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Grid Search

What is Grid Search?

GridSearch is a technique for hyperparameter tuning that identifies the most suitable values for a certain model. Building a grid of hyperparameter values, training a model with each set of these values, and evaluating the results are required. The goal is to find the hyperparameter setting combination that gives the model the best performance on the validation set.

Grid search can be expensive since a model needs to be developed and tested for each possible collection of hyperparameter values. As a result, grid search is a brute-force technique for optimizing hyperparameters. The performance of a model can be improved by applying this simple and effective approach of hyperparameter tweaking.


How Does Grid Search Work?

The hyperparameters of a machine learning model can be adjusted with the help of grid search. It operates by, first, training the model with various hyperparameter combinations and then evaluating the model's performance via cross-validation. The goal is to find the right hyperparameter mix for performance. 

The hyperparameters needed to search across and the values needed to test for each hyperparameter must be specified when using grid search. The performance of the model will then be assessed using cross-validation and every possible combination of these variables will be tested using the grid search approach. The grid search ultimately finds the set of hyperparameters that produced the best performance.


Why is Grid Search important?

Grid search is essential since it enables users to choose the hyperparameters of a machine-learning model that should be set to their ideal values. These hyperparameters can have a big influence on the model's performance. If another technique for hyperparameter optimization wasn't available, the hyperparameters would have to be manually experimented with, looking for different settings to assess the model's performance for each combination of grid search. This could take a considerable amount of time and bears the risk of not providing the ideal set of hyperparameters.

Grid search speeds up the hyperparameter optimization process by training and testing the model over a range of different hyperparameter values. Users can save time and effort by having someone else find the collection of hyperparameters that results in the greatest model performance.


How is Grid Search used?

In machine learning, the grid search approach is used to identify the ideal values for a model's hyperparameters. Building a grid of hyperparameter values, training a model for each set of values, and assessing the model's performance are the steps to make this model function.

Think about a situation where it is being attempted to determine the best depth for a decision tree model that is currently being developed (i.e., the maximum number of levels the tree can have). The maximum depth of the grid can take one of the following values: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. Then, using a criterion like an accuracy or F1 score, the decision tree model would be trained to have the greatest depth feasible for each value in the grid. The value that led to the best outcomes would then be selected.


Grid Search VS Cross Validation

When developing and evaluating machine learning models, grid search and cross-validation are two separate techniques that are commonly combined.

A hyperparameter optimization approach known as "grid search" entails specifying a grid of hyperparameter values, training a model for each combination of these values, and evaluating the performance of each model. The goal is to find the hyperparameter combination that offers the best performance, as measured by metrics.

Contrarily, cross-validation is a method for gauging how well a machine-learning model is doing. The training data are divided into "folds," the model is trained on a subset of the data, and then it is tested on the remaining folds. Each fold serves as the evaluation set just once throughout the course of this method, which is repeated numerous times. The final performance estimate is obtained by averaging the performance overall folds.