points, making the optimization process more complex.

  • 2.3

    Gradient-Based Optimization

    Gradient-Based Optimization involves techniques like Gradient Descent that iteratively adjust parameters to minimize an objective function.

  • 2.3.1

    Gradient Descent (Gd)

    Gradient descent is an optimization algorithm that iteratively updates model parameters in the direction of the negative gradient to minimize an objective function.

  • 2.3.2

    Variants Of Gd

    This section discusses the different variants of Gradient Descent (GD) used in optimization, namely Batch Gradient Descent, Stochastic Gradient Descent (SGD), and Mini-batch Gradient Descent.

  • 2.3.3

    Challenges

    This section discusses the challenges encountered in gradient-based optimization methods.

  • 2.4

    Advanced Gradient-Based Optimizers

    This section covers advanced gradient-based optimizers that enhance the traditional gradient descent method, aiming to improve convergence speed and efficiency in machine learning models.

  • 2.4.1

    Momentum

    Momentum helps optimize convergence by smoothing updates in gradient descent algorithms.

  • 2.4.2

    Nesterov Accelerated Gradient (Nag)

    Nesterov Accelerated Gradient (NAG) offers an advanced optimization technique that improves convergence speed by looking ahead at the gradients of the objective function.

  • 2.4.3

    Adagrad

    Adagrad is an adaptive gradient descent algorithm that modifies the learning rate for each parameter based on the historical gradients.

  • 2.4.4

    Rmsprop

    RMSprop is an advanced optimizer that enhances the Adagrad method by utilizing a decaying average of past squared gradients, allowing for adaptive learning rates.

  • 2.4.5

    Adam (Adaptive Moment Estimation)

    Adam is an advanced optimization algorithm that combines the benefits of Momentum and RMSprop to ensure fast convergence in deep learning models.

  • 2.5

    Second-Order Optimization Methods

    Second-order optimization methods use second derivatives to achieve faster convergence in optimizing objective functions.

  • 2.5.1

    Newton’s Method

    Newton’s Method is an optimization approach that utilizes both the gradient and Hessian matrix to find faster convergence in minimizing an objective function.

  • 2.5.2

    Quasi-Newton Methods

    Quasi-Newton methods are optimization techniques that improve upon Newton's method by approximating the Hessian matrix, allowing for faster and more efficient optimization without the need for full Hessian computations.

  • 2.6

    Constrained Optimization

    Constrained optimization deals with optimizing an objective function subject to certain constraints, which is crucial for practical applications in machine learning.

  • 2.7

    Optimization In Deep Learning

    This section addresses the unique optimization challenges in deep learning, including non-convex loss surfaces and gradient issues, alongside effective strategies to mitigate these challenges.

  • 2.8

    Regularization And Optimization

    Regularization techniques are essential in optimizing machine learning models to improve their performance and prevent overfitting.

  • 2.9

    Hyperparameter Optimization

    Hyperparameter optimization involves selecting the best set of parameters for machine learning algorithms to enhance performance.

  • 2.10

    Optimization Libraries And Tools

    This section covers the optimization libraries and tools available in modern machine learning frameworks, highlighting their utility and functionalities.

References

AML ch2.pdf

Class Notes

Memorization

What we have learnt

  • Optimization is central to ...
  • Different types of objectiv...
  • Advanced optimization metho...

Final Test

Revision Tests