How do you avoid overshooting or underfitting with gradient descent?

In the learning phase, I found it's helpful to plot things out if possible, it can help understanding the underlining algorithm and make learning fun. There's a lot of math in ML. Anything making it more fun is good. :)

Overshooting happens when the learning rate is too high, causing the algorithm to jump over the minimum of the loss function, leading to oscillations or divergence. Conversely, underfitting occurs when the learning rate is too low, resulting in slow convergence or getting stuck in a local minimum, which negatively impacts accuracy and generalization.

Overshooting occurs when the learning rate is set too high. The consequence is oscillations or divergence, where the algorithm fails to converge to an optimal solution. To mitigate this problem, it is essential to carefully tune the learning rate and consider using techniques such as learning rate decay or adaptive learning rate algorithms. On the other hand, underfitting occurs when the learning rate is too low. In this case, the algorithm converges slowly or gets stuck in a local minimum. The result is poor accuracy or generalization of the model. To overcome underfitting, it is important to experiment with different learning rates and consider increasing the learning rate if convergence is too slow.

To avoid overshooting or underfitting with gradient descent, start by carefully choosing the learning rate. If it's too high, the model may overshoot the optimal solution; if it's too low, training can become slow and may lead to underfitting. Consider using learning rate scheduling to adjust the rate during training, allowing for larger steps initially and smaller ones as you converge. Implement early stopping to prevent overfitting by halting training when validation performance starts to decline. Finally, experiment with different optimization algorithms which adapt the learning rate dynamically to improve convergence.

Instead of using entire dataset for each step, we can use mini batch in training (batch gradient descent). This provides a more stable estimate of the gradient and helps avoid getting stuck on local minima. Also, we can consider gradually increasing the learning rate from a small value to the intended value over the initial few epochs (LR warm up) and early stopping if the cost function keeps oscillating around the same minimum or stops improving. Also, Gradient Clipping is effective to prevent overfitting (where we clip the gradients by setting a threshold for the gradient values).

Choosing the right learning rate for gradient descent is crucial for effective training. Start with a common value like 0.01, but be prepared to adjust based on performance. Consider using learning rate annealing, where you begin with a higher rate and gradually decrease it, or cyclical learning rates that vary between set boundaries to escape local minima.

While there is no one-size-fits-all formula, there are effective methods and guidelines to help you navigate this crucial hyperparameter. One approach is to start with a small learning rate, such as 0.01, and gradually increase it. Monitor the behavior of the loss function as you increase the learning rate. If you observe that the loss function starts to increase or fluctuate, it is a sign that the learning rate may be too high. At this point, you can dial back to a lower value that provides more stability. Another method involves utilizing a validation set. By training your model with different learning rates and monitoring the loss and accuracy on the validation set, you can identify the learning rate that yields the best performance.

The value of learning rate always results in a tradeoff between the time and result. Higher values of learning rate results in more rapid changes resulting in faster training but cannot ensure reaching the global optimum. On the other hand, smaller learning rates can result in slow and steady changes and can lead to global optimum, however consuming a lot of time.

One simple method is to try out different learning rates using a grid search. This involves training the model with different learning rates and selecting the one that performs best on the validation set. However, this can be time-consuming and computationally expensive.

Another approach is to use a learning rate scheduler, which adjusts the learning rate during training based on a predefined schedule. One common approach is to decrease the learning rate gradually over time, such as using a step-wise decay or exponential decay.

To improve gradient descent, consider the following techniques: Momentum: Adds a fraction of the previous update to the current update, helping to accelerate convergence and smooth out oscillations. Adaptive Learning Rates: Methods like AdaGrad, RMSProp, or Adam adjust the learning rate based on the gradients' magnitude and frequency, improving parameter updates. Batch Normalization: Normalizes the inputs of each layer to reduce internal covariate shift, which stabilizes training and accelerates convergence.

Beyond choosing the right learning rate, these techniques improve the optimization process and achieve better results. One such technique is momentum, which adds a fraction of the previous update to the current update. This helps create a smoother and faster direction, allowing the algorithm to overcome small local optima and navigate towards the global minimum more efficiently. Adaptive learning rates are another technique. Methods like AdaGrad, RMSProp, or Adam adjust the learning rate for each parameter based on the magnitude and frequency of the gradients. By dynamically adapting the learning rate, these methods can effectively handle different scales and variations in the data, leading to faster convergence and improved performance.

Gradient descent faces several challenges, including choosing an optimal learning rate that balances convergence speed and stability, converging to local minima instead of the global minimum in non-convex loss landscapes, getting stuck at saddle points where gradients are zero in some directions, incurring significant computational costs for large datasets, and dealing with vanishing or exploding gradients in deep networks that hinder effective training. Overcoming these limitations requires careful tuning of hyperparameters and exploring alternative optimization strategies to enhance gradient descent's performance in machine learning applications.

gradient descent is not without its challenges and limitations. It's important to be aware of these factors to make informed decisions and optimize your models effectively. One challenge you may encounter is dealing with noisy or sparse gradients. In some cases, the gradients may not provide accurate or reliable information about the direction and magnitude of the updates. To address this issue, a technique called mini-batch gradient descent can be employed. By averaging the gradients over a subset of samples, the variance and noise can be reduced, leading to more stable and reliable updates. Another challenge arises when dealing with non-convex loss functions. These functions can have multiple local minima, plateaus, or saddle points.

When evaluating gradient descent methods, common metrics include the training loss, validation loss, test accuracy, and convergence speed. The training loss reflects how well the model fits the training data, while the validation loss and test accuracy provide insights into the generalization capabilities of the model. Additionally, considering the convergence speed can help assess the efficiency and effectiveness of the optimization process. It is also essential to evaluate gradient descent methods based on specific criteria. These criteria can include the robustness of the method, its scalability to handle large datasets or complex models, its simplicity in terms of implementation and computational requirements, and its interpretability.

Learning curves plot the training and validation loss as a function of training time or the number of epochs. By analyzing the learning curve, it's possible to see if the method is converging quickly, if there is overfitting, and if there is high variance or bias.

Two other methods are: 1) Generalization Performance: Ultimately, the goal of a gradient descent method is to produce a model that can generalize well to new, unseen data. This can be evaluated by measuring the performance of the model on a held-out test set, or by using cross-validation to estimate the generalization performance. 2) Hyperparameter Sensitivity: Gradient descent methods often have hyperparameters that need to be tuned, such as the learning rate or the momentum term. Evaluating the sensitivity of the method to different hyperparameters can help to choose the best values and improve performance.